Mono- and Di-Sc-Substituted Keggin Polyoxometalates: Effective Lewis Acid Catalysts for Nerve Agent Simulant Hydrolysis and Mechanistic Insights

Abstract

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.

Hydrolysis of Organophosphorus Agents Catalyzed by Cobalt Nanoparticles Supported on Three-Dimensional Nitrogen-Doped Graphene

“…Catalytic chemical degradations and other protocols have been used for the removal and/or degradation of OPs. − Early on, organophosphorus hydrolases (OPHs) were utilized as catalysts for the degradation of OPs. − However, the poor stability and limited availability of OPHs are the drawbacks for practical applications. In recent years, by mimicking the active center of OPHs, many heterogeneous catalysts − have been explored for hydrolysis of OPs. A series of metal–organic framework (MOF)-based catalysts were employed for the hydrolysis of OPs .…”

Functionalized nanomagnetic graphene by ion liquid containing phosphomolybdic acid for facile and fast synthesis of paracetamol and aspirin

“…Among the various heteropolyacids, phosphomolybdic acid (PMoA), as Brønsted acid catalyst, has attracted much attention. [ 11–20 ]…”

“…Among the various heteropolyacids, phosphomolybdic acid (PMoA), as Brønsted acid catalyst, has attracted much attention. [11][12][13][14][15][16][17][18][19][20] On the other hand, polyaniline (PANI), one of the well-known conductive polymers, is widely used as support for the designing of various hybrid composites. This is due to its interesting properties, such as low weight, ease of synthesis, low cost, flexibility, environmental stability, and optical and characteristic redox properties.…”

A Polyoxometalate-Based Inorganic Porous Material with both Proton and Electron Conductivity by Light Actuation: Photocatalysis for Baeyer–Villiger Oxidation and Cr(VI) Reduction

“…Polyoxometalates (POMs) are a kind of excellent molecule-based semiconductor with diverse structures, reversible redox activity, and ease of functionalization. − Especially, POMs are promising charge carriers because they can accept many electrons and protons in multielectron transfer processes without deforming their structures, which is beneficial for applications in heterogeneous photocatalysts and electrochromic or photochromic devices. − In comparison with the extensively reported POM-based MOFs (POMOFs), pure inorganic frameworks constructed by POMs linking solely with metal bridging units are rare and have recently gained attention as a unique class of materials. , In 2019, Schimpf’s group assembled a new metal oxide material from Preyssler anions [NaP 5 W 30 O 110 ] 14– linked with Co­(H 2 O) 4 2+ bridging units, which can be photochemically reduced, allowing the storage of multiple electrons under mild conditions. This addition of delocalized electrons is accompanied by a 1000-fold increase in the conductivity .…”