Copper(I)-catalyzed synthesis of nanoporous azo-linked polymers: Impact of textural properties on gas storage and selective carbon dioxide capture

A new facile method for synthesis of porous azo-linked polymers (ALPs) is reported. The synthesis of ALPs was accomplished by homocoupling of aniline-like building units in the presence of copper(I) bromide and pyridine. The resulting ALPs exhibit high surface areas (SA_BET = 862-1235 m² g^-1), high physiochemical stability, and considerable gas storage capacity especially at high-pressure settings. Under low pressure conditions, ALPs have remarkable CO₂ uptake (up to 5.37 mmol g^-1 at 273 K and 1 bar), as well as moderate CO₂/N₂ (29-43) and CO₂/CH₄ (6-8) selectivity. Low pressure gas uptake experiments were used to calculate the binding affinities of small gas molecules and revealed that ALPs have high heats of adsorption for hydrogen (7.5-8 kJ mol^-1), methane (18-21 kJ mol^-1), and carbon dioxide (28-30 kJ mol^-1). Under high pressure conditions, the best performing polymer, ALP-1, stores significant amounts of H₂ (24 g L ^-1, 77 K/70 bar), CH₄ (67 g L^-1, 298 K/70 bar), and CO₂ (304 g L^-1, 298 K/40 bar).