Adjusting Oxidation Pathways via Fine-tuning Atomic Ratios in Window-opening MO0F Membranes for Efficient Self-cleaning

Abstract

Peroxymonosulfate (PMS) can be used as a green oxidant to mitigate catalytic membranes fouling and restore filtration performance through advanced oxidation processes (AOP). However, the adjustment of oxidation pathways and the understanding of underlying mechanisms for efficient cleaning without sacrificing the filtration performance need to be studied systematically. We optimized the membranes microenvironment via thermal modification from 25 °C to 400 °C below the catalyst ZIF-8 framework's decomposition temperature. The modified membranes have a doubled pure water flux (158.3 LMH bar⁻¹) and remain rejection rates due to intact ZIF-8 framework structure with “window-opening” effect. The methyl dissociation and self-catalyzed graphitization were regulated by changing temperature, resulting in adjustable nonradical pathway proportion (correlated with the C/Zn atomic ratio at 0.96). The enhanced nonradical pathway targeted attacks on electron-rich regions of organic compounds, resulting in efficient cleaning and almost complete flux recovery (99.3%). The theoretical simulations revealed that methyl groups dissociation and graphitization significantly influence the electron density and adsorption energy at active sites for tunable oxidation pathways and enhanced catalytic performance. Our work offers a rational strategy to improve both filtration and catalytic performance in catalytic membranes. The enhanced understanding of oxidation mechanisms guides the design of designing efficient AOP membrane cleaning systems.