Synthesis and evaluation of porous azo-linked polymers for carbon dioxide capture and separation

Abstract

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 (SA_BET = 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.