Cationic Europium-Organic Framework for Chromatographic Column Separation of Ionic Dyes and Stimuli-Responsive Chromic Properties.

A novel 3D europium-based cationic framework (Eu-CMOF) has been constructed solvothermally by employing a viologen derivative as an organic functional building unit. Notably, Eu-CMOF demonstrates its capability as a proficient aqueous-phase ion-exchange host, facilitating the remarkable rapid chromatographic column separation of new coccine and malachite green (NC3-/MG+), as well as new coccine and methylene blue (NC3-/MLB+), in mere 2 to 4 min. Adsorption thermodynamics and kinetics of anionic dyes demonstrate that Eu-CMOF exhibits a higher adsorption capacity for NC3-, as evaluated by the Langmuir model, reaching a value of 173 mg·g-1. The pseudo-second-order rate constant is determined to be 3.84 × 10-3 mg-1·g·min-1. Additionally, Eu-CMOF displays reversible photochromic and amine- and ammonia-induced vapochromic behaviors. Further mechanistic studies reveal that these chromic behaviors are primarily attributed to the generation of free viologen radical stimulated by Xe-light or electron-rich amine/ammonia. This research contributes to the development of advanced materials with applications in rapid chromatographic separation and stimuli-responsive chromic properties, showcasing the potential of Eu-CMOF as a versatile platform for practical applications.

A viologen-based Cd(II) coordination polymer as a multifunctional platform for photochromism, chemochromism and a broad range of fluorescence pH sensing.

A multi-responsive Cd(II) coordination polymer (1) has been constructed by introducing a viologen derivative as both the framework backbone and ligand side pendant. Notably, compound 1 exhibits intriguing properties, including photochromism, methanol-assisted photochromism and chemochromism to ammonia. Furthermore, compound 1 also displays fluorescence pH sensing ability in a wide pH range.

A Multifunctional Coordination Polymer Constructed by Viologen Derivatives: Photochromism, Chemochromism, and MnO4- Sensing.

A multifunctional Cd-based coordination polymer based on a viologen derivative and a secondary carboxylic ligand, namely, {[Cd2(bcbp)(pta)2 (H2O)]·2H2O}n (1, H2bcbpCl2 = 1,1'-bis(4-carboxyphenyl)-(4,4'-bipyridinium) dichloride, H2pta = p-phthalic acid), has been solvothermally synthesized and structurally characterized. Compound 1 is a 3D framework built on {Cd2(pta)2 (H2O)}n net with square channels which intalls bcbp ligands at the diagonal position of the two adjacent square channels. Notably, compound 1 exhibits a reversible photochromic transformation between yellowish gray and dark green under xenon light irradiation, which should be attributed to the formation of free viologen radicals. Furthermore, compound 1 also displays a chemochromic phenomenon from yellowish gray to dark green after exposure to ammonia and hydrazine, which could be ascribed to the generation of viologen radicals and charge-transfer complexes triggered by nucleophilic attack of electron-rich ammonia and hydrazine molecules to the electron-deficient viologen moiety in the bcbp ligand. Moreover, compound 1 is capable of quickly and selectively detecting MnO4- with a high quenching coefficient and a low limit of detection via a luminescent quenching process caused by the competitive absorption of excitation energy.

Cationic coordination polymers with thirteen-fold interpenetrating dia networks: selective coloration and ion-controlled photochromism.

A novel Cd-based cationic coordination polymer (Cd-CCP) constructed using viologen derivatives, which exhibits an unusual thirteen-fold interpenetrating diamondoid network, has been synthesized. Notably, Cd-CCP displays selective and naked-eye distinguished coloration and ion-controlled photochromism towards halide anions.

Sodalite Cd66-Cage-Based Metal-Organic Framework Constructed by Cd9 and Cd5 Metal-Organic Clusters.

A sodalite Cd66-cage-based metal-organic framework (MOF), namely, CPM-9S, has been constructed based on Cd9 and Cd5 metal-organic clusters (MOCs), which, to the best our knowledge, represents the first Cd-cage-based MOF that contains the highest-nuclear Cd-based MOC and the largest number of Cd2+ ions in a cage. The iodine adsorption performances in terms of the iodine adsorption capacity, adsorption isotherm, and adsorption kinetics, as well as the adsorption mechanism, have been further studied.

