Energy transfer-induced enhanced photocatalytic hydrogen production in a D-π-A cyanine dye-encapsulated pyrene-based...

Photocatalytic hydrogen (H₂) production via water splitting offers a sustainable route to replace fossil fuels, yet inefficient charge separation in photocatalysts remains a critical bottleneck. Here, we present a novel strategy to overcome this challenge by encapsulating a donor-π-acceptor (D-π-A) cationic dye pyridinium hemicyanine, 4-[p-(dimethylamino)styryl]-1-methylpyridinium (DMASM) into the anionic pyrene-based metal-organic framework (MOF) [BMI][In(TBAPy)] (1, H₄TBAPy = 1,3,6,8-tetrakis(p-benzoic acid)pyrene; BMI = 1-butyl-3-methylimidazolium) via ion exchange. The resulting host-guest system, DMASM@1, achieves a narrowed bandgap (1.78 eV vs. 2.25 eV in the parent 1) and broadened visible-light absorption, enabling efficient energy transfer from TBAPy ligand to DMASM. This synergy suppresses electron-hole recombination, boosting photocurrent density and yielding an exceptional photocatalytic H₂ production rate of 679.9 μmol·g^-1·h^-1 without co-catalysts. Furthermore, DMASM@1 exhibits outstanding reusability, retaining > 96 % activity over five cycles. This work advances the design of MOF-based photocatalysts through non-covalent dye integration and offers a sustainable pathway for clean energy technologies.