Lanthanide metal–organic frameworks as multifunctional sensors for chemicals and temperature

Abstract

Finding simple and effective methods to detect pollutants in the environment has always been a topic of concern. In this study, the application of a conjugated amide tetracarboxylic acid ligand, namely, 5,5′-((pyridine-2,6-dicarbonyl)bis(azadiyl)diterephthalic acid (PDAI), in fluorescence sensing was investigated for the first time. Two two-dimensional isomorphic rare earth metal–organic frameworks, with the general formula [M–(PDAI)–(H₂O)] (M = Tb for CUST-923, Eu for CUST-924), were constructed under solvothermal conditions, and they exhibited strong luminescence and good water–acid–base stability. CUST-923 and CUST-924 displayed highly selective recognition ability for Fe³⁺, Cr₂O₇²⁻, CrO₄²⁻ and tetracycline (TCH). In addition, the mixed lanthanide metal–organic framework Eu_0.1Tb_0.9–PDAI could be used as a temperature sensing material over a wide temperature range, with a maximum relative sensitivity of 2.30% K⁻¹ at 413 K. This work demonstrates the potential of lanthanide metal–organic frameworks as multifunctional sensors for detecting pollutants and manufacturing fluorescence thermometers.