Hydrogenation of Carbon Dioxide to Formate Using a Cadmium-Based Metal–Organic Framework Impregnated with Nanoparticles

The burning of fossil fuels to meet energy demands has increased carbon dioxide (CO₂ ) in the atmosphere, causing global warming and associated climate change. Therefore, new materials are being developed to capture CO₂ effectively, limit its impact on the environment, and store and/or utilise it as an abundant C1 building block. In this study, we investigate a cadmium(II) metal–organic framework, [Cd(bdc)(DMF)]_n (MOF1), synthesised by treating benzene-1,4-dicarboxylic acid with four equivalents of [Cd(NO₃ )₂ ]. MOF1 was then used to support Pd, Ni, and Pt nanoparticles in forming MOF1/Pd MOF1/Ni and MOF1/Pt, respectively. These MOF-based materials were characterised using powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR), energy-dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HR-TEM). MOF1/Pd MOF1/Ni and MOF1/Pt proved highly active in the catalytic hydrogenation of CO₂ to formate selectively; in contrast, MOF1 did not hydrogenate CO₂ to formate. The MOF1/Pd, MOF1/Ni, and MOF1/Pt catalysts produced formate selectively, with the highest TON of 1500 (TOF of 69 h⁻¹ ) achieved using MOF1/Pd as the catalyst at 170^◦C within 2 h. A formate yield of 98% was obtained, which demonstrates that the combination of nanoparticles and MOFs greatly enhances the catalytic activity of the active sites.