Two routes, one framework: Tuning acidity and catalytic activity of Zr(IV) and Hf(IV)-doped hollow silica nanospheres
(2026) Chemical Engineering Journal — Vol. 547, p. 180189 (2026)
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- The valorization of waste-derived feedstocks is a pertinent approach to develop sustainable routes for energy and chemical production within a circular economy framework. In this context, the acid-catalyzed conversion of glycerol to solketal and ethyl levulinate to γ-valerolactone have attracted significant attention, as these processes require catalysts with different Lewis (L) and Brønsted (B) acid sites ratios. Herein, we investigated the activity-acidity correlation of a series of metal(IV) hollow silica nanospheres. The catalysts were synthesized via a sol-gel method using both co- and post-synthetic approaches to add tetravalent metal cations, namely Zr4+ and Hf4+. The synthetic pathway allowed to tune the L/B ratio of the acid sites of the materials, assessed by 31P solid-state NMR spectroscopy, using trimethylphosphine as a probe molecule. Catalytic tests for glycerol ketalization and ethyl levulinate hydrogenation revealed a clear correlation between acidity and catalytic performance. The higher L/B ratios of the post-synthesized materials and stronger Lewis acid sites favored γ-valerolactone production, whereas lower L/B ratios enhanced solketal formation, where the co-synthesized solids displayed the best performances. The higher calculated Natural Bond Orbital (NBO) charge of Hf4+ within the silica framework compared to Zr4+ allowed to explain its stronger Lewis acid character, hence mainly depending on the nature of the metal cations. Leaching and recyclability experiments confirmed the stability and the heterogeneous nature of the catalysts.
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Saitta, M., Morena, A., Rubirigi, C., Ngueteu, M. L. T., Tomer, R., Fusaro, L., Champagne, B., Hermans, S., & Aprile, C. (2026). Two routes, one framework: Tuning acidity and catalytic activity of Zr(IV) and Hf(IV)-doped hollow silica nanospheres. Chemical Engineering Journal, 547, 180189. https://doi.org/10.1016/j.cej.2026.180189 (Original work published 2026)