Design of Donor‐Acceptor Type 2D Covalent Organic Frameworks as Efficient Photocatalysts for Visible‐Light‐Driven Water Splitting

Abstract

Abstract Benefitting from the substantially accessible catalytic sites and porous architecture enhancing mass transport, 2D covalent organic frameworks (COFs) show great potential for photocatalytic overall water splitting (OWS). However, the performance of many known COFs for this application remains unsatisfactory, primarily due to stringent requirements for precise band alignment, the limitation posed by overpotentials in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and mutual interference between the two half‐reactions. Herein, by incorporating donor‐acceptor (D‐A) pairs into frameworks with the photosensitizer carbonyl‐bridged triphenylamine (CTPA) as a basic building block, few D‐A type 2D covalent CTPA‐based framework (CCFs) with experimental synthesis possibilities verified by Ullman C─C coupling mechanism are proposed. These 2D CCFs exhibit significant intermolecular charge transfer as anticipated, facilitating efficient carrier separation in photocatalytic OWS. The combination of D/A units in these 2D CCFs regulates their electronic structure with bandgaps ranging from 2.31 to 3.15 eV and band‐edge arrangement suitable for photocatalytic OWS. Crucially, the co‐existence and separate presentation of HER and OER active sites on their surface without overpotentials enables them capable of spontaneous OWS under visible light. Among them, the 2D CTPA‐TPA COF shows the best photocatalytic performance with an ideal solar‐to‐hydrogen (STH) efficiency up to 18.6%.