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Lanthanide (Ln) metal–organic frameworks (Ln-MOFs) have attracted attention in anti-counterfeiting and white light-emitting diodes (WLEDs) due to their high quantum efficiency, long lifetimes, and characteristic linear spectrum. However, Ln-MOFs have some disadvantages, such as harsh luminescence modulation, low transparency, and poor film formation. In this study, Ln-MOF (Ln = Eu and/or Tb)-modified TEMPO-oxidized cellulose nanofibrils were employed for preparing transparent nanopapers and luminescence modulation. These luminescent nanopapers achieved an excellent light emission color tuning from green, yellow, and red under 365 nm excitation, while 254 nm radiation on these nanopapers only emitted characteristic pink light. Thus, the luminescent nanopapers combined color-tuning and photo-switching properties through the control of Eu³⁺/Tb³⁺ molar ratio and excitation wavelength (λEₓ at 365 and 254 nm), respectively, which greatly improved them for anti-counterfeiting applications. In addition, Ln-MOFs endowed these nanopapers with excellent optical haze (>90%), such that softening of white light from WLEDs was realized in 254 nm-driven UV-LED chips, corresponding white light with good color quality [Commission International de I’Eclairage coordinates, correlated color temperature, and color-rendering index of (0.34, 0.36), 5536 K and 86, respectively].

A new porous metal–organic framework (MOF) {[Cd(Hbptc)]·H2O}n (Cdbptc) was assembled by Cd(II) ions and a rigid (1,1′-biphenyl)-2,4,6-tricarboxylic acid (H3bptc) ligand via a solvothermal method. C...

The discharge of excessive metal ions and anions into water bodies leads to the serious pollution of water and environment, which in turn has a certain impact on industry, agriculture, and human life. Because of the unique advantages of luminescent metal-organic frameworks (LMOFs), they have been successfully explored as various fluorescent probes to quickly and effectively detect these pollutants. This perspective not only introduces the design strategy and classification of LMOFs, especially the construction methods of water-stable LMOFs, but also reports the latest progresses in some LMOFs between 2016 and 2020 as well as expounds the mechanisms of LMOFs for detecting anions and cations. Moreover, the luminescence properties of LMOFs are related to the selection of metal ions, the structure of organic ligands, the pore size, and the interaction of guest molecules. Finally, the further development of LMOFs is summarized and prospected in this field.

Suitable chemical components in water systems for human health are a crucial prerequisite for mankind's survival. Simple and effective innovations are being developed to efficiently monitor healthy and toxic substances. Here, with a hydrothermal technique, a novel thermostable metal–organic framework (MOF) [Cd2(L)(bib)0.5(H2O)3]n·1.75n(H2O) (MOF-1, H4L = biphenyl-2,3,3′,5′-tetracarboxylic acid, bib = 1,4-bis(imidazolyl)butane) was designed and synthesized. MOF-1 shows a 4,5-connection binodal 3D fsx-type topological net with irregular cages, which the bulk materials show high phase purity, excellent thermo/aqua-stability and intense fluorescence. The luminescent MOF was studied for the highly sensitive detection of trace amounts of Fe3+ ions and nitrobenzene and shows high KSV values of 4.653 × 104 and 5.724 × 104, respectively. It was also demonstrated that MOF-1 possesses superior probing ability towards nine other nitroaromatic explosives with remarkable quenching percentages. These results offer a new possibility for the potential multiple recognition of various chemical substances in human body and water systems by utilizing novel dual-functionalized luminescent MOF sensors.

Two new metal–organic frameworks (MOFs), formulated as [Cd3(L)2(H2O)2]·2H2O (1) and [Zn2(L)(OH)(H2O)]·2DMA (2, DMA = N,N-dimethylacetamide), were first constructed via an unsymmetrical N-heterocyclic 5-((4-carboxypyridin-2-yl)oxy)isophthalic acid (H3L) ligand. Then, a proportion of the Zn(II) ions of 2 were substituted by fine-tuning the contents of Co(II) ions to obtain two new isomers, Co1-MOF 2 and Co2-MOF 2, the successful doping of which can be proved by PXRD, IR spectra, ICP, XPS, and SEM. The luminescent experiments suggested that complex 1 should be a good detector for detecting Fe3+ and Cr2O72− ions. More remarkably, the Co-rich MOF materials have increased gas capture for CO2 and CH4 compared to that of the Co-free isomer 2, and the absorption amount of CO2 and CH4 may rise with the increasing content of Co(II) ions in the system at higher pressure and lower temperature.

A new 3D luminescent Ba-organic framework {[Ba3L2(NMP)2(H2O)2]·2NMP·H2O}n (1) was first synthesized based on Ba(II) and a triangular-shaped bridging rigid ligand, namely 1,3,5-tris(4-carboxyphenly)benzene (H3L), via solvothermal reaction (NMP = N-methyl pyrrolidone), thereby forming a stabilized network including a one-dimensional (1D) infinite rod-like helical metal chain. 1 may be explored as a recyclable heterogeneous catalyst for the efficient fixation of CO2 to form serviceable cyclic carbonate since 1D channels remain decorated with abundant open metal sites (OMSs), and the catalytic efficiency of 1 was up to 98% for 1-bromo-2,3-propylene oxide. Simultaneously, the luminescence sensing shows that 1 has excellent response and sensitivity towards pollutants such as Fe3+, Cr2O72−, CrO42−, and [Fe(CN)6]3− ions. Moreover, 1 exhibits the particularly selective sorption towards the Congo red (CR) dye. Consequently, this study may provide a facile synthetic route for the construction of multi-functional Ba-MOF materials.

