Construction of Single Ni Atom-Immobilized ZIF-8 with Ordered Hierarchical Pore Structures for Selective CO2 Photoreduction

The rational construction of single-atom-modified porous metal-organic frameworks (MOFs) for efficient CO2 photoconversion is a promising avenue, yet the one that poses a significant challenge. In this study, we demonstrate the successful construction of a Ni single-atom-immobilized ZIF-8 with an ordered hierarchical (macro-micro) pore structure for highly efficient photocatalytic CO2 reduction to CO. The interpenetrated macroporous structure in microporous ZIF-8 is built up by employing polystyrene (PS) opal as a hard template, while the high stability of the framework is achieved through the double-solvent-induced crystallization. The hierarchical porous structure enables rapid mass transport and strong adsorption of CO2, while Ni single atoms as active sites and electron-trapping sites optimize the reaction energy and hinder the competitive H2 evolution. As a result, the Ni single-atom-immobilized hierarchical porous ZIF-8 achieves high stability and an activity of 4.2 mmol g-1 h-1 for CO yield with an electronic selectivity of 94%, which shows a 47-fold CO yield of that for ZIF-8. This work highlights the significance of constructing a hierarchical porous structure of MOFs and single-atom-active sites to improve the activity and selectivity of CO2 photoreduction for realizing carbon neutralization.

Automated summary

In this study, a Ni single-atom-immobilized hierarchical porous ZIF-8 catalyst is successfully constructed for efficient CO2 photoreduction to CO. The hierarchical porous structure enables rapid mass transport and strong adsorption of CO2, while the Ni single atoms act as active sites to optimize the reaction energy. This work highlights the significance of constructing a hierarchical porous structure and single-atom-active sites to improve the activity and selectivity of CO2 photoreduction.