Bifunctional metal-free porous polyimide networks for CO2 capture and conversion†

Carbon dioxide (CO₂) capture and conversion into valuable chemicals is a promising and sustainable way to mitigate the adverse effects of anthropogenic CO₂ and climate change. Porous polyimides (pPIs), a class of highly cross-linked porous organic polymers (POPs), are promising candidates for CO₂ capture as well as catalytic conversion to valuable chemicals. Here, two metal-free perylene-based pPIs were synthesised via polycondensation reaction. The pPIs exhibit excellent heterogeneous catalytic activities for cycloaddition of CO₂ to epoxides under very mild and sustainable conditions (slight CO₂ overpressures, solvent- and co-catalyst free at 80 °C) with 98% conversion. The effects of reaction conditions, such as reaction temperature, reaction time and catalyst loading on the cycloaddition performance were investigated. Moreover, the pPIs can be recycled and reused five times without a substantial loss of catalytic activity. Furthermore, these materials were used in the electroreduction of CO₂ to form formate and methanol with faradaic efficiencies (FEs) of 20% and 95%, respectively, in the applied potential range from 0 to −1 V vs. RHE.