Molecularly Engineered Crystalline Donor–acceptor Linear Conjugated Polymer for 2 D /2D Heterostructures Toward Efficient Photocatalytic Hydrogen Evolution

Abstract

Breaking through the structural limitations of linear conjugated polymers (LCPs) is critical for high-performance heterojunctions. Herein, we report the rational molecular engineering of a crystalline two-dimensional (2D) donor–acceptor (D–A) polymer, poly(4,7-dithienyl-2,1,3-benzothiadiazole) (PDB), addressing conventional polythiophenes’ amorphous/zero-dimensional (0D) drawbacks of poor charge transport and interfacial compatibility. PDB’s rigid D–A backbone (thiophene donors + benzothiadiazole acceptors) enforces high crystallinity and 2D sheet morphology, endowing enhanced π–π overlap, high charge mobility, and abundant binding sites. Capitalizing on this, we fabricate a 2D/2D PDB/ZnIn2S4 (ZIS, denoted as PZS) heterostructure via in situ growth of vertical ZIS nanosheets on PDB. ZIS’s intrinsic 2D morphology enables intimate atomic contact, while its suitable bandgap and favorable band alignment facilitate efficient interfacial charge transfer. Combined experimental and DFT studies collectively support a Type-II band alignment, enabling directional electron transfer with minimized resistance. Consequently, the optimized PZS heterostructure with 0.2 mg PDB loading (denoted as PZS-0.2) delivers a remarkable visible-light H2 evolution rate of 4.99 mmol g–1 h–1, representing a 26.3-fold and 5.1-fold enhancement over pristine PDB and ZIS, respectively. This work establishes a new paradigm for high-performance LCP-based heterojunctions by integrating molecularly engineered 2D D–A conjugated polymers with inorganic semiconductors, providing a versatile design principle for efficient solar-to-fuel conversion.