Self-assembly of CPO-27-Mg/TiO2 nanocomposite with enhanced performance for photocatalytic CO2 reduction

• CPO-27-Mg/TiO2 composite was constructed via a hydrothermal in situ growth method.
• The composite showed enhanced performance for CO2 photo-conversion.
• High adsorption toward CO2 and the existence of open alkaline sites in CPO-27-Mg led to enhanced performance.
• The reduction of H2O to H2 over CPO-27-Mg/TiO2 composite was totally inhibited.

CPO-27-Mg (also referred to as Mg2(DOBDC), DOBDC = 2,5-dioxido-1,4-benzenedicarboxylate), a Mg2+ based metal-organic framework which shows the highest CO2 uptake among the already reported MOF materials, was chosen to combine with TiO2 to form CPO-27-Mg/TiO2 nanocomposite via a hydrothermal self-assembly method. The as-obtained CPO-27-Mg/TiO2 nanocomposite is composed of TiO2 nanospheres on the spindle-shaped CPO-27-Mg microcrystal. Intimate contact between CPO-27-Mg and TiO2 nanospheres exists due to the coordination between the carboxylate groups in DOBDC and Ti4+ in TiO2. The as-obtained CPO-27-Mg/TiO2 nanocomposite exhibited enhanced performance for the photocatalytic CO2 reduction to form CO and CH4 due to its high adsorption capacity toward CO2 and the existence of open alkaline metal sites in CPO-27-Mg. By incorporating MOFs with open alkaline metal center into TiO2, the reduction of H2O to H2, a competitive reaction to photocatalytic CO2 reduction, was totally inhibited. This study highlights the promising prospect of incorporating MOFs with open alkaline metal sites into semiconductors for artificial CO2 photo-conversion.

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