Efficient removal of organic pollutants from wastewater has become a hot research topic due to its ecological and environmental importance. Traditional water treatment methods such as adsorption, coagulation, and membrane separation suffer from high operating costs, and even generate secondary pollutants. Photocatalysis on semiconductor catalysts (TiO₂, ZnO, Fe₂O₃, CdS, GaP, and ZnS) has demonstrated efficiency in degrading a wide range of organic pollutants into biodegradable or less toxic organic compounds, as well as inorganic CO₂, H₂O, NO₃ ⁻, PO₄ ³⁻, and halide ions. However, the difficult post-separation, easy agglomeration, and low solar energy conversion efficiency of these inorganic catalysts limit their large scale applications. Exploitation of new catalysts has been attracting great attention in the related research communities. In the past two decades, a class of newly-developed inorganic–organic hybrid porous materials, namely metal–organic frameworks (MOFs) has generated rapid development due to their versatile applications such as in catalysis and separation. Recent research has showed that these materials, acting as catalysts, are quite effective in the photocatalytic degradation of organic pollutants. This review highlights research progress in the application of MOFs in this area. The reported examples are collected and analyzed; and the reaction mechanism, the influence of various factors on the catalytic performance, the involved challenges, and the prospect are discussed and estimated. It is clear that MOFs have a bright future in photocatalysis for pollutant degradation.

Metal–organic frameworks (MOFs), a new class of porous crystalline materials, have attracted great interest as a promising candidate for sustainable energy and environmental remediation. In this study, ZIF-8, a versatile MOF based on imidazolate ligands, was selected as a photocatalyst to decompose methylene blue (MB) under UV light irradiation. The influence factors, kinetics, and mechanism of photocatalytic MB degradation and stability of ZIF-8, were also studied. The results revealed that the ZIF-8 photocatalyst exhibited efficiently photocatalytic activity for MB degradation under UV irradiation, which was confirmed through the detection of hydroxyl radicals (˙OH) by a fluorescence method. The MB degradation over the ZIF-8 photocatalyst followed a pseudo-first-order kinetics model. ZIF-8 worked effectively over a wide pH range from 4.0 to 12.0, and showed both high adsorption capacity and degradation efficiency for MB in a strong alkaline environment. The enhanced efficiency in a strong alkaline environment resulted from the higher charged ZIF-8 (pH > pH_pzc) and the elevated yield of ˙OH facilitated by increased OH⁻ concentration. The possible pathway of photocatalytic degradation of MB in ZIF-8 was proposed. The results indicated that ZIF-8 can be used as a highly efficient photocatalyst to decompose organic pollutants.