Three isostructural lanthanide metal–organic frameworks (Ln-MOFs), {[Ln(L)(H2O)2]·H2O}n (M-Ln, Ln = Eu/Tb/Dy), were prepared with a flexible 3,5-(4-carboxybenzyloxy) benzoic acid (H3L) ligand and lanthanide ions by a solvothermal method. M-Ln are two-dimensional (2D) grid layer-stacking frameworks. M-Eu exhibits excellent chemical stabilities against organic solvents and shows strong luminescence. The experimental results indicated that M-Eu could be used as an ideal fluorescent probe to detect nitrobenzene (NB) in different solvents with a lower detection limit. M-Eu can also be used as a pH sensor because of its superior water stability. Furthermore, M-Eu and M-Tb show unique strong luminescence properties with high absolute quantum yields. The quantum yields can even reach up to 11.8% and 60.5%, respectively. Simultaneously, various kinds of heterometallic doped M-EuxTb1−x MOFs were acquired by tuning the ratios of Eu3+/Tb3+ ions, showing the unique color changes from red, orange-red, orange, orange-yellow, light yellow, yellow to green.

A new series of isomorphic lanthanide metal–organic frameworks (Ln-MOFs), {[Ln2(L)3·DMF·H2O]·DMF·H2O}n (denoted as 1-Ln, Ln = Eu, Gd, Tb or EuxTb1−x), were constructed using the 4′-(1H-1,2,4-triazol-1-yl)-[1,1′-biphenyl]-3,5-dicarboxylic acid (H2L) ligand and Ln3+ ions under solvothermal conditions. 1-Ln shows a binodal (3,3,8)-connected three-dimensional (3D) framework based on a π-conjugated and uncoordinated Lewis basic triazolyl ligand. Then, six two-color doped 1-EuxTb1−x and the tri-metallic doped 1-Eu0.01Gd0.6015Tb0.3885 with white light emitting MOFs were fabricated by doping diverse concentrations of Eu3+, Tb3+ and Gd3+ ions. More interestingly, 1-Eu0.01Gd0.6015Tb0.3885 has a higher quantum yield (36.49%). Meanwhile, 1-Ln shows excellent performance in fluorescence sensing (Ksv = 1.5143 × 104 M−1) and anticounterfeiting applications.

Several new isostructural lanthanide metal-organic frameworks (Ln-MOFs), {[Ln

Tuning the emissive color changes of lanthanide (Ln) complexes is an important and appealing project for promoting the applications of Ln-complexes. A solvothermal reaction of 4-cyano-3-methylbenzoic acid (HL) and Ln(NO3)3·6H2O affords three isostructural Ln-complexes [Eu(L)3(H2O)2]n (1-Ln) (Ln = Eu, Gd and Tb) with one-dimensional chain structures. 1-Eu and 1-Tb show bright red and green emissions with absolute quantum yields of 3.06% and 11.96%, respectively, and the energy transfer was analyzed in detail through combined calculations. Interestingly, a series of heterometallic doped 1-TbxEu1-x coordination polymers were also obtained by mixing different ratios of Eu3+ and Tb3+ ions, which possess continuous luminescent color changes from green to yellow, orange and red. In addition, 1-Eu exhibits high quenching efficiency and low detection limit (∼10-4 M) for the simultaneous sensing of MnO4-, CrO42- and Cr2O72- ions in water.

Utilizing 5,5′-oxidiisophthalic acid (H4odip) ligand, one 3D framework {[Ni2(odip)(H2O)4(DMF)]·DMF·2H2O}n (1) with a rare 3-nodal (3,3,4)-connected topological net based on two types of Ni12(odip)1...

With the aid of a pyridyl tetracarboxylate ligand, 2,5-bis(2',5'-dicarboxylphenyl)pyridine (H4L), two indium-organic frameworks, [In2(L)(OH)2]·2DMF·2H2O (1) and [Me2NH2][In(L)]·2.5NMF·4H2O (2), with (6,8)- and (4,4)-connected nets have been constructed in different solvent systems. Both 1 and 2 exhibit high thermal and chemical stability. Gas sorption behavior of 1 and 2 for N2, C2H2, C2H4, CO2, and CH4 indicate excellent separation selectivities of C2Hx/CH4 and CO2/CH4. Furthermore, 1 possesses a high density of Bronsted sites and shows efficient catalytic conversion for CO2 cycloaddition with epoxides. Meanwhile, luminescence investigations reveal that 2 can detect nitrofurazone efficiently.

Based on the mixed carboxylate ligands synthesis strategy, an indium-organic framework, (Me2NH2)1.5[In1.5(FBDC)(BDC)]·2.5NMF·CH3CN (1) has been constructed by using the mixed (2,5-di(2',5'-dicarboxylphenyl)-difluorobenzene (H4FBDC) and terephthalic acid (H2BDC). Compound 1 contains a 3D intersecting pore system which surface is modified by F atoms, and it has excellent stability in pH = 2-12 aqueous solutions. The activated 1 shows high separation for C2H2/CO2 and C2H2/CH4. Moreover, 1 not only has strong luminescence but also has the high selectivity and sensibility of fluorescence detection to nitrofurazone (NZF) in antibiotic sensing experiments, which can be used as a luminescence sensor for NZF detection.

