in MOFs 873 1.3. Scope and Structure of This Review 874 2. MOFs for Gas-Phase Adsorptive Separations 874 2.1. Selective Adsorptions and Separations of Gases 874 2.1.1. Carbon Dioxide (CO 2 ) 874 2.1.2. Oxygen (O 2 ) 879 2.1.3. Hydrogen (H 2 ) 881 2.1.4. Gaseous Olefin and Paraffin 882 2.1.5. Harmful and Unsafe Gases 884 2.1.6. Nobel Gases and Others 886 2.2. Selective Adsorptions and Separations of Chemicals in the Vapor Phase 887 2.

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A porous polymer network (PPN) grafted with sulfonic acid (PPN-6-SO(3)H) and its lithium salt (PPN-6-SO(3)Li) exhibit significant increases in isosteric heats of CO(2) adsorption and CO(2)-uptake capacities. IAST calculations using single-component-isotherm data and a 15/85 CO(2)/N(2) ratio at 295 K and 1 bar revealed that the sulfonate-grafted PPN-6 networks show exceptionally high adsorption selectivity for CO(2) over N(2) (155 and 414 for PPN-6-SO(3)H and PPN-6-SO(3)Li, respectively). Since these PPNs also possess ultrahigh physicochemical stability, practical applications in postcombustion capture of CO(2) lie well within the realm of possibility.

One of the most pressing environmental concerns of our age is the escalating level of atmospheric CO 2 , which is largely correlated to the combustion of fossil fuels. For the foreseeable future, however, it seems that the ever-growing energy demand will most likely necessitate the consumption of these indispensable sources of energy. Carbon capture and sequestration (CCS), a process to separate CO 2 from the flue gas of coal-fired power plants and then store it underground, has been proposed to reduce the anthropogenic CO 2 emissions. Current CO 2 capture processes employed in power plants worldwide are post-combustion "wet scrubbing" methods involving the chemical adsorption of CO 2 by amine solutions such as monoethanolamine (MEA). The formation of carbamate from two MEA molecules and one CO 2 molecule endows the scrubber with a high capacity and selectivity for CO 2 . However, this process suffers from a series of inherent problems, such as high regeneration costs that arise from heating the solution (ca. 30 % of the power produced by the plant), fouling of the equipment, and solvent boil-off. [1] To sidestep the huge energy demand, corrosion problem, and other limitations of traditional wet scrubbers, intensive efforts have been made to investigate the use of solid adsorbents as an alternative approach. [2] Compared to wet scrubbing, in which a large amount of water (70 % w/w) must be heated and cooled during the regeneration of the dissolved amines, the solid adsorbent approach has the tremendous advantage of improving the energy efficiency of the regeneration process by eliminating the need to heat water.Porous materials, such as MOF-210, [3] NU-100, [4] and PPN-4, [5] have been deemed to be viable storage alternatives because of their high porosity and, therefore, significantly increased accessible contact area with gas molecules. This could be advantageous because separation and regeneration could be performed under relatively mild conditions compared to amine wet scrubbing systems. Unfortunately, the record high storage capacities do not translate to high selectivities and only moderate CO 2 -uptake capacities were observed under carbon capture conditions.The polarizability and large quadrupole moment of CO 2 can be taken advantage of by introducing CO 2 -philic moieties that create strong interactions between the material surface and the CO 2 . This will improve the loading capacities and selectivity of CO 2 over other gases. Indeed, this approach has already been proven to be very successful in enhancing the enthalpy of CO 2 adsorption, [6] which can be calculated from CO 2 sorption isotherms at different temperatures and used to quantify the interaction between the material and CO 2 . It is worth pointing out that the porosity of the material will be compromised by the introduction of functional groups. CO 2 loading capacities at ambient conditions are dependent on the adsorption enthalpy and porosity (both surface area and pore volume), which must be balanced to achieve high loading.Besides the load...

Despite tremendous efforts, precise control in the synthesis of porous materials with pre-designed pore properties for desired applications remains challenging. Newly emerged porous metal-organic materials, such as metal-organic polyhedra and metal-organic frameworks, are amenable to design and property tuning, enabling precise control of functionality by accurate design of structures at the molecular level. Here we propose and validate, both experimentally and computationally, a precisely designed cavity, termed a 'single-molecule trap', with the desired size and properties suitable for trapping target CO 2 molecules. Such a single-molecule trap can strengthen CO 2 -host interactions without evoking chemical bonding, thus showing potential for CO 2 capture. Molecular single-molecule traps in the form of metal-organic polyhedra are designed, synthesised and tested for selective adsorption of CO 2 over N 2 and CH 4 , demonstrating the trapping effect. Building these pre-designed singlemolecule traps into extended frameworks yields metal-organic frameworks with efficient mass transfer, whereas the CO 2 selective adsorption nature of single-molecule traps is preserved.