A robust 3D In–MOF with an imidazole acid ligand as a fluorescent sensor for sensitive and selective detection of Fe3+ ions

Abstract

A stable 3D In(III)-based metal–organic framework, [In(L)(μ₂-OH)]·0.5H₂O (1) (where H₂L = 5-(1H-imidazol-1-yl)isophthalic acid), was successfully synthesized and fully characterized. As established by single-crystal X-ray diffraction, the compound 1 has a 4,6-connected 3D architecture crystalized in the monoclinic C2/c space group. On the basis of thermodiffractometry, 1 retains the crystallinity and the main framework below 450 °C. The structural integrity of 1 is sustainable in water, under harsh acidic and basic conditions (pH 2–13), and in common organic solvents, presenting excellent water stability and chemical stability. The photoluminescence properties of 1 are investigated as well. Remarkably, luminescence studies reveal that 1 can recognize Fe³⁺ ions with high selectivity from mixed metal ions in aqueous solution through a luminescence quenching phenomenon. The results suggest that the MOF may serve as a potentially useful sensory material for the detection of metal cations, and this work also demonstrates that highly hydrolytically stable In(III)-MOFs could be constructed and used for some meaningful applications in water.