Light and Guest Responsive Behavior in a Porous Coordination Network Enabled by Reversible [2 + 2] Photocycloaddition.

Stimuli-responsive physisorbents that undergo reversible structural transformations induced by external stimuli (e.g. light, guests, or heat) offer the promise of utility in gas storage and separation. Whereas reports on guest or light-responsive sorbents have increased in recent years, we are unaware of reports on sorbents that exhibit both light and guest-induced structural transformations. Herein, we report that the square lattice, sql, topology coordination network Zn(fba)(bis)Ù 2DMF (sql-5,6-Zn-a, 5 = trans-4,4'-bis(1-imidazolyl)stilbene = bis, 6 = 2,2-bis(4-carboxyphenyl)hexafluoropropane = H2fba) underwent single-crystal-to-single-crystal transformation (SCSC) upon activation, affording nonporous sql-5,6-Zn-b. Parallel alignment at 3.23 Å of olefinic moieties on adjacent bis ligands in sql-5,6-Zn-a enabled SCSC [2 + 2] photocycloaddition upon exposure to UV light (365 nm) or sunlight. sql-5,6-Zn-α thereby transformed to mot-5,6-Zn-α, which was subsequently activated to the narrow pore phase mot-5,6-Zn-b. sql-5,6-Zn-b and mot-5,6-Zn-b both exhibited S-shaped adsorption isotherms characteristic of guest-induced structural changes when exposed to CO2 at 195 K (type-F-IV and type F-I, respectively). Cycling experiments conducted upon sql-5,6-Zn-b reduced particle size after cycle 1 and induced transformation into a rare example of a shape memory coordination network, sql-5,6-Zn-g. Insight into this smorgasbord of SCSC phase changes was gained from in-situ PXRD, single crystal XRD and 1H nmr spectroscopy experiments.

Cross-Linking CdSO4-Type Nets with Hexafluorosilicate Anions to Form an Ultramicroporous Material for Efficient C2H2/CO2 and C2H2/C2H4 Separation.

A 44.610.8 topology hybrid ultramicroporous material (HUM), {[Cu1.5F(SiF6)(L)2.5]·G}n, (L = 4,4'-bisimidazolylbiphenyl, G = guest molecules), 1, formed by cross-linking interpenetrated 3D four-connected CdSO4-type nets with hexafluorosilicate anions is synthesized and evaluated in the context of gas sorption and separation herein. 1 is the first HUM functionalized with two different types of fluorinated sites (SiF6 2- and F- anions) lining along the pore surface. The optimal pore size (≈5 Å) combining mixed and high-density electronegative fluorinated sites enable 1 to preferentially adsorb C2H2 over CO2 and C2H4 by hydrogen bonding interactions with a high C2H2 isosteric heat of adsorption (Qst) of ≈42.3 kJ mol-1 at zero loading. The pronounced discriminatory sorption behaviors lead to excellent separation performance for C2H2/CO2 and C2H2/C2H4 that surpasses many well-known sorbents. Dynamic breakthrough experiments are conducted to confirm the practical separation capability of 1, which reveal an impressive separation factor of 6.1 for equimolar C2H2/CO2 mixture. Furthermore, molecular simulation and density functional theory (DFT) calculations validate the strong binding of C2H2 stems from the chelating fix of C2H2 between SiF6 2- anion and coordinated F- anion.

Ultramicroporous Lonsdaleite Topology MOF with High Propane Uptake and Propane/Methane Selectivity for Propane Capture from Simulated Natural Gas.

Propane (C3H8) is a widely used fuel gas. Metal-organic framework (MOF) physisorbents that are C3H8 selective offer the potential to significantly reduce the energy footprint for capturing C3H8 from natural gas, where C3H8 is typically present as a minor component. Here we report the C3H8 recovery performance of a previously unreported lonsdaleite, lon, topology MOF, a chiral metal-organic material, [Ni(S-IEDC)(bipy)(SCN)]n, CMOM-7. CMOM-7 was prepared from three low-cost precursors: Ni(SCN)2, S-indoline-2-carboxylic acid (S-IDECH), and 4,4'-bipyridine (bipy), and its structure was determined by single crystal X-ray crystallography. Pure gas adsorption isotherms revealed that CMOM-7 exhibited high C3H8 uptake (2.71 mmol g-1) at 0.05 bar, an indication of a higher affinity for C3H8 than both C2H6 and CH4. Dynamic column breakthrough experiments afforded high purity C3H8 capture from a gas mixture comprising C3H8/C2H6/CH4 (v/v/v = 5/10/85). Despite the dilute C3H8 stream, CMOM-7 registered a high dynamic uptake of C3H8 and a breakthrough time difference between C3H8 and C2H6 of 79.5 min g-1, superior to those of previous MOF physisorbents studied under the same flow rate. Analysis of crystallographic data and Grand Canonical Monte Carlo simulations provides insight into the two C3H8 binding sites in CMOM-7, both of which are driven by C-H···π and hydrogen bonding interactions.

