Metal-organic framework (MOF) catalysts for piezocatalytic water treatment: Progress, limitations, and future prospects

Advanced oxidation processes (AOPs) are widely studied for the rapid degradation of recalcitrant compounds that are not fully removed during conventional water treatment. One such AOP, piezocatalysis, involves the deformation of a catalyst under mechanical force to generate a piezoelectric effect that will produce reactive oxygen species capable of decomposing persistent pollutants. This technique is competitive because it combats the limitations of light and electricity use in other AOPs while enabling coupling with catalytic processes such as photocatalysis (i.e. piezo-photocatalysis) to enhance degradation efficiency. Metal-organic frameworks (MOFs) materials have emerged as a promising class of piezocatalysts attributed to their high surface area and porosity coupled with ease of modification. Recent MOF piezocatalysis research demonstrates promising results, often degrading >80% of organic dyes, antibiotics, and heavy metals under 60 minutes. MOF catalysts can improve piezo-photocatalytic technologies by enhancing charge carrier separation. Comparative evaluation of the most commonly applied MOF classes: UiO, MIL, ZIF, and Bi-based MOFs, demonstrates distinct benefits and limitations regarding catalytic performance, stability, and synthesis complexity. This review comprehensively outlines the design principles governing MOF piezocatalysts for water treatment, including inherent and induced piezoelectricity, synthetic engineering strategies, and structure–property relationships governing charge transport behavior and catalytic performance. Despite recent progress, there are still challenges surrounding catalyst reusability, testing in realistic water matrices, experimental standardization, and reliance on complex MOF composite structures to maximize catalytic performance. Future MOF piezocatalyst research should prioritize scalable, stable catalyst design in addition to high degradation performance.