g-Tian Yan

Highly selective luminescence sensing for the detection of nitrobenzene and Fe3+ by new Cd(II)-based MOFs

Herein, three new luminescent metal–organic frameworks (MOFs), namely {[Cd4(H3L)4(H2O)12]·2.5H2O}n (1), {[Cd(L)]·2.5H2O·3[H2N(Me)2]}n (2), and {[Cd2(L)(DMA)]·[H2N(Me)2]}n (3), were designed and successfully prepared via a solvothermal reaction using V-shaped rigid multicarboxylate 2,4-di(3′,5′-dicarboxylphenyl)benzoic acid (H5L) and Cd(II) salts in various solvent systems. The structural analyses indicated that the H3L2−/L5− ligands took three different coordination fashions in 1–3; this resulted in a diversity of targeted MOFs. The solid-state luminescence properties of three MOFs were studied under ultraviolet light irradiation at ambient temperature, and 3 showed a high selectivity and sensitivity for nitrobenzene and Fe3+ because of the quenching effect. Thus, it could be a potential crystalline material for detecting these substances. The mechanisms of the quenching effect and sensing properties of 3 have been discussed in detail.

Solvent-induced diversity of luminescent metal–organic frameworks based on different secondary building units

By using a symmetrical V-shaped rigid 5′-carboxyl-(1,1′-3′,1′′-terphenyl)-4,4′′-dicarboxylic acid (H3L), three Cd(II)-based metal–organic frameworks (MOFs), [Cd3(L)2(H2O)4]·DMF (1), [Cd2(L)(SO4)2]·3(Me)2NH2 (2) and [Cd(HL)(H2O)]·0.5H2O (3), have been synthesized under solvothermal conditions. Due to the reactions in different solvent systems, L3−/HL2− in 1–3 show different coordination modes with Cd(II) ions to form various secondary building units (SBUs) in the final structures. The desolvated structure of 1 (1a) contains two shapes of 1D channels with suitable pore sizes. 2 is a 3D dense packing pattern with a three nodal (5,6,7)-connected new topological net, and 3 is a 2D layered (4,4)-connected sql network connected with partly deprotonated HL2− ligands. As a result, 1a possesses not only high CO2 loading but also excellent CO2/CH4 selectivity. In addition, all complexes display solid-state luminescence stemming from ligand-to-metal charge transfer.

Seven luminescent metal–organic frameworks constructed from 5-(triazol-1-yl)nicotinic acid: luminescent sensors for CrVI and MnO4− ions in an aqueous medium

Seven new luminescent metal–organic frameworks (LMOFs), [Cd1.5(L)2(H2O)(NO3)]n (1), [Cd(L)2(H2O)2]n (2), [Pb(L)(H2O)2(NO3)]n (3), [Pb(L)2(H2O)]n (4), [Zn(L)2(H2O)4]n (5), [Zn2(L)(btc)(H2O)2]n (6) and {[Zn(L)(p-bdc)0.5(H2O)](p-H2bdc)0.5}n (7), were assembled employing 5-(triazol-1-yl)nicotinic acid (HL) with Cd(II), Pb(II) and Zn(II) ions, revealing versatile frameworks as well as various types of coordination modes of HL. Single-crystal X-ray diffraction analyses reveal the different dimensionalities (0D, 1D, 2D or 3D) of complexes 1–7. Complex 1 displays a 3D dense-packing structure with a 3-nodal 3,4,6-connected net with a symbol of {4·64·8}2{4·2·64·89}{62·8}2. Complex 2 presents a 2D layered structure with a uninodal 4-connected sql net with a symbol of (44·62). Complex 3 shows a 1D chain based on [Pb2(COO)2(H2O)4(NO3)2N2] secondary building units (SBUs) and 4 exhibits a 1D dimeric chain. Complex 5 is a 0D structure. Complexes 6 and 7 display 2D layered structures based on binuclear [Zn2(COO)4(H2O)2N2] SBUs, which are designated as a 4-nodal 3,3,3,6-connected net with a symbol of {4·62}2{42·610·83}{63}4 and a 4-connected sql net, respectively. Further, the solid-state luminescence properties of the complexes were measured at room temperature. Meanwhile, 2 shows high selectivity and sensitivity for CrO42−, Cr2O72− and MnO4− ions by luminescence quenching effect with low detection limits, and the mechanisms of the quenching effect are discussed in detail.

Ln(III)-MOFs (Ln = Tb, Eu, Dy, and Sm) based on triazole carboxylic ligand with carboxylate and nitrogen donors with applications as chemical sensors and magnetic materials

Abstract Using a triazole carboxylic ligand (H2L = 4-(1H-1,2,4-triazol-1-yl) isophthalic acid), four water-stable lanthanide metal–organic frameworks (Ln(III)-MOFs) (1-Ln, Ln(III) = Tb, Eu, Dy, and Sm), [Ln(L)(HL)(H2O)2], where the deprotonated H2L ligands have two different coordination modes: L2− and HL− [(a): η2μ2χ2, η2μ1χ2; (b): η2μ1χ2], have been synthesized by solvothermal reaction and characterized by elemental analysis, FT-IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Single-crystal X-ray diffraction analyses show that Ln(III)-MOFs are isostructural with 2D-layered structures with uncoordinated carboxylic and triazole groups. The luminescent properties of 1-Tb in aqueous solution containing different cationic solutions and small organic solvents have been explored under ultraviolet irradiation at room temperature. The high quenching constant KSV values and low detection limits indicate that 1-Tb exhibits extremely high detection sensitivity and selectivity toward Fe3+ ions and nitrobenzene; 1-Tb can keep its original network and be reused after the sensing experiments, which provide us with an optical material for detecting Fe3+ ions and nitrobenzene. Magnetic studies show that antiferromagnetic exchange interactions exist between Dy(III) ions in 1-Dy.