Viologen-Based Cationic Metal-Organic Framework for Efficient Cr2O72- Adsorption and Dye Separation.

A novel cationic metal-organic framework composed of {Cu2(COO)4} paddle-wheel units and a tetracarboxylic viologen derivative, namely, {[Cu2(bdcbp)(H2O)2]·2NO3·2H2O}n (Cu-CMOF, H4bdcbpCl2 = 1,1'-bis(3,5-dicarboxyphenyl)-4,4'-bipyridinium dichloride), has been successfully synthesized and structurally characterized. In Cu-CMOF, the {Cu2(COO)4} unit and viologen derivative both act as four-connected nodes forming an ssb-type cationic network with 42.84 topology, in which the positive charges are distributed on the organic viologen moieties. Deeper insight of the structure indicates that the 3D architecture of Cu-CMOF can be seen as packing of a 26-faceted polyhedral cage and two cuboid cages. Notably, Cu-CMOF displays a highly efficient anion exchange ability for capture and removal of anionic pollutants. UV-vis absorption spectra and digital images demonstrate that Cu-CMOF is capable of adsorbing the dichromate anion and anionic dyes effectively, such as methyl orange (MO-), Congo red (CR2-), and New Coccine (NC3-). Meaningfully, anionic dyes (MO-, CR2-, and NC3-) can be efficiently and selectively removed by Cu-CMOF in the presence of cationic dye methylene blue (MLB+). Such behaviors of anionic pollutant adsorption and dye separation are mainly caused by an ion-exchange process facilitated by the large cavity and decentralized distribution of positive charge in Cu-CMOF.

Two novel lead-based coordination polymers for luminescence sensing of anions, cations and small organic molecules.

Two novel lead-based coordination polymers, namely [Pb(cbdcp)]·0.5H2O·0.5CH3OH (1) and [Pb(cbdcp)] (2), have been solvothermally constructed by using a zwitterionic ligand 4-carboxy-1-(3,4-dicarboxy-benzyl)-pyridinium chloride (abbreviated as H3cbdcpCl). Compound 1 has a three-dimensional framework displaying a valence-bonded SrAl2 topology with the 42·63·8 symbol, while compound 2 has a two-dimensional sheet structure that can be simplified into a three-dimensional ππ interaction-connected topology with the {44·62}2{48·615·85} symbol. Notably, compound 1 proved to be a promising potential luminescent sensor capable of selectively detecting anions, cations and small organic molecules, especially Cr2O72-, CrO42-, Fe3+ and nitrobenzene.

A new strategy for constructing a disulfide-functionalized ZIF-8 analogue using structure-directing ligand-ligand covalent interaction.

Inter-ligand van der Waals forces play a key role in the synthesis of different ZIF types. Here we report an unusual case involving covalent inter-ligand interactions through disulfide bond formation in a ZIF-8 analogue. It exhibits high CO2 uptake and stepwise adsorption of light hydrocarbons with potential applications in ethane/ethylene separation.

Extremely stable europium-organic framework for luminescent sensing of Cr2O72- and Fe3+ in aqueous systems.

Three novel 3D lanthanide-organic frameworks, namely [Ln2L(1,3-bdc)3]·5H2O (Ln: Eu, Sm and Dy), with a 412·63 topology based on a zwitterionic ligand, 4-bis(4-carboxylatopyridinium-1-methylene)benzene dichloride (H2LCl2), and 1,3-benzene dicarboxylic acid (1,3-H2bdc) have been synthesized hydrothermally. Notably, the Ln-MOFs are extremely stable in an aqueous system and are capable of resisting acids or bases over a wide pH range from 3 to 11. Meanwhile, an Eu-MOF is further proven to be a promising dual sensor in an aqueous system toward Cr2O72- and Fe3+.

A cyano-bridged Cu(i)-based organic framework coupled with the C-C bond cleavage of acetonitrile for selective and sensitive sensing of Fe3+ ions.

A cyano-bridged Cu(i) organic framework based on [Cu6(CN)6]n was synthesized, in which cyano anions were generated in situ from the C-C bond cleavage of acetonitrile. The as-synthesized compound displays orange-red luminescence and is further proven to be a promising Fe3+ luminescent sensor with high selectivity and sensitivity.

Open pentameric calixarene nanocage.

