Hierarchically organized metal supported carbon catalysts for C-C bond forming reactions

The preparation of heterogeneous catalysts is decisive to the development of catalytic processes that are environmentally acceptable. Therefore, the methodology used in the preparation of such catalysts is a key factor in the development of high catalytic activity and with concern to environmental value. Herein, we report the design of catalysts by dispersing nanoparticles of cobalt oxide (Co3O4) on micrometric supports of zinc oxide (ZnO) and activated carbon (AC) using a fast and green methodology free of waste and solvents and with a low-energy consumption. In particular, the partial reaction that takes place, at room temperature, between both metal oxides and between these oxides and AC, due to proximity and diffusion effects of the corresponding materials, results in the formation of different interfaces (ZnCo, ZnAC, CoAC Co-Co). Specifically, such interfaces are new reactive surfaces that lead to very interesting and innovative properties. Thus, depending on its application, it is possible to control and modify the catalytic properties (activity / conversion / selectivity) of a solid by tuning surface and interface. This fact is proved in the model reaction of Knoevenagel condensation between aldehydes and malonic esters. Therefore, our results prove that controlling the interfaces is a feasible way to achieve in the Knoevenagel condensation, which is a reaction widely used in the formation of C-C bonds for the organic synthesis of important intermediates and final products.

Automated summary

The preparation of heterogeneous catalysts is crucial for the development of environmentally friendly catalytic processes. In this study, a fast and green method was used to disperse cobalt oxide nanoparticles on micro-sized supports of zinc oxide and activated carbon. The reaction between these materials at room temperature resulted in the formation of different interfaces, leading to unique catalytic properties. The results demonstrate that controlling the interfaces is a feasible way to achieve control in catalytic reactions. This is particularly important for the formation of important intermediates and final products in organic synthesis.