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The shape of water in zeolites and its impact on epoxidation catalysis
Nature Catalysis ( IF 37.8 ) Pub Date : 2021-09-20 , DOI: 10.1038/s41929-021-00672-4
Daniel T. Bregante 1 , Matthew C. Chan 1 , Jun Zhi Tan 1 , E. Zeynep Ayla 1 , Diwakar Shukla 1 , David W. Flaherty 1 , Christopher P. Nicholas 2, 3
Affiliation  

Solvent structures that surround active sites reorganize during catalysis and influence the stability of surface intermediates. Within zeolite pores, H2O molecules form hydrogen-bonded structures that differ substantially from bulk H2O. Here, we show by spectroscopic measurements and molecular dynamics simulations that H2O molecules form bulk-like three-dimensional structures within 1.3 nm cages, whereas H2O molecules coalesce into oligomeric one-dimensional chains when the pore diameter falls below 0.65 nm. The differences between these solvent structure motifs provide opportunities to manipulate enthalpy–entropy compensation relationships and greatly increase the rates of catalysis. We describe how the reorganization of these pore-size-dependent H2O structures during alkene epoxidation catalysis gives rise to entropy gains that increase the turnover rates by up to 400-fold. Collectively, this work shows that solvent molecules form distinct structures with a highly correlated motion within microporous environments, and the reorganization of these structures may be controlled to confer stability to the desired reactive intermediates.



中文翻译:

沸石中水的形态及其对环氧化催化的影响

围绕活性位点的溶剂结构在催化过程中会重组并影响表面中间体的稳定性。在沸石孔隙中,H 2 O 分子形成与本体 H 2 O显着不同的氢键结构。在这里,我们通过光谱测量和分子动力学模拟表明,H 2 O 分子在 1.3 nm 笼内形成块状三维结构, 而 H 2当孔径低于 0.65 nm 时,O 分子会聚结成低聚一维链。这些溶剂结构基序之间的差异提供了操纵焓-熵补偿关系并大大提高催化速率的机会。我们描述了烯烃环氧化催化过程中这些依赖于孔径的 H 2 O 结构的重组如何产生熵增益,从而将周转率提高多达 400 倍。总的来说,这项工作表明溶剂分子在微孔环境中形成具有高度相关运动的不同结构,并且可以控制这些结构的重组以赋予所需的反应性中间体稳定性。

更新日期:2021-09-20
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