Chen Haoyuan, Snurr Randall Q
Department of Chemical & Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.
ACS Appl Mater Interfaces. 2020 Apr 1;12(13):14631-14640. doi: 10.1021/acsami.9b19484. Epub 2020 Jan 7.
Zirconium-based metal-organic frameworks (Zr-MOFs) have been reported to be efficient catalysts for the hydrolysis of organophosphate chemical warfare agents (CWAs) in buffered solutions. However, for the gas-phase reaction, which is more relevant to the situation in a battlefield gas mask application, the kinetics of Zr-MOF catalysts may be severely hindered by strong product inhibition. To improve the catalytic performance, we computationally screened a series of synthetically accessible Zr-MOF-supported bimetallic metal-oxo clusters in which the metal-oxygen-metal active motif is preserved, aiming to find catalysts that have lower binding affinities to the hydrolysis product. For the promising catalyst AlO(OH)@NU-1000 identified from the screening using density functional theory, we mapped out the full reaction pathway of gas-phase dimethyl p-nitrophenolphosphate (DMNP) hydrolysis and analyzed the free energy profile as well as the turnover frequency (TOF). We found that the catalytic mechanism on the new catalyst is slightly different from the one on NU-1000, which also led to a different TOF-limiting step. Additional factors that can affect the overall catalytic performance in practical application, such as the amount of ambient moisture and the existence of acid gases that may poison the catalyst, have also been evaluated.
据报道，锆基金属有机框架材料（Zr-MOFs）是缓冲溶液中有机磷酸酯类化学战剂（CWAs）水解的高效催化剂。然而，对于与战场防毒面具应用情况更相关的气相反应，Zr-MOF催化剂的动力学可能会受到强烈的产物抑制作用的严重阻碍。为了提高催化性能，我们通过计算筛选了一系列可合成获得的、保留了金属-氧-金属活性基序的Zr-MOF负载双金属金属氧簇，旨在找到对水解产物具有较低结合亲和力的催化剂。对于通过密度泛函理论筛选出的有前景的催化剂AlO(OH)@NU-1000，我们绘制了气相对硝基苯酚磷酸二甲酯（DMNP）水解的完整反应途径，并分析了自由能分布以及周转频率（TOF）。我们发现新催化剂上的催化机理与NU-1000上的略有不同，这也导致了不同的TOF限制步骤。还评估了在实际应用中可能影响整体催化性能的其他因素，如环境湿度和可能使催化剂中毒的酸性气体的存在。
