Constructing Interconnected Hollow Mesopore Sn-Si Mixed Oxide Microspheres by Aerosol-Assisted Alkali Treatment with Enhanced Catalytic Performance in Baeyer-Villiger Oxidation

In this work, Sn-Si mixed oxide microspheres with concave hollow morphologies were first synthesized by a simple aerosol method using the very common commercial surfactant cetyl trimethyl ammonium bromide (CTAB) as a template, and then highly interconnected mesoporous and hollow Sn-Si mixed oxide microspheres were synthesized via an alkali (NaOH) treatment in the presence of CTAB. The results show that CTAB plays a crucial role not only in forming hollow morphologies during the aerosol process, but also protecting the amorphous framework and thus preventing the excessive loss of Sn species during the NaOH treatment. More importantly, it widens mesoporous distribution and forms interconnected mesoporous channels. The catalytic performance of Baeyer–Villiger oxidation on the interconnected mesoporous and hollow Sn-Si mixed oxide microspheres with 2-adamantanone and hydrogen peroxide was 9.4 times higher than that of the sample synthesized without the addition of CTAB; 2.3 times that of the untreated parent, which was due to the excellent diffusion properties derived from the hollow and interconnected mesopore structure. This method is mild, simple, low-cost, and can be continuously produced, which has the prospect of industrial application. Furthermore, the fundamentals of this study provide new insights for the rational design and preparation of highly interlinked mesoporous and hollow metal-oxides with unique catalytic performances.