Design and Construction of D-A-Extended 3D Covalent-Organic Frameworks for Boosting Photocatalytic Hydrogen Evolution

The development of donor-acceptor (D-A) covalent-organic frameworks (COFs) has emerged as a promising strategy for enhancing photocatalytic performance. Although most studies have concentrated on 2D COFs, research into their 3D counterparts remains limited. In this study, we rationally designed and synthesized a carbazoyl dicyanobenzene derivative (TBFCC) as an intrinsic D-A building block. By selecting TAPA, TAPB, and TAPT as the donor, acceptor-π, and acceptor donors, respectively, we synthesized three distinct D-A-extended COF materials: D-D-A, A-π-D-A, and A-D-A. Among these, 3D-TAPT-COF, featuring an A-D-A structure, exhibited the highest hydrogen evolution rate of 31.3 mmol g^-1 h^-1, surpassing most previously reported 3D COF-based photocatalysts. This superior performance is attributed to its A-D-A configuration, which provides multiple charge transfer pathways in 3D space, overcoming the electron transport limitations inherent in 2D COFs. Consequently, this feature facilitates efficient separation of photogenerated charges within the framework and reduces carrier recombination, thereby optimizing photocatalytic efficiency.