Engineering the core–shell structure CoMnOx@OTS cubic catalyst with excellent water resistance for low-temperature catalytic combustion of VOCs†

Abstract

The design of core–shell structure catalysts with excellent activity, stability and water resistance is one of the effective strategies to realize their application in catalytic combustion of VOCs. Since octadecyltrichlorosilane (OTS) is an excellent hydrophobic coating, it was used to prepare superhydrophobic surfaces by forming hydrophobic monolayers on the surface of CoMnO_x nanostructured templates. The CoMnO_x@OTS core–shell structures were successfully constructed by overcoating OTS on the surface of CoMnO_x-MOF nanocubes and evaluated for the catalytic combustion of toluene. The thickness of the CoMnO_x@OTS cubic crystal was adjusted by controlling the content of OTS (2 wt%, 4 wt% and 10 wt%). Due to the synergistic effect between CoMnO_x and OTS, CoMnO_x@OTS-1 exhibited superior catalytic activity, stability and water resistance. The catalytic activity of CoMnO_x@OTS-1 was consistently maintained at about 90% in the presence of 5 vol% H₂O. The content of the OTS hydrophobic layer at 2 wt% reached the optimum water resistance. This is mainly attributed to the role and contribution of the hydrophobic functional group –OH from the OTS surface, which can greatly prevent the adsorption of water molecules on the active site. This work reveals new ideas for the preparation of core–shell structured cubic crystals using hydrophobic layer-coated bimetallic oxides, as well as a deeper understanding of the catalytic oxidation of toluene.