Zn-MOFs based luminescent sensors for selective and highly sensitive detection of Fe3+ and tetracycline antibiotic

Abstract

Either reduced or excessive metal ions level in biological systems might induce serious metabolic diseases, and the abuse of antibiotics has seriously affected the environment. Despite the significant progress in the development of fluorescence probes over the past decade, the ability to sensitively and selectively detect these metal ions and antibiotics remains a pressing problem. Herein, we demonstrated some effective fluorescence probes for sensing metal ions and antibiotics, six novel and stable Zn(II) metal-organic frameworks (Zn-MOFs), namely [Zn₃(L)₂(1,4-bimb)₃]_n (1), [Zn₃(L)₂(4,4'-bbibp)₂(H₂O)₂]_n·2(CH₃CN) (2), [Zn(HL)(4,4'-bidpe)]_n (3), [Zn(HL)(4,4'-bibp)]_n (4), [Zn(HL)(3,5'-bip)]_n (5) and [Zn(HL)(1,3'-bit)]_n (6) (flexible H₃L = 5-(2-carboxylphenoxy)isophthalic acid, semi-flexible 1,4-bimb = 1,4-bis(imidazol-l-ylmethyl) benzene, rigid 4,4'-bbibp = 4,4'-bis(benzoimidazo-1-ly)biphenyl, semi-flexible 4,4'-bidpe = 4,4'-bis(imidazolyl)diphenyl ether, rigid 4,4'-bibp = 4,4'-bis(imidazolyl)biphenyl, rigid 3,5'-bip = bis(1-imidazoly)pyridine and rigid 1,3-bit = 1,3-bis(l-imidazoly)toluene) have been successfully synthesized via solvothermal conditions and further characterized by IR spectra, elemental analysis, powder X-ray diffraction (PXRD), single-crystal X-ray diffraction, and thermogravimetric (TG) analysis. These Zn MOFs have exhibited diversely architectural frameworks via the assistant N-donor ligands: 1, 2, 5 and 6 show unprecedented topological networks, 1 affords a 3-nodal (3, 4, 4)-connect 2-fold interpenetrating topology structure with the Point Schläfli symbol of (5·6·7·9²·10)₂(5·6·7)₂(5·7³·8²), 2 shows a 3-nodal (3, 4, 6)-c topology with (4·8²)₂(4²·8¹¹·10·12)(8⁶), 5 and 6 display 3-nodal (2, 2, 4)-c topology with (2·4⁴·6)(2)(4). 3 and 4 show 4-connected sql topology with (4⁴·6²). As expected, Zn MOFs 1-6 not only revealed a highly sensitive and selective fluorescence quenching effect on Fe³⁺ ions in aqueous solution, but also toughed the interference of a myriad of other metal ions. It is noteworthy that they could also be used as luminescent sensors for detection of tetracycline antibiotic.

Keywords: Fe(3+) ions and tetracycline antibiotic; Fluorescence probes; Highly sensitive and selective; Unprecedented/sql topology; Zn-MOFs.