Atomic-Level Modulation of Cs3Sb2Br9/COP Heterointerfaces for Enhanced Synergistic CO2 Photoreduction and Organic Synthesis

Rational modulation of interfacial electronic structure has been regarded as an appealing strategy to achieve effective charge separation and synergistic active-site cooperation in heterojunction photocatalysts, yet it remains a significant challenging. In this study, two-dimensional (2D) vinylene-linked conjugated covalent organic polymer (COP) functionalized with –F and –CN groups was designed through Knoevenagel condensation reaction. The influence of these groups on the interfacial properties and the photocatalytic performances of Cs 3 Sb 2 Br 9 /COP heterojunction were investigated systematically. Combined experimental and theoretical calculations revealed that introducing strong electron-withdrawing groups improves charge separation by inducing strong electron delocalization within the COP framework, enhances CO 2 adsorption and activation, and most importantly, significantly facilitates the interfacial growth of Cs 3 Sb 2 Br 9 nanocrystals. It was found that the strengthened interfacial interaction via Sb─N bonding effectively promoted a fast Z-scheme charge transfer and enabled effective spacial separation of photoelectron and holes, in contrast to the type II mechanism observed in the un-functionalized heterojunction. This enables effective multifunctional collaboration of Cs 3 Sb 2 Br 9 and FN-COP. Consequently, the optimized Cs 3 Sb 2 Br 9 /FN-COP heterojunction achieved a total electron rate of 135.42 µmol·g -1 ·h -1 for CO 2 reduction coupled with a benzaldehyde production rate of 179.73 µmol·g -1 ·h -1 , representing a 2.4 and 2.6-fold enhancement over the un-functionalized heterojunction. This work demonstrates a novel "molecular engineering–interface modulation–function cooperation" strategy to construct high-quality heterojunction precisely, providing valuable insights for the design of high-performance photocatalysts for next-generation energy conversion applications.