Highly optimized CO2 capture by inexpensive nanoporous covalent organic polymers and their amine composites

Abstract

Carbon dioxide (CO₂) storage and utilization requires effective capture strategies that limit energy penalties. Polyethylenimine (PEI)-impregnated covalent organic polymers (COPs) with a high CO₂ adsorption capacity are successfully prepared in this study. A low cost COP with a high specific surface area is suitable for PEI loading to achieve high CO₂ adsorption, and the optimal PEI loading is 36 wt%. Though the adsorbed amount of CO₂ on amine impregnated COPs slightly decreased with increasing adsorption temperature, CO₂/N₂ selectivity is significantly improved at higher temperatures. The adsorption of CO₂ on the sorbent is very fast, and a sorption equilibrium (10% wt) was achieved within 5 min at 313 K under the flow of simulated flue gas streams. The CO₂ capture efficiency of this sorbent is not affected under repetitive adsorption–desorption cycles. The highest CO₂ capture capacity of 75 mg g⁻¹ at 0.15 bar is achieved under dry CO₂ capture however it is enhanced to 100 mg g⁻¹ in the mixed gas flow containing humid 15% CO₂. Sorbents were found to be thermally stable up to at least 200 °C. TGA and FTIR studies confirmed the loading of PEIs on COPs. This sorbent with high and fast CO₂ sorption exhibits a very promising application in direct CO₂ capture from flue gas.