Visible light-assisted photocatalytic degradation of methylene blue by 1D/2D CdxOy clusters based on metal-organic frameworks without H2O2

Abstract

Metal-organic frameworks (MOFs) photocatalysts, which contain metal oxo-clusters and organic chromophore linkers, have high visible light absorption utilization, large porosity, specific surface area, effective photogenerated electron and hole separation capabilities. Herein, two types of CdxOy cluster complexes, namely 1D CdxOy cluster Cd-mBDC (mBDC: 1,3-benzenedicarboxylic acid) and 2D CdxOy cluster Cd-2-NH2-mBDC (2-NH2-mBDC: 2-aminoisophthalic acid) were successfully synthesized, and their photocatalytic activity were evaluated by photocatalytic degradation of methylene blue (MB) under visible light without H2O2. The 2D CdxOy cluster of Cd-2-NH2-mBDC can be simplified as a two-dimensional mesh (3.82)(32.82) topology by considering the Cd ions as connected nodes. In addition, conditional experiments showed that the clusters photocatalyst could achieve the best catalytic efficiency under initial dye concentration of 10 mg/L and pH value of 7. Compared with Cd-mBDC, the introduction of amino auxochrome in Cd-2-NH2-mBDC broadened the absorption range and improved the visible light utilization, and the rigid 2D cluster structure facilitated the transfer of photogenerated electrons and enhanced stability. For Cd-2-NH2-mBDC, the photodegradation efficiency of MB could reach 88.44% within 180 min (0.121 min−1) and basically unchanged during five-cycles degradation process. Therefore, Cd-2-NH2-mBDC displays excellent photocatalytic activity and stability for degradation of MB under visible light. Furthermore, the possible mechanism of photocatalytic degradation properties has been also deduced.