Cluster-based CaII, MgII and CdII coordination polymers based on amino-functionalized tri-phenyl tetra-carboxylate: Bi-functional photo-luminescent sensing for Fe3+ and antibiotics

Abstract

Excess and deficiency of iron(III) and antibiotics from normal permissible limits will induce serious disorders, so their detection is important but challenging. In this work, the asymmetric amino-functionalized tetra-carboxylate H4L (2′-amino-1,1’:4′,1″-terphenyl-3,3″,5,5″-tetracarboxylic acid) containing large conjugated ter-phenyl aromatic backbones have been synthesized and employed. Through a one-pot powerful solvo-thermal synthetic strategy, a series of unique tri-nuclear cluster-based CaII, MgII and CdII coordination polymers, namely [Ca1.5(μ8-HL)(DMF)]n (1), {[Mg1.5(μ7-HL)·(H2O)2]·3H2O}n (2) and {[Cd1.5(μ10-L)0.75]n·H2O·DMF}n (3) have been successfully prepared. 1–3 exhibit excellent photo-luminescent properties and good fluorescence stability. Structural analyses reveal that tri-nuclear CaII secondary building blocks (SBUS) are linked via HL3−, forming the 2D clustered-based micro-porous coordination polymer 1. As for 2, three carboxylate groups of partly de-pronated HL3− also link these neighboring tri-nuclear MgII SBUS, which constructs the 2D MgII coordination framework 2. As for 3, fully de-pronated L4− also links these neighboring tri-nuclear CdII SBUS, which ultimately constructs the 3D micro-porous coordination framework 3. Experimental powder x-ray diffraction (PXRD) patterns coincide well with the theoretical patterns, which indicate that we have successfully synthesized the pure phase material 1–3. Photo-luminescent experiments demonstrate that coordination polymers 1–3 can be successfully applied towards bi-functional sensing for sensitive detection of Fe3+ and the antibiotics NZF (Nitrofurazone). To the best of our knowledge, this is the first example of the application of amino-functionalized tri-phenyl tetra-carboxylate based MOFs towards bi-functional discrimination of Fe3+ and NZF antibiotics with high efficiency Ksv values (For Fe3+: 7.28 × 104 M−1 for 1; 3.38 × 104 M−1 for 2 and 3.29 × 104 M−1 for 3 and for NZF antibiotics: 4.47 × 103 M−1 for 1; 4 × 103 M−1 for 2 and 5.6 × 103 M−1 for 3).