A Co-MOF-Derived Co 3 O 4 /C/SiO 2 Nanocomposite as a Multifunctional Heterogeneous Catalyst for Hydrogenation of Nitroarenes and Organic Dyes

We report the synthesis of a newer heterogeneous nanostructured catalyst, Co 3 O 4 /C/SiO 2 (ZCCO) or Co 3 O 4 /SiO 2 (ZCO), prepared via the pyrolysis of a ZnO/ZIF-9/SiO 2 (ZOZFS) composite under controlled conditions. ZnO evaporation during pyrolysis introduced structural defects that enhanced the catalytic performance. The material was thoroughly characterized by physicochemical, optical, electrochemical, spectroscopic, and microscopic techniques including DRS, ESR, PL, CV, and EIS, revealing excellent chemical, thermal, photochemical, and electrochemical properties with low band gaps (1.38 and 1.85 eV). ZCCO demonstrated high efficiency as a multifunctional heterogeneous catalyst for the hydrogenation of nitroarenes and azo dyes like methylene blue (MB) and methyl orange (MO) in water, with excellent recyclability over six cycles without significant loss in its activity. The pseudo-first-order rate constants were estimated as 15 × 10 –3 s –1, 15 × 10 –2 min –1, and 3 × 10 –2 s –1 for 4-nitrophenol, MO, and MB, respectively. The findings highlight ZCCO as a promising non-noble metal-based catalyst for sustainable chemical transformations.