Solar thermal swing adsorption on porous carbon monoliths for high-performance CO2 capture

Utilizing solar energy for sorbent regeneration during the CO2 swing adsorption process could potentially reduce CO2 capture costs. This study describes a new technique—solar thermal swing adsorption (STSA) for CO2 capture based on application of intermittent illumination onto porous carbon monolith (PCM) sorbents during the CO2 capture process. This allows CO2 to be selectively adsorbed on the sorbents during the light-off periods and thereafter released during the light-on periods due to the solar thermal effect. The freestanding and mechanically strong PCMs have rich ultramicropores with narrow pore size distributions, displaying relatively high CO2 adsorption capacity and high CO2/N2 selectivity. Given the high CO2 capture performance, high solar thermal conversion efficiency, and high thermal conductivity, the PCM sorbents could achieve high CO2 capture rate of up to 0.226 $${\rm{k}}{{\rm{g}}_{{\rm{C}}{{\rm{O}}_2}}} \cdot {\rm{k}}{{\rm{g}}_{{\rm{carbon}}}}^{ - 1} \cdot {{\rm{h}}^{ - 1}}$$ from a gas mixture of 20 vol.% CO2/80 vol.% N2 under STSA conditions with a light intensity of 1000 W·m−2. In addition, the combination of STSA with the conventional vacuum swing adsorption technique further increases the CO2 working capacity.