A dual-functional Zr(iv)-based metal–organic gel obtained via a cage-to-gel strategy: nerve agent simulant degradation and blister agent simulant adsorptive sensing

Abstract

The adsorption, degradation, and sensing of chemical warfare agents are highly important. In this work, a new Zr(IV)-based metal–organic gel (MOG) was designed and synthesized, which demonstrated dual-functional performance in the degradation of nerve agent simulants and the adsorptive sensing of blister agent simulants. A Zr(IV)-based MOG, namely, Zr-MOG-taBDC (H₂taBDC = 2-(1H-1,2,4-triazol-1-yl) terephthalic acid), was synthesized through the thermal transformation of a tetrahedral Zr(IV)-based metal–organic cage, {[Cp₃Zr₃(μ₃-O)(μ₂-OH)₃]₄(taBDC)₆}·(Cl⁻)₄ (Zr-MOC-taBDC), in a mixed acetonitrile/water solvent system, bypassing the need for tedious anion exchange and high-boiling solvents. The resulting MOG exhibited hierarchical porosity and high stability across a wide pH range (1–11). Catalytic tests revealed that Zr-MOG-taBDC achieved 95.4% degradation efficiency for the nerve agent simulant diethyl phenylphosphonate (DEPPT), with a half-life of 49.5 minutes, outperforming its crystalline MOC precursor. Additionally, the gel demonstrated a high adsorption capacity (0.6 g g⁻¹) for the mustard gas simulant 2-chloroethyl ethyl sulfide (CEES), enabling real-time detection via a quartz crystal microbalance (QCM) with a linear response range up to 100 ppm. Mechanistic studies indicated that degradation proceeds via P–S bond cleavage catalyzed by Zr–OH–H₂O Lewis acid–base sites, whereas adsorption involves reversible physical and irreversible chemical interactions with triazole groups and Zr-oxo clusters. This work highlights the potential of Zr-MOGs as multifunctional materials for chemical warfare agent mitigation and sensing.