Mono- and Di-Sc-Substituted Keggin Polyoxometalates: Effective Lewis Acid Catalysts for Nerve Agent Simulant Hydrolysis and Mechanistic Insights.
Mono- and Di-Sc-Substituted Keggin Polyoxometalates: Effective Lewis Acid Catalysts for Nerve Agent Simulant Hydrolysis and Mechanistic Insights.
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DOI：
10.1021/acs.inorgchem.0c00976
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发表时间：
2020-07
影响因子：
4.6
通讯作者：
Dingkun Zhang;Wenqi Zhang;Zhengguo Lin;Jing Dong;Ni Zhen;Yingnan Chi;Changwen Hu
中科院分区：
文献类型：
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作者：
Dingkun Zhang;Wenqi Zhang;Zhengguo Lin;Jing Dong;Ni Zhen;Yingnan Chi;Changwen Hu
近年来，路易斯酸催化剂对神经毒剂的水解引起了广泛的关注。具有Lewis酸位的多金属氧酸盐（pom）等分子催化剂的开发有助于提高降解效率，并在分子水平上了解催化机理。本文成功合成了单Sc-取代的K4[Sc(H2O)PW11O39]·22H2O·2(CH3COOK)(1)和双Sc-取代的Na7[Sc2(CH3COO)2PW10O38]·10H2O·2CH3COONa(2)两种新型keggin型pom，并通过常规技术对其进行了表征。据我们所知，1和2代表离散sc取代Keggin簇的第一个例子。通过31P核磁共振波谱和傅里叶变换红外波谱分析表明，与已有报道的含sc的POMs相比，1和2在水溶液中具有较好的溶解度和稳定性。两种sc取代的POMs均能在接近中性的ph下有效催化神经毒剂模拟物二甲基4-硝基苯基磷酸二甲酯（DMNP）的水解去污，其中2（转化率97%）的催化性能明显优于1（转化率28%）。发现Sc的配位环境不同是影响其活性的关键因素。包括对照实验和波谱分析（13C核磁共振波谱和电喷雾电离质谱）在内的机理研究表明，在转换条件下，配位乙酸酯与2解离，暴露的配位不饱和Sc中心比1中的水配位Sc更活跃地与DMNP结合。
Recently, the hydrolysis of nerve agents by Lewis acid catalysts has attracted considerable attention. The development of molecular catalysts, such as polyoxometalates (POMs) with Lewis acidic sites, is helpful to improve degradation efficiency and understand the catalytic mechanism at a molecular level. Herein, two novel Keggin-type POMs, namely, mono-Sc-substituted K4[Sc(H2O)PW11O39]·22H2O·2(CH3COOK) (1) and di-Sc-substituted Na7[Sc2(CH3COO)2PW10O38]·10H2O·2CH3COONa (2), have been successfully synthesized and thoroughly characterized by routine techniques. To our knowledge, 1 and 2 represent the first example of discrete Sc-substituted Keggin clusters. Compared with the reported Sc-containing POMs, 1 and 2 exhibit relatively good solubility and stability in aqueous solution, as evidenced by 31P nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy. The two Sc-substituted POMs can effectively catalyze the hydrolytic decontamination of dimethyl 4-nitrophenyl phosphate (DMNP), a nerve agent simulant, at near-neutral pH. Notably, the catalytic performance of 2 (conversion: 97%) is much better than that of 1 (conversion: 28%). It is found that the different coordination environment of Sc is the key factor to impact their activity. Mechanistic studies including the control experiments and spectroscopy analysis (13C nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry) show that under the turnover conditions the coordinated acetate dissociates from 2 and the exposed coordinatively unsaturated Sc center is more active than the water-coordinated Sc in 1 for binding with DMNP.