Inducing Orientation Polarisation via Regional Isomerisation in Covalent Organic Frameworks for Enhanced O2 Photoactivation.

Boosting the O2 photoactivation for efficient generation of reactive oxygen species is crucial to the synthesis of high-value chemicals. Inducing strong dipole interaction is an effective strategy to strengthen the built-in electric field (BIEF). However, it remains a great challenge to realize the precise regulation of polarisation orientation. Herein, a strategy to precisely control the polarity orientation of covalent organic frameworks (COFs) by regulating the regioisomerism of building blocks is proposed. Specifically, we integrated three regioisomeric thiophene derivatives into COF skeletons for H2O2 photosynthesis. Experimental and theoretical results show that the presence of adjacent S atoms in TTDA-TAPT-COF facilitates oriented dipole alignment, significantly enhancing the BIEF strength. Furthermore, this unique structure forms concave-convex pore walls with adjacent double-S atomic binding sites, inducing a switch of the O2 adsorption configuration from Pauling-type to Yeager-type, thereby significantly enhancing H2O2 photosynthesis. This work reveals the decisive role of regional isomerisation in tuning polarity orientation and BIEF, and this strategy is expected to be extended to other photocatalytic reactions involving oxygen activation, such as organic oxidation and pollutant degradation.