Enhancing CO₂ Hydrogenation Using a Heterogeneous Bimetal NiAl-Deposited Metal-Organic Framework NU-1000: Insights...

The hydrogenation of CO₂ to high-value-added liquid fuels is crucial for greenhouse gas emission reduction and optimal utilization of carbon resources. Developing supported heterogeneous catalysts is a key strategy in this context, as they offer well-defined active sites for in-depth mechanistic studies and improved catalyst design. Here, we conducted extensive first-principles calculations to systematically explore the reaction mechanisms for CO₂ hydrogenation on a heterogeneous bimetal NiAl-deposited metal-organic framework (MOF) NU-1000 and its catalytic performance as atomically dispersed catalysts for CO₂ hydrogenation to formic acid (HCOOH), formaldehyde (H₂CO), and methanol (CH₃OH). The present results reveal that the presence of the NiAl-oxo cluster deposited on NU-1000 efficiently activates H₂, and the facile heterolysis of H₂ on Ni and adjacent O sites serves as a precursor to the hydrogenation of CO₂ into various C1 products HCOOH, H₂CO, and CH₃OH. Generally, H₂ activation is the rate-determining step in the entire CO₂ hydrogenation process, the corresponding relatively low free energy barriers range from 14.5 to 15.9 kcal/mol, and the desorption of products on NiAl-deposited NU-1000 is relatively facile. Although the Al atom does not directly participate in the reaction, its presence provides exposed oxygen sites that facilitate the heterolytic cleavage of H₂ and the hydrogenation of C1 intermediates, which plays an important role in enhancing the catalytic activity of the Ni site. The present study demonstrates that the catalytic performance of NU-1000 can be finely tuned by depositing heterometal-oxo clusters, and the porous MOF should be an attractive platform for the construction of atomically dispersed catalysts.