One-Pot Method Synthesis of Bimetallic MgCu-MOF-74 and Its CO(2) Adsorption under Visible Light

[Image: see text] A magnesium-based metal–organic framework (Mg-MOF-74) exhibits excellent CO(2) adsorption under ambient conditions. However, the photostability of Mg-MOF-74 for CO(2) adsorption is poor. In this study, Mg(x)Cu(1–x)-MOF-74 was synthesized by using a facile “one-pot” method. Furthermore, the effects of synthesis conditions on the CO(2) adsorption capacity were investigated comprehensively. X-ray diffraction, Fourier transform infrared, scanning electron microscopy, thermo gravimetric analysis, inductively coupled plasma atomic emission spectroscopy, ultraviolet–visible spectroscopy and photoluminescence spectroscopy, and CO(2) static adsorption–desorption techniques were used to characterize the structures, morphology, and physicochemical properties of Mg(x)Cu(1–x)-MOF-74. CO(2) uptake of Mg(x)Cu(1–x)-MOF-74 under visible light illumination was measured by the CO(2) static adsorption test combined with the Xe lamp. The results revealed that Mg(x)Cu(1–x)-MOF-74 exhibited excellent photocatalytic activity. Furthermore, the CO(2) adsorption capacity of Mg(x)Cu(1–x)-MOF-74 was excellent at a synthesis temperature and time of 398 K and 24 h in dimethylformamide (DMF)-EtOH-MeOH mixing solvents, respectively. Mg(x)Cu(1–x)-MOF-74 retained a crystal structure similar to that of the corresponding monometallic MOF-74, and its CO(2) uptake under visible light was superior to that of the corresponding monometallic MOF-74. Particularly, the CO(2) uptake of Mg(0.4)Cu(0.6)-MOF-74 under Xe lamp illumination for 24 h was the highest, up to 3.52 mmol·g(–1), which was 1.18 and 2.09 times higher than that of Mg- and Cu-MOF-74, respectively. The yield of the photocatalytic reduction of CO(2) to CO was 49.44 μmol·g(cat)(–1) over Mg(0.4)Cu(0.6)-MOF-74 under visible light for 8 h. Mg(2+) and Cu(2+) functioned as open alkali metal that could adsorb and activate CO(2). The synergistic effect between Mg and Cu metal strengthened Mg(x)Cu(1–x)-MOF-74 photostability for CO(2) adsorption and broadened the scope of its photocatalytic application. The “bimetallic” strategy exhibits considerable potential for use in MOF-based semiconductor composites and provides a feasible method for catalyst design with remarkable CO(2) adsorption capacity and photocatalytic activity.