5.01 多孔金属有机骨架
5.01.1 Introduction
5.01.2 Inorganic SBUs and Organic Linkers
5.01.3 Architecture of the Networks
5.01.4 Porous Structures
5.01.4.1 0D Cage
5.01.4.2 1D Channels
5.01.4.3 2D Layers
5.01.4.4 3D Channels
5.01.5 Synthesis of MOFs
5.01.5.1 Influencing Factors
5.01.5.2 Solvent-Evaporation Synthesis
5.01.5.3 Diffusion Synthesis
5.01.5.4 Hydrothermal or Solvothermal Synthesis
5.01.5.5 Microwave-Reaction Synthesis
5.01.5.6 Ionothermal Synthesis
5.01.5.7 Electrochemical Synthesis
5.01.5.8 High-Throughput Synthesis
5.01.6 Functions of MOFs
5.01.6.1 Gas Storage
5.01.6.1.1 Hydrogen Storage
5.01.6.1.2 Methane Storage
5.01.6.1.3 Carbon Dioxide Storage
5.01.6.2 Selective Gas Adsorptions and Separations
5.01.6.3 Catalysis
5.01.6.4 Magnetism
5.01.6.5 Optics
5.01.6.6 Sensor
5.01.6.7 Drug Delivery
5.01.7 Summary and Outlook
References
5.02 纳米粒子配体
5.02.1 Introduction
5.02.2 Ligands, Chief Cook, and Bottle Washer
5.02.2.1 Ligands Control the Synthesis of NPs
5.02.2.2 A Brief Introduction to Classical Nucleation Theory
5.02.2.3 Ligands Stabilize NP Suspensions
5.02.2.4 Ligands and the Shape of NPs
5.02.2.5 Ligands Give NPs Physicochemical Functionality
5.02.3 What to Expect,Ab Initio Calculations
5.02.4 Experimental Observation of NP Ligands
5.02.4.1 Indirect Probing of Ligand Exchange
5.02.4.2 Direct Probing of Ligands
5.02.5 Observing NP Ligands with Solution NMR Spectroscopy
5.02.5.1 Solution NMR Techniques for Observing QD Ligands
5.02.5.1.1 A brief introduction in solution NMR spectroscopy
5.02.5.1.2 Pulsed field gradient NMR spectroscopy
5.02.5.1.3 Nuclear Overhauser effect NMR spectroscopy
5.02.5.2 The Tightly Bound Ligand
5.02.5.2.1 What to expect?
5.02.5.2.2 The basic experiment:1D 1H NMR
5.02.5.2.3 Tracing down the ligand resonances by diffusion NMR
5.02.5.2.4 Identifying ligands, proton-carbon correlations
5.02.5.2.5 A note on relaxation rates and peak broadening
5.02.5.3 Adsorption-Desorption Equilibria,1H NMR as a Quantitative Technique
5.02.5.3.1 Quantitative NMR
5.02.5.3.2 Observing adsorption-desorption equilibria by NMR
5.02.5.3.3 Understanding the adsorption isotherm
5.02.5.4 Adsorption-Desorption Kinetics,Exploiting the NOE
5.02.5.4.1 Dodecylamine stabilized Q-CdTe,does the tightly bound ligand model work?
5.02.5.4.2 Observed NMR resonances,a story of timescales
5.02.5.4.3 Tightly bound ligands have strongly negative NOEs
5.02.5.4.4 Rapidly exchanging ligands show strongly negative transfer NoEs
5.02.5.5 In Situ Monitoring of NP Synthesis
References
5.03 纳米粒子组装
5.03.1 Introduction
5.03.2 Assembly Methods for 1D NPs
5.03.2.1 Assembly of NPs for Nanorod and Nanowire Formation
5.03.2.2 Assembly of 1D NPs on Polymer Templates
5.03.3 Assembly of NPs to Form 2D Nanocomposites
5.03.4 Biomolecules as Templates for Assembling NPs in 1D and 2D Architectures
5.03.5 Modulation of the Properties of 1D and 2D Structures
5.03.5.1 Optical Response
5.03.5.2 Electronic Behavior
5.03.5.3 Magnetic Properties
5.03.6 Summary and Outlook
References
5.04 周期的介孔材料:充满机遇的孔道
5.04.1 Introduction
5.04.2 Hierarchical Organization of Mesoporous Materials
5.04.2.1 Self-Assembly of Sol-Gel Precursors and Templates-From Micro to Meso
5.04.2.2 Growing Complexity:Powder,Films,and the Importance of Form
5.04.3 Bringing Function into Voids
5.04.3.1 Grafting
5.04.3.2 Co-Condensation
5.04.3.3 Periodic Mesoporous Organosilicates
5.04.4 Nonsiliceous Mesoporous Materials
5.04.4.1 Mesoporous Metal Oxides and Phosphates
5.04.4.1.1 Synthesis strategies and objectives
5.04.4.1.2 Realized compositions
5.04.4.1.3 Perspectives I:Toward crystallized mesoporous oxides
5.04.4.1.4 Perspectives II:Form and function
5.04.4.2 Mesoporous Metals and Semiconductors
5.04.4.2.1 Mesoporous semiconductors
5.04.4.2.2 Mesoporous metals
5.04.4.3 Mesoporous Carbon
5.04.4.3.1 OMCs obtained by hard templating
5.04.4.3.2 OMCs obtained by soft templating
5.04.4.4 Mesoporous Ceramic Materials
5.04.4.4.1 Silicon-based mesoporous ceramics
5.04.4.4.2 Mesoporous carbon and boron-based ceramics
5.04.5 Mesoscience to Mesotechnology-Why Meso?
5.04.5.1 Sorbents and Separation Science
5.04.5.2 Catalysis
5.04.5.3 Drug Delivery
5.04.5.4 Sensing
5.04.5.5 Low-k Materials
5.04.5.6 Photovoltaics
5.04.6 Conclusion and Outlook
References
5.05 单层自组装
5.05.1 Molecular Self-Assembly and Nanoscience
5.05.2 Driving Forces for Molecular Assembly:Molecular Interactions in Self-Assembled Monolayers
5.05.3 Overview of Previous Studies of Molecular Self-Assembled Monolayers
5.05.4 Brief Summary of Synthetic Methods of 2D Self-Assembled Monolayers and the Main Techniques to Study them
5.05.5 Molecular Self-Assembly on Au111
5.05.5.1 CH3CH2nSH
5.05.5.2 CH3CH2nCS2H
5.05.5.3 C6H5CH2nSH
5.05.5.4 CH3-C6H42-CH2n-SH
5.05.5.5 CF3CH2nSH
5.05.5.6 Diamidothiol
5.05.6 Organic Monolayers on Ag111
5.05.7 Self-assembly of Organic Molecules on Cu,Al,Hg,Al2O3,and SiOxSi Substrates
5.05.8 Molecular Self-Assembly on Highly Oriented Pyrolytic Graphite
5.05.8.1 Single-Component Long-Chain Molecules:Linear Packing and Molecular Distortion
5.05.8.1.1 Molecular parallel packing
5.05.8.1.2 Molecular distortion
5.05.8.2 Multicomponent Self-Assembly and Formation of Nanostructures
5.05.8.3 Molecular Chirality upon Self-Assembly
5.05.9 Summary
References
5.06 纳米晶体合成
5.06.1 Introduction
5.06.1.1 Milestones of Progress in Nanocrystal Synthesis
5.06.1.2 Synthetic Methods
5.06.1.2.1 High-temperature organo-metallic method
5.06.1.2.2 Single-source molecular precursor method
