Bifunctional Catalysts with Core–Shell Distributed ZrO<sub>2</sub> and Co Nanoparticles Derived from MOF-on-MOF Heterostructures for Economical One-Pot Tandem CO<sub>2</sub> Fixation
Ze Qin, Liyu Chen, Yingwei Li, Kui Shen
Abstract
The N -formylation of aryl amines with CO 2 is an emerging strategy to simultaneously reduce carbon emission and produce high-value formamides. Considering that aryl amines are usually produced from the hydrogenation of their corresponding nitroarenes in the chemical industry, the one-pot tandem hydrogenation–formylation of nitroarenes with CO 2 to formamides is obviously a much more economical but still unexploited strategy for efficient CO 2 fixation. Herein, we report the rational synthesis of bifunctional catalysts with core–shell distributed ZrO 2 and Co nanoparticles (NPs) from the controlled pyrolysis of a ZIF-67-on-UiO-66 heterostructure for this one-pot tandem reaction. To fabricate such MOF-on-MOF heterostructures, we develop a facile surfactant-assisted strategy to seed ZIF-8 nuclei on the UiO-66 surface, followed by the successful growth of a thickness-controlled ZIF-67 shell on the UIO-66 core. Based on further pyrolysis, the highly mesoporous derivants with core–shell distributed ZrO 2 and Co NPs can be obtained, of which the reductive Co and Lewis basic ZrO 2 can serve as highly active sites for the hydrogenation of nitroarenes and the N -formylation of aryl amines with CO 2, respectively, due to their favorable electronic structures and good mass diffusion of reactants/intermediates. Impressively, the optimized core–shell catalyst achieves a much higher yield of N -(4-methoxyphenyl)formamide (99.5%) than its ZrO 2 /C (0%), Co-NC (14.1%), and physically mixed counterparts (52.3%) for the one-pot tandem hydrogenation–formylation between 4-nitroanisole and CO 2 with good recyclability and a broad substrate scope, shedding light on the rational design of efficient bifunctional catalysts for this tandem CO 2 fixation reaction.