Series of highly stable Cd(ii)-based MOFs as sensitive and selective sensors for detection of nitrofuran antibiotic

Abstract

The abuse of antibiotics has caused global problems including critical environmental ecology impacts. Herein, four new metal–organic frameworks (MOFs) – {[Cd(HL)(bic)(H₂O)]·2H₂O}(1), {[Cd₃(L)₂(bbi)₂(H₂O)₂]·2H₂O}(2), [Cd₃(L)₂(bib)₂(H₂O)₂] (3) and [Cd₃(L)₂(idy)₂] (4), where bic = 3,6-bis(imidazol-1-yl)-9H-carbazole, bbi = 1,1′-(1,4-butanediyl)bis(imidazole), bib =1,4-bis(1-imidazoly)benzene and idy = 2-imidazol-1-ylpyridine – have been synthesized and fully characterized. 1 is a 1D chain with a large loop, stacked parallel to each other in 2D supramolecular layers by hydrogen-bonded and packing interactions. 2 and 3 are isostructural and show a 3D (3,8)-connected tfz-type network with (4³)₂(4⁶·6¹⁸·8⁴) topology. 4 has a 2D grid framework. The oxygen atom of the ether-bridging group acts as a Lewis base site, which improves the connection strength and allows the detection of 11 types of antibiotics through the fluorescence quenching effect. Among them, 2 exhibits sensitive and selective detection for nitrofural (NZF) (K_SV = 8.26 × 10³ M⁻¹ and LOD = 1.83 ppm). Moreover, the highly selective probe behavior towards NZF ions could be maintained even if there are other interfering antibiotics.