Double-shelled hollow mesoporous silica nanospheres as an acid-base bifunctional catalyst for cascade reactionsElectronic supplementary information (ESI) available: Fig. S1-S5. See DOI: 10.1039/c7nj04670g

• Main Authors: You, Chunzi, Yu, Chunqi, Yang, Xiaohui, Li, Yudong, Huo, Hang, Wang, Zhe, Jiang, Yanqiu, Xu, Xianzhu, Lin, Kaifeng
• Format: Journal Article
• Language: English
• Published: 12.03.2018
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c7nj04670g

Double-shelled hollow mesoporous silica nanospheres (HMS-Al@MS-NH 2 ) have been successfully obtained using the shell-by-shell strategy, by which the isolated acidic (-Al) and basic (-NH 2 ) sites were spatially incorporated in different shells. The characterization results indicate that HMS-Al@MS-NH 2 possesses a hollow void and mesopores in both shells, and this favors the mass transfer of the reactants and products. As a spatially isolated acid-base bifunctional catalyst, HMS-Al@MS-NH 2 proved to exhibit high catalytic performances in the one-pot deacetalization-Knoevenagel cascade reaction. Under the optimized conditions, the conversion of benzaldehyde dimethyl acetal approached ca. 100% for 2 h at 110 °C, mainly attributed to the isolated acidic and basic sites and to the hollow architecture and mesopores in the shells. Notably, the catalyst could be reused up to 4 times without obvious loss of activity and selectivity, indicating the high stability of the active acidic and basic sites in the framework. Moreover, the double-shelled hollow mesoporous silica spheres are also active and selective for the other cascade sequence of the deacetalization-Henry reaction. Double-shelled hollow mesoporous silica nanospheres as an acid-base bifunctional catalyst for cascade reactions.