Green Synthesis of MOF-Based Materials for Electrochemical Reduction of Carbon Dioxide.

Porous ZIF-8 and ZIF-67 were synthesized via a green steam-assisted dry-gel technique and investigated as potential catalysts for CO electroreduction. The synthesis conditions are found to significantly influence the growth of these metal-organic frameworks (MOFs). Notably, the water content employed during synthesis plays a crucial role in shaping the morphological properties of ZIF-8. Specifically, a moderate water content results in the formation of uniform ZIF-8 with a size distribution ranging from 240-440 nm. During CO electroreduction, these morphological properties exert substantial effects on the selectivity for CO formation, thereby facilitating the production of syngas with adjustable CO: H ratios. This feature holds promise for the widespread adoption of syngas as a clean alternative to fossil fuels, offering potential benefits for electricity generation and liquid fuel production. Despite sharing similar structural properties with ZIF-8, ZIF-67 exhibits distinct performance characterized by its limited selectivity for CO electroreduction. This discrepancy is attributed to the different metal centers of the two MOFs, resulting in the distinct activation of CO and HO molecules and their further reduction. This finding highlights the critical role of metal centers in MOF-based materials for electrocatalysis application.