Silica-supported silver nanoparticles exhibit outstanding efficiency in the CO₂ hydrogenation to methyl formate in the presence of methanol under high pressure. Here, we show that ZrO₂ and Al₂O₃ supports significantly increase the catalyst activity, in line with their higher Lewis acidity. The weight time yield of methyl formate over Ag/ZrO₂ is up to 16.2 g_MF g_Ag h⁻¹ without detectable side-products, 25 times higher compared to Ag/SiO₂ at the same temperature. Transient in situ and operando DRIFTS studies uncover spillover processes of formate species from Ag onto the acidic support materials and show that the surface formates can further react with adsorbed methanol at the sites near the perimeter between Ag and the support to yield methyl formate.

Continuous synthesis of formic acid and methyl formate via CO₂ hydrogenation is demonstrated using a molecular iridium complex stably immobilized on a solid covalent triazine framework (CTF) under high-pressure conditions. Compared to formic acid synthesis, methyl formate synthesis is advantageous to enhance the selectivity and yield of formates under kinetically favorable high temperature conditions. Transient in situ vibrational spectroscopy shows that the CTF strongly interacts with CO₂ and H₂, and even activates methanol. Hence, CTF is a promising support for molecular catalysts, even under harsh supercritical and flow conditions, through its strong binding capability.

Selective hydrogenation of CO₂ into methanol is a key sustainable technology, where Cu/Al₂O₃ prepared by surface organometallic chemistry displays high activity towards CO₂ hydrogenation compared to Cu/SiO₂, yielding CH₃OH, dimethyl ether (DME), and CO. CH₃OH formation rate increases due to the metal–oxide interface and involves formate intermediates according to advanced spectroscopy and DFT calculations. Al₂O₃ promotes the subsequent conversion of CH₃OH to DME, showing bifunctional catalysis, but also increases the rate of CO formation. The latter takes place 1) directly by activation of CO₂ at the metal–oxide interface, and 2) indirectly by the conversion of formate surface species and CH₃OH to methyl formate, which is further decomposed into CH₃OH and CO. This study shows how Al₂O₃, a Lewis acidic and non-reducible support, can promote CO₂ hydrogenation by enabling multiple competitive reaction pathways on the oxide and metal–oxide interface.