5.06.1.2.3 Solvothermalhydrothermal method
5.06.1.2.4 Water-phase synthesis
5.06.1.2.5 Template-assisted growth methods
5.06.1.2.6 Synthesis of semiconductor nanocrystals in microfluidic reactors
5.06.2 Size Tuneability of Nanocrystals
5.06.2.1 Introduction
5.06.2.2 Mechanisms of Size Control
5.06.2.2.1 Nucleation and growth of nanocrystal
5.06.2.2.2 Concepts in size control
5.06.3 Shape,Phase,and Composition Control of Nanocrystals
5.06.3.1 Shape Control of Nanocrystals
5.06.3.1.1 Dynamic-induced anisotropic growth
5.06.3.1.2 Seed-mediated growth
5.06.3.1.3 The Oriented attached method
5.06.3.2 Composition Control
5.06.4 Overview of the Nanocrystal Synthesis by Material
5.06.4.1 II-VI Semiconductor Nanocrystals
5.06.4.2 III-V Semiconductor Nanocrystals
5.06.4.3 IV-VI Semiconductor Nanocrystals
5.06.4.4 IV Semiconductor Nanocrystals
5.06.4.5 III-VI and I-III-V Nanocrystals
5.06.4.6 Metal Oxides
5.06.4.6.1 Sol-gel method
5.06.4.6.2 Nonhydrolytic route
5.06.5 New-Generation Semiconductor Nanocrystals
5.06.5.1 Nanocrystal Heterostructures
5.06.5.1.1 Synthetic techniques for the preparation of nanocrystal heterostructures
5.06.5.1.2 Synthesis of 0D core-shell Nanocrystal heterostructures
5.06.5.1.3 Synthesis of anisotropic and more complex nanocrystal heterostructures
5.06.5.2 Doped Nanocrystals
5.06.5.2.1 Synthesis of doped nanocrystals
5.06.6 Summary
References
5.07 纳米粒子自组装基元
5.07.1 Introduction
5.07.1.1 Self-Assembly Principle
5.07.1.2 NBB Classification
5.07.2 NBB Self-Assembly Approaches
5.07.2.1 Self-Assembly on a Substrate
5.07.2.2 Interfacial Assembly
5.07.2.3 Template-Assisted Assembly
5.07.3 Self-Assembly of Complex-Shaped NBBs:Tetrapods
5.07.4 Computational Approach to Nanoparticle Self-Assembly
5.07.4.1 Computational Framework for Nanoparticle Self-Assembly
5.07.4.2 Computational Studies on the Self-Assembly of NBBs on a Substrate
5.07.4.3 Computational Studies on the Interfacial Assembly of NBBs
5.07.4.4 Computational Studies on NBB Self-Assembly on a Templated Surface
5.07.4.5 A Proposed Approach for Modeling Tetrapod Self-Assembly
5.07.5 Summary
References
5.08 组装嵌段共聚物的化学过程
5.08.1 Introduction
5.08.2 Work Prior to 1992 on Chemical Processing of Self-Assembled Block Copolymers
5.08.3 Our Research Program and Activities
5.08.4 Architectures from Chemically Processing Assembled Block Copolymers
5.08.4.1 Cyclic Polymers
5.08.4.2 Thin Films Containing Nanochannels
5.08.4.3 Cell-Like Microspheres
5.08.5 Block Copolymer Nanofibers and Nanotubes
5.08.5.1 Nanofiber Preparation
5.08.5.2 Nanotube Preparation
5.08.5.3 Dilute Solution Properties
5.08.5.4 Chemical Reactions
5.08.5.4.1 Backbone modification
5.08.5.4.2 Surface grafting
5.08.5.4.3 End functionalization
5.08.6 Concluding Remarks
References
5.09 生物模版制备半导体纳米晶体
5.09.1 Introduction
5.09.2 Living Cells as Semiconductor Nanocrystal Factories
5.09.3 Peptides and Proteins as Templates for Semiconductor-Based Nanomaterials
5.09.4 Nucleic Acids as Templates for Semiconductor-Based Nanomaterials
5.09.4.1 Monomeric Nucleotides as Semiconductor Nanocrystal Ligands:Roles of Base and Backbone
5.09.4.2 Oligomeric Nucleotides as Semiconductor Nanocrystal Ligands:Roles of Length and Sequence
5.09.4.3 Studies of Nucleic Acids with 3D Structure as Semiconductor Nanocrystal Ligands:Control of Nanomaterials Properties with Biomolecular Structure
5.09.4.4 One-Step Synthesis of Biofunctionalized Semiconductor Nanocrystals Using Nucleic Acids Ligands
5.09.5 Summary and Outlook
References
5.10 高分子层状硅酸盐纳米复合物
5.10.1 Introduction and Historical Perspective
5.10.2 Basic Structures of Layered Silicates and Polymers
5.10.2.1 Layered Silicate Structure
5.10.2.2 PLSN Structure: Degree of Silicate Layer Dispersion
5.10.2.3 Polymers Used in PLSNs
5.10.3 Synthetic Methods
5.10.3.1 In Situ Polymerization
5.10.3.2 Solution IntercalationExfoliation
5.10.3.3 Melt Processing
5.10.4 Characterization and Properties of PLSN Structures
5.10.4.1 Structure of Modified Silicates
5.10.4.1.1 XRD and TEM
5.10.4.2 Thermal and Mechanical Properties of PLSNs
5.10.4.2.1 Mechanical properties
5.10.4.2.2 Thermal and flame-retardant properties
5.10.4.3 Other Properties
5.10.4.3.1 Gas-barrier properties
5.10.4.3.2 Electrical properties
5.10.4.3.3 Compatibilization of polymer blends
5.10.5 Conclusions
References
5.11 介晶和介相
5.11.1 Introduction
5.11.1.1 Classification of Thermotropic Mesophases
5.11.1.2 Classification of Mesogens
5.11.1.3 Self-Assembly of Mesogens to Mesophases
5.11.1.4 Alignment,Self-Healing,and Fixation
5.11.1.5 Length Scales
5.11.2 Thermotropic Mesophases
5.11.2.1 Carbon Allotropes-from Conventional Mesogens based on Polycondensed Aromatics to Hybrid Systems of Carbon Nanoparticles
5.11.2.1.1 Molecular structure of graphenes,synthetic strategies and interaction motifs
5.11.2.1.2 The supramolecular self-assembling of discotic or sanidic mesogens
5.11.2.1.3 Applications of graphene LCs
5.11.2.1.4 Macrocycles
5.11.2.1.5 CNTs-mesogens from enrolled graphenes
5.11.2.1.6 LCs and fullerenes
5.11.2.1.7 Miscellaneous carbon mesogens
5.11.2.2 Supramolecular Mesogens
5.11.2.2.1 Hydrogen-bonded systems
5.11.2.2.2 Mesogens formed by halogen bonds
5.11.2.2.3 Metallomesogens
5.11.2.2.4 Ionic liquid crystals
5.11.2.2.5 Donor?acceptor interactions,charge transfer,and polytopic interactions
5.11.2.3 Bolaamphiphiles and Facial Amphiphiles-Nanostructured Mesophases by Multicolor Tiling
5.11.2.4 Star-Shaped Mesogens
5.11.2.5 Dendrons and Dendrimers
