Next-generation metal-organic framework-based photoelectrodes for sustainable hydrogen production via solar-driven water splitting

Solar-driven photoelectrochemical (PEC) water splitting is a promising route for sustainable hydrogen production, addressing the growing global energy demand projected to increase by ∼50% by 2050. Metal–organic frameworks (MOFs), with high surface areas (up to 6240 m² g⁻¹) and tunable band gaps (1.5–3.5 eV), have emerged as advanced photoelectrode materials. This review critically examines recent progress in MOF-based photoelectrodes, focusing on design strategies, charge transport mechanisms, and performance optimization. The thermodynamic requirement of 1.23 V for water splitting typically increases to ∼1.8–2.0 V due to kinetic overpotentials (η_OER: 0.3–0.6 V; η_HER: 0.05–0.3 V). Pure MOF systems exhibit limited photocurrent densities ('0.5 mA cm⁻²), whereas MOF-based heterostructures (e.g., MOF/BiVO₄, MOF/Fe₂O₃) achieve enhanced values up to ∼5 mA cm⁻² at 1.23 V vs. RHE. Integration with co-catalysts further improves charge separation efficiency ('80%) and stability ('30 h). Strategies such as band gap engineering, interface modification, and MOF-derived nanostructures significantly boost PEC performance. Despite these advances, challenges including low conductivity (10⁻¹⁰–10⁻⁴ S cm⁻¹) and long-term stability remain. This review provides insights into next-generation MOF architectures for efficient solar hydrogen production.