Quaternary functionalized mesoporous adsorbents for ultra-high kinetics of CO₂ capture from air

Obstacles to widespread deployments of direct air capture of CO₂ (DAC) lie in high material and energy costs. By grafting quaternary ammonium (QA) functional group to mesoporous polymers with high surface area, a unique DAC adsorbent with moisture swing adsorption (MSA) ability and ultra-high kinetics was developed in this work. Functionalization is designed for efficient delivery of QA group through mesopores to active substitution sites. This achieved ultra-high kinetics adsorbent with half time of 2.9 min under atmospheric environment, is the highest kinetics value reported among DAC adsorbents. A cyclic adsorption capacity of 0.26 mmol g⁻¹ is obtained during MSA process. Through adsorption thermodynamics, it is revealed that adsorbent with uniform cylindrical pore structure has higher functional group efficiency and CO₂ capacity. Pore structure can also tune the MSA ability of adsorbent through capillary condensation of water inside its mesopores. The successful functionalization of mesoporous polymers with superb CO₂ adsorption kinetics opens the door to facilitate DAC adsorbents for large-scale carbon capture deployments.