5.11.2.5.1 Supramolecular dendromesogens
5.11.2.5.2 Side-chain liquid-crystalline dendrimers
5.11.2.5.3 Main-chain liquid-crystalline dendrimers
5.11.3 Lyotropic Mesophases
5.11.3.1 Lyotropic Phases-Templates for the Synthesis of Nanomaterials
5.11.3.2 Cubosomes,Hexosomes,Lamellarsomes:Nanostructured Reverse Phases Stable in Excess Solvent
5.11.3.3 From Mineral LCs to LCs of Nanobiomolecules
5.11.3.3.1 Introduction
5.11.3.3.2 Colloidal suspensions: The Derjaguin?Landau?Verwey?Overbeek theory,steric stabilization,and Onsager theory
5.11.3.3.3 Mineral LCs
5.11.3.3.4 Applications
5.11.3.3.5 From nanobiomolecules toward viruses
5.11.4 Nanoparticles and LCs
5.11.4.1 Synthesis of Nanoparticles from LC phases
5.11.4.2 LC Phases from Nanoparticles
5.11.4.3 Nanoparticle Doped LCs
References
5.12 层层自组装胶囊在生物医药的应用
5.12.1 Introduction
5.12.2 LbL Assembly:Background
5.12.3 Engineering the Capsule Layers
5.12.3.1 pH-Responsive Capsules
5.12.3.2 Redox-Responsive Capsules
5.12.3.3 Light-Responsive Capsules
5.12.3.4 Temperature-Responsive Capsules
5.12.3.5 Enzyme-Responsive Capsules
5.12.3.6 Chemically Responsive Capsules
5.12.3.7 Other Stimuli-Responsive Capsules
5.12.4 Engineering the Capsule Surface
5.12.5 Encapsulating Cargo
5.12.6 Applications of LbL Capsules
5.12.6.1 Glucose-Responsive Systems-Delivery and Sensing
5.12.6.2 LbL Drug Delivery Systems
5.12.6.3 Bioreactors
5.12.7 Conclusion
References
5.13 功能化石墨烯:合成和性能
5.13.1 Introduction
5.13.2 Chemical Functionalization of Fullerenes
5.13.2.1 Nucleophilic Additions to Fullerenes
5.13.2.2 Nucleophilic Addition?Elimination Mechanism:The Bingel-Hirsch Reaction with Fullerenes
5.13.2.3 Cycloaddition Reactions to Fullerenes
5.13.2.4 1,3-Dipolar Cycloaddition of Azomethine Ylides to Fullerenes
5.13.2.5 Diels-Alder Cycloaddition Reactions with Fullerenes
5.13.3 Molecular Machines
5.13.4 Molecular Charge-Transfer Conjugates
5.13.5 Molecular Wires
5.13.6 Conclusion and Outlook
References
5.14 微乳化制备方法综述
5.14.1 Introduction
5.14.1.1 Basic Concepts:Micelles and Microemulsions
5.14.1.2 Properties and Applications
5.14.2 Synthesis of NanoparticlesNPsMicroemulsion
5.14.2.1 Synthesis of Metal and Mixed-Metal NPs
5.14.2.2 Synthesis of Semiconductor NPs
5.14.2.3 Synthesis of Magnetic NPs
5.14.2.4 Synthesis of Oxide NPs in Microemulsion
5.14.3 Synthesis of Rare EarthRENanocrystalsNCsin Microemulsion
5.14.3.1 Synthesis of Regular RE NCs with Well-Defined Facets
5.14.3.2 Synthesis of 1D RE NCs
5.14.3.3 Synthesis of RE Super Nanostructures
5.14.4 Silica Coating of NPs
5.14.4.1 Hydrophilic Metallic NPs
5.14.4.2 Hydrophilic Semiconductor NPs
5.14.4.3 Hydrophilic Magnetic NPs
5.14.4.4 Miscellaneous Hydrophilic NPs
5.14.4.5 Hydrophobic Metallic NPs
5.14.4.6 Hydrophobic Magnetic NPs
5.14.5 Direct Coating of Hydrophobic Semiconductor QDs
5.14.5.1 Hydrophobic Multifunctional NCs
5.14.5.2 Silica Coating of RE NCs
5.14.6 Conclusions and Outlook
References
5.15 纳米技术、社会和环境
5.15.1 Introduction
5.15.2 Twenty-first Century Relationships between Science,Technology,Society,and the Environment
5.15.3 Economy
5.15.3.1 Technoscience and Business
5.15.3.2 Nanoproducts and Society
5.15.3.3 Patenting Nanoproducts
5.15.3.4 Military Applications
5.15.4 Ecology
5.15.4.1 Nanotechnology and the Environment
5.15.4.2 Nature,Technology,and Public Discourse
5.15.4.3 NGOs and Local Communities
5.15.5 Health
5.15.5.1 Nanotechnology and Health
5.15.5.2 Nanotoxicity
5.15.6 Equity
5.15.6.1 Global Equity and Rights:Implications for Developing Countries
5.15.6.2 Power
5.15.6.3 Identity
5.15.6.4 Gender
5.15.6.5 Privacy
5.15.7 Governance
5.15.7.1 Science and Technology Policy:Funding Nanotechnology Research and Development
5.15.7.2 Nanotechnology Regulatory Capacity
5.15.7.3 Public Attitudes and Media Coverage
5.15.7.4 Nanotechnology Public Engagement and Democracy
5.15.8 Imagined Futures
5.15.8.1 Fact and Fiction:Social and Cultural Influences
5.15.8.2 The Construction of Utopias and Dystopias
5.15.8.3 Scenario Planning
5.15.9 Conclusion: Nature and Nanotechnology
References
內容試閱：
5.01 Porous Metal-Organic Frameworks
Q Fang, J Sculley, and H-C J Zhou, Texas A&M University, College Station, TX, USA G Zhu, Jilin University, Changchun, P.R. China a 2011 Elsevier B.V. All rights reserved.
5.01.1 Introduction 1 5.01.2 Inorganic SBUs and Organic Linkers 2 5.01.3 Architecture of the Networks 2 5.01.4 Porous Structures 3 5.01.4.1 0D Cage 3 5.01.4.2 1D Channels 3 5.01.4.3 2D Layers 4 5.01.4.4 3D Channels 5 5.01.5 Synthesis of MOFs 5 5.01.5.1 Influencing Factors 5 5.01.5.2 Solvent-Evaporation Synthesis 5 5.01.5.3 Diffusion Synthesis 5 5.01.5.4 Hydrothermal or Solvothermal Synthesis 6 5.01.5.5 Microwave-Reaction Synthesis 6 5.01.5.6 Ionothermal Synthesis 6 5.01.5.7 Electrochemical Synthesis 6 5.01.5.8 High-Throughput Synthesis 6 5.01.6 Functions of MOFs 7 5.01.6.1 Gas Storage 7 5.01.6.1.1 Hydrogen Storage 7 5.01.6.1.2 Methane Storage 8 5.01.6.1.3 Carbon Dioxide Storage 8 5.01.6.2 Selective Gas Adsorptions and Separations 10 5.01.6.3 Catalysis 11 5.01.6.4 Magnetism 13 5.01.6.5 Optics 13 5.01.6.6 Sensor 14 5.01.6.7 Drug Delivery 15 5.01.7 Summary and Outlook 15 References 16
5.01.1 Introduction
Porousmaterials,eithernaturalorartificial,havelongattractedtheattentionofchemists,physicists,andmate-rialsscientists,muchofthisinterestowingtothepotentialpropertiesoflargepores.Basedontheircom-position,theseporousmaterialscanbeclassifiedastwotypes:inorganicandcarbon-basedmaterials[1-5].
