Molecular Engineering of Calixarene Dyes on UiO-66-NH2: Boosting Electron Transfer for High-Efficiency Photocatalytic Hydrogen Evolution

Developing efficient photocatalysts for visible-light-driven hydrogen evolution is crucial for sustainable energy conversion. Herein, a series of D-π-A-structured calixarene dyes (BFT-1COOH, BFT-2COOH, BFT-CNCOOH) with varied π-bridges and acceptor groups are molecularly engineered and integrated with Pt-loaded UiO-66-NH₂ (Pt@U6N) to enhance photocatalytic hydrogen production. Systematic characterizations confirm the structural integrity of the composites and reveal reduced charge recombination due to hydrogen bonding between the dye carboxyl groups and U6N. The BFT-1COOH/Pt@U6N composites exhibit the highest hydrogen evolution rate of 1160 μmol g^-1 h^-1 under visible light, outperforming analogs with extended π-bridges (BFT-2COOH) or cyanoacetic acid acceptors (BFT-CNCOOH), which can be attributed to optimal LUMO energy alignment and robust dye-MOF interactions. This work underscores the significance of rational molecular engineering in balancing light absorption, electron injection driving force, and interfacial stability for advancing dye-sensitized MOF photocatalysts toward solar-to-hydrogen energy conversion.