Miriam Vos-Gracia

While solar‐driven photoelectrochemical (PEC) water splitting offers a promising route for sustainable hydrogen production, sluggish interfacial charge transfer and long‐term instability remain critical bottlenecks. To address these limitations, a chemically integrated Ti‐squarate metal–organic framework (IEF‐11)/ n ‐GaN nanowire (NW) hybrid photoanode is designed via a (3‐aminopropyl) triethoxysilane (APTES) interlayer for efficient PEC water splitting. Density functional theory (DFT) calculations support energetically favorable interfacial bonding and the associated charge redistribution across the APTES‐mediated interface, highlighting the dual role of APTES in chemical anchoring and interfacial electronic modulation. This interfacial modification is accompanied by a reduced work function and a cathodic shift in the apparent flat‐band potential. Consequently, the hybrid photoanode demonstrates accelerated charge‐transfer kinetics, featuring reduced charge‐transfer resistance and a 10.4‐fold enhancement in applied‐bias photon‐to‐current efficiency (ABPE) compared to pristine NWs. Furthermore, this chemical anchoring supports the retention of principal structural and chemical features after 100 h of continuous operation, thereby promoting durable solar‐driven hydrogen production.

Herein, defect engineering strategies were applied to enhance the photocatalytic activity of squarate-based MOFs (IEF-11) for green hydrogen generation via water splitting. The textural properties of pristine IEF-11(Ti) were significantly improved using microwave (MW)-assisted synthesis, leading to a four-fold increase in surface area (350 m² g^–1) due to the formation of mesopores associated with defect aggregation, primarily arising from linker vacancies (24%). Vanadium doping (0–100%) progressively reduced the optical band gap (2.44–1.87 eV), shifting absorption toward the visible region. The IEF-11 series was evaluated as photocatalysts for the hydrogen evolution reaction under simulated sunlight irradiation, revealing a volcano-type trend correlating activity with V content. Doped with 11% V, the MW-synthesized IEF-11(Ti_0.89V_0.11)_MW solid exhibited the highest activity (1053 vs. 536 μmol g^–1 h^–1 H₂ for IEF-11(Ti)), attributed to optimized band alignment, enhanced charge separation, and structural robustness. It also showed activity in photocatalytic overall water splitting (83 μmol g^–1 h^–1 H₂, 30% higher than the undoped IEF-11(Ti)). Theoretical calculations further confirmed band gap narrowing and the generation of new electronic states upon V-doping, facilitating charge transfer and reducing electron–hole recombination. These findings highlight the relevance of inducing artificial porosity and V-doping of IEF-11(Ti) to prepare efficient MOF-based photocatalysts. Importantly, this work not only reports the first V-squarate frameworks but also represents one of the first systematic studies addressing the effect of metal doping in MOFs for photocatalytic water splitting, achieving competitive efficiencies operating in the absence of cocatalysts.