Recently,anewclassofporousmaterials,metal-organicframeworksMOFs,alsoreferredtoaspor-ouscoordinationpolymersPCPs,hasundergonerapiddevelopmentandbeguntobridgethegap
betweenthetwopreviouslymentionedclassesofporousmaterials[6-26].MOFsarebuiltupofmetalionsormetalionclustersconnectedtoorganicligandspossessingmultidentategroupsbystrongionocovalentordativebonds.ThereareexamplesofMOFscontainingmetalsrangingfromalkalineearthtotransitiontop-blockmetalsandlanthanides.MOFsattractedagreatdealofattentioninthe1990s,asisapparentfromtheremarkableincreaseinthenumberofpaperspublishedinthisareaduringthistime.TheattentionstemsfromthesynthesisofMOFs,whichcanexhibitcompletelyregularlarge
a b
Figure 1 View of the structures of a MOF-5 and b HKUST-1.
cavitiesandoropenchannels.TopicalexamplesareHKUST-1andMOF-5,whichresultinlargeporesizesandBrunauer,Emmett,andTellerBETsur-faceareasof1800and3800m2 g 1 respectivelyFigure1[21,24].Theatomsthatcomposethewallsoftheseporescreateanastonishinglylargesurfaceareaonwhichinteractionsandreactionscanoccur.ThesynthesisofsuchMOFsoccursundermildconditionsandtheselectionofacertaincombi-nationofdiscretemolecularunitsleadstothedesiredextendednetwork.Asalreadymentioned,researchintoMOFsisgainingmomentumbecauseMOFspossesstheadvantagesofbothorganicandinorganicmaterialsincludingfunctionalgroupsandopen-metalsites[27].ThesefeaturesofMOFsgiverisetoagreatnumberofpotentialandrealizedapplica-tions,suchasgasseparationsandstorage,catalysis,drugdelivery,aswellasnewfunctionalmaterialsbasedonpost-syntheticmodification[28-33].
MOFshavegreatlyexpandedthescopeofporousmaterials,eventhoughtheyarelargelyrestrictedtothemicroporousdomainporeslessthan2nm.Recently,somemesoporousMOFswithporesizesrangingfrom2to50nmhavebeenreported.ThesecompoundsexpandthepotentialapplicationsofMOFsintoareassuchasmacromolecularcatalysisandseparation[34-44].Forexample,Yaghietal.preparedthefirst3DmesoporousMOF,isoreticularmetal-organicframe-workIRMOF-16,bysuccessfullyusingalonglinker,[1,19:49,10-terphenyl]-4,40-dicarboxylateTPDC[34].ThisMOFhastheexpectedtopologyofCaB6adaptedbytheprototypeIRMOF-1alsodesignatedasMOF-5inwhichanoxide-centeredZn4Otetrahedronisedge-bridgedbysixcarboxylategroupstogivetheoctahedron-shapedsecondarybuildingunitSBUthatreticulatesintoa3Dcubicporousnetwork.Inthisstructure,thefree-andfixed-diametervaluesare19.1and28.8A. ,respectively.
5.01.2 Inorganic SBUs and Organic Linkers
Inadditiontothetwocentralcomponentswithwhichtheprincipalframeworkisconstructed,metalionsandligands,thereareauxiliarycomponents,suchascounteranions,nonbondingguests,andtemplatemolecules,whichmayallinfluencethefinalstructure.DuetothecomplexanddynamicconditionsunderwhichMOFsaresynthesized,itisdifficulttopredicttheresultingstructureofaMOFbasedsolelyonthestartingmaterialsandconditions.
Theimportantcharacteristicsofmetalionsandligandsaretheircoordinationnumbersandcoordinationgeometries.Asmetalcentershavetoomanybindingsitesfortheorganicligandsandcontainlittledirectionalinformation,itisdifficulttopredictthestructuresthatwillresultfromanycombinationofsimplemetalsaltsandorganiclinkers.Recently,YaghiandcoworkershavedefinedmetalcentersofMOFsasSBUsandillustratedthepossibleinorganicSBUsFigure2.ThedesignofMOFsbasedontheseinorganicSBUsfacilitatesframe-worksynthesis[13].Themostcommonlinkersaremultidentateorganicligandssuchascarboxylates,4,49-bipyridine,andimidazolederivatives.Theseorganiclinkersaffordawidevarietyoflinkingsiteswithtunedbindingstrengthanddirectionality.Theseligandscanbeselectedforthenodesinthetargetnetworkandtheycanbealsosynthesizedandmodifiedbyorganicsynthesis.
5.01.3 Architecture of the Networks
Figure3showssomesimplearchitecturesofthenet-worksassembledfrommetalionsandorganicligands[11].However,morecomplicated3Dframeworkscanbeobtainedbymimickingthetopologiesofthetradi-tionalinorganicsolids[25,26].Theapproachisbased
Inorganic units SBUs Inorganic units SBUs
a
b
c
Figure 2 Examples of inorganic SBUs: a triangle, b square planar, c tetrahedron, d octahedron, and e trigonal prism. Reprinted by permission from Macmillan Publishers Ltd: Nature Yaghi OM, O’Keeffe M, Ockwig NW, Chae HK, Eddaoudi M, and Kim J 2003 Reticular synthesis and the design of new materials. Nature 423: 705-714, Copyright 2003.
a b c d e f
Figure3Schematicrepresentationsofsomeofthesimplenetworkarchitectures:a2Dhoneycomb,b1Dladder,
c 3Doctahedral,d3Dhexagonaldiamondoid,e2Dsquaregrid,andf1Dzigzagchain.ReproducedfromMoultonBandZaworotkoMJ2001Frommoleculestocrystalengineering:Supramolecularisomerismandpolymorphisminnetworksolids.
Chemical Reviews 101: 1629-1658.
ontheideaofnets,whicharetheabstractmathema-ticalentitiesincludingacollectionofpointsornodeswithdefinedconnectivity[45].Yaghietal.haveexplainedthetopologyoftheorderednetworksbysimplifyingthemathematicalexpressions[25].WhenallverticesarelinkedtoNneighbors,thetopologyisreferredtoasanN-connectednet.Whensomever-ticesareconnectedtoNneighborsandsometoMneighbors,itisaN,M-connectednet.Figure4showsexamplesoftopologicalnets.
5.01.4 Porous Structures
5.01.4.1 0D Cage
MOFswith0Dcagesareframeworkswhicharetoosmalltopermittheguestmoleculestopassthroughandmaybedefinedaseithersolidswithoutwindowsorsolidswithnarrowwindows.Forinstance,Robsonetal.reportedaninterpenetrated3Dnetwork[ZnCNNO3tpt23]?C2H2Cl434?CH3OH34tpt.2,4,6-tri4-pyridyl-1,3,5-triazinethatprovidesabarrierimpenetrabletoeventhesmallestmolecules,whicheffectivelyisolateseachporefromitsneighborsandfromtheoutsidespace[46].Inthisstructure,eachcageiswideopenandcanaccommodateapproximatelynine1,1,2,2-tetrachloroethanemoleculesandninemethanolmolecules,allofwhicharehighlydisordered.ThedistanceacrosstheinnershellofthecagefromoneZn4squaretotheoppositeandparallelZn4squareis23.4484A. . However, due to narrow windows, guest molecules are unable to pass out of these cages.