A mixed-ligand strategy has been used to construct stable luminescent coordination polymers (CPs). An ultra-stable Zn(ii) coordination polymer, [Zn(H3tpb)(Hbtc)]n (1) was hydrothermally synthesized by employing a new tripodal pyrazole ligand H3tpb and a classical carboxylic ligand H3btc (H3tpb = 1,3,5-tris(pyrazolyl)benzene, H3btc = 1,3,5-benzenetricarboxylic acid). Complex 1 exhibits a 2D sql network. Importantly, 1 not only possesses excellent thermal stability but also shows superior chemical stability in terms of water resistance, acid/base aqueous solutions tolerance (pH = 2-12), and organic solvents resistance. This excellent structural stability was further illustrated from the perspective of thermal decomposition kinetics. The luminescence properties were investigated, showing that complex 1 displays high sensitivity and selectivity for detecting Fe3+ and Cr2O72- ions in aqueous solutions via luminescence quenching effects.

Three new isostructural 3D lanthanide metal-organic frameworks (Ln-MOFs), {H[LnL(H2 O)]⋅2 H2 O}n (1-Ln) (Ln=Eu3+ , Gd3+ and Tb3+ ), based on infinite lanthanide-carboxylate chains were constructed by employing an ether-separated 5,5'-oxydiisophthalic acid (H4 L) ligand under solvothermal reaction. 1-Eu and 1-Tb exhibit strong red and green emission, respectively, through the antenna effect, as demonstrated through a combination of calculation and experimental results. Moreover, a series of dichromatic doped 1-Eux Tby MOFs were fabricated by introducing different concentrations of Eu3+ and Tb3+ ions, and they display an unusual variation of luminescent colors from green, yellow, orange to red. 1-Eu with channels decorated by ether O atoms and the open metal sites displays good performance for CO2 capture and conversion between CO2 and epoxides into cyclic carbonates.

The new indium-based organic framework {(Me2NH2)[In(BDPO)]·DMF·2H2O}n (1) was successfully constructed by using the oxalamide group modified ligand N,N'-bis(isophthalic acid)oxalamide (H4BDPO). This framework presents a 2-fold interpenetrating structural characteristic, and the unique polar pore environment leads to a high capture ability for CO2, C2Hn and CH3OH and good separation ability for CO2 and C2Hn over CH4 as well as for CH3OH over C2H5OH, which was further verified by an ideal adsorbed solution theory (IAST) calculation. Theoretical simulations pointed out the possible adsorption sites of different adsorbed gases in 1. In addition, the excellent chemical stability and strong luminescence of 1 give it an effective selective detection ability for 2,6-dichloro-4-nitroaniline (DCN) in water with a low detection limit of 3.85 ppm, and the detection mechanism is discussed in detail.

In order to explore the metal ions-controlled syntheses of coordination polymers (CPs), the temperature and solvent ratio were fixed in the reaction processes. By selecting a series of s- and d-block metal ions, five new CPs, [ZnL0.5(H2O)2]n (1), [CoL0.5(H2O)2]n (2), [Mn(H2L)(H2O)2]n (3), [Ca(H2L)(H2O)2]n (4) and [Ba(H2L)(H2O)2]n (5), have been synthesized by employing a less-investigated oxalamide N,N′-bis(4-phthalic acid) (H4L) ligand. H4L shows very versatile coordination modes and leads to various frameworks, including isomorphous 2D grid-like layer based on M2O2 cores for 1 and 2, isomorphous 4-connected 3D PtS frameworks based on 1D [M(CO2)2]n chains for 3 and 4, and a 2D wave-like layer based on [BaO3]n chains for 5.2 and 3 reveal the antiferromagnetic and ferromagnetic properties, respectively, while 1, 4 and 5 possesses strong solid state luminescence.

Four new water-stable luminescent metal-organic frameworks (MOFs), namely {[Zn4(L)2(H2O)4(OH)2]·3NMP}n (1), {[Zn3(L)2(H2O)2]·Diox}n (2), {[Cd3(L)2 (H2O)5]·NMP·3H2O}n (3), and {[Pb3(L)2(NMP)2(H2O)]·H2O}n (4), (H3L = 5-(1-(carboxymethyl)pyrazol-3-yl)isophthalic acid; NMP = N-methyl-2-Pyrrolidoneand; Diox = 1,4-Dioxane) have been solvothermally synthesized with different solvents. The single crystal structures of 1–4 reveal that complexes 1 and 2 form the 2D (3,6)-connected kgd nets based on the tetranuclear [Zn4(μ1-COO)2(μ2-COO)4] clusters and trinuclear [Zn3(μ1-COO)2(μ2-COO)4] clusters, respectively. Complex 3 displays a 2D (3,6)-connected kgd net based on the trinuclear [Cd3(μ1-COO)4(μ2-COO)2] clusters. Complex 4 presents a 2D layer with a rod-shaped SBUs. The solid-state luminescence properties and water stability of these complexes were investigated carefully, showing that 1 displays high selectivity for Fe3+, CrO42−, and Cr2O72− via luminescence quenching effects with low detection limits. The probable quenching mechanisms have been studied in detail.

Five new 3D MOFs: {[Zn3(HL)2H2O]·4H2O}n (1), {[Ba2L5H2O]·2H2O}n (2), {[Ba4(L)2·5H2O]·2H2O}n (3), {[Cd3(HL)2·Cl2·2H2O]·2H2O}n (4) and {[Cu2(L)2·2H2O]·4H2O}n (5), were constructed based on 1-(3,5-dicarboxylatobenzyl)-3,5-pyrazole dicarboxylic acid. Structural analysis shows that 1–5 have 3D frameworks, among which 1(Zn) exhibits high luminescence sensing for Fe3+ ions, excellent framework stability and reusability. The sensing mechanism of 1(Zn) is briefly discussed. In addition, 5(Cu) displays antiferromagnetic exchange phenomena.

