Heteroatom-fused tetraphenylethylene-based conjugated microporous polymers for sacrificial photocatalytic H2O2 production

Abstract

Hydrogen peroxide (H₂O₂) is an extremely valuable feedstock and environmentally friendly oxidising agent widely used in the modern chemical industry. While current industrial methods for H₂O₂ synthesis are energy-intensive, photocatalysis presents a sustainable alternative. However, the efficiency of existing photocatalytic systems remains insufficient for practical large-scale applications. Herein, a range of tetraphenylethylene-based conjugated microporous polymers (CMPs) have been designed and synthesized through Suzuki-Miyaura polycondensation, incorporating either biphenyl, dibenzo[b,d]thiophene, or dibenzo[b,d]thiophene sulfone. We investigate how the presence of dibenzo[b,d]-thiophene sulfone units correlates with enhanced photocatalytic activity, which is attributed to increased wettability and improved charge separation. The CMP which contains biphenyl ring functionality shows a H₂O₂ production rate of 10,500 µmol h⁻¹ g⁻¹, which more than doubles to 26,650 µmol h⁻¹ g⁻¹ upon incorporation of dibenzo[b,d]thiophene sulfone building blocks, with an apparent quantum yield of 17.1% at 420 nm. This work also explores the stability of CMP photocatalysts for H₂O₂ production and evaluates a potential superoxide radical-mediated mechanism.