One-step microwave hydrothermal preparation of Cd/Zr-bimetallic metal–organic frameworks for enhanced photochemical properties

Abstract

A new bimetallic metal–organic framework (Cd/Zr-MOF) was successfully synthesized via microwave hydrothermal method using Zr4+ and Cd2+ as two metal ions and terephthalic acid (H2BDC) as organic ligand. The effects of Cd/Zr molar ratio and the reaction temperature on the Cd/Zr-MOF structure and its photocatalytic performance to degrade Rhodamine B (RhB) under simulated sunlight were explored in detail. The results show that the Cd/Zr-MOF with Cd/Zr molar ratio of 5:1 obtained at the reaction temperature of 160 °C exhibits the best photocatalytic performance, and the photocatalytic efficiency can reach 95.82% after 105 min irradiation, which is much higher than that of pure UiO-66 or pure Cd-MOF. The result of Mott–Schottky tests certified the formation of n–n heterojunction between Cd-MOF and UiO-66, which is conducive to the transfer and separation of photogenerated electrons and holes and is the main reason of the enhanced photocatalytic performance. In addition, the mechanism of photocatalytic degradation of Cd/Zr-MOF was studied by adding different eliminating agents. The photodegradation of RhB was mainly caused by superoxide ion (·O2−) and electron hole (h+). The Cd/Zr-MOF composites with excellent photocatalytic activity to Rhodamine B were synthesized via one-step microwave hydrothermal method.