pH-Stable Eu- and Tb-organic-frameworks mediated by an ionic liquid for the aqueous-phase detection of 2,4,6-trinitrophenol (TNP)

Abstract

Two pH-stable luminescent metal-organic frameworks (LMOFs), {[Ln(L)(OH)(HCOO)]·[HO]} (Ln = Eu 1, Tb 2), based on a new π-conjugated organic building block involving both carboxylate and terpyridine groups were rationally synthesized under a combination of hydro/solvothermal and ionothermal conditions (HL = 4'-(4-(3,5-dicarboxylphenoxy)phenyl)-4,2':6',4''-terpyridine). 1 and 2 are isostructural and feature noninterpenetrated open 3D condensed frameworks constructed by rod-shaped lanthanide-carboxylate building units. Their excellent water-stability and pH-stability allow them to be used in aquatic systems. 1 and 2 both exhibit selective and sensitive aqueous phase detection of the well-known nitroaromatic explosive environmental pollutant 2,4,6-trinitrophenol (TNP), which is highly desirable for practical applications. The presence of a free pyridine group on the LMOF particle surface was strategically utilized for the purpose of exclusive TNP-sensing.

A Highly Sensitive and Recyclable Ln‐MOF Luminescent Sensor for the Efficient Detection of Fe3+ and CrVI Anions

“…In recently, Ln‐MOFs have gained much attention as fluorescent probes and luminescent bioassays for the detection of cations, anions and small molecules, because of their outstanding luminescence features as well as their uniform pore sizes/environments, unparalleled surface areas, excellent thermal and chemical stability, which are convenient for trapping/adsorbing analytes . Luminescent sensors based on Ln‐MOFs always present unique advanced characteristics such as high stability, operability, and recyclability, as well as high sensitivity and excellent selectivity …”

Cobalt(II) and silver(I) coordination polymers containing flexible bis (benzimidazol‐1‐yl)hexane ligands: synthesis, crystal structures, sensing and photocatalytic properties

“…Where I 0 is the fluorescence emission intensity of blank sample; I is the luminescence intensity after adding analyte; K sv is the quenching constant, [M] represents the molar concentration of analyte …”

Terpyridine‐Based 3D Metal–Organic‐Frameworks: A Structure–Property Correlation

“…Nitrobenzene (NB) sensing was explored over many organic, inorganic solvent molecules (MeOH, EtOH, isopropanol, N , N ‐dimethylformamide (DMF), CH 3 CN, THF, CH 2 Cl 2 , CHCl 3 , CCl 4 , DMSO) [21c, 39a] as the energy transfer occurred from the 3D tpy frameworks to electron‐deficient NB efficiently to quench the luminescence through the interspecies contacts [21c] . Similarly, 2,4,6‐trinitrophenol (TNP) is selectively sensed among other nitroaromatics by these frameworks [39a, 31b] . TNP filters the light adsorbed by the ligand, which causes the quenching of fluorescence in {[Eu 2 (L1) 2 (OH)(HCOO)] ⋅ [H 2 O]} n .…”

“…TNP filters the light adsorbed by the ligand, which causes the quenching of fluorescence in {[Eu 2 (L1) 2 (OH)(HCOO)] ⋅ [H 2 O]} n . TNP‐type molecules interact strongly with the free basic sites of the fluorophore (pyridine nitrogen on the surface), owing to which the quenching effect is carried out by the energy transfer mechanism, leading to an amplified response [31b] . The luminescence response towards different analytes is shown in Scheme 4.…”