Switching Adsorbent Layered Material that Enables Stepwise Capture of C8 Aromatics via Single-Crystal-to-Single-Crystal Transformations.

Separation of the C8 aromatic isomers, xylenes (PX, MX, and OX) and ethylbenzene (EB), is important to the petrochemical industry. Whereas physisorptive separation is an energy-efficient alternative to current processes, such as distillation, physisorbents do not generally exhibit strong C8 selectivity. Herein, we report the mixed-linker square lattice (sql) coordination network [Zn2(sba)2(bis)]n·mDMF (sql-4,5-Zn, H2sba or 4 = 4,4'-sulfonyldibenzoic acid, bis or 5 = trans-4,4'-bis(1-imidazolyl)stilbene) and its C8 sorption properties. sql-4,5-Zn was found to exhibit high uptake capacity for liquid C8 aromatics (∼20.2 wt %), and to the best of our knowledge, it is the first sorbent to exhibit selectivity for PX, EB, and MX over OX for binary, ternary, and quaternary mixtures from gas chromatography. Single-crystal structures of narrow-pore, intermediate-pore, and large-pore phases provided insight into the phase transformations, which were enabled by flexibility of the linker ligands and changes in the square grid geometry and interlayer distances. This work adds to the library of two-dimensional coordination networks that exhibit high uptake, thanks to clay-like expansion, and strong selectivity, thanks to shape-selective binding sites, for C8 isomers.

Effect of Extra-Framework Anion Substitution on the Properties of a Chiral Crystalline Sponge.

Chiral metal-organic materials, CMOMs, are of interest as they can offer selective binding sites for chiral guests. Such binding sites can enable CMOMs to serve as chiral crystalline sponges (CCSs) to determine molecular structure and/or purify enantiomers. We recently reported on the chiral recognition properties of a homochiral cationic diamondoid, dia, network {[Ni(S-IDEC)(bipy)(H2O)][NO3]}n (S-IDEC = S-indoline-2-carboxylicate, bipy = 4,4'-bipyridine), CMOM-5[NO3]. The modularity of CMOM-5[NO3] means there are five feasible approaches to fine-tune structures and properties via substitution of one or more of the following components: metal cation (Ni2+); bridging ligand (S-IDEC); linker (bipy); extra-framework anion (NO3-); and terminal ligand (H2O). Herein, we report the effect of anion substitution on the CCS properties of CMOM-5[NO3] by preparing and characterizing {[Ni(S-IDEC)(bipy)(H2O)][BF4]}n, CMOM-5[BF4]. The chiral channels in CMOM-5[BF4] enabled it to function as a CCS for determination of the absolute crystal structures of both enantiomers of three chiral compounds: 1-phenyl-1-butanol (1P1B); methyl mandelate (MM); ethyl mandelate (EM). Chiral resolution experiments revealed CMOM-5[BF4] to be highly selective toward the S-isomers of MM and EM with enantiomeric excess, ee, values of 82.6 and 78.4%, respectively. The ee measured for S-EM surpasses the 64.3% exhibited by [DyNaL(H2O)4] 6H2O and far exceeds that of CMOM-5[NO3] (6.0%). Structural studies of the binding sites in CMOM-5[BF4] provide insight into their high enantioselectivity.

Effect of Proinflammatory S100A9 Protein on Migration and Proliferation of Microglial Cells.