A novel two-dimensional Cd-based metal–organic framework, {[Cd(Hcpnc)(DMF)]·DMF·2H2O}n (Cd-MOF) has been synthesized successfully under solvothermal conditions by utilizing a multifunctional N,O-building block ligand, 2-(2,5-dicarboxylphenyl)nicotinic acid (H3cpnc), which is a new and virtually unexplored multifunctional pyridine-tricarboxylic building block. The product was isolated as a stable crystalline solid and was fully characterized by IR spectroscopy, elemental analyses, thermogravimetry and differential scanning calorimetry, powder X-ray diffraction, single-crystal X-ray diffraction analyses, and X-ray photoelectron spectroscopy. The solid-state luminescence properties of the Cd-MOF were studied at ambient temperature. The compound shows high selectivity and sensitivity for Cu2+ ions and nitrobenzene by the luminescence quenching behavior with excellent repeatability. Additionally, the Cd-MOF exhibits an excellent specific capacitance of 321 F g−1 at 0.5 A g−1 and it still retains 95.2% of the original capacitance after 1000 cycles. Therefore, the Cd-MOF as a kind of bifunctional material will have broad application prospects in luminescence detection and supercapacitors.

The reactions of an unexploited N,N'-5-carboxyl-1,3-phenylenebis(ethyl oxamate) (HEt2 L) ligand with different Mn2+ and Cd2+ salts under solvothermal conditions afforded four three-dimensional (3D) coordination polymers (CPs): [Mn1.5 L(H2 O)2 ]⋅H2 O (1) [Mn2 L(C2 O4 )0.5 (NMP)(H2 O)] ⋅ NMP (2), [Cd1.5 L(H2 O)2.5 ] ⋅ H2 O (3) and [Cd2 L(C2 O4 )0.5 (H2 O)3 ] ⋅ H2 O (4) (NMP=N-methyl pyrrolidone). L, generated by the in-situ hydrolysis of HEt2 L, displays four kinds of coordinating modes through oxamate and carboxylate groups as well as different syn-syn and syn-trans configurations. The resulting novel (3,4,5)-, (3,4,6)-, (4,5)- and (4,4,4,5)-connected topologies for 1-4 were formed. Among them, 1 has interesting 1D metal-oxamate zigzag chains, 2 contains 1D channels with a free void of 52.5 %, 3 consists of an unprecedented Cd-oxamate layer, 4 has a novel Cd-oxamate-oxalate chain. The antiferromagnetic interactions of 1 and 2 were observed, meanwhile 3 and 4 exhibit solid-state luminescence with the maximum emission bands at 483 and 479 nm, respectively, under an excitation of 332 nm.

Recent materials research based on fluorescent nanocelluloses (NCs) used in the field of sensing and bioimaging is reviewed. Many designed morphologies have been reported, such as nanoparticles, fibers, nanopapers, hydrogels and aerogels, that have been produced by physical or chemical methods. In the field of sensing and bioimaging, these studies have involved, but not been limited to, special optical properties including fluorescence, long-lived luminescence, polarized light, and/or aggregation-induced emission. The fluorescence sensing platforms can be categorized according to stimuli such as pH and temperature, as well as the presence of toxic compounds, and anions and metal cations. In addition, NCs exhibit unique low toxicity, good biocompatibility, biodegradability and cell membrane penetration, and can be modified into fluorescent nanoprobes for in vivo imaging and tracing. As an excellent platform for fluorescent sensing and bioimaging, NCs are bound to be increasingly studied and widely applied in the field of production and life sciences.

An achiral 2,2′-bipyridyl-3,3′-dicarboxylate (H2LN) can be oxidized to a C2 axially chiral N-oxide analogy (R,S)-2,2′-bipyridyl-3,3′-dicarboxylate-1,1′-dioxide ((R,S)-H2LNO), converting normal bipyridyl-N to a charge-separated N-oxide group. The achiral H2LN connects the Ag(I) ions into a 4-connected mesomeric 3D network [Ag4(LN)2·(H2O)]·3H2O (1). However, as expected, with the introduction of N-oxide groups, {Ag4[(R,S)-LNO]2·2(H2O)}·H2O (2) and {Ag2[(R,S)-LNO]}·H2O (3) contain right- and left-handedness homochiral layers. Such opposite handedness layers are linked together to give a racemic compound in 2 but meso double-layers in 3. Notably, both ligands in 1–3 support argentophilic interactions. Moreover, a luminescent comparison of 1–3, pyridyl-N, and its functional N-oxide ligands is also investigated in detail.

Six new coordination polymers (CPs), [Ni(L)(H₂O)₄]n (1), [Co(HL)₂(H₂O)₂]n (2), {[Cu(L)(H₂O)₃]·H₂O}n (3), [Mn(L)(H₂O)₂]n (4), [Cd(L)(H₂O)₂]n (5) and {[Zn₂(L)₂]·H₂O}n (6), have been solvothermally synthesized by employing imidazol-carboxyl bifunctional ligand 4-(1H-imidazol-1-yl) phthalic acid (H₂L). Single-crystal X-ray diffraction indicated that the L2-/HL- ligands display various coordination modes with different metal ions in 1-6. Complexes 1 and 2 are isostructures and both present one-dimensional (1D) chain structures, while complexes 3-6 show the 2D layered structures. The magnetic properties of these complexes were investigated. Complexes 1 and 3 indicate the weak ferromagnetic interactions, while complexes 2 and 4 demonstrate the antiferromagnetic interactions. In addition, luminescence properties of 5 and 6 were measured and studied in detail.