A novel open helmetlike coordination cage has been synthesized based on Co4-calixarene shuttlecock-like secondary building units and in situ generated phosphate anions, where the opening of the cage comprises a large 16-membered ring. The above unprecedented Co20 nanocage presents the first pentameric calixarene coordination compound. Sorption behavior and magnetic properties are also investigated.

Photophysical studies of europium coordination polymers based on a tetracarboxylate ligand.

Reaction of europium sulfate octahydrate with p-terphenyl-3,3″,5,5″-tetracarboxylic acid (H4ptptc) in a mixed solvent system has afforded three new coordination polymers formulated as {[Eu(ptptc)0.75(H2O)2]·0.5DMF·1.5H2O}n (1), {[Me2H2N]2 [Eu2(ptptc)2(H2O)(DMF)]·1.5DMF·7H2O}n (2), and {[Eu(Hptptc)(H2O)4]·0.5DMF·H2O}n (3). Complex 1 exhibits a three-dimensional (3D) metal-organic framework based on {Eu2(µ2-COO)2(COO)4}n chains, complex 2 shows a 3D metal-organic framework constructed by [Eu2(µ2-COO)2(COO)6](2-) dimetallic subunits, and complex 3 features a 2D layer architecture assembling to 3D framework through π···π interactions. All complexes exhibit the characteristic red luminescence of Eu(III) ion. The triplet state of ligand H4ptptc matches well with the emission level of Eu(III) ion, which allows the preparation of new optical materials with enhanced luminescence properties. The luminescence properties of these complexes are further studied in terms of their emission quantum yields, emission lifetimes, and the radiative/nonradiative rates.

A series of novel zinc(II) entangled coordination polymers based on carboxyphenyl-terpyridine ligands.

Hydrothermal synthesis has afforded five divalent zinc coordination polymers containing 4-(4-carboxyphenyl)-2,2':6',2''-terpyridine (HL1) or its isomer 4-(4-carboxyphenyl)-2,2':4',4''-terpyridine (HL2), with or without the addition of auxiliary ligands, 1,3,5-benzenetricarboxylic acid (H3btc) and 1,4-benzenedicarboxylic acid (H2bdc). Their structures have been characterized by single crystal X-ray analyses and further characterized by infrared spectra, elemental analyses, powder X-ray diffraction, thermogravimetric analyses and photoluminescent spectra. Across this series, the π···π interactions have a dramatic impact on the self-assembly of these entanglement structures, in either case it can exert an important structure-directing role. In addition, the disposition of pyridine nitrogen atoms in ligands also plays a large role in structure direction in this system. Complex 1 is a 2D + 2D→3D inclined polycatenated coordination polymer based on the resulting array of 2D (6,3) layers constructed by 1D→2D π···π directed self-assembly. Complex 2 is assembled into a 3D framework by means of 1D + 1D→3D mutual interdigitation based on 1D→1D self-assembly driven by π···π stacking interactions. Complex 3 shows a 2D + 2D→3D interdigital network involving 2D + 2D→2D parallel interpenetrated and 2D + 2D→2D interdigital (4,4) layer motifs. Complex 4 displays a 2D + 2D→3D polythreaded framework based on a 2D (4,4) network comprised of alternating rings and rods. Complex 5 is a (3,4)-connected 3D framework with topology (4.8(2).10(3))(4.8(2)). In comparison with covalently connected entanglements, such π···π directing self-assembly of entanglements are far less explored, especially, polycatenane based on 1D chain motifs and polythread based on 2D layer motifs are rarely reported. Furthermore, the luminescent properties of complexes 1-5 at room temperature have also been studied in detail herein.

Thiacalix[4]arene-supported kite-like heterometallic tetranuclear Zn(II)Ln(III)3 (Ln = Gd, Tb, Dy, Ho) complexes.

Four kite-like tetranuclear Zn(II)Ln(III)3 (Ln= Gd 1, Tb 2, Dy 3, Ho 4) clusters supported by p-tert-butylthiacalix[4]arene (H4BTC4A) have been prepared under solvothermal conditions and structurally characterized by single crystal X-ray diffraction and powder X-ray diffraction (PXRD). In the structures of these four complexes, each of them is capped by two tail-to-tail p-tert-butylthiacalix[4]arene molecules to form a bent sandwich-like unit. The photoluminescent analyses reveal that the H4BTC4A is an efficient sensitizer for Tb(3+) ions in 2. The magnetic properties of complexes 1-4 are also investigated, in which complex 3 exhibits slow magnetization relaxation typical for single molecule magnets.

