A Multiunit Catalyst with Synergistic Stability and Reactivity: A Polyoxometalate–Metal Organic Framework for Aerobic Decontamination

Abstract

A combination of polyanion size and charge allows the Keggin-type polyoxometalate (POM), [CuPW(11)O(39)](5-), a catalyst for some air-based organic oxidations, to fit snuggly in the pores of MOF-199 (HKUST-1), a metal-organic framework (MOF) with the POM countercations residing in alternative pores. This close matching of POM diameter and MOF pore size in this POM-MOF material, [Cu(3)(C(9)H(3)O(6))(2)](4)[{(CH(3))(4)N}(4)CuPW(11)O(39)H] (1), results in a substantial synergistic stabilization of both the MOF and the POM. In addition, this heretofore undocumented POM-MOF interaction results in a dramatic increase in the catalytic turnover rate of the POM for air-based oxidations. While 1 catalyzes the rapid chemo- and shape-selective oxidation of thiols to disulfides and, more significantly, the rapid and sustained removal of toxic H(2)S via H(2)S + 1/2 O(2) → 1/8 S(8) + H(2)O (4000 turnovers in <20 h), the POM or the MOF alone is catalytically slow or inactive. Three arguments are consistent with the catalytic reactions taking place inside the pores. POM activation by encapsulation in the MOF likely involves electrostatic interactions between the two components resulting in a higher reduction potential of the POM.

Understanding the Regioselective Hydrolysis of Human Serum Albumin by Zr(IV)-Substituted Polyoxotungstates Using Tryptophan Fluorescence Spectroscopy

“…As shown in Figure 3, there is no shift in the peak positions of the characteristic Zr1-WD2 resonances (at −9.33 and −13.94 ppm) in the presence of HSA, indicating the stability of the POM upon interaction with the protein. It should not be surprising that these polyoxotungstates are stable as this was already previously demonstrated by various techniques [63][64][65]. In addition, the slight decrease in the intensity of the POM peaks can be correlated with the formation of a large molecular complex with HSA which has a longer correlation time and thus a faster relaxation.…”

Preparation of a Composite of Sulfated Zirconia/Metal Organic Framework and its Application in Esterification Reaction

“…Several materials such as polyoxometalate (POM), 21,[23][24][25][26] iron oxide [27][28][29] and graphite oxide (GO) [16][17][18][19][20] have been used for the formation of MOF composites. POM/MOF composites have been used in various fields including acid catalyses, oxidation catalyses, adsorption/decontamination and so on.…”

An Innovative Approach to Oxidative Removal of Hydrogen Sulfide Using the Solution of Peroxo Heteropolyacid

“…For example, the system of HPA/H 2 O 2 has been widely employed in the field of deep-desulfurization of fuel oil (Te et al, 2001;Ying et al, 2009;Wang et al, 2010). However, there are only quite limited reports on H 2 S removal using HPA (Kuznetsova and Yurchenko, 1989;Harrup and Hill, 1994;Wang, 2003;Song et al, 2011;Ma et al, 2012;Zou et al, 2013;Kim et al, 2014). Furthermore, the study on H 2 S removal using PHPA has never been reported to date.…”