5.01.4.2 1D Channels
AccordingtotheInternationalUnionofPureandAppliedChemistryIUPACdefinition,aporethatisinfinitelyextendedinonedimensionandislargeenoughtoallowguestspeciestodiffusealongitslengthiscalledachannel[47].SeveralMOFswithregular1Dchannelshavebeensynthesizedandcrystallographi-callycharacterized.Forexample,Qiuetal.describedthesynthesisandstructureofamesoporousMOF,JUC-48,fromarigidandlinearorganicO-donorligand,4,49-biphenyldicarboxylatebpdc[36].InthisMOF,CdIIcentersarelinkedtogetherbycarboxylategroupsofbpdctoconstruct1DCd-O-Cchainsthatareinter-connectedthroughthebiphenylgroupsofbpdcto
Figure4Examplesoftopologicalnets:aSrSi2net,bThSi2net,cdiamondnet,dCdSO4net,eNbOnet,fPtScooperitenet,gPt3O4netfilledcirclesarePt,hboracitenet,iBNnet,jBCTnet,kbody-centeredcubicnet,andlReO3arrangementofcorner-sharingoctahedral.ReproducedfromO’KeeffeM,EddaoudiM,LiHL,ReinekeT,andYaghiOM2000Frameworksforextendedsolids:Geometricaldesignprinciples.JournalofSolidStateChemistry152:3-20,withpermissionfromElsevier.
a b
Figure 5 Representation of a hexagonal nanotube-like channel of JUC-48 of dimensions 24.5 . 27.9A. 2 viewed along the a
[001] andb[100]directions.ReprintedfromFangQR,ZhuGS,JinZ,etal.2007Mesoporousmetal-organicframeworkwithrareetbtopologyforhydrogenstorageanddyeassembly.AngewandteChemieInternationalEdition46:6638-6642.Copyright2007AmericanChemicalSociety.
generatea3Dnoninterpenetratingextendednetworkincorporatedbetweenthelayers.Kitagawaetal.havewith1Dhexagonalchannelsof24.527.9A. 2 viewedsynthesizedaseriesoflayeredintercalationMOFs,alongthe[001]directionFigure5.Eachhexagonal[MCAH2O2]GM.Fe2t,Co2t,orMn2t; channel of JUC-48 can be viewed as a nanotube-like H2CA . chloranilic acid; G . H2Oorphenazine,architecture.whicharesupportedbyhydrogen-bondinginter-
actions[48].Thehostlayersareclassifiedintotwo
groups:thefirsttypeofsheetisformedbyzigzag
5.01.4.3 2D Layers
chains,andthesecondoneisconstructedfromWhilethereareseveralMOFswith2Dlayers,fewstraightchains.Inthisstructure,themolecularhavebeenreportedinwhichseveralguestscanbeassembliesofmetalII-CA2chainsandguestmoleculesrevealthreekeyfactorsthatcontrolthecrystalstructures.Thefirstfactoristheconstructionofahydrogen-bond-supported2Dsheet,whichisflexibleandamenabletointercalationofvariouskindsofmoleculesusingthehydrogen-bondinginteraction.Thesecondaspectisthattheintercalatedguestmoleculesaffectthesheetstructureanditsdynamics.Thehydrogenbondingincreasesthedimensionalityofthesystemandthusprovidesstruc-turalvarietiesinthecrystalstructure.Thethirdfeaturecontrollingthecrystalstructureistheselec-tionofthemetalthatmediatesthefine-tuningofthesheet’sstructureandtheconformationoftheguestmolecules.
5.01.4.4 3D Channels
3Dintersectingchannels,whichfrequentlyoccurinzeolites,areconstructedbytheinterconnectionof1Dchannelsfromthreedirections.SomeMOFswithhighporosityassociatedwithsuch3Dchannelshaverecentlybeenpresented.Forinstance,ZhouandcoworkersreportedanoninterpenetratedmesoporousMOF,mesoMOF-1[35].Inthisstructure,twocopperatomsarebridgedbyfourcarboxylategroupstoformthewell-knownpaddlewheelSBUwithaxialaqualigands.EachSBUconnectsfour4,49,40-s-triazine-1,3,5-triyltri-p-aminobenzoateTATAB,andeachTATABbindsthreeSBUstoformaTdoctahedron,inwhichallsixverticesareoccupiedbytheSBUs,andfouroftheeightfacesarespannedbyTATABligands.EightsuchTdoctahedraoccupytheeightverticesofacubetoformacuboctahedronthroughcornersharing.Thesecuboctahedrapropagatetoa3Dframeworkwithatwistedboracitenettopology.Openchannelsfromallthreeorthogonaldirectionsareidenticalinsizeandcanbeaslargeas22.526.1A. 2 Figure6.
a b
Figure6aApaddlewheelstructuralunitofmesoMOF-1.
b A view of packing of mesoMOF-1 with 22.5 . 26.1A. 2 fromthe[001]direction.ReproducedfromWangXS,MaSQ,SunDF,ParkinS,andZhouHC2006Amesoporousmetal-organicframeworkwithpermanentporosity.JournaloftheAmericanChemicalSociety128:16474-16475.
5.01.5 Synthesis of MOFs
5.01.5.1 InfluencingFactors
Theself-assemblyofMOFsisinfluencedbymanyfactors,suchasthestructuralcharacteristicsoftheligands,coordinationnatureofmetalions,thesolventsystem,anytemplatemolecules,thepHvalueofthesolution,stericrequirementofthecounterion,reactiontemperature,andtheratioofmetaltoligand[49-54].SomestudiesoftheinfluenceofthetemperatureandpHhavebeensurveyed[55-57].TheyindicatedthathigherpHandtemperatureproducemorecondensedphases.InthecaseofthecobaltIIsuccinatesystem,thedimensionalityofboththeframeworkandtheinorganicchainshasincreasedwithtemperature.Morerecently,aseriesofMOFshavebeensynthe-sizedbyQiuetal.usingdifferentorganicaminesastemplates[58].Thesystematicanalysisofthenon-bondinginteractionenergiesofthesecompounds,includingH-bondingandvanderWaals,showedthattheorganicaminecationsresideintheinterlayerorchannelspacewheretheyplayimportantrolesastemplating,space-filling,andcharge-balancingagents.
5.01.5.2 Solvent-EvaporationSynthesis
Solvent-evaporationsynthesisproducescrystalsbyslowlyincreasingtheconcentrationofthemotherliquor.Crystalscanslowlygrowasthesolutionbecomessaturatedbyeithercoolingofthesolutionorbyevaporationofexcesssolvent.Forinstance,Chenetal.dissolved2-hydroxymethyl-1-methylimidazoleHmmiandtwodifferentkindsofmetalionsinmethanol,andthenthemixturewasstoredatroomtemperature.ThreediscretedinuclearcopperII-lanthanideIIIMOFsweresynthesizedbyslowsolventevaporationafterabout10days[59].
5.01.5.3 Diffusion Synthesis
Theadvantageofdiffusionsynthesisisthatthistechniqueslowlybringsthedifferentsolventsintocontact[36].Oneapproachissolvent-liquiddiffu-sion,whichinvolvestheformationofthreediscretelayers.Onelayercontainstheproductinthesolvent,anotheristheprecipitantsolvent,andthethirdlayerservestoseparatetheothertwolayerstherebyallow-ingfordiffusiontooccurataslowerrate.Astheprecipitantsolventandtheproductsolutionslowlydiffuseintothemiddlelayer,crystalgrowthcanoccurattheinterface.Theotherapproachistheslowdiffusionofreactantsandtheavoidanceofpre-cipitationofbulkmaterialbytheseparationofphysicalbarriers,suchasgels.DiffusionmethodsareusefulforisolatingsinglecrystalssuitableforX-raydiffractionanalysisinsteadofprecipitatingpolycrystallineproducts.
5.01.5.4 HydrothermalorSolvothermalSynthesis
Hydrothermalorsolvothermalsynthesisfacilitatestheself-assemblyofproductsbyexploitingthesolubilityofprecursorsinhotwaterororganicsolventunderhighpressure.Thecrystalgrowthoccursinasteelpressurevessel,alsocalledanautoclave,atrunningtemperaturesrangingfrom60Cto260 C.Atemperaturegradientismaintainedattheoppositeendsofthegrowthchambersothatthehotterenddissolvesthenutrientandthecoolerendcausesseedstocontinuetogrow.Thismethodwasoriginallyusedforthesynthesisofzeolites,buthasbeenwidelyadaptedforthesynthesisofMOFs,suchasthehighlyporousMIL-101Figure7[39].
