Electron-acceptor-controlled polyimides for photoredox-neutral trifluoromethylation

Abstract

Heterogeneous photocatalysts present notable benefits over homogeneous systems. However, their application is often hindered by spontaneous electron-hole recombination, undermining photoconversion efficiency. Addressing this, our study introduces a diversity-oriented synthesis of electron-donor-acceptor (D-A)-type polyimides via N-amidation of aromatic dianhydrides with anilines. These polyimides exhibit segregated D-A alignments that facilitate enhanced charge separation, rapid electron transfer, and long-lived photogenerated electron-hole pairs, attributed to superior electron-donating and -accepting capabilities alongside predictable π-π stacking. Their efficacy is demonstrated in catalyzing visible-light-driven redox-neutral C–H trifluoromethylation, transforming pharmaceuticals and bioactive molecules into trifluoromethyl-functionalized products with high yield and selectivity. A continuous-flow fixed-bed photoreactor supports gram-scale synthesis, and the photocatalyst maintains activity through at least four recycling rounds. Time-dependent density functional theory (TD-DFT) and non-covalent interaction (NCI) analyses suggest that the observed performance enhancement is due to controlled photoinduced electron transfer within the D-A system and intrachain π-π stacking.