Novel approach for catalytic conversion of carbon dioxide (CO2)

Abstract: The abundance of CO₂ in the atmosphere makes it a readily available feedstock to produce chemicals and materials, though it has yet to achieve optimal development. Even though syngas (CO + H₂) hydrogenation to methanol is an established industrial process, when the same catalytic system based on Cu/ZnO/Al₂O₃ is employed with CO₂, the water formed as a by-product reduces the activity, stability, and selectivity of the process. Here, we explored the potential of phenyl polyhedral oligomeric silsesquioxane (POSS) as hydrophobic support of Cu/ZnO for direct CO₂ hydrogenation to methanol. Mild calcination of the copper-zinc-impregnated POSS material affords the formation of CuZn-POSS nanoparticles able to reach a 3.8% yield of methanol with a 4.4% of CO₂ conversion and with selectivity as high as 87.5% within 18 hours. The structural investigation of the catalytic system reveals that CuO/ZnO are electron withdrawers in the presence of the siloxane cage of POSS. The catalytic system metal-POSS is stable and recyclable under H₂ reduction and CO₂/H₂ conditions. The increased number of phenyls in the structure of POSS results in an increased hydrophobic character that plays a decisive role in the methanol formation after comparison with CuO/ZnO supported on reduced graphene oxide (RGO) with 0% selectivity to methanol under the study conditions. The materials were characterized using SEM, TEM, ATR FT-IR, XPS, powder XRD, FTIR, BET, contact angle, and TGA. The gaseous products were characterized by GC coupled with TCD/FID