Ti(IV)-MOF with Specific Facet-Ag Nanoparticle Composites for Enhancing the Photocatalytic Activity and Selectivity of CO 2 Reduction.

Metal nanoparticles deposited in the photocatalyst not only can serve as a cocatalyst but also can act as a light harvester to extend the light absorption, resulting from the surface plasmon resonance (SPR). In this study, we deposited silver nanoparticles (Ag NPs) onto NH 2 -MIL-125(Ti) with exposed specific facets and achieved effectively improved activity and selectivity for photocatalytic CO 2 reduction. Loading Ag NPs on the exposed {111} facets of NH 2 -MIL-125(Ti) generates a highly effective composite catalyst for the photoreduction of CO 2 , resulting in the maximal CO and CH 4 yields of 26.7 and 63.3 μmol g -1 h -1 , respectively, which are 2.2- and 16.2-fold those of the NH 2 -MIL-125(Ti) exposing {111} facets, and a CH 4 selectivity of 90.5%. Incorporation of Ag NPs not only optimizes the electronic structure of the photocatalyst but also suppresses the recombination of photogenerated electron-hole pairs. This study provides an exciting example for creating and understanding metal-decorated facet-dependent effects on metal-organic frameworks (MOFs) for photocatalytic reactions.