In Situ Transformation of ZIF-8 into Porous Overlayer on Ru/ZnO for Enhanced Hydrogenation Catalysis

Supported metal catalysts play a significant role in heterogeneous catalysis in liquid phase reaction systems, but they usually suffer from a stability problem. Encapsulation of active metal species without the compromise of catalytic performance has been considered as an effective strategy. Here, we report an ultrastable Ru-based catalyst with particle size of around 1.1 nm for selective hydrogenation reaction. The highly dispersed Ru species are covered by the in situ formed porous N-C-ZnO overlayer, which is induced through the transforming of ZIF-8 shell that derives from a ZnO substrate. The resulting Ru/ZnO@N-C-ZnO catalyst can exhibit good stability in the hydrogenation of p-chloronitrobenzene after 20 cyclic runs with 100% selectivity toward p-chloroaniline. Comparatively, the naked Ru/ZnO catalyst with larger Ru particles shows serious metal leaching issue with inferior stability and poor selectivity. It is revealed that the excellent performance of Ru/ZnO@N-C-ZnO is attributed to the porous overlayer, which strengthens the bonding of Ru nanoparticles on ZnO.