Anchoring Redox Mediator on COFs for Efficient Solar to Hydrogen Conversion

Abstract

Abstract To address severe carrier recombination in Z‐scheme heterojunctions, redox mediators such as IO 3 − / I− or Fe 3 ⁺/Fe 2 ⁺ are often introduced, yet their dispersion in solution causes instability, low electron transport efficiency and side reactions. Herein, an innovative Fe‐coordinated 2D Z‐scheme heterojunction composed of TpPa‐1‐COF (TP1C) and Bi 2 WO 6 (BWO) is developed for efficient photocatalytic H 2 production. Unlike traditional indirect Z‐scheme heterojunctions, the Fe 3+ /Fe 2+ mediator is firmly anchored on the skeleton of COFs, thus enhancing recyclability, charge migration and long‐lasting stability, which is supported by extended X‐ray absorption fine structure (EXAFS) and a range of electrochemical tests. In addition, the formation of 2D Z‐scheme heterojunctions not only retains high redox properties but also provides abundant active sites for photocatalytic reactions. Consequently, the photocatalytic H 2 production rate of 25% BWO/Fe/TP1C reaches up to 6.31 mmol·g −1 ·h −1 without the addition of co‐catalysts, being about 28.68 times as high as that of pure COFs and 2.3 folds over that of 25% BWO/TP1C, exceeding a host of COF‐based photocatalysts. The findings of this research highlight the potential of novel indirect Z‐scheme heterojunctions for advanced photocatalytic applications, offering a new pathway to overcome the limitations of traditional COF‐based systems in hydrogen production.