Zirconium-metal–organic framework@activated carbon composites for prevention of secondary emission of nerve agents

Abstract

We have studied the formation of core–shell hybrid metal–organic framework@activated carbon sphere (MOF@AC) adsorbents, by means of a layer-by-layer (LBL) growth method of MOFs on shaped AC materials. The hybrid MOF@AC materials are useful for preventing the secondary emission problems of chemical warfare agent protective filters. Mesopores on AC materials facilitate carbon surface oxidation and a subsequent MOF growth, allowing Zr6O4(OH)4(benzene-1,4-dicarboxylate-2-X)6 (X = H, UiO-66; X = NH2, UiO-66-NH2) thin film formation. By contrast, microporous spheres do not allow a significant MOF layer growth. The MOF@AC hybrids are able to capture the G-type nerve agent surrogate, diisopropylfluorophosphate (DIFP), and quantitatively hydrolyse a P–F bond, within 24 h at room temperature, to yield non-toxic diisopropylphosphate (DIP) in unbuffered moist media. Neither the MOF nor the carbon spheres alone can hydrolyse the model toxic compound to that extent. The enhanced performance of the MOF@AC composites is attributed to a synergistic interplay of the hydrolytic degradation of DIFP at the MOF layer and the physisorption of DIP at the carbon pore structure, allowing the regeneration of the MOF catalytic sites.