Hypercrosslinked Natural Biopolymers with Quasi-Unimodal Micropores for Carbon Capture

Abstract

Ultra-microporous solid sorbents with high CO2 adsorption capacities and gas selectivity are preferred for carbon capture. Here we deliver such sorbents via a combination of narrow micropores, lack of mesopores and an abundance of CO2-philic functional groups. This was achieved by crosslinking lignin waste obtained from a local paper factory, in Lewis’s acid deep eutectic solvents (DESs) such as [ChCl][ZnCl2]2 and [ChCl][FeCl3]2, varying crosslinker types and optimising experimental parameters. Hypercrosslinked polymers (HCPs) prepared in [ChCl][FeCl3]2 with 1,4-dichloroxylene crosslinkers comprised quasi-unimodal, ultra-narrow micropores. At 298 K, 1 bar, and using a gas mixture comprising 15 vol.% CO2 and 85 vol.% N2 (similar to post-combustion flue gas), the CO2 adsorption capacity and CO2/N2 selectivity of this HCP reached 18.1 cm3 g-1 and 835, respectively. Deployed in temperature swing adsorption and evaluated for vacuum pressure swing adsorption, the CO2 recovery rates of this HCP were more than 87%, outperforming commercial solid sorbents. The optimisation of sorbent microporosity with CO2-philic functional groups could pave the route towards developing bio-derived solid sorbents for carbon capture.

Keywords: lignin, Deep eutectic solvents, Carbon capture, hypercrosslinked polymers