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A pH-stable and solvent-stable Eu3+-based MOF can selectively and sensitively recognize Cr3+/Al3+/Ga3+via obvious turn-on and blue-shift fluorescence. More interestingly, the fluorescence test papers and LED lamps have been successfully developed.

A water and pH stable CdII-based MOF can be used as a good sensor for Hg2+ ions in aqueous solution. Intriguingly, LED lamps, test papers and luminescent films have been successfully developed to simply detect Hg2+ ions.

A stable CdII-based MOF with a narrow band gap could selectively and sensitively recognize l-histidine via obvious turn-on and fluorescence blue-shift effects. More interestingly, LED lamps of JXUST-14 and JXUST-14@His were developed successfully.

The water and pH stabilities of JXUST-12 have been greatly improved by SCSC transformation and JXUST-12a exhibits high selectivity and sensitivity toward drug.

A novel Co-based metal–organic framework (MOF) with the formula of {[Co3(BIBT)3(BTC)2(H2O)2]·solvents}n (JXUST-2, where JXUST denotes Jiangxi University of Science and Technology, BIBT = 4,7-bi(1H-...

A ZnII-based metal-organic framework (MOF) with a rare tcj topology has been solvothermally synthesized and displays relatively good thermal and chemical stabilities. Interestingly, the MOF can sensitively and selectively sense acetylacetone (acac) via a fluorescence enhancement effect with a detection limit of 0.10 ppm and good reusability, which demonstrates the first example of a MOF-based turn-on fluorescent sensor for acac.

Three zinc(II) metal-organic frameworks have been solvothermally synthesized with V-shaped 1,3-bis(1-imidazolyl)benzene (bib) and 4,4'-oxydibenzoic acid (4,4'-H2oba), namely {[Zn(bib)(oba)]⋅solvents}n (1), {[Zn(bib)(oba)]·2H2O}n (2) and {[Zn2(bib)2(oba)2]⋅2EtOH⋅H2O}n (3). All of them are characterized by single-crystal X-ray diffraction, infrared spectra and powder X-ray diffraction. Complex 1 presents a two-fold interpenetrating three-dimensional structure with 4-connected (65.8) topology. While, complexes 2 and 3 exhibit double layer cavity and double chains based two-dimensional structure, respectively. Luminescent studies indicate that 2 and 3 display selectively sensitive to electron-deficient nitroaromatic explosives with excellent anti-interference abilities.

Two LnIII complexes derived from one aromatic monocarboxylate ligand, namely [Tb2(mnba)6(H2O)4]n (1) and [Dy2(mnba)4(μ3-OH)2(H2O)]n (2) (Hmnba = m-nitrobenzoic acid), have been prepared by similar synthetic procedures and structurally characterized. Complex 1 contains two identical one-dimensional (1D) chains with the syn,syn-carboxylate as linkers, while complex 2 takes the 1D chain structure with μ3--OH and carboxylate as bridge. Magnetic studies indicate that ferromagnetic interactions between intra-chain metal centers exist in 1 and 2 and only complex 2 exhibits field-induced slow magnetic relaxation behavior.

Two di- and trinuclear Gd(III) clusters with the formulas {[Gd2(omba)6(phen)2]·2H2O} (1) and [Gd3(Hsa)5(sa)2(phen)3] (2) (Homba = o-methoxybenzoic acid, H2sa = salicylic acid and phen = 1,10-phenanthroline) have been prepared through the hydrothermal reactions. Complex 1 takes a dinuclear structure and two Gd(III) are bridged by two syn-syn-μ2-η1:η1 and two syn-syn-μ2-η1:η2 carboxylates. While complex 2 is a trinuclear cluster linked by one syn-syn-μ2-η1:η2 and two syn-syn-μ2-η1:η1 carboxylates. Magnetic studies reveal the key impact of magnetic density on the magnetocaloric effect in Gd(III) systems. They exhibit relatively weak magnetic interactions and significant magnetic entropy changes with −ΔSmmax = 17.1 J kg−1 K−1 and 22.5 J kg−1 K−1 (T = 2 K, ΔH = 7 T), respectively.

By using Gd2O3, propanedioic acid (H2pda) and oxalic acid (H2ox), a new Gd-based metal–organic framework (MOF) [Gd(pda)(ox)0.5(H2O)2]n (1) has been successfully constructed and structurally characterized. Interestingly, temperature- and vapor-induced reversible single-crystal-to-single-crystal transformations occurred and two new MOFs, namely [Gd(pda)(ox)0.5(H2O)]n (1a) and [Gd(pda)(ox)0.5]n (1b), have been obtained. Complex 1 displays a two-dimensional (2D) layer structure composed of zigzag [Gd(pda)]n chains and it could also be made up of numerous Gd6 macrocycles. Thermal dehydration leads to more complicated three-dimensional (3D) ‘pillar-layer’ structures (1a and 1b) with the same coordination mode of pda2− anions. Magnetic studies suggest the presence of ferromagnetic couplings between the intrachain or intralayer GdIII ions and large magnetocaloric effects (MCEs) with −ΔSmaxm = 45.0 J kg−1 K−1 (1), 46.1 J kg−1 K−1 (1a) and 46.8 J kg−1 K−1 (1b) under a 7 T applied field. Therefore, the interest of ‘robust magnetocaloric MOFs’ is now extended to compounds showing weak ferromagnetic couplings and hence having better magnetocaloric performances for small field changes.

