[2009年10月17日]

 

   In Situ UV Raman Spectroscopic Study     on the Synthesis Mechanism of AlPO-5

 

AlPO-5分子筛合成机理示意图

A proposed synthesis mechanism of AlPO-5


         微孔化合物生成中模板或结构导向作用的研究一直非常受到人们的关注,合理地选择适合的结构导向剂是合成具有新颖骨架结构微孔化合物的关键问题。然而直到目前为止,由于人们对客体分子在在微孔化合物生成中的作用机理的认识还不够明确,很多认识还最终停留在最终产物和结构导向剂之间的关系上,对于它们在晶化过程中所起的关键作用了解较少。而原位光谱技术能够很好地解答上述问题。继我组成功地将原位紫外拉曼技术 以及共振拉曼技术应用于分子筛合成机理研究之后(范峰滔、冯兆池、李灿等Chem. Eur. J., 14: 5125-5129, 2008;Chem. Eur. J., 15:3268-3276, 2009)。最近,我组将原位紫外拉曼技术
拓展到了含有机模板剂的分子筛合成体系(TEA-AlPO-5)的晶化机理研究中, 范峰滔等人利用巧妙设计的原位拉曼光谱池结合紫外拉曼光谱技术研究了AlPO4-5分子筛的晶化过程,首次实现了模板剂信息和分子筛结构信息的同时检测,这是其它表征技术所无法做到的。通过原位光谱结果,他们发现了模板剂的振动与分子筛孔道结构形成之间的关联,推测出了含有四元环无定形孔道中间物的存在,并利用Fenton氧化试剂结合紫外拉曼光谱观测到了四元环向六元环转换的过程。为磷铝分子筛合成机理中长期存在的合成机理推测提供了有力的实验证据,进一步完善了磷铝分子筛的合成机理,为理性设计分子筛合成、分子筛前体设计以及模板剂的选择方面提供了理论指导依据。该工作受到审稿人的高度评价,审稿人认为“这项工作为磷铝分子筛的合成机理中添加了崭新且重要的一个环节。” 文章发表在近期出版的Angew. Chem. Int. Ed., 2009, 48, 8743
 

AlPO-5分子筛合成过程中的原位紫外拉曼光谱图

UV Raman spectra recorded in situ during crystallization of AlPO-5.

 

用于研究含有机模板剂分子筛合成体系的原位紫外拉曼光谱池

Schematic diagram of in situ Raman cell for the monitor of organic template-containing zeolite synthesis process

 

   

Communication

In Situ UV Raman Spectroscopic Study on the Synthesis Mechanism of AlPO-5
 

Fengtao Fan, Zhaochi Feng, Keju Sun, Meiling Guo, Qiang Guo, Yu Song, Weixue Li, Can Li

Angew. Chem. Int. Ed., 2009, 48, 8743
 

 
Keywords

hydrothermal synthesis • Raman spectroscopy • reaction mechanisms • UV/Vis spectroscopy

Abstract

    In situ UV Raman spectroscopy has been found to be a potential tool to study the evolution of both the organic templates and inorganic framework simultaneously, thus revealing the interaction between the organic template and framework formation.

      In this manuscript, we propose, for the first time, a detailed synthesis mechanism of AlPO-5 using in situ UV Raman spectroscopy. The building blocks from the intermediates to the final crystals were well identified by taking the advantage of this powerful technique. . A very important intermediate composed of 4-membered rings for the channel formation has been detected. The intermediate was formed due to the existence of the templates which provide steric support for channel formation via its specific molecular vibrations in the very early stages. The building blocks from the intermediate to the final crystals were well identified by taking the advantage of this powerful technique. This work provides molecular-level insights into the role of the template in channel formation. We anticipate that this will facilitate the choice of organic templates and tailoring the building blocks for the rational synthesis of zeolites.