Four isostructural lanthanide metal–organic frameworks (Ln-MOFs) {[Ln(L)1.5(H2O)]·4H2O}n (1-Ln) (Ln = Sm, Eu, Gd, and Tb) have been successfully synthesized under solvothermal conditions with 2-(1H-1,2,4-triazol-1-yl) terephthalic acid (H2L) and Ln(NO3)3·nH2O (n = 0, 6). 1-Ln shows a binodal (3,8)-connected three-dimensional framework that possesses a one-dimensional pore channel decorated with uncoordinated Lewis basic triazolyl sites. 1-Eu and 1-Tb exhibit bright red and green emissions with absolute quantum yields of 9.1% for 1-Eu and 53.3% for 1-Tb. The luminescence explorations demonstrated that 1-Tb exhibits high quenching efficiency and low detection limit for sensing Fe3+ and nitrobenzene. Meanwhile, the fluorescence intensity of the quenched 1-Tb samples was resumed after washing with ethanol, which shows highly selective and recyclable luminescence sensing for Fe3+ and nitrobenzene. Importantly, by doping different concentrations of Eu3+ and Tb3+ ions, a series of dichromatic doped 1-EuxTb1-x MO...

A new luminescent metal-organic framework, {[Cd3(HL)2(H2O)3]·3H2O·2CH3CN}n (1) (H4L = 1-(3,5-dicarboxylatobenzyl)-3,5-pyrazole dicarboxylic acid), has been synthesized by solvothermal reaction and characterized by infrared spectroscopy, powder X-ray diffraction, thermogravimetry measurements and so on. 1 shows a new trinodal (4,4,6)-connected topology. Importantly, 1 displays intense luminescence in the solid state and high luminescent sensitivity and selectivity for Fe3+, CrO42- and Cr2O72- ions in aqueous solution, making it a potential probe for detecting these substances. The quenching mechanisms are also further discussed in detail. In addition, further research on the adsorption of dyes shows that 1 can selectively adsorb Congo red dye from other dye molecules.

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.

Three new lanthanide compounds, [Ln(HL)(H2O)3]n (1-Ln) (Ln = Eu, Tb and Dy), with isostructural structures have been constructed by a semi-rigid ligand 1-(3,5-dicarboxylatobenzyl)-3,5-pyrazole dicarboxylic acid (H4L) and Ln(NO3)3·6H2O using the solvothermal method. Three compounds show two-dimensional (2D) grid layer-stacking frameworks with interlayer channels decorated with carboxylic acid groups. 1-Eu exhibits excellent water stability and strong luminescence. Importantly, as a probe for sensing different metal ions and anions, 1-Eu shows highly specific recognition to Fe3+, CrO42− and Cr2O72− ions. Meanwhile, the mechanisms of luminescence quenching were studied, and antiferromagnetic exchange interactions existed in 1-Dy.

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.

Employing a V-shaped rigid multicarboxylate ligand 1,3-di(2′,5′-dicarboxypheny)benzene acid (H4L), three microporous metal–organic frameworks (MOFs), H2[Co4(O)L2(H2O)2]·3DMA·8H2O (1), H3[Zn2.5L2]·NMP·5H2O (2), and H3[Cd2.5L2]·4DMF·3H2O (3) were synthesized and characterized. Compound 1 exhibits a cage-based (3,6)-connected rtl topological MOF with [Co4O(COO)8] clusters and highly selective adsorption of CO2 over CH4. Compounds 2 and 3 are isostructural and display a rare 4,8-connected flu net with linear trinuclear [Zn3(COO)6] clusters. Interestingly, when compound 3 was soaked in DMF solution containing Eu3+ ions, an Eu-loaded compound Eu@3 with bright red fluorescence was obtained, which reveals highly selective sensing for Cu2+, Fe3+, and Cr2O72– ions. This represents an unusual example to achieve the detection of Cu2+, Fe3+, and Cr2O72– ions simultaneously by fluorescence spectrometry based on a recyclable Eu-loaded MOF sensor.

Herein, three new solvents induced metal-organic frameworks (MOFs), [Zn(H2L)H2O] (1), [Zn2(L)H2O] (2) and [Zn3(HL)2]·(CH3CN)2 (3) were synthesized via the solvothermal reaction procedure by using a rigid v-shaped 3,5-di (2,4-dicarboxylphenyl)pyridine (H4L) and Zn(II) ions. Structural analyses show that the organic ligand H4L adopt various degrees deprotonation (H2L2− for 1; L4− for 2 and HL3− for 3), which obtain different structures for three new MOFs: 2D layer network for 1; 3D dense packing structure for 2 and 3D porous structure with the pore size of 10.3 ​× ​10.6 ​A2 for 3. The gas sorption behavior of the guest-free phase 3’ shows an ultra-high adsorption selectivity and affinity for CO2 over CH4. The experiment results provide us with a reasonable facile route for designing and synthesizing new potential gas sorption and separate materials in CO2 purification. And the solid-state luminescence properties of 1–3 were measured and studied intensively at room temperature.

