Exploiting Cross-Responsiveness of Fluorescent Interpenetrated Zirconium-Organic Frameworks Integrated in Polymeric Membranes as a Multi-Analyte Gas Sensor Array

In this paper, a series of Zr metal-organic frameworks, whose hexanuclear clusters of Zr are connected with luminescent rodlike dicarboxylic acids, are used for the construction of a sensor array to selectively detect various analyte vapors. The chemical functionalization of the ligand (HOOC[PE-aryl-EP]COOH) (which alternates phenylene(P) and ethynylene(E) units) through the aryl core, is focused on obtaining six Porous Interpenetrated Zirconium-Organic Frameworks (PIZOFs) with distinctive luminescent properties. Particularly, the synthesis of two new ligands (aryl = nitrobenzene;metal-organic frameworks aryl = pyrazine) enabled the preparation of new PIZOFs (UPO-1 and UPO-2) with submicron sizes, thanks to the use of a microwave-assisted synthetic method. The fluorescence properties of these two new PIZOFs, along with four others already reported, are thoroughly evaluated and noticeable changes are observed in their optical properties based on variations in the aryl core of the ligands. Furthermore, the presence of various volatile analyte vapors particularly modified their characteristic emission, resulting in multiple optical responses that are combined to achieve selectivity in detecting these analytes. Specifically, the construction of a fluorescent sensor array is proposed, incorporating the six PIZOFs into polyvinylidene-fluoride (PVDF) films, capable of producing unique identification patterns for each analyte by leveraging the cross-responsiveness of these sensing materials. Functionalizing the aryl core of rod-like ligands yields interpenetrated Zr-organic frameworks with distinct fluorescence emission spectra, responsive to analyte vapors. When integrated into polymeric matrices and combined in a sensor array, these metal-organic frameworks exhibit cross-responsive behavior, generating unique recognition patterns for each analyte. image