Two benzothiadiazole-based compounds, namely 4,7-di(1H-1,2,4-triazol-1-yl)benzo- [2] , [1] , [3] thiadiazole (1) and 4,7-di(1H-pyrazol-1-yl)benzo- [2] , [1] , [3] thiadiazole (2), have been constructed with Cu-catalyzed cross-coupling reactions. The fluorescence studies show that compound 1 has high selectivity and sensitivity toward TEA (triethylamine), EDA (ethylenediamine), TMEDA (N,N,N’,N’-tetramethylethylenediamine), MnO4− and ClO− by fluorescence quenching, and compound 2 also has high selectivity and sensitivity toward TEA and TMEDA via fluorescence quenching. The calculated detection limits of 1 for TEA, EDA, TMEDA, MnO4− and ClO− are 0.129, 0.635, 0.320, 9.820 and 12.740 μM, respectively. Meanwhile, the detection limits of compound 2 for TEA and TMEDA are 0.400 and 0.278 μM, respectively. Interestingly, compounds 1 and 2 are the first fluorescent sensors for the selective recognition of TMEDA.

Two dinuclear GdIII cluster complexes with the formulas [Gd2(iba)6(bipy)2] (1) and [Gd2(nic)6(H2O)4] (2) (Hiba = isobutyric acid, Hnic = nicotinic acid and bipy = 2,2´-bipyridine) have been constructed by using gadolinium oxide as GdIII ion source under hydrothermal conditions. Although both 1 and 2 exhibit dinuclear structures, the coordination fashions are totally different. In 1, the carboxylate groups of Hiba take syn-syn-μ2-η1:η1, syn-syn-μ2-η1:η2 and syn-μ-η1:η1 modes and bipy acts as the chelating ligand. While the carboxylate groups of Hnic display syn-syn-μ2-η1:η1 and syn-μ-η1:η1 modes in 2 and two water molecules take part in coordination. Magnetic studies reveal weak ferromagnetic couplings and significant magnetic entropy changes with −ΔSmmax = 29.3 J kg−1 K−1 and 27.4 J kg−1 K−1 (ΔH = 7 T), respectively.

Isostructural CoII and MnII organic frameworks with anionic frameworks and counterions (Me2NH2)+, namely {[M2Cl2(BTC)4/3]·(Me2NH2)+2·4/3H2O}n (M = Co (1) and Mn (2)), have been constructed by one-pot synthesis. Complexes 1 and 2 take paddle-wheel-like dinuclear metal cluster-based three-dimensional structures. Thermogravimetric analysis and variable-temperature powder X-ray diffraction spectra suggested that 1 displays better thermal stability than 2. Both exhibit relatively high proton conductivities at 65% relative humidity (RH) and room temperature (σ > 2.5 × 10–4 S cm–1); however, complex 1 possesses the better cycling capability and stability with Ea = 0.21 eV under 65% RH.

Two Gd2 cluster complexes with the formulas of [Gd2(dnba)6(phen)2] (1) and [Gd2(Hnsa)2(nsa)2(phen)2(H2O)2] (2) (Hdnba = 3,5-dinitrobenzoic acid, H2nsa = 5-nitrosalicylic acid and phen = 1,10-phenanthroline) respectively have been successfully synthesized under hydrothermal conditions. The GdIII ions of 1 are bridged by four carboxylates with syn-syn-μ2-η1:η1 and syn-syn-μ2-η1:η2 modes, while the GdIII ions of 2 are linked by two carboxylate ligands with only syn-syn-μ2-η1:η2 mode. Magnetic studies indicate that weak antiferromagnetic and ferromagnetic interactions exist between the adjacent GdIII ions within Gd2 clusters, respectively. Complexes 1 and 2 display distinct magnetocaloric effects induced by different magnetic interactions and magnetic densities. Notably, the maximum magnetic entropy changes (−ΔSmmax) of 1 and 2 reach 16.8 J kg−1 K−1 and 22.2 J kg−1 K−1 with ΔH = 7 T at 2 K and 3.5 K, respectively.

The hydrothermal reaction of CrO3, Gd2O3 and iminodiacetic acid (H2IDA) yields a three-dimensional (3D) two-fold interpenetrated complex [CrGd(IDA)2(C2O4)]∞ (1). The oxalate anions were generated in situ under hydrothermal conditions. Magnetic studies suggest the presence of weak antiferromagnetic coupling between CrIII and GdIII ions, and negligible GdIII⋯GdIII and CrIII⋯CrIII couplings. Complex 1 exhibits a large magnetocaloric effect with − ΔSmaxm = 39.86 J kg−1 K−1 (the mass aspect) and 93.69 mJ cm−3 K−1 (the volumetric aspect), making it an attractive refrigerant for low-temperature applications.

Two GdIII coordination polymers with the formula [Gd(cit)(H2O)]∞ (1) and [Gd(nta)(H2O)2]∞ (2) (H4cit = citric acid, H3nta = nitrilotriacetic acid) have been successfully prepared under hydrothermal conditions. Complex 1 exhibits a three-dimensional (3D) structure based on carboxylate-bridged layers, while complex 2 is a double-layer structure containing eight-coordinated GdIII. Magnetic investigations reveal that weak antiferromagnetic couplings between adjacent GdIII ions in both 1 and 2 with different Weiss values result in large cryogenic magnetocaloric effects. It is notable that the maximum entropy changes (−ΔSmaxm) of 1 and 2 reach 31.3 J kg−1 K−1 and 32.2 J kg−1 K−1 at 2 K for a moderate field change (ΔH = 3 T), and a remarkable −ΔSmaxm (41.5 J kg−1 K−1 for 1 and 42.0 J kg−1 K−1 for 2) could be obtained for ΔH = 7 T.