In situ ligand-induced Ln-MOFs based on a chromophore moiety: white light emission and turn-on detection of trace antibiotics

Abstract

A series of four novel 3-D Ln-MOFs containing both carboxyphenyl and pyridinyl moieties, with the general formula [Ln₂(tcptp)(btca)(H₂O)_m]_n {Ln = Sm³⁺(1), m = 13; Eu³⁺(2), m = 12; Gd³⁺(3) m = 13 and Tb³⁺(4), m = 14; H₃tcptp = 4-(2,4,6-tricarboxyl phenyl)-4,2′:6′,4′′-terpyridine}, have been constructed. During reaction, benzene-1,2,3,5-tetracarboxylic acid (H₄btca) was generated in situ as a second linker, resulting in the formation of a 3D framework, bearing 1D elliptical channels. MOF-1 exhibits dual emissions based on the ligand and Sm³⁺, through which single-component complementary near-white-light emission was realized. Both MOF-2 and MOF-4 display strong ligand–metal charge transfer (LMCT) emissions due to an antenna effect. Remarkably, for MOF-4, Tb³⁺-based fluorescence turn-on sensing of levofloxacin in solution with high sensitivity and excellent selectivity was achieved through a donor photoinduced electron transfer (d-PET) approach, which distinguishes it from other antibiotics, meaning that MOF-4 can be employed as a promising specific fluorescence sensor.