Currently, postcombustion capture methods, which separate CO2 at low partial pressures from N2 in flue streams, are the most economically viable CO2 capture methods in the short — to mid-term as they can be easily retrofitted to existing power plants. Due to the dilute amount of CO2 present in these flue-gas streams, pro­spective materials for this purpose are required to have a high selectivity for CO2 over N2, which may be achieved by surface or pore functionalisation with strongly — polarising chemical groups. This may be achieved via the incorporation of open — metal cation sites, often exposed upon desolvation or “activation” of the frame­work, which provide strong, highly-charged binding sites for CO2 [55, 56]. Another strategy is the introduction of strongly-polarizing organic functional-groups into the pore. Functional groups investigated previously for CO2 separation from other gases include amines [22, 57], carboxylic acids, nitro, hydroxy, and sulfone groups [23]. Although more strongly polarizing groups enhance CO2 adsorption mani­fested through higher isosteric heats of adsorption, this factor must be balanced against the ease of regenerability of the resulting material in an industrial setting.