Photo‐Modulating CO2 Uptake of Hypercross‐linked Polymers Upcycled from Polystyrene Waste

Incorporating photo‐switches into skeletal structures of microporous materials or as guest molecules yield photo‐responsive materials for low‐energy CO2 capture but at the expense of lower CO2 uptake. Here, we overcome this limitation by exploiting trans–cis photoisomerization of azobenzene loaded into the micropores of hypercross‐linked polymers (HCPs) derived from waste polystyrene. Azobenzene in HCP pores reduced CO2 uptake by 19 %, reaching 37.7 cm3 g−1, but this loss in CO2 uptake was not only recovered by trans–cis photoisomerization of azobenzene, but also increased by 22 %, reaching 56.9 cm3 g−1, when compared to as‐prepared HCPs. Computational simulations show that this increase in CO2 uptake is due to photo‐controlled increments in 10–20 Å micropore volume, i. e., adsorption sites and a photo‐reversible positive dipole moment. Irradiating these HCPs with visual‐range light reverted CO2 uptake to 33 cm3 g−1. This shows that it is feasible to recycle waste polystyrene into advanced materials for low‐energy carbon capture. Radiant CO2 capture: To overcome CO2 uptake reduction for incorporating photo‐switches into adsorbents that could replace high‐energy‐consuming pressure or temperature swing procedures, we enrolled azobenzene with photo‐isomerization as guest molecules into hypercross‐linked polymers (HCPs) to yield HCPs@Azo. With UV irradiation, the CO2 uptake of HCPs@Azo is 22 % higher than as‐prepared HCPs because of the enlargement of pore sizes and dipole‐quadrupole interactions between cis‐azobenzene and CO2.