Ahn Sang Hyun, Wang Qiang, Wang Yongxiang, Chu Yueying, Deng Feng, Hong Suk Bong
Center for Ordered Nanoporous Materials Synthesis, Division of Environmental Science and Engineering, POSTECH, Pohang, 37673, Korea.
State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, China.
Angew Chem Int Ed Engl. 2022 Jun 13;61(24):e202203603. doi: 10.1002/anie.202203603. Epub 2022 Apr 14.
A clear understanding of the acidic properties of bridging Si-OH-Al groups containing crystallographically different oxygen atoms in zeolites is a prerequisite for optimizing their performance as industrial solid catalysts and developing new acid-catalyzed reactions, but presents many challenges. Here, we report the direct observation of yet unrecognized bridging Si-OH-Al groups in the LTA zeolite whose oxygen atoms are crystallographically different from those of already known Brønsted acid sites. We also report that the creation of a crystallographically particular type of bridging OH groups in zeolites and its concentration and acid strength can vary strongly with the content and spatial distribution of framework Al atoms, thus being synthetic in nature, which has been rationalized in terms of the secondary building unit concept.
清楚了解沸石中含有晶体学上不同氧原子的桥连Si-OH-Al基团的酸性性质，是优化其作为工业固体催化剂的性能以及开发新的酸催化反应的先决条件，但这也带来了许多挑战。在此，我们报告了在LTA沸石中直接观察到尚未被认识的桥连Si-OH-Al基团，其氧原子在晶体学上与已知的布朗斯特酸位点的氧原子不同。我们还报告称，沸石中晶体学上特定类型的桥连OH基团的产生及其浓度和酸强度会随骨架Al原子的含量和空间分布而强烈变化，因此本质上是可合成的，这已根据二级结构单元概念得到了合理的解释。
