Gribov Evgueni N, Cocina Donato, Spoto Giuseppe, Bordiga Silvia, Ricchiardi Gabriele, Zecchina Adriano
NIS (Nanostructured Interfaces and Surfaces) Center of Excellence (Dipartimento di Chimica IFM, Università di Torino), Via P. Giuria 7, I-10125, Torino, Italy.
Phys Chem Chem Phys. 2006 Mar 14;8(10):1186-96. doi: 10.1039/b513367j. Epub 2006 Jan 4.
The adsorption of Ar, H2, O2, N2 and CO on (H,Na)-Y zeolite (Si/Al = 2.9, H+/Na+ approximately 5) has been studied at variable-temperature (90-20 K) and sub-atmospheric pressure (0-40 mbar) by FTIR spectroscopy. Unprecedented filling conditions of the zeolite cavities were attained, which allowed the investigation of very weakly adsorbed species and of condensed, liquid-like or solid-like, phases. Two pressure regimes were singled out, characterized by: (i) specific interaction at low pressure of the probe molecules (P) with the internal Brønsted and Lewis sites, and (ii) multilayer adsorption at higher pressure. In the case of CO the perturbation of the protonic sites located inside the sodalite cages was also observed. As the molecule is too large to penetrate the sodalite cage, the perturbation is thought to involve a proton jump tunneling mechanism. The adsorption energy for the (HF)OH...P (P = Ar, H2, O2, N2 and CO) specific interaction involving the high frequency Brønsted acid sites exposed in the supercages was derived following the VTIR (variable temperature infrared spectroscopy) method described by E. Garrone and C. Otero Areán (Chem. Soc. Rev., 2005, 34, 846).
通过傅里叶变换红外光谱（FTIR），在可变温度（90 - 20 K）和低于大气压（0 - 40 mbar）的条件下，研究了Ar、H₂、O₂、N₂和CO在（H,Na）-Y沸石（Si/Al = 2.9，H⁺/Na⁺约为5）上的吸附情况。实现了前所未有的沸石空腔填充条件，这使得能够研究吸附非常弱的物种以及凝聚态、类似液态或固态的相。区分出了两种压力状态，其特征分别为：（i）在低压下探针分子（P）与内部布朗斯台德和路易斯位点的特定相互作用，以及（ii）在较高压力下的多层吸附。对于CO，还观察到了位于方钠石笼内的质子位点的扰动。由于该分子太大而无法穿透方钠石笼，这种扰动被认为涉及质子跳跃隧穿机制。遵循E. Garrone和C. Otero Areán（《化学学会评论》，2005年，34卷，846页）描述的VTIR（可变温度红外光谱）方法，得出了涉及超笼中暴露的高频布朗斯台德酸位点的（HF）OH...P（P = Ar、H₂、O₂、N₂和CO）特定相互作用的吸附能。
