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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-stable and pH-stable CP-based fluorescence probe (JXUST-27) can sense SA via fluorescence quenching with high selectivity and sensitivity. Remarkably, the fluorescence film and LED lamp have been further developed to detect SA.

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 new Dy-based complex, [Dy

Two novel anionic lanthanide metal–organic framework materials showed magnetic and proton conductivity properties and specific adsorption of RhB, which could be considered as multifunctional molecular materials.

A new TbIII-based metal–organic framework (Tb-MOF) was prepared and characterized, which was used as a fluorescence sensor with high selectivity and sensitivity for l-Asp, l-Glu, and Al3+ and Ga3+ ions, respectively.

Blue-green-yellow tricolor luminescence conversion is attributed to the loss and recovery of CH2Cl2 solvent molecules and the destruction and restoration of the orderly packing array caused by the breaking and rebuilding of NH⋯O hydrogen bonds.

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 new ZnII-based coordination polymer could selectively and sensitively recognize NFT and DCN via turn-off effect. Interestingly, a mixed matrix film for visualizable sensing has been successfully developed.

A ZnII-based coordination polymer was synthesized by a mixed-ligand strategy, and it could be viewed as the first bifunctional fluorescent sensor with good stability for acac and l-His via a fluorescence red shift and enhancement.

A novel ZnII-based metal-organic framework with the formula of {[Zn2(BBIP)2(NDC)2]·H2O}n (JXUST-5) derived from 3,5-bis(benzimidazol-1-yl)pyridine (BBIP) and 1,4-naphthalenedicarboxylic acid (H2NDC) has been synthesized. The adjacent ZnII ions are linked through two BBIP ligands to form a [Zn2(BBIP)2] secondary building unit (SBU). The neighbouring SBUs are further connected by NDC2− with μ2-η1:η1 and μ2-η1:η1:η1 bridging modes to form a two-dimensional (2D) framework. Topological analysis shows that JXUST-5 could be simplified as an uninodal fes topology with a point symbol of {4.82}. Furthermore, the 2D framework net could be extended through C-H···π interaction to form the three-dimensional supramolecular structure. Luminescent experiments suggest that JXUST-5 could selectively and sensitively recognize Al3+ and Ga3+ through fluorescence enhancement effect along with a relatively large red shift. The detection limits for Al3+ and Ga3+ are 0.17 and 0.69 ppm, respectively. Interestingly, the sensing process for both Al3+ and Ga3+ could be directly observed with naked eyes under 365 nm UV lamp. Notably, JXUST-5 could be recycled at least five times as a fluorescent sensor toward Al3+ and Ga3+, which is the second example of turn-on MOF based fluorescent sensor toward Ga3+.

Gd(iii)-based molecular magnetorefrigerants are reviewed and discussed in detail, with an emphasis on the synthetic strategy towards good stability and large magnetocaloric effect.

A stable benzothiadiazole-based Eu(iii) metal–organic framework with cco topology has been successfully constructed, and represents the multifunctional fluorescence sensor toward Fe3+, MnO4− and Cr2O72− in aqueous solutions.

Three lanthanide-based MOFs with a pyrene-based carboxylate ligand were solvothermally synthesized, which could be considered as fluorescence sensors toward acetylacetone and aspartic acid via a turn-on effect.

A new CdII-based luminescent metal-organic framework (LMOF) with the formula {[Cd(BIBT)(NDC)]∙solvents}n (JXUST-32, BIBT = 4,7-bi(1H-imidazol-1-yl)benzo-[2,1,3]thiadiazole and H2NDC = 2,6-naphthalenedicarboxylic acid) was successfully synthesized by solvothermal method. JXUST-32 shows a two-dimensional...

An in-depth study on a stimuli-responsive tetranuclear cuprous luminescent complex is reported and gives new insights into the origin and possible use of the observed stimuli-responsive luminescence. Its crystalline polymorphs with two different shapes are obtained by using different crystallization solvents and show distinct emissions, with one being blue emissive and the other being yellow emissive. Upon grinding, only the blue-emitting polymorph has a marked change in the emission color from blue to yellow, and its ground sample exhibits a yellow emission similar to that of the yellow-emitting polymorph. Interestingly, the yellow-emitting polymorph after exposure to acetone vapor can emit a blue emission and display luminescence mechanochromism similar to that of the blue-emitting polymorph. Single-crystal structural analyses of the two different polymorphs reveal the relationship between the mechanochromic luminescence and the geometrical configuration of the {Cu(μ-dppm)

A dual-functional sensor based on a two-dimensional metal–organic framework (MOF), namely, {[Cd(BBZB)(2,6-NDC)]·CH3OH}n (JXUST-6, BBZB = 4,7-bis(1H-benzimidazole-1-yl)-2,1,3-benzothiadiazole and 2,...

