Silver-confined SVNIT-1 metal–organic framework as a promising H2S sensor for asthma monitoring and diagnosis

Abstract

The development of reliable, real-time, and non-invasive sensors for early asthma diagnosis remains a significant clinical challenge. In this work, a new zinc-based metal–organic framework (MOF), SVNIT-1, developed using an amine-functionalized ligand; 4,4′-(((2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene))bis(azanediyl))dibenzoic acid (PMBADH₂), was post-synthetically modified with silver ions to afford Ag@SVNIT-1, a chemodosimetric sensor for sulfide (S²⁻) detection. The embedded Ag⁺ ions in the composite material coordinate with the –NH groups of the MOF, forming emissive centers via metal–ligand charge transfer interactions. Upon exposure to Na₂S, a specific conversion of Ag⁺ to Ag₂S disrupts the Ag–NH interaction, resulting in a fluorescence “turn-on” response at 352 nm. This irreversible transformation underpins the sensor's high sensitivity (LOD = 2.03 μM), excellent selectivity, rapid response time (≤1 min), and robust performance in aqueous and biologically relevant media. An AND-type molecular logic gate was also fabricated using Na₂S and Ag@SVNIT-1 as chemical inputs, with fluorescence intensity as the output, enabling binary decision-making for H₂S levels. The sensor successfully differentiated physiological and pathological H₂S concentrations in a model simulating asthma severity. Post-sensing structural integrity was validated by PXRD, XPS, and FTIR, confirming the framework's stability. These results establish Ag@SVNIT-1 as a promising MOF-based platform for intelligent biosensing applications and early-stage asthma diagnostics.