Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University of Prague, Hlavova 2030, Prague 2, 128 00, Czech Republic.
Phys Chem Chem Phys. 2012 Feb 7;14(5):1552-69. doi: 10.1039/c2cp23237e. Epub 2011 Dec 21.
Gas adsorption on zeolites constitutes the base of many technological applications of these versatile porous materials. Quite often, especially when dealing with small molecules, individual extra-framework (exchangeable) cations are considered to be the adsorption site on which molecules coming from a gas phase form the corresponding adsorption complex. Nonetheless, while that can be the case in some instances, recent research work that combines variable temperature infrared spectroscopy with periodic DFT calculations showed that some types of adsorption sites involve two or more cations, which constitute dual and multiple cation sites, respectively. Adsorption complexes formed on these cationic adsorption sites differ in both structure and stability from those formed on a single cation alone. Examples concerning CO, CO(2) and H(2) adsorption on alkali and alkaline-earth metal exchanged zeolites are reviewed, with the double purpose of clarifying concepts and highlighting their relevance to practical use of zeolites in such fields as gas separation and purification, gas storage and heterogeneous catalysis.
沸石上的气体吸附构成了这些多功能多孔材料许多技术应用的基础。在很多情况下，特别是在处理小分子时，人们通常认为单个骨架外（可交换）阳离子是吸附位，来自气相的分子在该吸附位上形成相应的吸附配合物。然而，尽管在某些情况下可能是这样，但最近结合变温红外光谱和周期性 DFT 计算的研究工作表明，某些类型的吸附位涉及两个或更多的阳离子，它们分别构成双阳离子位和多阳离子位。在这些阳离子吸附位上形成的吸附配合物在结构和稳定性上与单独在一个阳离子上形成的吸附配合物不同。本文综述了碱金属和碱土金属交换沸石上 CO、CO(2)和 H(2)吸附的例子，其双重目的是澄清概念，并强调它们与沸石在气体分离和净化、气体储存和多相催化等领域的实际应用的相关性。
