An unprecedented type of Hf-doped silica nanotubes was synthesized using a straightforward one-pot sol–gel procedure. The well-defined nanotubes with a diameter of 14–20 nm exhibited high specific surface area and a widely open texture. The method – involving a key pH adjustment step – allowed a quantitative insertion of hafnium in the materials (Si/Hf = 74) and favored the insertion of Hf as dispersed species. Depending on the synthesis parameters, the chemical environment around Hf was modified, as evidenced by XPS, NH₃-TPD and NH₃-IR. Hf-doped silica nanotubes showed excellent activity in the conversion of glycerol to solketal, a reaction of high relevance in the context of biorefineries. Importantly, the turnover frequency and the acidity were unambiguously correlated with the insertion of Hf in the silica matrix. The best catalyst was proven to be stable and recyclable, and this sustainable reaction was also amenable to further catalytic enhancement upon optimized reaction conditions.

使用简单的一锅溶胶-凝胶程序合成了一种前所未有的 Hf 掺杂二氧化硅纳米管。直径为 14-20 nm 的定义明确的纳米管表现出高比表面积和广泛开放的纹理。该方法 - 涉及一个关键的 pH 调节步骤 - 允许在材料中定量插入铪 (Si/Hf = 74)，并有利于将 Hf 作为分散物质插入。根据合成参数，Hf 周围的化学环境发生了改变，如 XPS、NH ₃ -TPD 和 NH _3所示-红外。掺 Hf 的二氧化硅纳米管在将甘油转化为溶缩醇方面表现出优异的活性，这是在生物精炼厂环境中高度相关的反应。重要的是，周转频率和酸度与二氧化硅基质中 Hf 的插入明确相关。最好的催化剂被证明是稳定和可回收的，而且这种可持续的反应也可以在优化反应条件下进一步增强催化作用。