Tailoring Crystal Facets of Metal–Organic Layers to Enhance Photocatalytic Activity for CO₂ Reduction

Abstract

It is common that different crystal facets in metal and metal oxide nanocrystals display different catalytic performances, whereas such phenomena have been rarely documented in metal-organic frameworks (MOFs). Herein, we demonstrate for the first time that a nickel metal-organic layer (MOL) exposing rich (100) crystal facets (Ni-MOL-100) shows a much higher photocatalytic CO₂ -to-CO activity than the one exposing rich (010) crystal facets (Ni-MOL-010) and its bulky counterpart (bulky Ni-MOF), with a catalytic activity up to 2.5 and 4.6 times more active than Ni-MOL-010 and bulky Ni-MOF, respectively. Theoretical studies reveal that the two coordinatively unsaturated Ni^II ions with a close distance of 3.50 Å on the surface of Ni-MOL-100 enables synergistic catalysis, leading to more favorable energetics in CO₂ reduction than that of Ni-MOL-010.