Synthesis and evaluation of porous azo-linked polymers for carbon dioxide capture and separation†
A series of new azo-linked polymers (ALPs) was synthesized via copper(I)-catalyzed oxidative homocoupling of 2D and 3D aniline-like monomers. ALPs have moderate surface areas (SABET = 412–801 m2 g−1), narrow pore sizes (<1 nm), and high physiochemical stability. The potential applications of ALPs for selective CO2 capture from flue gas and landfill gas at ambient temperature were studied. ALPs exhibit high isosteric heats of adsorption for CO2 (28.6–32.5 kJ mol−1) and high CO2 uptake capacities of up to 2.94 mmol g−1 at 298 K and 1 bar. Ideal adsorbed solution theory (IAST) selectivity studies revealed that ALPs have good CO2/N2 (56) and CO2/CH4 (8) selectivities at 298 K. The correlation between the performance of ALPs in selective CO2 capture and their properties such as surface area, pore size, and heat of adsorption was investigated. Moreover, the CO2 separation ability of ALPs from flue gas and landfill gas under pressure-swing adsorption (PSA) and vacuum-swing adsorption (VSA) processes was evaluated. The results show that ALPs have promising working capacity, regenerability, and sorbent selection parameter values for CO2 separation by VSA and PSA processes.