A novel water-stable Cd

A terbium-based metal-organic framework, namely {[Tb

Two new hydrostable two-dimensional (2D) uranyl coordination complexes [(UO2)5(μ3-O)2(nbca)2]·7H2O (1) and [(UO2)3(nbca)2(H2O)3]·2H2O (2) (H3nbca = 5-nitro-1,2,3-benzenetricarboxylic acid) were hydrothermal synthesized. Single-crystal structural refinements reveal that both of the two complexes were formed by the packing of 2D uranyl coordination sheets via the hydrogen bonds. The nbca ligand coordinating to the uranyl polyhedron centers constructed the 2D sheets. There are UO8 hexagonal bipyramids and UO7 pentagonal bipyramids in 1 while only UO7 pentagonal bipyramids in 2. Photocatalytic degradation of rhodamine B (RhB) in aqueous solution was studied. Complex 2 possesses better performance than 1 with 96.2 % of the RhB was degraded in only 60 min. Mechanism studies reveal that the dissolved oxygens are essential to the RhB degradation. The photocurrent density of 2 is more stable than that of 1, which indicating the stronger ability to separate photoexcited electrons and hole pairs of 2.

Color regulation of solid-state luminescence is desirable and challenging. Herein, we report two new three- and four-coordinate bimetallic cuprous complexes 1 and 2, which bear a NH-deprotonated 3-(2′-pyridyl)pyrazole adopting the monoanionic tridentate μ-η1(N)η2(N,N) bonding mode and exhibit reversible stimuli-responsive luminescence. It is revealed that the reversible stimuli-responsive luminescence for 1 and 2 is triggered by the destruction and restoration of orderly molecular stacking, along with the loss and recovery of the CH2Cl2 solvent molecules for 1. Virtually, this reversible stimuli-responsive luminescence originates from the breaking and rebuilding of various CH⋯O hydrogen bonds around ClO4−, as supported by X-ray single-crystal analysis, the 1H NMR spectra, and the PXRD and FT-IR spectra in various forms. In addition, the possible applications of this reversible stimuli-responsive luminescence have also been investigated.

Two isostructural Ni(II)/Co(II)-based metal-organic frameworks (MOFs), namely {[M3(L)2(bpb)3(H2O)4]·2DMF·2H2O}n [M = Ni (HL-5, HL is short for Hui-Ling Liu); M = Co (HL-6); H3L = 2′,6′-dimethyl-[1,1′-biphenyl]-3,4′,5-tricarboxylic acid; bpb = 1,4-bis(pyrid-4-yl)benzene], have been hydrothermally synthesized and structurally characterized. Both HL-5 and HL-6, which have the same three-interpenetrated 3D pillared-layer framework with sqc306 type topology, present good selective methyl orange (MO) adsorption over rhodamine B (RhB). Moreover, the catalytic CO2 cycloaddition properties with epoxides of the two MOFs have also been studied at ambient pressure and temperature.

A new benzothiadiazole-based MOF {[Zn(BIBT)(oba)]·DMA}n (JXUST-3, BIBT = 4,7-bi(1H-imidazol-1-yl)benzo-[2,1,3]thiadiazole and H2oba = 4,4′-oxybisbenzoate) has been solvothermally synthesized and characterized by single crystal X-ray diffraction, IR spectroscopy and TGA. The fluorescence studies suggest that JXUST-3 could simultaneously selectively sense trivalent metal ions including Al3+, Cr3+ and Fe3+ by a turn-off effect, and the detection limits are 0.055, 0.049 and 0.056 μM, respectively. Moreover, JXUST-3 exhibits relatively good thermal and chemical stabilities and reusability. The fluorescent test paper also displayed an obvious turn-off effect, indicating that JXUST-3 can be used as a potential multi-response fluorescent probe. The possible quenching mechanisms of JXUST-3 for Al3+ and Fe3+ were competitive energy absorption, and for Cr3+ ions, they were competitive energy absorption and weak interactions between Cr3+ and the framework. Therefore, JXUST-3 could be viewed as a transition metal MOF fluorescence sensor for Al3+, Cr3+ and Fe3+ by the turn-off effect, simultaneously.

