Covalent organic frameworks (COFs) have emerged as promising photocatalysts for hydrogen peroxide (H₂O₂) production, yet their performance is often limited by inefficient photogenerated charge separation and transport. Herein, a sp² carbon-conjugated donor–acceptor–acceptor (D–A–A) COF (TFPT-TCPB-COF) (TFPT = 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, and TCPB = 2,2'-(5'-(4-(cyanomethyl)phenyl)-[1,1':3',1''-terphenyl]-4,4''-diyl)diacetonitrile) incorporating a strong electron-withdrawing cyano group was rationally designed and synthesized via an optimized solvothermal method. The unique D–A–A architecture, together with abundant reductive active sites (triazine and cyano groups) for two-electron oxygen reduction and oxidative sites (benzene rings) for two-electron water oxidation, enables efficient H₂O₂ generation in pure water without sacrificial agents. As a result, TFPT-TCPB-COF achieves a high H₂O₂ production rate of 4.43 mmol·g⁻¹·h⁻¹, which is 1.72 times greater than that of its imine-linked analogue (TFPT-TAPB-COF). Additionally, it exhibits an apparent quantum yield of 12.4% at 420 nm, outperforming most reported COF-based photocatalysts. Experimental and theoretical analyses reveal that the enhanced activity originates from improved charge separation and transport, as well as a modulated electronic structure that lowers the energy barriers for key *OOH and *OH intermediates during the photocatalytic process. This work provides important molecular insights into the design of advanced COF photocatalysts with donor–acceptor architectures for efficient solar energy conversion.

Electrochemical CO₂ reduction is a viable, economical, and sustainable method to transform atmospheric CO₂ into carbon-based fuels and effectively reduce climate change and the energy crisis. Constructing robust catalysts through interface engineering is significant for electrocatalytic CO₂ reduction (ECR) but remains a grand challenge. Herein, SnO₂/Bi₂O₂CO₃ heterojunction on N,S-codoped-carbon (SnO₂/BOC@NSC) with efficient ECR performance was firstly constructed by a facile synthetic strategy. When the SnO₂/BOC@NSC was utilized in ECR, it exhibits a large formic acid (HCOOH) partial current density (J_HCOOH) of 86.7 mA·cm⁻² at −1.2 V versus reversible hydrogen electrode (RHE) and maximum Faradaic efficiency (FE) of HCOOH (90.75% at −1.2 V versus RHE), respectively. Notably, the FE_HCOOH of SnO₂/BOC@NSC is higher than 90% in the flow cell and the J_HCOOH of SnO₂/BOC@NSC can achieve 200 mA·cm⁻² at −0.8 V versus RHE to meet the requirements of industrialization level. The comparative experimental analysis and in-situ X-ray absorption fine structure reveal that the excellent ECR performance can be ascribed to the synergistic effect of SnO₂/BOC heterojunction, which enhances the activation of CO₂ molecules and improves electron transfer. This work provides an efficient SnO₂-based heterojunction catalyst for effective formate production and offers a novel approach for the construction of new types of metal oxide heterostructures for other catalytic applications.