Polypyrrole reinforced ZIF-67 with modulated facet exposure and billion-fold electrical conductivity enhancement towards robust photocatalytic CO2 reduction

Abstract

A novel strategy is deployed to synthesize the ZIF-67 reinforced with polypyrrole (ZIF-67@PPy) where pyrrole monomer modulates the crystal morphology of ZIF-67. The ZIF-67@PPy demonstrated improved catalytic activity and stability for photocatalytic CO 2 reduction. The implementation of metal organic frameworks (MOFs) as the co-catalysts in hybrid photocatalytic systems puts requirements on both their charge-carrying capability and solvent stability. In the current study, in order to simultaneously promote the electrical conductivity and water stability of ZIF-67, an in-situ monomer trapping strategy is deployed to synthesize polypyrrole (PPy)-reinforced ZIF-67 ensembles. Through coordination modulation, the incremental addition of pyrrole monomers enables to alter the crystal morphology of ZIF-67 from rhombic dodecahedra to truncated rhombic dodecahedra, and further to cubes. Upon polymerization, the resulted composite, in comparison to ZIF-67, demonstrates a billion-fold conductivity enhancement, much improved chemical stability in pronated solvents, as well as largely retained specific surface area and porosity, enabling it functioning as an outstanding co-catalyst for catalyzing robust photocatalytic CO 2 reduction. Furthermore, a PPy-mediated electron harvest and relay mechanism is proposed for rationalizing the enhanced photocatalytic performance.