Amine-functionalized macroporous resin for direct air capture with high CO2 capacity in real atmospheric conditions: Effects of moisture and oxygen

•Optimizing the amine content in the DAC adsorbents for good CO2 capacity and high adsorption and desorption kinetics.•Revealing the relation between the pore nature of resins and the performance of DAC adsorbents.•Revealing the effect of humidity and oxygen on the stability of amine-functionalized DAC adsorbents. Direct air capture (DAC) is an important negative carbon emission technology that has attracted increasing attention. Amine-functionalized porous CO2 adsorbents are promising materials for DAC because of their high CO2 capacities, fast adsorption and desorption kinetics, and low energy costs during regeneration. In this study, inexpensive macroporous resins with high specific surface areas and pore volumes were selected as carriers of tetraethylenepentamine (TEPA) or polyethyleneimine (PEI). Their DAC performances in relation to their microstructures were explored under different humidity and oxygen conditions. Moisture simultaneously enhanced the CO2 capacity and slowed the adsorption/desorption process. Oxygen did not react with the resin and amine under ambient conditions, but physically adhered to the active sites of the adsorbents and caused a slight decrease in the CO2 uptake capacity. The optimized material reached adsorption equilibrium in 7269 s with CO2 uptake capacity of 5.4 mmol g−1 and desorbed CO2 in 1611 s with CO2 desorption capacity of 5.0 mmol g−1. After five cycles, the materials retained 82.2 % of the adsorption capacity. The findings indicate that amine-functionalized macroporous resins are promising DAC adsorbents under atmospheric conditions.