Zirconium-based MOF nanocrystals confined on amphoteric halloysite nanotubes for promoting the catalytic hydrolysis of an organophosphorus nerve agent simulant

Abstract

Exploiting efficient and practical catalysts for hydrolyzing organophosphorus nerve agents is significant and highly desirable. Herein, a new class of self-detoxifying composites, namely, halloysite nanotubes@NU-912 (HNTs@NU-912), HNTs@NU-912-I and HNTs@UiO-66-NH₂, is constructed by in situ synthesis of hexanuclear zirconium cluster-based metal–organic frameworks (Zr–MOFs) NU-912, NU-912-I and UiO-66-NH₂, respectively, with HNTs, which are natural nanotubular materials consisting of Si–O–Si tetrahedral sheets on the outer surface and Al–OH octahedral sheets on the inner surface. The results show that crystalline Zr–MOFs uniformly cover the outer surface of HNTs and the particle size of Zr–MOFs is greatly reduced to less than 50 nm. Furthermore, HNTs@NU-912, HNTs@NU-912-I and HNTs@UiO-66-NH₂ display much higher catalytic efficiency for the hydrolysis of dimethyl-4-nitrophenyl phosphate (DMNP) than the corresponding Zr–MOFs both in an aqueous N-ethylmorpholine (NEM) buffer solution and under ambient conditions. Specifically, HNTs@NU-912-I shows a turnover frequency (TOF) of 0.315 s⁻¹ in aqueous buffer solution, placing it among the best Zr–MOF-based heterogeneous catalysts for the hydrolysis of DMNP. The composites show high stability, and more importantly, can replace the buffer solvent and control the pH to a certain degree by virtue of its acidic Si–O–Si sheets and alkaline Al–OH sheets. This work provides a certain reference for the subsequent development of personal protective equipment.