MOF-derived materials for photoelectrochemical water splitting: design principles, mechanisms, and solar-to-hydrogen applications

Abstract

The development of sustainable hydrogen production technologies is central to addressing the global energy crisis and mitigating climate change. Among available strategies, photoelectrochemical (PEC) water splitting stands out as a promising route for direct solar-to-fuel conversion, though it remains hindered by poor light absorption, charge recombination, and sluggish surface reaction kinetics. Metal-organic framework (MOF)-derived materials have emerged as versatile candidates to overcome these bottlenecks, offering tunable compositions, high surface areas, and well-defined morphologies. This review critically examines the design and synthesis strategies employed to transform MOF precursors into functional photoelectrodes, including controlled pyrolysis, calcination, heterostructure engineering, and defect modulation. Special emphasis is placed on the mechanistic insights into charge carrier generation, separation and transport, highlighting the debate surrounding the identity of the true active sites, whether nanoparticles, N-doped carbon, or single-atom centres. Performance benchmarking demonstrates that MOF-derived photoanodes and photocathodes can achieve photocurrent densities exceeding 5 mA cm–2 in three-electrode PEC configurations, while device-level STH efficiencies (>10%) are achieved only when these materials function within unbiased two-electrode architectures (PEC tandems or PV–electrolysis tandems) where the full photovoltage is supplied by paired absorbers and/or integrated photovoltaics. To avoid ambiguity, this review now reports STH only for unbiased device demonstrations, and reports ABPE (applied-bias photon-to-current efficiency) or other electrode-level metrics for half-cell photoelectrode studies. The review also underscores the challenges of stability, scalability, and standardised testing protocols, while showcasing promising trends such as operando characterisation, defect engineering, and artificial intelligence (AI)-assisted material discovery. By mapping current advances and future perspectives, this work provides a comprehensive overview of how MOF-derived systems can accelerate the transition to efficient and durable PEC water splitting technologies.