Two luminescent coordination polymers (LCPs), namely [CdL2]n (1) and [ZnL2]n (2) based on a new ligand 2-(2-methyl–benzimidazole-1-yl)-benzoic acid (HL), have been synthesized and characterized by single crystal X-ray diffraction, powder X-ray diffraction, infrared spectroscopy, elemental analysis, and thermogravimetric analysis. 1 and 2 exhibit similar 1D looped chains with different coordination modes of L. Both LCPs show strong fluorescent emission in the visible region. The fluorescence quenching response of 1 and 2 towards Fe3+ over other metal ions in DMF has been demonstrated by quenching titrations. Thus, 1 and 2 can be used as potential and highly selective luminescent sensors for Fe3+ ions.

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.

Five coordination polymers, {[Zn(dtp)]·H2O} (1), {[Zn(dtp)]·2CH3OH·NMP} (2), {[Mn2(dtp)2(H2O)4]·12(H2O)} (3), {[Mn(Hdtp)(Cl)]} (4) and {[Mn(dtp)(H2O)]·1.5H2O} (5) with different dimensional structures, have been solvothermally synthesized by utilizing the H2dtp ligand (H2dtp = 4′-(3,-5-dicarboxyphenyl)-2,2′:6′,2′′-terpyridine). All complexes are characterized by single-crystal X-ray diffraction, elemental analysis, IR spectra, thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD). The Zn(II)-based complexes 1 and 2 display a 2D wavy layer structure and a 3D porous framework with a 1D channel, respectively. The three Mn(II)-based complexes 3–5 exhibit two 1D chain and one 2D layer structures, respectively. Complexes 1 and 2 reveal their luminescence properties, whereas complexes 3–5 display an antiferromagnetic exchange. Meanwhile, an unusual stepwise adsorption for CO2 was also observed in 2.

A new metal–organic framework, [Zn3(μ3-OH)(tzba)2(bpy)(H2O)]OH·DMF (1), was solvothermally synthesized by employing tetrazolate-carboxylate 4-(1H-tetrazol-5-yl) benzoic acid (H2tzba) linker and 2,2′-bipyridine (bpy) chelating coligand. 1 contains novel Zn6(μ3-OH)2(μ2-H2O)2(COO)4(N4C)2 hexanuclear clusters and reveals a three-dimensional (3D) microporous supramolecular framework based on the stacked 2D layers. The highly polar pores cause not only strong affinity towards CO2 molecules but also a significant selective adsorption of CO2 over CH4. Meanwhile, the multiple binding sites for CO2 in the framework were determined by Grand Canonical Monte Carlo (GCMC) simulations. 1 also shows strong blue luminescence from ligand-to-metal charge transfer (LMCT).

Three metal-organic frameworks (MOFs), [Cd(Hpzbpdc)(H2 O)]⋅H2 O (1), [Mn2 (Hpzbpdc)2 (dmf)2 ] (2), and [H2 N(CH3 )2 ]0.5 [Eu(Hpzbpdc)1.5 (HCOO)0.5 (dmf)0.5 ]⋅DMF⋅0.5 H2 O (3) (H3 pzbpdc=4'-(2 H-pyrazol-3-yl)biphenyl-3,5-dicarboxylic acid), have been solvothermally synthesized from one pyrazoyl-carboxyl bifunctional ligand and characterized by single-crystal structures. The H3 pzbpdc ligand in 1-3 displays various coordination modes through the pyrazoyl and carboxyl groups. Both 1 and 3 contain dinuclear cluster building units and reveal a four-connected gismondine (gis) zeolite 3D framework and a 2D grid layer structure, respectively. Compound 1 shows blue luminescence, compound 3 reveals red luminescence that arises from efficient energy transfer from the organic ligand to the europium(III) ion, and compound 2 reveals an uncommon (3,8)-connected tfz-d; UO3 net with a rare Mn4 (COO)6 cluster and shows antiferromagnetic interactions between the manganese(II) ions.

A systematic study has been conducted on a novel luminescent metal-organic framework, {[Zn(bpyp)( L -OH)]·DMF·2H2O}n (1), to explore its sensing mechanisms to Fe3+. Structure analyses show that compound 1 exist pyridine N atoms and -OH groups on the pore surface for specific sensing of metal ions via Lewis acid-base interactions. On this consideration, the quenching mechanisms are studied and the processes are controlled by multiple mechanisms in which dynamic and static mechanisms are calculated, achieving the quantification evaluation of the quenching process. This work not only achieves the quantitative evaluation of the luminescence quenching but also provides certain insights into the quenching process, and the possible mechanisms explored in this work may inspire future research and design of target luminescent metal-organic frameworks (LMOFs) with specific functions.

A series of isomorphic lanthanide metal-organic frameworks (Ln-MOFs), {[Ln(L)(H2O)2]·5H2O}n (1-Ln, where Ln = Eu, Tb, Gd, and EuxTb1-x), have been synthesized by a rigid 1,3-bis(3,5-dicarboxyphenyl)imidazolium chloride (H4L+Cl-) ligand and Ln3+ ions via a solvothermal method. Single-crystal X-ray diffraction indicated that 1-Ln exhibited similar three-dimensional porous frameworks with one-dimensional channels decorated by the uncoordinated carboxylate oxygen atoms. The luminescent sensing studies indicated that 1-Eu is an outstanding reusable luminescent probe suitable for the simultaneous detection of Cr2O72-, CrO42-, and MnO4- ions in an aqueous solution. Remarkably, the different proportions of Eu3+ and Tb3+ can be combined into the same Ln-MOF to yield a new series of differently doped 1-EuxTb1-x MOFs. At the same excitation wavelength, they generated dual-emission peaks of Eu3+ and Tb3+ to show a gradual change in luminous color between yellow-green, yellow, orange, orange-red, and red. On the basis of the excellent optical properties of 1-Ln complexes, they can be employed as promising luminescent probe and multicolor tunable photoluminescence materials.

