Defect-engineered UiO-66-NH2 (AO)-3: Achieving enhanced fluorescence sensing of uranyl ions

Abstract

Advances in nuclear technology have accentuated the imperative of uranyl ions (UO₂²⁺) monitoring in aquatic ecosystems, due to their significant environmental and health repercussions. Metal–Organic Frameworks (MOFs), celebrated for their tunable porosity and substantial surface area, offer a promising platform for enhancing analytical detection capabilities. Empirical evidence from recent scholarly work indicates that defect engineering within MOFs can significantly improve their physicochemical properties, encompassing sensing performance. In this study, the fluorescence behavior of UiO-66-NH₂ (Zr-MOF) was successfully modulated through the deliberate incorporation of defects, which reduced the exciton dissociation energy and subsequently increased fluorescence emission efficiency. Additionally, the introduction of engineered defects engendered a more permeable structure, which facilitated the rapid entry and enrichment of UO₂²⁺ within the internal cavities, consequently promoting a pronounced fluorescence quenching response. The synergistic effects of defect modulation and amidoxime functionalization endowed UiO-66-NH₂(AO)-3 with enhanced detection sensitivity and selectivity for UO₂²⁺, realizing a detection limit as low as 24.6 nmol·L⁻¹ (12.4 ppb), indicative of its robust signal amplification capacity for the trace detection of UO₂²⁺. Our findings proffer a novel approach to enhance the sensing capabilities of MOFs, contributing a sensitive and selective analytical technique for the detection of UO₂²⁺.