Design and Synthesis of NiO@Co₃O₄@ZSM-5 Heterogeneous Multitask Hollow Structures for Tandem Catalysis

Precipitation and impregnation procedures unevenly distribute metals on zeolite, limiting chemical transformation in Lewis-acid, Brönsted-acid and metal-catalyzed tandem reactions. Although, heterogeneous multitask transition metals oxides@zeolites are promising catalysts for sustainable processes; nevertheless, synthesis is fascinating and complex. Herein, the construction of purposely designed multitask materials segregated in selective shells reveals the remarkable spatial organization of metals-zeolite, resulting in them being suitable for a wide range of tandem reactions. The synthesis of multi-site catalysts begins with a universal wet chemistry approach that yields nickel oxide (NiO) crystals. Then, the NiO crystals are stabilized using cationic dodecyltrimethylammonium bromide, followed by achieving cross-linking carbon growth by emulsion polymerization of glucose in hydrothermal treatment to yield uniformed NiO@carbon spheres (NiO@CSs). Next, sequential adsorption of cobalt cations and colloidal ZSM-5 (1% in H₂O, mass fraction), followed by calcination in air, yielded NiO@cobalt oxide@zeolite denoted as NiO@Co₃O₄@ZEO hollow spheres. The hollowing mechanism and materials segregation within shells are revealed by scanning and transmission electron microscopy, thermogravimetric analysis, and X-ray diffraction. The finding advances the rational synthesis of heterogenous core-shell hollow structures for various gas phase catalytic tandem reactions to yield valuable chemicals.