sp2 Carbon‐Conjugated Covalent Organic Frameworks (sp2c‐COFs): Synthesis and Application in Photocatalytic Water Splitting

Abstract Preparation of irreversible sp 2 carbon‐conjugated covalent organic frameworks (sp 2 c‐COFs) with specific porosity, easy structural functionalization, high chemical stability, and unique π‐electron conjugation structure (especially the combination of π–π stacking interactions and conjugation system), can remove the barrier of electron transfer and provide a unique advantage for photocatalytic water splitting. Herein, based on three kinds of reactions (Aldol condensation reaction, Knoevenagel condensation reaction, and Horner‐Wadsworth‐Emmons reaction) and guided by the precise modulation of ligand structure and topology, this review summarizes the synthesis of sp 2 c‐COFs and their applications in photoelectrocatalytic water splitting (hydrogen evolution and oxygen evolution reactions). Furthermore, challenges and possible research directions for sp 2 c‐COFs in photocatalytic water splitting are also provided.