Visible and NIR photoluminescence properties of a series of novel lanthanide-organic coordination polymers based on hydroxyquinoline-carboxylate ligands.

A series of novel two-dimensional (2D) lanthanide coordination polymers with 4-hydroxyquinoline-2-carboxylate (H(2)hqc) ligands, [Ln(Hhqc)(3)(H(2)O)](n)·3nH(2)O (Ln = Eu (1), Tb (2), Sm (3), Nd (4), and Gd (5)) and [Ln(Hhqc)(ox)(H(2)O)(2)](n) (Ln = Eu (6), Tb (7), Sm (8), Tm (9), Dy (10), Nd (11), Yb (12), and Gd (13); H(2)ox = oxalic acid), have been synthesized under hydrothermal conditions. Complexes 1-5 are isomorphous, which can be described as a two-dimensional (2D) hxl/Shubnikov network based on Ln(2)(CO(2))(4) paddle-wheel units, and the isomorphous complexes 6-13 feature a 2D decker layer architecture constructed by Ln-ox infinite chains cross-linked alternatively by bridging Hhqc(-) ligands. The room-temperature photoluminescence spectra of complexes Eu(III) (1 and 6), Tb(III) (2 and 7), and Sm(III) (3 and 8) exhibit strong characteristic emissions in the visible region, whereas Nd(III) (4 and 11) and Yb(III) (12) complexes display NIR luminescence upon irradiation at the ligand band. Moreover, the triplet state of H(2)hqc matches well with the emission level of Eu(III), Tb(III), and Sm(III) ions, which allows the preparation of new optical materials with enhanced luminescence properties.

Heterometallic thiacalix[4]arene-supported Na2Ni(II)12Ln(III)2 clusters with vertex-fused tricubane cores (Ln = Dy and Tb).

Two heterometallic thiacalix[4]arene-supported complexes possess a trinary-cubane core composed of one [Ni(2)Ln(2)] cubane unit and two [NaNi(2)Ln] cubane units sharing one Ln(III) ion (Ln = Dy and Tb). Only the Dy(III) complex exhibits slow magnetic relaxation behaviour of single molecule magnet nature.

Chlorine-induced assembly of a cationic coordination cage with a µ5-carbonato-bridged Mn(II)24 core.

Chlorine caged in! The chlorine-induced assembly of six shuttlecock-like tetranuclear Mn(II) building blocks generated in situ based on p-tert-butylthiacalix[4]arene and facial anions gave rise to a novel truncated distorted octahedral cationic coordination cage with a µ(5)-carbonato-bridged Mn(II)(24) core.

A series of octanuclear-nickel(II) complexes supported by thiacalix[4]arenes.

A series of discrete complexes, [Ni(8)(BTC4A)(2)(µ(6)-CO(3))(2)(µ-CH(3)COO)(4)(dma)(4)]·H(2)O (1), [Ni(8)(BTC4A)(2)(µ(6)-CO(3))(2)(µ-Cl)(2)(µ-HCOO)(2)(dma)(4)]·2DMF·2CH(3)CN (2), [Ni(8)(PTC4A)(2) (µ(6)-CO(3))(2)(µ-CH(3)COO)(4)(dma)(4)]·DMF (3), and [Ni(8)(PTC4A)(2)(µ(6)-CO(3))(2)(µ-OH)(µ-HCOO)(3) (dma)(4)] (4) (p-tert-butylthiacalix[4]arene = H(4)BTC4A, p-phenylthiacalix[4]arene = H(4)PTC4A, dma = dimethylamine, and DMF = N,N'-dimethylformamide), have been prepared under solvothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses, powder XRD, and IR spectroscopy. These four complexes are stacked by dumbbell-like building blocks with one chairlike octanuclear-nickel(II) core, which is capped by two thiacalix[4]arene molecules and connected by two in situ generated carbonato anions and different auxiliary anions. This work implied that not only the solvent molecules but also the upper-rim groups of thiacalix[4]arenes have significant effects on the self-assembly of the dumbbell-like building blocks. The magnetic properties of complexes 1-4 were examined, indicating strong antiferromagnetic interactions between the nickel(II) ions in the temperature range of 50-300 K.