Vinylene-Linked Fully Conjugated 3D Covalent Organic Polymers for Photocatalytic H₂O₂ Production

Covalent organic polymers (COPs), featuring conjugated architectures, high porosity, and structural tenability, have emerged as promising candidates for photocatalytic applications. However, the design and synthesis of three-dimensional (3D) sp²-carbon-conjugated COPs, along with their photocatalytic performances, remain underexplored. Here, we synthesized two novel vinylene-linked fully conjugated 3D COPs (BUCT-COP-50 and BUCT-COP-51) through the saddle-shaped building blocks. Under visible-light irradiation, both materials demonstrated efficient hydrogen peroxide (H₂O₂) generation, with BUCT-COP-51 (thiophene-enriched) achieving a remarkable production rate of 3.21 mmol g^-1 h^-1 in pure water, higher than BUCT-COP-50 (benzene-modified, 2.16 mmol g^-1 h^-1). Mechanistic investigations revealed that the H₂O₂ generation predominantly proceeded via the indirect two-electron oxygen reduction reaction pathway. The superior performance for BUCT-COP-51 could attributed to its narrower bandgap, broader light absorption range, and higher conductivity. This work illustrates that vinylene linked fully conjugated 3D COPs could be as promising semiconductors in environmental and energy-related fields.