Introduction 724 1.1. Carbon Dioxide Emission from Anthropogenic Sources 725 1.2. CO 2 Capture at Stationary Point Sources 726 1.3. Options for CO 2 Sequestration 727 1.4. Current CO 2 Capture Materials 727 1.4.1. Aqueous Alkanolamine Absorbents 728 1.4.2. Solid Porous Adsorbent Materials 729 1.5. MetalÀOrganic Frameworks 731 1.5.1. Synthesis and Structural Features 731 1.5.2. Physical Properties 732 2. CO 2 Adsorption in MetalÀOrganic Frameworks 733 2.1. Capacity for CO 2 733 2.2. Enthalpy of Adsorption 733 2.3. Selectivity for CO 2 739 2.3.1. Estimation from Single-Component Isotherms 741 2.3.2. Ideal Adsorbed Solution Theory (IAST) 742 2.3.3. Gas Mixtures and Breakthrough Experiments 742 2.4. In Situ Characterization of Adsorbed CO 2 742 2.4.1. Structural Observations 743 2.4.2. Infrared Spectroscopy 744 2.5. Computational Modeling of CO 2 Capture 745 3. Post-combustion Capture 746 3.1. MetalÀOrganic Frameworks for CO 2 /N 2 Separation 746 3.2. Enhancing CO 2 /N 2 Selectivity via Surface Functionalization 746 3.2.1. Pores Functionalized by Nitrogen Bases 746 3.2.2. Other Strongly Polarizing Organic Functional Groups 749 3.2.3. Exposed Metal Cation Sites 750 3.3. Considerations for Application 752 3.3.1. Stability to Water Vapor 752 3.3.2. Other Minor Components of Flue Gas 754 4. Pre-combustion Capture 754 4.1. Considerations for Pre-combustion CO 2 Capture 755 4.1.1. Advantages of Pre-combustion Capture 755 4.1.2. Hydrogen Purification 755 4.1.3. Metrics for Evaluating Adsorbents 755 4.1.4. Non-CO 2 Impurities in CO 2 /H 2 Streams 756 4.1.5. MetalÀOrganic Framework-Containing Membranes for Pre-combustion CO 2 Capture 756 4.2. MetalÀOrganic Frameworks as Adsorbents 756 4.2.1. Investigations Based on Single-Component Isotherms 757 4.2.2. Computational Studies 757 5. Oxy-fuel Combustion 760 5.1.

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The escalating level of atmospheric carbon dioxide is one of the most pressing environmental concerns of our age. Carbon capture and storage (CCS) from large point sources such as power plants is one option for reducing anthropogenic CO2 emissions; however, currently the capture alone will increase the energy requirements of a plant by 25–40 %. This Review highlights the challenges for capture technologies which have the greatest likelihood of reducing CO2 emissions to the atmosphere, namely postcombustion (predominantly CO2/N2 separation), precombustion (CO2/H2) capture, and natural gas sweetening (CO2/CH4). The key factor which underlies significant advancements lies in improved materials that perform the separations. In this regard, the most recent developments and emerging concepts in CO2 separations by solvent absorption, chemical and physical adsorption, and membranes, amongst others, will be discussed, with particular attention on progress in the burgeoning field of metal–organic frameworks.

New materials capable of storing hydrogen at high gravimetric and volumetric densities are required if hydrogen is to be widely employed as a clean alternative to hydrocarbon fuels in cars and other mobile applications. With exceptionally high surface areas and chemically-tunable structures, microporous metal-organic frameworks have recently emerged as some of the most promising candidate materials. In this critical review we provide an overview of the current status of hydrogen storage within such compounds. Particular emphasis is given to the relationships between structural features and the enthalpy of hydrogen adsorption, spectroscopic methods for probing framework-H(2) interactions, and strategies for improving storage capacity (188 references).

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