Synthesis and evaluation of N, O-doped hypercrosslinked polymers and their performance in CO₂ capture

A series of N, O-doped hypercrosslinked microporous polymers (HCPs) with high surface area and rich microporosity were constructed via facile Friedel-Crafts alkylation promoted by anhydrous ferric chloride (FeCl₃), which used benzyl alcohol (BA) and 2-phenylimidazole (PID) as the basic building blocks. The effects of structural composition on the pore properties and gas adsorption properties of prepared HCPs were systematically investigated. The results show that by adjusting the ratio of PID to BA, the Brunauer–Emmett–Teller (BET) specific surface area and pore volume of the prepared HCPs can be controlled, and the BET specific surface area of the polymers range from 732–992 m²/g. Gas uptake experiments indicate that the obtained HCPs exhibit very high CO₂ adsorption capacity up to 3.55 mmol/g at 273 K/1.0 bar. Simultaneously, these N, O-doped HCPs also show quite high isosteric heat of CO₂ sorption at the low coverage (up to 33 kJ/mol). In addition, the prepared HCPs have excellent selective adsorption performance, and the optimal selective adsorption of CO₂/N₂ is 62. These results demonstrate that these prepared HCPs are potential candidates for applications in CO₂ capture.