Rational Engineering of Multilayered Co3O4/ZnO Nanocatalysts Through Chemical Transformations from Matryoshka‐Type ZIFs

Hybrid metal oxides with multilayered structures exhibit unique physical and chemical properties, particularly important to heterogeneous catalysis. However, regulations of morphology, spatial location, and shell numbers of the hybrid metal oxides still remain a challenge. Herein, binary Co3O4/ZnO nanocages with multilayered structures (up to eight layers) are prepared via chemical transformation from diverse Matryoshka-type zeolitic imidazolate frameworks (ZIFs) via a straightforward and scalable calcination method. More importantly, the obtained ZIF-derived metal oxides (ZDMOs) with versatile layer numbers exhibit remarkable catalytic activity for both gas-phase CO oxidation and CO2 hydrogenation reactions, which are directly related to the sophisticated shell numbers (i.e., Co3O4-terminated layers or ZnO-terminated layers). Particularly, in situ reflectance infrared Fourier transform spectroscopy (DRIFTS) results indicate that the promotional effects of the multilayered structures indeed exist in CO2 hydrogenation, wherein the key reaction intermediates are quite different for five-layer and six-layer ZDMOs. For instance, *HCOO is the predominant intermediate over the six-layer ZDMO; on the contrary, *H3CO is the crucial species over the five-layer ZDMO. The ZnO/Co3O4 interface should be the active sites for CO2 hydrogenation to *HCOO and *H3CO species, which are ultimately converted to the products (CH4 or methanol). Accordingly, the work here provides a convenient way to facilely engineer multilayered Co3O4/ZnO nanocomposites with precisely controlled shell numbers for heterogeneous catalysis applications.