Preparation of Zr-doped MXene@MIL-125(Ti) composite to mediate the ultrasonic removal of organic dyes and microplastics

In recent years, the ultrasonic removal of organic pollutants has attracted a great deal of attention. In this study, a novel MOF-based sonocatalyst with bimetallic center was formed by doping Zr atoms into the MX@MIL-125(Ti), aiming to improve the ultrasonic removal performance of organic pollutants. The successfully prepared MX@MIL-125(Ti/Zr) showed a porous structure with abundant grooves and channels (average pore size of 21.8 nm, and specific surface area of 36.910 m 2 /g), and significantly had a higher quantum yield (13.24 %) than MIL-125(Ti) and MX@MIL-125(Ti), thereby producing more OH and O 2 − free radicals under ultrasonic irradiation. The experimental results showed that the MX@MIL-125(Ti/Zr) had good sonocatalytic activity and could effectively deal with small-molecule dyes and macro-molecule microplastics under ultrasonic conditions, where the removal efficiency achieved approximately 95 % for Rhodamine B (within 12 min) and approximately 90 % for micro-polyethylene (within 4 h in the presence of persulfate). In addition, a possible degradation-dominant mechanism was proposed to explain the MX@MIL-125(Ti/Zr)-mediated sonocatalytic removal, where the existence of Zr atoms could help sono-excited electrons generate and transfer onto the conductive MXene, thereby facilitating more charge carriers to create reactive free radicals. Therefore, the study would provide a green and feasible approach for the industrial treatment of organic pollutants in water bodies.