A Trimetallic NiZrCu-Metal–Organic Framework Nanosheet for Superior Peroxymonosulfate Activation

Incorporation of redox-active metal ions with positive synergism in Two-dimensional (2D) metal-organic frameworks (MOFs) is a promising strategy for the creation of highly electroactive catalytic sites with high accessibility. This study reports the ultrasonic-assisted synthesis of novel 2D trimetallic NiZrCu-MOF nanosheets specifically engineered for efficient PMS activation. The ultrathin 2D framework maximizes the exposure of active sites and enhances mass transport, while the strategic incorporation of nickel and copper (redox activity) and zirconium (structural stability) creates a synergistic catalytic environment. When applied to the degradation of 2,4-dichlorophenol (2,4-DCP), the optimized NiZrCu-MOF/PMS system achieved exceptional performance, removing over 99% of the pollutant within 8 min with a high pseudo-first-order rate constant of 0.561 min^-1, significantly outperforming its mono- and bimetallic counterparts. Optimized conditions are 50 mg/L catalyst dosage, 150 mg/L PMS concentration, and pH = 7. Quenching experiments and XPS analysis revealed a multipathway mechanism where radical species (SO₄^-· and HO^·) and nonradical species (¹O₂ and O₂^-·) contribute to degradation, with the Cu(II)/Cu(I) and Ni(II)/Ni(III) redox cycles being paramount for PMS activation. The catalyst demonstrated remarkable stability and reusability over five cycles with minimal metal leaching and preserved structural integrity, as confirmed by PXRD and BET analysis. Furthermore, the system exhibited high efficiency against various pollutants, including sulfamethazine and p-nitrophenol, across a range of concentrations. This work underscores the potential of rationally designed 2D polymetallic MOFs as efficient, stable, and versatile catalysts for sustainable water purification.