Beyond removal efficiency: Evidence-gated coordination design of MOF photocatalysts for contaminant risk reduction

Metal-organic framework (MOF) photocatalysis is commonly judged by a single end-point percentage pollutant removal even though the reported decrease can combine adsorption, photolysis, partial transformation, true catalytic degradation, and catalyst decomposition. This metric-centered literature has produced many high-performing materials but few transferable design rules. Here, MOF photocatalysts are re-evaluated through an evidence-gated coordination-to-risk framework that asks whether five sequential conditions are satisfied including the contaminant can access and be productively positioned within the pore or interfacial microenvironment, absorbed photons generate charges with adequate lifetime and redox potential, those charges produce a verified reactive pathway rather than a diagram inferred from band edges alone, chemical conversion yields mineralization or demonstrable toxicity reduction, and the active material remains recoverable, compositionally stable, and effective in realistic matrices and reactor formats. Using this framework, the roles of metal-node identity, linker electronics, pore matching, defects, mixed-metal coordination, MOF-on-MOF interfaces, semiconductor coupling, MOF-derived phases, and immobilized photo-Fenton architectures are critically compared. Representative systems are treated as causal tests rather than as a catalogue of efficiencies, and mechanistic claims are ranked according to the strength of optical, electrochemical, spectroscopic, radical, pathway, leaching, and post-reaction evidence. The analysis shows that improved adsorption and faster apparent kinetics are valuable only when they preserve charge utilization, product safety, and structural continuity. A recommended reporting framework is therefore proposed to distinguish disappearance, degradation, mineralization, detoxification, and process durability. By shifting the unit of comparison from "best removal percentage" to "verified contaminant-risk reduction per stable catalytic cycle," this review establishes a more discriminating basis for designing MOF photocatalysts that can progress from elegant coordination solids to credible water- and air-treatment technologies.