Molecular bridged s-scheme heterojunction of Zn-TCPP(Co)/Ti3C2 for efficient photocatalytic hydrogen evolution

The strategic integration of metal-organic frameworks (MOFs) with MXenes presents a promising avenue to overcome charge separation bottlenecks in photocatalysis. This study constructs a hierarchical S-scheme heterojunction by in-situ growing ultrafine Zinc–Tetrakis(4-carboxyphenyl) porphyrin (Cobalt-incorporated) Zn-TCPP(Co) MOF nanoparticles (15 nm) on two-dimensional functionalized MXene nanosheets. This unique “particle-on-lamella” architecture is engineered with molecular bridges, establishing a chemically bonded interface via C–Ti–O and N–Ti bonds that facilitate rapid charge transfer. The optimized heterostructure exhibits a narrow bandgap of 1.95 eV, a significantly prolonged charge carrier lifetime of 35.5 ns, and a high photocurrent density of 1.7 µA cm− 2. By leveraging synergistic S-scheme charge separation, MXene’s metallic conductivity, and molecular single-atom Co sites, the composite achieves an exceptional hydrogen evolution rate of 24.3 mmol g− 1 h− 1 with an apparent quantum efficiency of 10.2% at 420 nm—representing a sixfold enhancement over pristine Zn-TCPP(Co). This performance surpasses many recently reported MOF- and MXene-based photocatalysts. Combined density functional theory calculations and experimental analyses confirm the critical role of the internal electric field in driving the S-scheme mechanism, which effectively preserves strong redox potentials. This work provides a definitive blueprint for high-performance photocatalytic systems through molecular-level interfacial engineering.