Bimetallic UiO-66-NH2(Zr–Hf) synergistic photocatalytic and piezoelectric effects for the degradation of rhodamine B

A series of bimetallic UiO-66-NH₂(Zr-Hf) metal-organic frameworks (MOFs) were prepared by a green hydrothermal method and tested for their photocatalytic and piezo-catalytic properties. Among them, UN(0.75Zr) (metal node: 0.75Zr : 0.25Hf) shows the most superior piezo-photocatalytic activity. The degradation rate for 40 mg L^-1 rhodamine B (Rh B) could reach 96.78% within 30 min, which was ∼4.66 and ∼3.30 times higher than that of photocatalysis and piezo-catalysis, respectively. Moreover, the main reactive oxidizing substances (ROS), including vacancies (h⁺) and hydroxyl radicals (˙OH), were identified by free radical scavenging experiments. In addition, the intermediates generated during Rh B degradation were analyzed by HPLC-MS, while a reasonable degradation pathway was presented. Our work utilizes a green and environmentally friendly method to prepare bimetallic MOFs, providing a novel solution for the rapid degradation of highly concentrated dye wastewater.