Incorporation Of Metal-Organic Framework And Polyoxometalate With Fibrous Materials And Their Effectiveness In Removal And Degradation Of An Organophosphate

Abstract

The adsorption and degradation of methyl parathion an organophosphate with Cu-BTC metal-organic framework (MOF-199) and a polyoxometalate are investigated in multiple fibrous systems. Immobilizing MOF particles in a fibrous system adds functionality to the fibers and allows the MOF particles to be in a workable and flexible substrate. First, a method is presented to immobilize Cu-BTC metal-organic framework (MOF-199) particles by enmeshing them in nonwoven polyacrylonitrile (PAN) nanofibers creating a fibrous membrane with the potential ability to remove chemical warfare agents or pesticides from solution. These membranes were shown to effectively adsorb methyl parathion, an organophosphate pesticide. Based on solubility theory and experimental results, partitioning was determined to be the main mechanism of removal. After 2 hours, the PAN/MOF-199 membranes removed 88% more methyl parathion than the unmodified PAN membranes and 62% as much as the MOF-199 crystal powder. Further experiments revealed that degradation of methyl parathion was occurring within the MOF cages. Degradation of methyl parathion adsorbed in metalorganic framework (MOF)-199 cages was studied using nuclear magnetic resonance (NMR), Raman spectrometry, and solvent extractions. NMR was completed using solid-state 31 P NMR with magic-angle spinning with cross polarization or direct polarization. Results show that constitutional isomerization is the main mechanism of methyl parathion degradation within the MOF-199 framework within the 5-67 day time frame studied. Secondly, A combination of a Keggin-type polyoxometalate (POM), [CuPW11O39]5-, with a metal-organic framework (MOF), MOF-199 (HKUST-1) was successfully self-assembled on a cellulose substrate (cotton) with a newly developed room-temperature process. This material was found to effectively remove 2.75 times as much of a target organophosphate toxin, methyl parathion, from a hexane solution as MOF-cotton and cotton control samples after 2 h. The combination of the catalytic activity of the POM and the adsorption properties of the MOF both immobilized on a textile is ideal for potential applications in protective self-decontaminating materials. In addition to this, hydrophilicity of the fabrics is maintained, which leads to a material that maintains the thermal comfort of cotton. The functionalized fibrous PAN/MOF-199 membranes also have potential to be used in protective clothing for occupational or military applications or as filtration media.