Sustainable Synthesis of Formic Acid from CO2 Hydrogenation Using Pd/ZnO Catalysts Derived from a Modified Zeolitic Imidazolate Framework

CO₂ hydrogenation to formic acid is a promising strategy for CO₂ mitigation, but requires high temperatures, pressure, additives and catalysts. This study reports the synthesis of Pd/ZnO obtained through the calcination of a palladium-modified zeolitic imidazolate framework (ZIF-8), applied in the CO₂ hydrogenation to formate, under mild reaction conditions. The crystal structure, crystallite size, microstrain, and morphological properties were characterized using XRD and TEM. Crystallite size and microstrain were evaluated by Scherrer and Williamson-Hall methods. The Pd/ZnO catalyst exhibited a hexagonal wurtzite ZnO structure and Pd in the face-centered cubic (fcc) phase, with small crystallite size and few imperfections in ZnO. The catalytic activity was evaluated for CO₂ hydrogenation in the aqueous phase, yielding 52.42 µmol of formate. The results suggest that Pd species are responsible for H₂ activation, while ZnO facilitates CO₂ activation. The ZIF-derived Pd/ZnO material demonstrates potential as catalyst for CO₂ conversion, contributing to environmental mitigation and development of carbon-neutral chemical processes.

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