Innovative approaches to the molecular design, synthesis, and functionalization of conjugated organic polymer (D–A, D–π–A, A–A–D, and A–D–A) photocatalysts for sustainable hydrogen production

Abstract

As an exciting new approach to solar energy harvesting, photocatalytic hydrogen (H₂) production from water using a polymeric photocatalyst holds great promise as a tool for chemical energy conversion. As an alternative to inorganic photocatalysts, organic semiconductor-based materials have garnered much attention lately. These materials have several advantages over inorganic ones, such as improved stability, reduced costs, simpler microarchitecture, readily adjustable electrical conductivity, and molecular design. The first part of this review provides an overview of the background material, followed by a current and comprehensive summary of the latest research on organic polymers as possible new materials for efficient hydrogen photocatalysts. This review highlights key advancements in various methods for synthesizing conjugated polymers, including metal-mediated polymerization reactions (e.g., Suzuki, Sonogashira, and Stille), direct C–H arylation, and others that rely on CC and CN functionalities for photocatalytic hydrogen generation. These approaches have enabled the synthesis of conjugated polymers that can harness solar energy to generate hydrogen more efficiently than inorganic materials. The exploration of conjugated polymers with various donor–acceptor types (D–A, D–π–A, D–A–A, and D–π–A–A) for developments in side-chain substitution, conjugation expansion, and the creation of photocatalysts for hydrogen generation is reviewed. By outlining the current state of the art, engineering approaches, key findings, obstacles, and future prospects, this review aims to provide useful recommendations for the advancement of conjugated organic polymer catalysts for use in laboratory studies of large-scale hydrogen production. We conclude by discussing the current challenges and suggesting new opportunities for rationally designed and fundamentally advanced catalysts.