A series of supramolecular assemblies of types [Ag8 (L)4 ](PF6 )8 and [Ag4 (L)2 ](PF6 )4 , obtained from the tetraphenylethylene (TPE) bridged tetrakis(1,2,4-triazolium) salts H4 -L(PF6 )4 and AgI ions, is described. The assembly type obtained dependends on the N-wingtip substituents of H4 -L(PF6 )4 . Changes in the lengths of the N4-wingtip substituents enables controlled formation of assemblies with either [Ag4 (L)2 ](PF6 )4 or [Ag8 (L)4 ](PF6 )8 stoichiometry. The molecular structures of selected [Ag8 (L)4 ](PF6 )8 and [Ag4 (L)2 ](PF6 )4 assemblies were determined by X-ray diffraction analyses. While H4 -L(PF6 )4 does not exhibit fluorescence in solution, their tetra-NHC (NHC=N-heterocyclic carbene) assemblies do upon NHC-metal coordination. Upon irradiation, all assemblies undergo a light-induced, supramolecule-to-supramolecule structural transformation by an oxidative photocyclization involving phenyl groups of the TPE core, resulting in a significant change of the luminescence properties.

The hydrothermal reaction of Ln(NO3)3·6H2O with H2tyia (H2tyia = 5-(triazol-1-yl) isophthalic acid) afforded the lanthanide organic frameworks (Ln-MOFs), [Eu2(tyia)3(H2O)3]n (1) and {[Ln2(tyia)3·(H2O)3]· 3H2O}n (Ln = Tb 2, Dy 3, Sm 4, Gd 5, and Nd 6). Compounds were characterized by routine methods: PXRD, elemental analysis, solid-state luminescence properties analysis, TGA, FT-IR, and single-crystal X-ray crystallography. In this work, the luminescent properties of 2, 4, 5, and 6 and the responsiveness of various chemical components contained in urine were investigated. These MOFs detect 1-naphthol (1-N), urinary thiodiglycolic acid (TDGA), uric acid (UA), and hippuric acid (HA), which are the final metabolites of carbaryl, vinyl chloride monomers, purine, and toluene, respectively. These new Ln-MOFs offer the potential for biomarkers or metabolic sensors and show excellent selective and sensitive luminescence detection of 1-N, TDGA, UA, and HA.

A lead carboxylate-azolate framework, [Pb3 (μ4 -O)(L)2 (H2 O)] ⋅ 2H2 O (1), has been constructed from the reaction of 2-methyl-4-(1H-tetrazol-5-yl) benzoic acid (H2 L) and Pb(NO3 )2 under solvothermal conditions. Compound 1 contains an unprecedented hexanuclear cluster [Pb6 (μ4 -O)2 (COO)4 (CN4 )2 ], which as an 8-connected node is connected by 3-connected L linkers to give rise to a three-dimensional framework with an uncommon (3,8)-connected tfz-d; UO3 topology. Framework 1 possesses strong solid-state yellow luminescence (563 nm), which stems from ligand-to-metal charge transfer (LMCT), however, the removal of water molecules in 1 lead to the significant luminescent decrease of the sample. Importantly, in the presence of 1, the thermal decomposition of ammonium perchlorate is significantly accelerated.

Two new three-dimensional isostructural lanthanide metal–organic frameworks (Ln(III)-MOFs), [LnL(H2O)3]·3H2O·0.75DMF (1-Ln; Ln = Dy(III) and Eu(III) ions, H3L = biphenyl-3′-nitro-3,4′,5-tricarboxylic acid, DMF = N,N′-dimethylformamide), were synthesized and characterized. The appearance of temperature-dependent out-of-phase (χ″M) signal reveals that complex 1-Dy displays slow magnetic relaxation behavior with the energy barrier (ΔUeff) of 57 K and a pre-exponential factor (τ0) of 3.89 × 10–8 s at 1200 Oe direct current field. The luminescence explorations demonstrated that 1-Eu exhibits high quenching efficiency and low detection limit for sensing nitrobenzene and Cr2O72–. Meanwhile, the fluorescence intensity of the quenched 1-Eu samples will be resumed after washing with DMF or water, indicating that 1-Eu may be used as a highly selective and recyclable luminescence sensing material for sensing nitrobenzene and Cr2O72– anion.

Five new Cd(II) complexes, {[Cd1.5(tzia)(H2O)2]·H2O}n (1), {[Cd1.5(tzia)(H2O)4]·1.5H2O}n (2), [Cd(H2tzia)2(H2O)4]·H2O (3), [Cd5(μ3-OH)(tzia)3(H2O)7]·2H2O}n (4), and {[Cd2(μ3-OH)(tzia)(H2O)2]·H2O}n (5) (H3tzia = 5-(1H-tetrazol-5-yl)isophthalic acid), were assembled employing a tetrazolyl-carboxyl ligand H3tzia with Cd(II) ions, revealing versatile structures from zero-dimensional (0D) mononuclear molecule, 2D layer to 3D framework, in which five new types of coordination modes of H3tzia were observed. Complex 1 shows a 3D (3,6)-connected ant net based on trinuclear [Cd3(COO)2(N4C)2] cluster; 2 forms an unusual 3D (3,4)-connected 3,4T1 net with 1D tubes based on the 26-membered metallocycles; 3 is a mononuclear molecule; 4 displays an unprecedented (3,4,10)-connected 2D layer based on pentanuclear [Cd5(μ3-OH)(COO)2(N4C)3] cluster; 5 is a 3D porous framework containing 1D Cd-hydroxy-tetrazolyl ribbons. Complexes 1–5 exhibit strong luminescence with different energies resulted from the various coordination mo...