5.01.5.5 Microwave-ReactionSynthesis
Microwave-reactionsynthesishasbeenusedtopro-ducesmallmetalandoxideparticles.Nanosizedcrystalsofmetalcanbeproducedbyheatingasolutionwithmicrowavesforaperiodofanhourormore.SuchprocesseswererecentlyemployedinthesynthesisofsomeMOFs,suchasIRMOFs,anickelglutarate,MIL-101,oranickeltrimesate[60-63].Theproper-tiesofthecrystalsmadebythemicrowavereactionareofthesamequalityasthoseproducedbythestandardsolvothermalprocesswiththeaddedbonusofmuch
a b
Figure7aThesupertetrahedronconstructedformtrimericbuildingblockandbdcligands.bStructuralrepresentationsofMIL-101withlargercavitiesof34A..ReproducedfromHorcajadaP,SerreC,Vallet-RegiM,SebbanM,TaulelleF,andFe′reyG2006Metal-organicframeworksasefficientmaterialsfordrugdelivery.AngewandteChemieInternationalEdition45:5974-5978.
morerapidcrystalgrowth.Sincethepropertiesofthemicrowavesynthesizedcrystalsareanalogoustothoseobtainedbytraditionalmethods,therangeofpracticalapplicationsisdramaticallyincreased.
5.01.5.6 IonothermalSynthesis
Thismethodwasusedforthefirsttimeintraditionalporousmaterials,suchaszeolitesandphosphates,andonlyrecentlyutilizedinMOFs[64,65].IonicliquidshavebeenappliedasexcellentandsafemediainthesynthesisofMOFsbecauseoftheirhighthermalsta-bility,avaporpressureclosetozero,andpoorcoordinationability.InthecaseofanioncontrolintheionothermalsynthesisoffourkindsofMOFs,itwasshownthatitispossibletocontroltheframeworksoftheresultingcompoundsbyusingdifferentanions[66].AnotherinterestingresultwasthesynthesisofachiralMOFwiththeuseofchiralionicliquid[67].
5.01.5.7 ElectrochemicalSynthesis
Differentfromconventionalsolvothermalsynthesis,Muelleretal.haverecentlydevelopedanelectroche-micalmethodtosynthesizeHKUST-1constructedfromCuIIand1,3,5-benzenetricarboxylatebtcligand[22].Inanelectrochemicalcell,copperplatesarearrangedastheanodeandcathodewithbtcdis-solvedinmethanol.Theproduct,agreenishblueprecipitate,wasformedinabout150minatavoltageof12-19Vandacurrentof1.3A.Thebenefitofthismethodliesinitsspeedanditshigherpurity,duetotheabsenceofcounterionsfromthemetalsaltsother-wiseusedduringthepreparation.
5.01.5.8 High-ThroughputSynthesis
High-throughputsynthesisisroutinelyusedinscreen-ingforactivityofdrugmoleculesandcatalysts.Recently,high-throughputtechniqueswereappliedinthesynth-esisofMOFs,thusreducingthetime-consumingprocessofphasediscoveryandshininglightontothehighversa-tilityofsuchsystems.Stocketal.haveperformed48synthesesonasmallscalevolumeofthecontaineris
0.25mlbyasemi-automatedsystemreagentweighing, productrecovery,andcharacterizationwhilesimulta-neouslyvaryingthereactionparametersstoichiometry,concentration,pH,andsooninasystematicfashion[68].Inaddition,ahigh-throughputmethodwaspro-posedbyYaghietal.forthesynthesisofnovelmetal-organiccompounds,zeoliticimidazolateframeworksZIFs.Twenty-fivedifferentZIFswereobtainedfromonly9600microreactionsofeitherzincIIorcobaltIIandimidazolate-typelinkers[69].
5.01.6 Functions of MOFs
5.01.6.1 Gas Storage
Amajoradvantageinusingporousmaterialsasanaidingasstorageisthatthesematerialsallowthepressureinagiventanktobelowerthanthatinanidenticaltankwithoutanadsorbent.Anumberofrecentstudieshavebeendevotedtotheadsorptionofhydrogen,methane,andcarbondioxideonMOFsbecausetheyhaveadsorp-tioncapacitiesthatareequivalenttoorbetterthanthecurrentzeoliteoractivatedcarbonsamples[70].
5.01.6.1.1 Hydrogen Storage
Hydrogenisanidealenergycarrierbecauseitiscarbonfreeandthemainproductafterenergyreleaseiswater.Anotherbenefitisthatthegravimetricheatofcombustionofhydrogenisalmosttriplethatofgasoline120MJkg1 vs. 44.5 MJ kg1[71].Thegravimetricandvolumetricstoragetargets,setbytheUSDepartmentofEnergy,foron-boardhydro-genstorageare6wt%,45gl1 for 2010 and 9 wt%, 81gl1 for 2015 [72].
SinceRosietal.presentedthefirstMOF-basedhydrogenstoragestudy[73],approximately150MOFshavebeentestedfortheirhydrogenuptakecapacity,andseveralreviewsfocusingonthistopichavebeenpublished[31,74-80].ItiswellknownthathydrogenstorageofMOFsisbasedonphysisorption.Thecontactbetweenhydrogenandtheadsorbentcanthereforebeincreasedbyincreasingthesurfacearea.Asurveyofpublisheddatarevealstheappropriate
a
positivecorrelationbetweentheuptakeofhydrogen
at77Kandthesurfacearea[81].Itisbelievedthat
increasingthesurfaceareaenhancesthecontact
betweenhydrogenandtheadsorbentresultinginan
increasedhydrogenuptake.Forexample,MOF-177,
whichhasaBETsurfaceareaof4500m2 g 1,ranks
highestforgravimetrichydrogenuptakes,withavalue
of7.5wt.%at70bar,77KFigure8[81,82].Another
waytoincreasetheinteractionbetweenhydrogenand
MOF’ssurfaceistotailortheporesizeintheMOF.
Theoreticalandexperimentalresultssupportthatthe
optimalporesizeisaround6A. ,abouttwicetheeffec-
tivekineticdiameterofthehydrogenmolecule[83].A
methodtoaltertheporesizeofaMOFistocreate
catenatedorinterpenetratedframeworks.Maetal.
preparedapairofcatenatedandnoncatenatedMOFs,
PCN-6andPCN-69[84].Theresultinghydrogen
uptakestudyathigherpressureandambienttempera-
tureshowedpromisingresults.ThecatenatedPCN-6
hadahigherhydrogenadsorbtionof6.7wt%at77K
50bar0.92wt.%at298K50barcomparedto4.0
wt.%at77K50bar0.40wt.%at298K50barfor
PCN-69Figure9.
UnsaturatedmetalcentersUMCs,another
viableoptiontoincreasethehydrogen-uptakecapa-
citiesinMOFs,canbegeneratedbytheremovalof
thecoordinatedsolventmolecules.Leeetal.reported
isostructural MOFs with and without UMCs and
comparedtheirhydrogen-sorptioncapacities[85].
Higherhydrogenuptakeatbothlowpressure
2.87 wt%vs.2.07wt%at77K1atmandhighpressure5.22wt%vs.3.70wt%at77K50barwasreportedfortheMOFswithUMCs.
