Highly Luminescent Lanthanide Metal‐Organic Frameworks with Tunable Color for Nanomolar Detection of Iron(III), Ofloxacin and Gossypol and Anti‐counterfeiting Applications

Abstract

Solvothermal reaction of 5,5′‐(pyridine‐2,6‐diylbis(oxy))diisophthalic acid (H4L) with europium(III) or terbium(III) nitrates in acetonitrile‐water (1 : 1) at 120 °C gave rise to isostructural 2D coordination polymers, [Ln(HL)(H2O)3]∞ (NIIC‐1‐Eu and NIIC‐1‐Tb), the layers of which are composed by eight‐coordinated lanthanide(III) ions interconnected by triply deprotonated ligands HL3−. The layers are packed in the crystal without any specific intermolecular interactions between them, allowing the facile preparation of stable water suspensions, in which NIIC‐1‐Tb exhibited top‐performing sensing properties through luminescence quenching effect with exceptionally low detection limits towards Fe3+ (LOD 8.62 nM), ofloxacin (OFX) antibiotic (LOD 3.91 nM) and cotton phytotoxicant gossypol (LOD 2.27 nM). In addition to low detection limit and high selectivity, NIIC‐1‐Tb features fast sensing response (within 60–90 seconds), making it superior to other MOF‐based sensors for metal cations and organic toxicants. The photoluminescence quantum yield of NIIC‐1‐Tb was 93 %, one of the highest among lanthanide MOFs. Mixed‐metal coordination polymers NIIC‐1‐EuxTb1−x demonstrated efficient photoluminescence, the color of which could be modulated by the excitation wavelength and time delay for emission monitoring (within 1 millisecond). Furthermore, an original 2D QR‐coding scheme was designed for anti‐counterfeiting labeling of goods based on unique and tunable emission spectra of NIIC‐1‐Ln coordination polymers.

Disproportionation Thermochromic Response in a Luminescent Lanthanide Metal–Organic Framework

“…27−30 The abundant 4f−4f transitions of lanthanide ions can generate emissions across the spectrum from the ultraviolet (UV) to the near-infrared region, which can be further tuned via controlling the energy transfer process between the lanthanide ions. 31,32 Besides, the luminescence of lanthanide ions in Ln-MOFs is highly susceptible to the coordination environment. 33,34 These features inspired us to explore the potential of Ln-MOFs for achieving tunable optical responses to thermal stimuli.…”

Synthesis, Structure and Magnetic Properties of Low-Dimensional Copper(II) trans-1,4-cyclohexanedicarboxylate

“…Polynuclear and polymeric blocks consisting of unpaired electron-rich metal ions can present valuable magnetic properties (such as ferro- [7], antiferro- [8], and ferrimagnets [9], as well as slow magnetic relaxation [10,11]), complex luminescence patterns [12,13], redox behavior [14], and unique chemical bonding features [15]. In particular, such metal centers are of interest for the synthesis of MOCPs with designable and unique properties and unveil the usage of coordination polymers in diverse magnetic materials [16], in highly efficient luminophores and sensors [4,17], for data storage [18], and for production of multifunctional and "smart" materials [19].…”