In this report, seven new luminescent metal–organic frameworks (LMOFs), [Zn(L)0.5(H2O)2]·H2O (1), [Zn(L)0.5(DMF)] (2), [Zn3(L)(μ3-OH)2(H2O)4] (3), [Zn2(L)(DMA)(H2O)]·5(H2O) (4), [Cd(L)]·2(H3O)·(H2O) (5), [Cd2(L)(H2O)3] (6), and [Pb(L)0.5(H2O)] (7) (H4L = [1,1′:4′,1′′-terphenyl]-2′,3,3′′,5′-tetracarboxylic acid; DMF = N,N-dimethylformamide; DMA = N,N-dimethylacetamide) have been solvothermally synthesized by using Zn(II), Cd(II), Pb(II) ions and H4L in different solvent systems, all of which have been routinely characterized by elemental analysis, FT-IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Single-crystal X-ray diffraction analyses show the different dimensionalities (1D, 2D or 3D) of complexes 1–7. Comparative structural studies of 1–7 reveal that the L4− ligands adopt different coordination morphologies: 1 (η1μ1χ1), 2 (η2μ2χ2), 3 (η2μ2χ2), 4 (η2μ2χ2; η1μ1χ1), 5 (η2μ1χ2), 6 (η2μ2χ2; η2μ2χ3), and 7 (η2μ2χ2; η2μ3χ4) with Zn(II) (74 pm), Cd(II) (97 pm) and Pb(II) (119 pm) in different solvent systems, which produce the complexes with different frameworks. Complex 1 displays a 1D dimeric chain. Complexes 2 and 5 present a 2D layer structure with a uninodal 4-connected sql net with a symbol of (44·62). Complexes 3, 6 and 7 have a 3D dense packing structure based on infinite 1D rod-like secondary building units (SBUs). Complex 3 is designated as a binodal (4, 6)-connected fry topological net with the point symbol (510·63·78)(54·62). The whole network of 6 can be simplified as a binodal (4, 8)-connected flu topological net with a point symbol of (412·612·84)(46)2. Complex 7 can be seen as a new binodal (5, 10)-connected topological net with the point symbol (410)2(428·616·8). Complex 4 shows a 3D framework based on a binuclear [Zn2(CO)3O3] SBU, which can be viewed as a uninodal 4-connected sra topological net with the point symbol (42·63·8). Further, the solid-state luminescence properties of the complexes were measured and studied intensively at room temperature.

Reaction-determined assemblies of 6,6′-dinitrobiphenyl-2,2′,4,4′-tetracarboxylic acid (H4nbtc), various N-donor ligands and transition metal ions produce ten complexes, namely, [Zn2(nbtc)(bpa)·H2O]n (1), [Zn2(nbtc)(bpe)·H2O]n (2), [Zn2(nbtc)(2,2′-dpy)]n (3), Zn(H3nbtc)(phen)2 (4), {(H3O)2[Cd3(nbtc)2(H2O)3]·5H2O}n (5), [Cd2(nbtc)(ndpy)·0.5H2O]n (6), [Ag2(H2nbtc)(bpp)]n (7), [Co2(nbtc)(phen)2(H2O)2]n (8), [Ni2(nbtc)(phen)2(H2O)2]n (9) and Co(H2nbtc)(phen)2·2H2O (10) (bpa = 1,2-bis(4-pyridyl)ethane, bpe = 1,2-di(4-pyridyl)ethylene, bpp = 1,3-bis(4-pyridyl)propane, 2,2′-dpy = 2,2′-dipyridyl, phen = 1,10-phenanthroline, ndpy = 2-pyridinamine). Isostructural 1 and 2 feature 3D “bilayered-pillared” frameworks constructed from Zn2(μ2-COO)2(μ1-COO)2-nbtc4− wave-bilayers and bpa/bpe pillars. Unlike 1 and 2, both 3 and 6 exhibit 3D “brick-wall” frameworks constructed from nbtc4− and various SBUs (0D Zn2(μ2-COO)3(μ1-COO)1 for 3, 1D [Cd2(μ2-COO)4]n for 6). However, 3D 5 can be viewed as a combination of 2D “brick-wall” layers and 1D [Cd3-nbtc] chains. Moreover, in comparison to neutral 3 and 6 with pensile and cosmetic terminal ligands, complex 5 without an N-donor ligand is particularly interesting, containing two hydronium ions to balance the anion unit [Cd3(nbtc)2(H2O)3]2− as well as three types of coordinated Cd(II) ions (6-, 7- and 8-). Unlike 3, complex 4 is mononuclear, despite the two complexes employing similar terminal ligands (2,2′-dpy for 3, phen for 4). In 2D layered Ag(I) 7, the 0D Ag4(μ2-COO)4 SBUs initially form Ag4(μ2-COO)4-H2nbtc2− chains before being bridged by bpp ligands. Isostructural Co(II) 8 and Ni(II) 9 exhibit 1D looped infinite chains. Structural comparisons indicate that the SBUs, the coordination modes of the H4nbtc ligand, the synthetic conditions and the nature of the N-donor ligands are crucial factors with respect to the structures of these compounds. Furthermore, the luminescence properties of 1–7 were investigated in the solid state at room temperature.