Amethoddenotedashydrogenspillover,toincreasethehydrogenuptake,hasbeenreported
b
Amount N2 sorbed mg g-1
1500 1200 900 600 300 0
0 0.2 0.4 0.6 0.8 1 PP0
Figure8aCrystalstructureandbnitrogengassorptionisothermat78KforMOF-177.ReprintedbypermissionfromMacmillanPublishersLtd:NatureChaeHK,Siberio-Pe′rezDY,KimJ,etal.2004Aroutetohighsurfacearea,porosityandinclusionoflargemoleculesincrystals.Nature427:523-527,Copyright2004.
a b
c
Amount absorbed mg g-1
80 60 40 20 0 0 10 20 30 40 50 01234567
P bar H2 Uptake m mol
Figure9aTheframeworkofcatenatedPCN-6.bTheframeworkofnoncatenatedPCN-69.cExcesshydrogensorptionisothermsofPCN-6andPCN-69at77redand298Kblack.dIsostericheatsofadsorptionforPCN-6andPCN-69.ReproducedfromMaSQ,SunDF,AmbrogioM,FillingerJA,ParkinS,andZhouHC2007Framework-catenationisomerisminmetal-organicframeworksanditsimpactonhydrogenuptake.JournaloftheAmericanChemicalSociety129:1858-1859.
byYangetal.ItconsistsofmixingaPtCcatalystwiththeMOF,thusallowingboththedissociativechemisorptionofhydrogenontothemetalsurfaceandthephysisorptionofH2intheporesoftheMOF.Remarkably,theresultingframeworkledtoastrongenhancement,asmuchaseightfold,ofthehydrogenadsorptionofMOF-5orIRMOF-8[86-88].
5.01.6.1.2 Methane Storage
Asaresultofmethane’savailabilityanditsgravimetricheatofcombustioncomparabletothatofgasoline
50.0 MJ kg1 vs.44.5MJkg1[71],itrankswithhydrogenintermsofbeingagoodcandidateforon-boardfuel.Intermsofavailability,methaneisthemaincomponentofnaturalgasatslightlyover95%[89].Theheatofadsorptionformethaneisapproxi-mately20kJmol1,whichisalreadywithintheidealscopeforpracticalusage.Theonlyrealdownsideofmethaneisthatwecurrentlydonothaveaneffectivestoragetechnology.TheDepartmentofEnergyDOEhassetamethanestoragetarget:180vvvv.volumeofadsorbatevolumeofadsorbentatambienttemperatureand35bar[90].
SinceKondoetal.reportedthefirstMOF-basedmethane-sorptionstudy[91],severalstudieshavebeenpresented.Table1summarizesthemethane-uptakedataforselectedMOFs.Forinstance,amicro-porousMOF,PCN-14,basedonapredesignedanthracenederivativeligandthatwassynthesizedbyZhouetal.containsnanoscopiccagessuitableformethaneuptake[92].High-pressuremethane-adsorptionstudiesshowthatPCN-14exhibitsanabso-lutemethane-adsorptioncapacityof230vv28%higherthantheDOEtargetof180vvatambienttemperatureandheatofadsorptionofmethanearound30kJmol1,bothrecordhighsamongthosereportedformethane-storagematerialsFigure10.
5.01.6.1.3 Carbon Dioxide Storage
TheDOEhassettargetsforcarbondioxide-storagesystemsat56wt.%[93].Besideszeolitesandcarbon-basedadsorbents,porousMOFsarecurrentlybeingconsideredasanalternative.ThisattentionisdrawnfromanumberofstudiesthathavereportedtheadsorptioncapacitiesofcarbondioxidetobehigherincertainMOFsthantheadsorptioncapacitiesinzeoliteoractivatedcarbonsamplesTable2[94].
Forexample,Yaghietal.haveinvestigatedthestoragecapacityofCO2inMOF-177[95].MOF-177showsahighcarbondioxidecapacitywith
Table 1 Methane uptake data for selected MOFs
Material Conditions Max loading wt.% Max loading vv Reference
Co24,49-bipy3NO34 3.04 MPaRT 3.6 71 91
Cu2pzdc2pyz 3.14 MPaRT 1.3 32 139
Cu2pzdc24,49-bipy 3.14 MPaRT 3.9 139
Cu2pzdc2pia 3.14 MPaRT 4.4 139
CuSiF64,49-bipy2 3.65 MPaRT 9.4 124 140
IRMOF-6 3.65 MPaRT 14.7 155 34
MIL-53Al 3.5 MPaRT 10.2 155 141
MIL-53Cr 3.5 MPaRT 10.2 165 141
PCN-14 3.5 MPaRT 16.0 220 92
PCN-11 3.5 MPaRT 14.1 171 142
HKUST-1 15.0 MPaRT 15.7 228 143
Zn2bdc2dabco 7.5 MPaRT 14.3 202 143
MIL-101 12.5 MPaRT 14.2 72 143
a
b
c
500
Uptake vSTPv
400
300
200
100 400
300
200
100
0
0
0 1020304050 0 1020304050 P bar P bar
Figure10aTheadipligandandpaddlewheelSBU.bNanoscopiccageinPCN-14.High-pressuremethanesorptionisothermsatvarioustemperatures:cexcessadsorptionanddabsoluteadsorption.ReproducedfromMaSQ,SunDF,SimmonsJM,CollierCD,YuanDQ,andZhouHC2008Metal-organicframeworkfromananthracenederivativecontainingnanoscopiccagesexhibitinghighmethaneuptake.JournaloftheAmericanChemicalSociety130:1012-1016.
33.5mmolg1 at298Kand42bar,whichtranslatesintoanimmensevalueof320vv.Astonishingly,acontainerfilledwithMOF-177under35barcancaptureninetimestheamountofCO2comparedtoacontainerwithoutadsorbent,andabouttwicetheamountcomparedtothebenchmarkmaterialszeolite13XandMAXSORB.Ataslightlyhighertemperatureandpressureof303Kand50bar,MIL-101,reportedbyFe′reyetal.,possessesanenormouscarbondioxidecapacitywith40mmolg1,whichisequivalenttothehighcapacityof390vv[96].Comparedtozeolites,saturationinlarge-poreMOFsoccursatmuchhigherpressures,whichcouldbeanimportantfactorfortherecoveryofCO2fromgasstreams.Furthermore,comparedwithzeolitesoractivecarbons,itisaclearadvantagethattheregenerationofMOFsisgenerallypossibleundermildconditions.
Table 2 Carbon dioxide adsorption capacities for various adsorbents
Adsorbent Conditions Maxloadingmmolg1 Maxloadingcm3cm3 Reference
Silicalite 302 K3.0 MPa 2.5 123 144
Zeolite NaX 302 K3.0 MPa 7.8 147 145
SBA-16 300 K3 MPa Nongrafted 6 NA 146
Grafted 3-4 NA
Active carbon NORIT R1 298 K3.0 MPa 10 96 94
Active carbon Maxsorb 298 K3.5 MPa 25 162 94
CubpyBF42 273 K3.0 MPa 4 153 147
MIL53Al, Cr 302 K2.5 MPa 10 225 141
HKUST-1 298 K4.2 MPa 10.7 210 95,148
MIL-47V 302 K2.0 MPa 11 250 141
IRMOF-1 298 K3.5 MPa 21.7 290 95
MOF-177 298 K4.2 MPa 33.5 320 95
MIL-100Cr 304 K5.0 MPa 18 280 96
MIL-101Cr 304 K5.0 MPa 40 390 96
ReprintedwithpermissionfromLlewellynPL,BourrellyS,SerreC,etal.2008HighuptakesofCO2andCH4inmesoporousmetal-organicframeworksMIL-100andMIL-101.Langmuir24:7245-7250.Copyright2008AmericanChemicalSociety.
