Determination of Zn Speciation, Siting, and Distribution in Ferrierite Using Luminescence and FTIR Spectroscopy,The Journal of Physical Chemistry C

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Determination of Zn Speciation, Siting, and Distribution in Ferrierite Using Luminescence and FTIR Spectroscopy
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2021-04-19 , DOI: 10.1021/acs.jpcc.1c00543
Joanna E. Olszowka ₁ , Mariia Lemishka _{1,

2} , Kinga Mlekodaj ₁ , Pavel Kubat ₁ , Dorota Rutkowska-Żbik ₃ , Jiri Dedecek ₁ , Edyta Tabor ₁

Affiliation

A methodology for the analysis of the siting of Zn²⁺ ions in extra-framework cationic sites of silicon-rich zeolite was developed and demonstrated on Zn-ferrierite samples (Si/Al 8.5, Zn/Al 0.04–0.33). This methodology is based on the FTIR spectroscopy of antisymmetric tetrahedral–octahedral–tetrahedral (T-O-T) vibrations of the zeolite framework perturbed by Zn²⁺ ions, combined with a complementary approach based on Zn²⁺ luminescence monitored by laser-induced time-resolved luminescence spectroscopy. Three vibration bands in the FTIR spectra of antisymmetric T-O-T vibrations of dehydrated zeolite reflect Zn²⁺ ligation in three extra-framework cationic sites of ferrierite zeolite. The band at 935 cm^–1 corresponds to Zn²⁺ ions in the α-site of ferrierite, the band at 917 cm^–1 correspondsto ions in β-site, and the band at 902 cm^–1 correspondsto Zn²⁺ ions in the γ-site. The extinction coefficient for quantitative analysis of Zn²⁺ ions in cationic sites was estimated and exhibited the same value for Zn²⁺ cations in all cationic sites, ε = 49.1 ± 3.8 cm·μmol^–1. In all Zn samples, Zn²⁺ siting in the β-site prevails, while Zn²⁺ ions in the γ-site are of low population or negligible. Time-resolved luminescence showed that bare Zn²⁺ ions in the extra-framework cationic sites can be distinguished from Zn²⁺ ions in ZnO by a decay time which is several magnitudes longer and a high sensitivity for quenching. The luminescence spectrum of Zn-ferrierites is composed of three bands at 545, 480, and 425 nm attributable to Zn²⁺ ions in the α-, β-, and γ-site with luminescence coefficients (for semiquantitative analysis) ζ_α = 10.1, ζ_β = 9.4, and ζ_γ = 8.8 mmol/g of Zn²⁺ ions in the α-, β-, and γ-sites, respectively. The analysis of Zn ions in ferrierites showed that ZnH-ferrierites exclusively contain Zn²⁺ ions in cationic sites. In the case of the ZnNa-FER sample with maximum Zn loading (Zn/Al 0.33), a small amount of Zn-oxo species can be formed.

中文翻译：

发光和FTIR光谱法测定镁碱沸石中锌的形态，分布和分布

开发了一种分析富硅沸石骨架外阳离子位点中Zn ²⁺离子的位置的方法，并在锌镁碱沸石样品（Si / Al 8.5，Zn / Al 0.04-0.33）上进行了演示。该方法基于FTIR光谱，该光谱由Zn ²⁺离子扰动的沸石骨架的反对称四面体-八面体-四面体（TOT）振动，以及基于激光诱导的时间分辨发光监测的基于Zn ²⁺发光的互补方法组成光谱学。脱水沸石的反对称TOT振动的FTIR光谱中的三个振动带反映了镁碱沸石的三个骨架外阳离子部位中Zn ^2+的结扎。乐队在935 cm ^–1处对应于镁碱沸石α位的Zn ²⁺离子，917 cm ^–1处的能带对应于β位的离子，而902 cm ^–1相带的902波段对应于镁碱位处的Zn ²⁺离子。估计了用于定量分析阳离子位点中Zn ²⁺离子的消光系数，并在所有阳离子位点中显示了相同的Zn ²⁺阳离子值，ε= 49.1±3.8 cm·μmol ^–1。在所有的样品的Zn，锌²⁺选址在β位点盛行，而锌²⁺在γ位离子是低人口或可忽略的。时间分辨发光表明裸露的Zn ²⁺骨架外阳离子位点中的离子可以与ZnO中的Zn ²⁺离子区分开，其衰减时间更长，衰减时间长几个数量级，并且对淬灭的灵敏度高。锌-镁碱沸石的发光光谱在545由三个频带，480和425nm的可归因于锌²⁺离子在α-，β-，γ-站点与发光系数（对于半定量分析）ζ _α = 10.1 ，ζ _β = 9.4，并且ζ _γ = 8.8毫摩尔的Zn /克²⁺在α-分别离子，β-和γ-位点，。镁碱沸石中Zn离子的分析表明，ZnH-镁碱沸石仅含有Zn ²⁺阳离子位中的离子。如果ZnNa-FER样品具有最大的Zn负载量（Zn / Al 0.33），则可能形成少量的Zn-氧代物质。

更新日期：2021-05-06

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