Alkaline-earth phosphonate MOFs with reversible hydration-dependent fluorescence

Abstract

A new rigid tritopic phosphonic ligand, 2,4,6-tris(4-phosphonophenyl)pyridine (H6L), was synthesized and used to assemble isostructural barium (1) and strontium (2) phosphonate metal organic frameworks that exhibit fully reversible and selective water-dependent fluorescence red-shift at room temperature.

Ratiometric and Turn-On Luminescence Detection of Water in Organic Solvents Using a Responsive Europium-Organic Framework

“…Luminescent metal–organic frameworks (MOFs) combining the intrinsic properties of MOFs and intense fluorescence have emerged as particularly exciting materials for chemical sensors in the past decade. − In comparison with traditional luminescent materials, luminescent MOFs show three major advantages in chemical sensing: (1) their hybrid nature gives rise to multiple emissions, because all the component metal cations, organic linkers, and guest species can potentially serve as photonic units; (2) their high and permanent porosity facilitates the preconcentration of analytes and the interactions between analytes and photonic units within the framework; (3) the structural and chemical tunability on the molecular level is extremely beneficial to the high detection selectivity through pore sieving functions or specific host–guest interactions. Luminescent MOFs have been intensively investigated to detect various targets, including metal cations, , small molecules, , gases, biomarkers, − and temperature. , Of particular interest is that luminescent MOFs have demonstrated considerable potential for water detection. − By taking advantage of various water-dependent processes, such as intramolecular proton-transfer (ESIPT), ,, structure transformation, − and energy transfer, − a number of water sensors based on MOF materials have been developed. However, the existing MOF water sensors mainly relied on a single emission intensity, − which is susceptible to the external errors introduced by optical occlusion, excitation power fluctuation, and concentration inhomogeneity.…”

A Solid-State Luminescent Cd(II) Supramolecular Coordination Framework Based on Mixed Luminophores as a Sensor for Discriminatively Selective Detection of Amine Vapors

“…38 Overall, the large bathochromic shift in the emission spectrum of 1 (Figure 3b) originates from a ligand-to-ligand charge (LLCT) transition, as highlighted from our computational studies (see below). [38][39][40] respectively, compared to that of the original 1 (λ em = 534 nm) (Figure 4a). The large blue-shift in emission spectra results in a color change from yellow to dark blue for 1@NH 3 and cyan for 1@EDA, which can be visibly noticeable with the naked eye under UV light, corresponding well with the CIE chromaticity diagram (Table S5 and Figure 4b).…”

Alkaline earth-organic frameworks with amino derivatives of 2,6-naphthalene dicarboxylates: structural studies and fluorescence properties

“…The significant red shift in the emission maximum of 1 compared to those of 2 and 3 can be possibly be assigned to a combination of structural and electrostatic factors related to the higher charge density of the Ca 2+ ion relative to Sr 2+ and Ba 2+ . 33 The stronger electron withdrawing effect of the Ca 2+ cation possibly induces a stabilizing effect on the π * orbitals of the aromatic core of ANDC 2− thereby decreasing the energy of the intraligand charge transfer transition. Additionally, as demonstrated by the solvatochromism exhibited by the uncoordinated ligands, the emission energies of the organic linkers also depend on the immediate environment around their chromophores such as the existence and relative strength of hydrogen boding interactions.…”

“…27 The closed-shell electronic structure of alkaline earth ions results in their MOFs exhibiting ligandbased fluorescence [28][29][30] which, in the cases where ligands contain suitable functional groups, can prove to be of interest for possible sensing applications. [31][32][33] In addition, there are examples of AEMOFs which show promising gas separation, 34,35 catalytic 36,37 and electrical properties. [38][39][40][41][42] Amino functionalized aromatic dicarboxylates are of particular interest for MOF synthesis as they can lead to materials with increased CO 2 adsorption 43 and favorable fluorescence 44 and photocatalytic [45][46][47][48] properties.…”