State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry , Jilin University , Changchun 130012 , People's Republic of China.
Key Laboratory of Advanced Molecular Engineering Materials, College of Chemistry and Chemical Engineering , Baoji University of Arts and Sciences , Baoji 721013 , People's Republic of China.
J Am Chem Soc. 2018 Apr 11;140(14):4770-4773. doi: 10.1021/jacs.8b00093. Epub 2018 Apr 3.
In the hydrothermal synthesis of highly ordered mesoporous silica material SBA-15, strong acid is typically required to catalyze the hydrolysis and condensation of silica species. Meanwhile, under strongly acidic conditions, the transition metal ions, e.g., iron ions, are difficult to incorporate into SBA-15 because of the facile dissociation of Fe-O-Si bonds. Here, we demonstrate an acid-free green synthetic strategy for the synthesis of highly ordered mesoporous SBA-15 and Fe-SBA-15 with the assistance of hydroxyl free radicals that are generated by physical or chemical methods. The prepared materials exhibit a large specific surface area compared to the counterparts prepared by conventional method under acidic conditions. Moreover, Fe-SBA-15 shows high metal loading efficiency as over 50%. Density functional theory calculations suggest that the hydroxyl free radicals exhibit higher catalytic activity than H ions for the hydrolysis of tetraethyl orthosilicate. This radical-facilitated synthesis approach overcomes the challenge to the direct synthesis of highly ordered SBA-15 and Fe-SBA-15 without adding any acid, providing a facile and environmentally friendly route for future large-scale production of ordered mesoporous materials.
在高度有序介孔硅材料 SBA-15 的水热合成中，通常需要强酸来催化硅物种的水解和缩合。同时，在强酸性条件下，过渡金属离子（如铁离子）难以掺入 SBA-15，因为 Fe-O-Si 键易于解离。在这里，我们展示了一种无酸的绿色合成策略，用于在羟基自由基的协助下合成高度有序的介孔 SBA-15 和 Fe-SBA-15，羟基自由基可以通过物理或化学方法产生。与在酸性条件下通过传统方法制备的对应物相比，所制备的材料具有更大的比表面积。此外，Fe-SBA-15 表现出超过 50%的高金属负载效率。密度泛函理论计算表明，羟基自由基对正硅酸乙酯的水解表现出比 H 离子更高的催化活性。这种自由基促进的合成方法克服了直接合成高度有序的 SBA-15 和 Fe-SBA-15 的挑战，而无需添加任何酸，为未来有序介孔材料的大规模生产提供了一种简单、环保的途径。