5.01.6.2 SelectiveGasAdsorptionsandSeparations
MOFshaverecentlyattractedmuchattentionforselectivegasadsorption,whichleadstogassepara-tion.MOFsforselectivegasadsorptionarechosenbasedontwomaincriteria:theadsorptioncapacityoftheadsorbentandtheselectivityoftheadsorbentforanadsorbate[33].ThesepropertiesofMOFsaredependentonthechemicalcompositionandstruc-tureoftheadsorbent,aswellastheequilibriumpressureandtemperatureduringtheadsorption.
TheprincipalmechanismsofselectivegasadsorptioninMOFsincludeadsorbate-surfaceinteractions,whichinvolvethechemicalandorphysicalinteractionbetweentheadsorbentandsize-exclusionalsoreferredtoasmolecularsievingeffectthatdependsonthedimensionandshapeoftheframeworkpores.Itisnotedthatthesetwoeffectsarecapableofworkingindependentlyorcooperatively.Forinstance,Zhouetal.reportedaninterestingMOF,PCN-13,whichexhibitsselectivegasadsorptionbasedonthesize-exclusionprinciple.PCN-13containsasquarehydrophobicchannelof
3.5 . 3.5A. 2 and a pore volume of 0.3 cm3 g 1 [97].TheresultsofgasadsorptionsofPCN-13showthatitcancompletelypreventN2kineticdiameterof3.64A. fromenteringtheaperturewhileallowingO2kineticdiameterof3.46A. topassthroughthepore.AnotherexampleofaMOFwithaporeopeningof3.46-3.64A. ,Mg3ndc3,showsalmostnoN2uptake,whereasabout3.5mmolg1 ofO2isadsorbedat77Kand880Torr[98].
Recently,theseparationofalkaneisomersthroughgaschromatographictechniqueshasbeendemonstratedbyMOF-508[99].Inthisstructure,reportedbyChenetal.,the3Dpillaredlayerpro-videsthenecessaryframeworktoselectivelyseparatelinearandbranchedalkanes.Thediffer-enceinvanderWaalsinteractionsbetweentheisomersandtheporesoftheframeworkisrespon-siblefortheadsorptionofthelinearalkaneswhileallowingthebranchedonestopass.Interestingly,MOFshavealsobeenincorporatedintothinfilmtoaidingasseparation.Qiuetal.preparedHKUST-1supportedbyathinfilmcoppernet,whichdemon-stratedthesuccessfulseparationofH2fromH2N2,H2CO2,andH2CH4mixturesFigure11[100].TheresultsshowthatthisfilmpossessesexcellentpermeationselectivityforH2andexhibitssepara-tionfactorsmuchhigherthantraditionalzeolites.Inaddition,therecyclabilityofthisfilmfurtherenhancesitspotentialuseinH2separationandpurification.
Itisnotedthatoneofthemostpromisingmate-rialsforselectivegasadsorptionistheMOF-basedmesh-adjustablemolecularsieveMAMS[101].Differentfromthepreviouslymentionedrigidstruc-tures,theporesizesofMAMScanbetunedacrossawiderangebyadjustingthetemperature.Zhouetal.haverecentlyreportedsuchacompound,designatedMAMS-1,whichisalayeredstructurewithhydrophilicchannelsandhydrophobicchambersinterconnectedthroughasize-adjustablegateFigure12[101].Thegateisconstructedoftwo5-tert-butyl-1,3-benzenedicarboxylatebbdc
H2 N2
7
H2CO2
6
Separation factor
H2CH4
5
Sweep rate = 150 mlmin Feed flow rate = 50 mlmin 4 Feed presure = 1.0 × 105 Pa Permeance temperature = 25 °C
3 0 5 10 15 2025 Test time h
experiment
InternationalEdition46:2458-2462.
ligands,positionedbetweenthehydrophilicchan-nelsandthehydrophobicchambers,whichcanbeopenedorclosedbyincreasingordecreasingthetemperature.Bychangingthetemperaturefrom60to300KthegatesizeofMAMS-1canbeadjustedbetween2.9and5.0A. .Gas-separationexperimentsofMAMS-1havebeenconductedandithasdis-playedselectiveadsorptionofH2overCO,O2,andN2at77K;O2overCOandN2at87K;N2overCOandCH4at113K;CH4overC2H4at143K;C2H4overC3H6at196K;andC3H6overiso-C4H10at241K.Likewise,isostructuralMAMSs,whichwerepreparedwithdifferentmetalcenters,alsodemon-stratedtemperature-dependentmolecularsievingeffects[102].
5.01.6.3 Catalysis
Theexploitationofpracticalcatalystsforefficientsynthesisisofkeyimportancetothechemicalindustry[103,104].Homogeneouscatalystsusuallyshowadvantagesofhighactivityandselectivityinabroadrangeofsyntheticreactions[105].However,theirpracticalapplicationsremainlimitedduetodifficultyincatalystproductseparationaswellascatalystinstability.RecentresultsshowingtheuseofMOFsassolidcatalystsareparticularlyinterestingbecausetheporesizeandfunctionalityoftheframe-workcanbeadjustedoverawiderangetoaccommodateavarietyofcatalyticreactions.MOFsareinsolubleintheconventionalreactionmediaandthushavepotentialtobeusefulinheterogeneouscatalysis[106].
Someexamplesofselectivecatalysishavebeenpublished[107,108].Forinstance,Kitagawaetal.reporteda3DMOFfunctionalizedwithamidegroups,whichshowsgoodselectivecatalysis.Theselectivecatalysishasbeenattributedtotheuniformdistributionoftheamidegroupsonthechannelsurfaces[107].Thecatalyticprocessstu-diedwasthereactionofbenzaldehydewitheachoftheactivemethylenecompoundsmalononi-trile,ethylcyanoacetate,orcyanoaceticacidtert-butylester,alsoknownastheKnoevenagelcondensation.Interestingly,mostofthesubstratesshowedverylittleconversiontotheadduct,whereas98%ofthemalononitrilewasconverted.Thisselectivitydependsontherelationshipbetweenthesizeofthereactantsandtheporewindowofthehost.
Bybeingdopedwiththelargecatalyticallyactivemolecules,metalloporphyrins,Eddaoudiandco-workersfoundanenhancementofcatalyticactivityofarho-MOF[109].Theyfirstassembledthefree-baseporphyrinintorho-ZMOF,followedbythemettalationoftheframeworkandpostsyntheticmod-ificationbyseveraltransitionmetalions.Inthisway,theywereabletoproducepreviouslyunknownencapsulatedmetalloporphyrinsinasystematicfash-ion.Toassesscatalyticactivity,hydrocarbonspecificallycyclohexaneoxidationwasperformed
on Mn-doped MOF.
a b
100
80
Fe′reyandcoworkershaverecentlystudiedthecatalyticpropertiesofMIL-101bypostsynthesizeddecoration[110].TheyfoundthatthepresenceoftrinuclearchromiumIIIUMCsinMIL-101canleadtotheformationofthethermallystableaminespeciesgraftedtothesurface.Thiswouldbeaccomplishedwiththehelpofelectron-richfunctionalgroups.SeveralcatalyticallyactiveMOFswerereportedalongwiththesedata.Thenovelamine-graftedMIL-101showedhighactivitiesintheKnoevenagelcondensationwhenusingethylenediamineEDordiethylenetriamineasthegraftingagents.TwootherMOFs,APS-MIL-101APS.3-aminopropyltrialk-oxysilaneandED-MIL-101,resultedinhighactivitiesduringtheHeckreactionuponfurtherloadingofpalladium.
Kimetal.forthefirsttimeshowedthatenantio-selectivetransesterificationispossibleinaMOFbyusingachiralporousMOF,D-POST-1Figure13[111].Thecatalytictransesterificationofethanolwasreportedata77%yield
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