Four new hydrogen-bonded organic frameworks (HOFs) with the formulas {[H4TCPE·bpa]·(CH3OH·H2O)}n (1), {[H4TCPE·bpe]·(CH3OH·0.56H2O)}n (2), {[H4TCPE·bpa]·CH3OH}n (3) and {[H4TCPE·bpe]·(0.41CH3OH·0.59CH3CN)}n (4) (H4TCPE = tetrakis(4-carboxyphenyl)ethylene, bpa = 1,2-bis(4-pyridyl)ethane, bpe = 1,2-bis(4-pyridyl)ethylene) have been prepared under different conditions and structurally characterized. X-ray crystallographic analysis reveals that the hydrogen bond strengths of 3 and 4 synthesized by solvothermal method are much stronger than those of 1 and 2 prepared by the volatilization method. An obvious fluorescence shift was observed during the sensing process of 3 and 4 toward Al3+ and Fe3+ ions. For HOF 3, a red-shift emission (ca. 28 nm) occurs upon the addition of Al3+ ion. When Al3+ ion is added to HOF 4 in acetonitrile suspension, a red-shift emission (ca. 30 nm) as well as a great fluorescence enhancement happens. Both 3 and 4 exhibit strong fluorescence quenching with high selectivity and sensitivity toward Fe3+ ion. In addition, they display relatively good stabilities as well as reusability. Therefore, HOFs 3 and 4 are excellent fluorescent sensors toward Al3+ and Fe3+ ions.

A novel Zn2+-based metal-organic framework (MOF) with the formula of {[Zn(μ2-η1:η1-BBIP)(μ2-η1:η1:η1-OBA)]•3H2O}n, denoted as JXUST-7, has been successfully assembled by the choice of semi-rigid N-donor 3,5-bis(benzimidazol-1-yl)pyridine (BBIP) and flexible 4,4′-oxybisbenzoate (H2OBA). The adjacent Zn2+ ions are linked through OBA2- ligand with μ2-η1:η1:η1 bridging mode to form an infinite one-dimensional (1D) Zn2+-OBA2- chain. The neighbouring 1D chains are further connected by BBIP ligand with μ2-η1:η1 bridging mode to gain a two-dimensional (2D) sheet layer structure. Topological analysis indicates that the whole 2D structure of JXUST-7 could be simplified as a uninodal sql topology with a point symbol of {44.62}. Furthermore, the opposite parallel 2D layers are further packed by face-to-face π-π interaction to generate a three-dimensional supramolecular structure. Luminescent experiments reveal that JXUST-7 could be considered as a multi-responsive MOF-based fluorescent probe toward Fe3+, Cr2O72- and acetylacetone (acac) via the fluorescence quenching (turn-off) effect. The detection limits for Fe3+, Cr2O72- and acac are 0.14, 1.33 and 6.53 ppm, respectively. The fluorescence quenching mechanism was analyzed in detail by powder X-ray diffraction, fluorescence lifetime measurement, XPS, theoretical calculation and UV-Vis absorption spectra. More importantly, JXUST-7 could be cyclically utilized at least five times for detecting Fe3+, Cr2O72- and acac.

A novel luminescent CdII-based metal–organic framework {[Cd(BBIP)(TBIP)]·EtOH}n (1) derived from the multidentate 5-tert-butylisophthalic acid (H2TBIP) and the semi-rigid N-donor 3,5-bis(benzimidazol-1-yl)pyridine (BBIP) has been solvothermally synthesized and structurally characterized by using infrared spectroscopy, thermal analysis, single-crystal X-ray diffraction and powder X-ray diffraction. The adjacent CdII ions are linked by two carboxylate groups of one TBIP2− ligand with chelating mode to form a one-dimensional CdII-TBIP2− chain, which is further connected by the BBIP ligand to obtain a two-dimensional network. Interestingly, the fluorescence experiments indicate that 1 could be considered as a good multi-responsive sensing material for detecting Fe3+, MnO4−, Cr2O72−, salicylaldehyde (SA) and ethylenediamine (EDA) via the turn-off effect, with the detection limits of 0.53, 0.98, 3.6, 0.42 and 5.3 ppm, respectively. The luminescence quenching effect induced by Fe3+ could be mainly ascribed to the competitive absorption mechanism. The electron-transfer transition and competitive absorption mechanism could be used to explain the luminescence quenching of MnO4− and Cr2O72−. The turn-off effect of 1 on SA could be ascribed to the photoinduced electron-transfer and competitive absorption mechanisms. Meanwhile, the possible mechanism of fluorescence quenching caused by EDA could be attributed to the structure collapse. More importantly, 1 could be regenerated and reused after five cycles for Fe3+, MnO4−, Cr2O72− and SA detection. In a nutshell, 1 could be employed as a multi-responsive luminescent sensor used for the highly selective and sensitive detection of metal ions, anions and small organic molecules.

