Removing Fluoride from Double Four-Membered Rings Yielding Defect-Free Zeolites under Mild Conditions Using Ozone

被引：1

作者：

Wang, Tongkun ^{[1
]}

Luo, Song ^{[2
]}

Shah, Muhammad ^{[2
]}

Qi, Long ^{[3
]}

Tompsett, Geoffrey A. ^{[4
]}

Timko, Michael T. ^{[4
]}

Auerbach, Scott M. ^{[1
,2
]}

Fan, Wei ^{[2
]}

机构：

[1] Univ Massachusetts Amherst, Dept Chem, Amherst, MA 01003 USA

[2] Univ Massachusetts Amherst, Dept Chem Engn, Amherst, MA 01003 USA

[3] Iowa State Univ, US DOE, Ames Lab, Ames, IA 50011 USA

[4] Worcester Polytech Inst, Dept Chem Engn, Worcester, MA 01609 USA

来源：

CHEMISTRY OF MATERIALS | 2024年 / 36卷 / 02期

基金：

美国国家科学基金会;

关键词：

FINDING SADDLE-POINTS; DETEMPLATION; OCTADECASIL; CALCINATION; MEMBRANES; TEMPLATE; SILICA;

D O I：

10.1021/acs.chemmater.3c02695

中图分类号：

O64 [物理化学（理论化学）、化学物理学];

学科分类号：

070304 ; 081704 ;

摘要：

We have investigated ozone treatment of as-made LTA zeolites under mild temperature conditions (175 degrees C) using experiments and periodic DFT as a method of energy savings and engineering defects such as silanol nests in comparison with conventional calcination at 550 degrees C. We have studied ozone treatment on LTA samples synthesized with 1,2-dimethyl-3-(4-methylbenzyl) imidazolium (denoted as "BULKY") as the primary organic structure-directing agent (OSDA) and with various amounts of tetramethylammonium (TMA) as a secondary OSDA. Ozone treatment of LTA-BULKY at 175 degrees C was found to give defect-free, pristine LTA materials as determined by Si-29 NMR, C-13 NMR, Raman spectra, and DFT to assign the spectra. This represents a significant and unexpected finding: that fluoride ions can be completely removed from double four-membered rings (D4Rs) under such mild conditions. Ozone treatment of LTA-BULKY-TMA samples removed BULKY but left behind TMA/F, giving a new and more diverse structural landscape of Si environments in LTA. Ab initio MetaDynamics calculations provide pathways with relatively low barriers, explaining how fluoride ions can be removed from D4Rs, leaving behind defect-free LTA materials under mild conditions.

引用

页码：870 / 880

页数：11