Tailoring the crystal forms of the Ni-MOF catalysts for enhanced photocatalytic CO2-to-CO performance

While semiconductor nanocrystals with different crystal forms typically show different catalytic performances, such behavior has been scarcely documented for metal-organic frameworks (MOFs). Herein, two Ni-MOF catalysts with different crystal forms have been successfully prepared and used in photo-reduction of CO2. With a prolonged lifetime (5 h vs 2 h) and higher yield of the product CO (34 μmol vs 18 μmol), Ni-MOF(H2O) demonstrates a much better performance than Ni-MOF. Theoretical studies reveal that the adsorption energy of a CO2 molecule is more negative on Ni-MOF(H2O) than on Ni-MOF (−0.85 eV vs −0.62 eV). Furthermore, the transfer and separation of the photo-generated charge carriers are also more efficient in the Ni-MOF(H2O) system. This study not only presents a superior Ni-MOF catalyst but also promotes the fabrication of highly active catalysts for the photo-reduction of CO2.