Porous Host-Guest MOF-Semiconductor Hybrid with Multisites Heterojunctions and Modulable Electronic Band for Selective Photocatalytic CO2 Conversion and H2 Evolution.

ABSTRACT

Optimizing catalysts for competitive photocatalytic reactions demand individually tailored band structure as well as intertwined interactions of light absorption, reaction activity, mass, and charge transport.  Here, a nanoparticulate host-guest structure is rationally designed that can exclusively fulfil and ideally control the aforestated uncompromising requisites for catalytic reactions. The all-inclusive model catalyst consists of porous Co3 O4 host and Znx Cd1- x S guest with controllable physicochemical properties enabled by self-assembled hybrid structure and continuously amenable band gap. The effective porous topology nanoassembly, both at the exterior and the interior pores of a porous metal-organic framework (MOF), maximizes spatially immobilized semiconductor nanoparticles toward high utilization of particulate heterojunctions for vital charge and reactant transfer. In conjunction, the zinc constituent band engineering is found to regulate the light/molecules absorption, band structure, and specific reaction intermediates energy to attain high photocatalytic CO2 reduction selectivity. The optimal catalyst exhibits a H2 -generation rate up to 6720 µmol g-1 h-1 and a CO production rate of 19.3 µmol g-1 h-1 . These findings provide insight into the design of discrete host-guest MOF-semiconductor hybrid system with readily modulated band structures and well-constructed heterojunctions for selective solar-to-chemical conversion.