Li Guangchao, Yoskamtorn Tatchamapan, Chen Wei, Foo Christopher, Zheng Jianwei, Tang Chiu, Day Sarah, Zheng Anmin, Li Molly Meng-Jung, Tsang Shik Chi Edman
Wolfson Catalysis Centre, Department of Chemistry, University of Oxford, Oxford, OX1 3QR, UK.
Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong.
Angew Chem Int Ed Engl. 2022 Jul 4;61(27):e202204500. doi: 10.1002/anie.202204500. Epub 2022 May 12.
Zeolites have found tremendous applications in the chemical industry. However, the dynamic nature of their active sites under the flow of adsorbate molecules for adsorption and catalysis is unclear, especially in operando conditions, which could be different from the as-synthesized structures. In the present study, we report a structural transformation of the adsorptive active sites in SAPO-34 zeolite by using acetone as a probe molecule under various temperatures. The combination of solid-state nuclear magnetic resonance, in situ variable-temperature synchrotron X-ray diffraction, and in situ diffuse-reflectance infrared Fourier-transform spectroscopy allow a clear identification and quantification that the chemisorption of acetone can convert the classical Brønsted acid site adsorption mode to an induced Frustrated Lewis Pairs adsorption mode at increasing temperatures. Such facile conversion is also supported by the calculations of ab-initio molecular-dynamics simulations. This work sheds new light on the importance of the dynamic structural alteration of active sites in zeolites with adsorbates at elevated temperatures.
沸石在化学工业中有着广泛的应用。然而，在吸附质分子流动下其活性位点在吸附和催化过程中的动态性质尚不清楚，尤其是在实际操作条件下，这可能与刚合成时的结构不同。在本研究中，我们报道了在不同温度下以丙酮作为探针分子时，SAPO - 34沸石吸附活性位点的结构转变。固态核磁共振、原位变温同步辐射X射线衍射和原位漫反射红外傅里叶变换光谱的结合，使得能够清晰地识别和量化：随着温度升高，丙酮的化学吸附可将经典的布朗斯台德酸位点吸附模式转变为诱导的受阻路易斯酸碱对吸附模式。从头算分子动力学模拟计算也支持了这种 facile 转变。这项工作为高温下沸石中活性位点与吸附质的动态结构改变的重要性提供了新的见解。
