S-Scheme Heterojunction Fabricated from Covalent Organic Framework and Quantum Dot for Enhanced Photosynthesis of Hydrogen Peroxide from Water and Air

Covalent organic frameworks (COFs) with stable crystalline porous structures and flexible assembly properties contribute to the direct photocatalytic synthesis of H2O2 to meet the growing global demand. To address the challenges of insufficient redox capacity and photogenerated carrier recombination of COFs, S-scheme heterojunction is constructed from COFs with quantum dots (QDs) to improve the photocatalytic production of H2O2. Herein, 0D ZnCdS QDs (ZCS) uniformly anchor on the surface of a 2D conjugated tetrathiafulvalene-based COF (TT-COF), affording the S-scheme heterojunction TT-COF/ZCS. Formation of S-scheme heterojunction effectively prevents the agglomeration of ZCS, modulates the energy band structure of TT-COF, and enhances the migration of photogenerated carriers and redox ability. As a total consequence, the optimized heterojunction (TZ-40) is able to afford H2O2 in the yield up to 5171 mu mol g-1 h-1 under visible light irradiation with H2O and O2, much higher than those for TT-COF, 2520 mu mol g-1 h-1, and ZCS, 2647 mu mol g-1 h-1. The present result demonstrates the great potential of COFs/QDs-based S-scheme heterojunctions for photocatalytic applications including photocatalytic H2O2 production. An S-scheme heterojunction catalyst constructed from 2D conjugated tetrathiafulvalene-based covalent organic framework (TT-COF) and ZnCdS quantum dots (ZCS) with adjusted energy band structure, enhanced photogenerated carriers separation and transportation, and improved photogenerated carriers redox ability is designed and prepared, exhibiting excellent photocatalytic H2O2 production performance without any sacrificial agents. image