Crystalline molecular materials exhibiting both proton conduction and single-molecule magnet (SMM) behavior would offer great opportunities for applications in fuel cell, molecular spintronic, and high-density data storage technologies. However, such kinds of materials have rarely been reported. Herein, the first example of a mononuclear proton-conductive DyIII-SMM, namely [Dy(H2bim)2(H2O)2(NO3)2](NO3) (1) (H2bim = 2,2′-biimidazole), was synthesized and characterized. Complex 1 displays high proton conductivity (σ) of 1.16 × 10−3 S cm−1 at 35 °C and 100% relative humidity (RH). The 1D H-bonding network, with 2,2′-biimidazole and coordinated water molecules acting as H-bonding donors and nitrate anions (NO3−) acting as H-bonding acceptors, plays a dominant role in allowing this high conductivity. Magnetic studies indicated that complex 1 exhibits single-ion magnet behavior.

The reaction of the redox-active tetrathiafulvalene ligand and lanthanide ions is an important approach to prepare photo-electro-magnetic multifunctional metal–organic framework materials. A series of isostructural lanthanide metal–organic frameworks (Ln-MOFs) based on the in situ generated tetrathiafulvalene dicarboxylate (TTF-DC) ligand, {[Ln4(TTF-DC)6(DMF)4(H2O)2]·4DMF}n (Ln = Gd (1-Gd), Tb (1-Tb), Dy (1-Dy) and Er (1-Er)), was synthesized and characterized. These Ln-MOFs display tunable redox-active properties and semiconductor performance, and their electronic conductivities have been significantly improved after oxidation. All MOFs except 2-Tb exhibit slow magnetic relaxation under an applied dc field. 1-Dy and 2-Dy show field-induced single-molecule magnet (SMM) behaviour with energy barriers (Ueff) of 30.77 K (τ0 = 5.23 × 10−8) and 26.41 K (1.04 × 10−8 s), respectively.

Two new ZnII–LnIII heterometallic complexes derived from the amine-phenol ligand, namely [Zn2Ln(L)2(H2O)2](ClO4)3·3.5H2O (Ln = Dy (1) and Tb (2), H2L = 1,2-bis(3-methoxysalicylideneethylaminooxy)ethane), have been synthesized and structurally characterized. Complexes 1 and 2 are isomorphic trinuclear clusters and crystallize in the triclinic P space group. Magnetic measurements indicate that complex 1 exhibits field-induced slow magnetic relaxation with energy barrier of 27.91 K. Both display strong fluorescence emissions, which are typical narrow emission bands of lanthanide ions. Moreover, complex 2 shows a proton conductivity of 6.43 × 10−5 S cm−1 at 60 °C and 98% relative humidity. Complexes 1 and 2 as multifunctional materials may offer a potential application in magnetic, luminescent, and electrical devices.

A new family of lanthanide complexes based on a tetrazole-1-acetate ligand and a 1,10-phenanthroline co-ligand were synthesized and characterized by IR spectroscopy, thermogravimetric analyses, powder X-ray diffraction and single-crystal X-ray diffraction, and their formula is [Ln2(μ-Cl)2(1-tza)2(phen)4](ClO4)2 [Ln = Eu (1), Tb (2), Gd (3), Dy (4); 1-Htza = tetrazole-1-acetate, phen = 1,10-phenanthroline]. They show dinuclear structures bridged by mixed μ-COO−1-tza and μ-Cl−. The solid-state luminescence emission properties of 1 and 2 exhibit the characteristic emission bands of Ln cations with a lifetime of 1.49 ms and 0.20 ms, respectively. Magnetic studies reveal that 3 shows a magnetocaloric effect with −ΔSmmax = 18.5 J kg−1 K−1 at 3 K for ΔH = 5 T and 4 displays a single-molecule magnet behaviour with Ueff of 15.19 K.

A three-dimensional metal–organic framework, namely {[Zn3(BIBT)(BTC)5/3(μ3-OH)]·solvents}n (JXUST-4), has been synthesized by using ZnII ions, and BIBT and H3BTC ligands (BIBT = 4,7-bi(1H-imidazol-1-yl)benzo-[2,1,3]thiadiazole and H3BTC = 1,3,5-benzenetricarboxylic acid). JXUST-4 shows a new (3,3,7)-connected topology net containing a trinuclear ZnII cluster, uncoordinated N atoms of BIBT and uncoordinated carboxylate O atoms of H3BTC, which facilitates the interaction between the framework and analytes. Fluorescence studies indicate that JXUST-4 generates light yellow luminescence, which could be ascribed to ligand-centered emission. More importantly, JXUST-4 could be viewed as an effective fluorescent sensor toward acetylacetone through an obvious fluorescence red-shift with high sensitivity, efficient selectivity, and outstanding recycling capacity. Furthermore, the possible sensing mechanism of JXUST-4 toward acetylacetone is due to electron transfer and weak interactions between the analyte and framework.