Robust Photocatalytic Hydrogen Evolution Over a Conjugated Metal-Organic Framework Heterojunction

Efficient photocatalysis requires the synergistic integration of charge separation and directional charge transport, yet achieving these features within a single framework remains challenging. Here, we report a conjugated coordination polymer, Cd-TMT (TMT = 1,3,5-trimercaptotriazine), featuring an intrinsic molecular-level charge transport network. The conjugated TMT ligands facilitate strong intra-ligand charge transfer, while their ordered π-π stacking along the [111] direction establishes a continuous pathway for directional electron migration, endowing Cd-TMT with intrinsic photocatalytic activity for hydrogen evolution. To further promote charge separation, Cd-TMT is integrated with the conductive metal-organic framework Cu-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) to construct a heterostructure. Spectroscopic investigations and density functional theory calculations demonstrate that this architecture accelerates charge separation while retaining highly reductive electrons. As a result, the Cd-TMT@Cu-HHTP composite achieves a H₂ evolution rate of 9692.83 µmol g^-1 h^-1, surpassing most reported MOF-based photocatalysts. This work provides fundamental insights into molecular-level charge transport and offers a viable strategy for designing high-performance heterostructures for solar-to-fuel conversion.