Directing Robust Built-in Electric Fields via Imine Linkage Orientation in COFs for Efficient Dehydrogenative Organic Transformation Coupled with H2O2 Photosynthesis

Abstract

The built-in electric field (IEF) could be improved via developing donor-acceptor (D-A) type COF photocatalysts, yet available modulation strategies remain limited and poor. Here, we design a series of D-A COFs with isomeric imine linkage to promote the IEF and redox activity. The orientation of imine linkages on D/A centers could effectively adjust dipole moment of COFs, which is increased by ~50%, thereby enhancing the IEF. The charge separation efficiency is also elevated through the enhancement of IEF, leading to exciton binding energy reduced by ~30% and charge-separated state lifetime prolonged by 7-fold. Accordingly, the optimal COF exhibits impressive photocatalytic redox activities (5-fold promoted), achieving a remarkable tetrahydroquinoline dehydrogenation rate of 10.02 mmol/g/h, far exceeding reported metal-free photocatalysts and even comparative with metal photocatalysts, along with a H2O2 production rate over 20.01 mmol/g/h. Our findings establish a universal strategy to modulate the IEF which contributes to designing high-performance COF photocatalysts.