Synthesis and characterization of Zn2GeO4/Mg-MOF-74 composites with enhanced photocatalytic activity for CO2 reduction†
Abstract
Strategies for effectively enhancing the photoreduction of CO2 have been studied for several decades. In this work, Zn2GeO4/Mg-MOF-74 composites were prepared via a hydrothermal method. The X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM) images and transmission electron microscopy (TEM) images demonstrate the successful synthesis of Zn2GeO4/Mg-MOF-74 composites. The infrared spectra and TEM images indicate a close interaction between Zn2GeO4 and Mg-MOF-74, which is attributed to tetramethylammonium hydroxide (TMAOH) adsorbed on Zn2GeO4 and interacts with 2,5-dioxide-1,4-benzenedicarboxylate (H4DOBDC) from Mg-MOF-74. The CO2 adsorption isotherms illustrate that the incorporation of Mg-MOF-74 into Zn2GeO4 nanorods improved the adsorption of CO2. Only with water as the sacrificial agent, the hydrothermally prepared Zn2GeO4/Mg-MOF-74 catalyst exhibited a superior performance for the conversion of CO2 into carbon monoxide compared to that of single Zn2GeO4 or a physical mixture of Zn2GeO4/Mg-MOF-74, which is attributed to its higher adsorption capacity for CO2 and reduced recombination of photogenerated electron–hole pairs. In situ photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) further demonstrated that the Zn2GeO4/Mg-MOF-74 catalyst exhibits superior charge-transfer properties. This work may provide a useful strategy to design novel and efficient photocatalysts to reduce the atmospheric concentration of CO2.