Enhancement of visible-light-driven CO2 reduction performance using an amine-functionalized zirconium metal-organic framework

By employing a conjugated amine-functionalized dicarboxylic ligand (H2L = 2,2'-diamino-4,4'-stilbenedicarboxylic acid, H(2)SDCA-NH2), we have successfully synthesized and characterized a porous and visible light responsive zirconium metal-organic framework ([Zr6O4(OH)(4)(L)(6)] center dot 8DMF, denoted as Zr-SDCA-NH2). This Zr-MOF showed good chemical stability and broad visible light absorption with an absorption edge at about 600 nm. When used as a photocatalyst, Zr-SDCA-NH2 exhibits visible-light activity for CO2 reduction with a formate formation rate of 96.2 mu mol h(-1) mmol(MOF)(-1), which is higher than the series of reported amine-functionalized Zr-MOFs. Mott-Schottky measurements, photoluminescence study and photocatalytic experiments demonstrated that the Zr-6 oxo cluster through the LMCT process and the organic ligand both contributed to the CO2 photoreduction. This study indicates that the combination of amino groups and highly conjugated molecules is a feasible and simple strategy to extend light absorption of the organic ligand, which is beneficial for designing a visible light responsive MOF photocatalyst.