Ab Initio Study of Metal Oxo-Trimer Nanoporous MOF Building Units for the Catalytic Conversion of CO2 to Methanol

Seeking catalysts with low overpotential is crucial to achieve efficient (photo)electrochemical CO2 reduction. Metal- organic frameworks (MOFs) with coordinatively unsaturated sites (CUSs) are promising candidates for this purpose. Density functional theory calculations explored the reaction mechanisms and activities for a series of metal oxo-trimer nodes within MOFs for catalytic CO2 reduction to methanol. We first demonstrate that all investigated systems fulfill the thermodynamic requirement for CO2 reduction regardless of the pH value. Then, we investigate the minimum energy pathway for CO2 reduction over a Fe-only system with experimentally proved activity as a benchmark. In comparison with Fe (II), Co(II) and Ni(II) lead to equivalent or even better catalytic activity with Ni(II) the most active metal, whereas Cu(I), Zn(II), Cd(II), Ti(III), Y(III) and Ce(III) show poor performance. Finally, we found that the stability of the intermediate species *COOH is a reliable descriptor to rank the catalytic activity of these oxo-trimers, and the origin is analyzed. Our computational efforts not only deliver a fundamental understanding of CO2 reduction process over CUSs in MOFs but also provide theoretical guidance for rational design of highly active catalysts for (photo)electrochemical CO2 reduction based on MOFs containing metal oxo-trimer nodes.

Automated summary

The search for catalysts with low overpotential is crucial for efficient CO2 reduction, and metal-organic frameworks (MOFs) with coordinatively unsaturated sites (CUSs) are promising candidates. Density functional theory calculations explored the reaction mechanisms and activities for a series of metal oxo-trimer nodes within MOFs for catalytic CO2 reduction to methanol. It was found that Ni(II) exhibited the highest catalytic activity, while Cu(I), Zn(II), Cd(II), Ti(III), Y(III), and Ce(III) showed poor performance. The stability of the intermediate species *COOH was identified as a reliable descriptor for ranking the catalytic activity.