Alzheimer's disease (AD) is a multifactorial disease affecting aging population worldwide. Neuroinflammation became a focus of research as one of the major pathologic processes relating to the disease onset and progression. Proinflammatory S100A9 is the central culprit in the amyloid-neuroinflammatory cascade implicated in AD and other neurodegenerative diseases. We studied the effect of S100A9 on microglial BV-2 cell proliferation and migration. The responses of BV-2 cells to S100A9 stimulation were monitored in real-time using live cell microscopy, transcriptome sequencing, immunofluorescence staining, western blot analysis, and ELISA. We observed that a low dose of S100A9 promotes migration and proliferation of BV-2 cells. However, acute inflammatory condition (i.e., high S100A9 doses) causes diminished cell viability; it is uncovered that S100A9 activates TLR-4 and TLR-7 signaling pathways, leading to TNF-α and IL-6 expression, which affect BV-2 cell migration and proliferation in a concentration-dependent manner. Interestingly, the effects of S100A9 are not only inhibited by TNF-α and IL-6 antibodies. The addition of amyloid-ß (Aß) 1-40 peptide resumes the capacities of BV-2 cells to the level of low S100A9 concentrations. Based on these results, we conclude that in contrast to the beneficial effects of low S100A9 dose, high S100A9 concentration leads to impaired mobility and proliferation of immune cells, reflecting neurotoxicity at acute inflammatory conditions. However, the formation of Aß plaques may be a natural mechanism that rescues cells from the proinflammatory and cytotoxic effects of S100A9, especially considering that inflammation is one of the primary causes of AD.

Shape-Memory Effect Enabled by Ligand Substitution and CO2 Affinity in a Flexible SIFSIX Coordination Network.

We report that linker ligand substitution involving just one atom induces a shape-memory effect in a flexible coordination network. Specifically, whereas SIFSIX-23-Cu, [Cu(SiF6 )(L)2 ]n , (L=1,4-bis(1-imidazolyl)benzene, SiF6 2- =SIFSIX) has been previously reported to exhibit reversible switching between closed and open phases, the activated phase of SIFSIX-23-CuN , [Cu(SiF6 )(LN )2 ]n (LN =2,5-bis(1-imidazolyl)pyridine), transformed to a kinetically stable porous phase with strong affinity for CO2 . As-synthesized SIFSIX-23-CuN , α, transformed to less open, γ, and closed, ß, phases during activation. ß did not adsorb N2 (77 K), rather it reverted to α induced by CO2 at 195, 273 and 298 K. CO2 desorption resulted in α', a shape-memory phase which subsequently exhibited type-I isotherms for N2 (77 K) and CO2 as well as strong performance for separation of CO2 /N2 (15/85) at 298 K and 1 bar driven by strong binding (Qst =45-51 kJ/mol) and excellent CO2 /N2 selectivity (up to 700). Interestingly, α' reverted to ß after re-solvation/desolvation. Molecular simulations and density functional theory (DFT) calculations provide insight into the properties of SIFSIX-23-CuN .

Crystal Engineering of a Chiral Crystalline Sponge That Enables Absolute Structure Determination and Enantiomeric Separation.

Chiral metal-organic materials (CMOMs), can offer molecular binding sites that mimic the enantioselectivity exhibited by biomolecules and are amenable to systematic fine-tuning of structure and properties. Herein, we report that the reaction of Ni(NO3)2, S-indoline-2-carboxylic acid (S-IDECH), and 4,4'-bipyridine (bipy) afforded a homochiral cationic diamondoid, dia, network, [Ni(S-IDEC)(bipy)(H2O)][NO3], CMOM-5. Composed of rod building blocks (RBBs) cross-linked by bipy linkers, the activated form of CMOM-5 adapted its pore structure to bind four guest molecules, 1-phenyl-1-butanol (1P1B), 4-phenyl-2-butanol (4P2B), 1-(4-methoxyphenyl)ethanol (MPE), and methyl mandelate (MM), making it an example of a chiral crystalline sponge (CCS). Chiral resolution experiments revealed enantiomeric excess, ee, values of 36.2-93.5%. The structural adaptability of CMOM-5 enabled eight enantiomer@CMOM-5 crystal structures to be determined. The five ordered crystal structures revealed that host-guest hydrogen-bonding interactions are behind the observed enantioselectivity, three of which represent the first crystal structures determined of the ambient liquids R-4P2B, S-4P2B, and R-MPE.

Efficient and Reversible Separation of Chloroform from Chlorinated Hydrocarbons and Water Utilizing a Two-Dimensional Coordination Network.

Chloroform is a volatile organic solvent and a contaminant that is slightly soluble in water, making the reversible separation of chloroform from water a critical and challenging task within the chemical and environmental industries. In this study, we present a newly developed coordination framework, [Zn(4-pmntd)(opa)] [4-pmntd, N,N'-bis(4-pyridylmethyl)naphthalene diimide; opa, o-phthalic acid], which demonstrates a high adsorption capacity for chloroform (2.5 mmol/g) and an excellent ability to separate chloroform from water. The effectiveness of chloroform extraction by Zn(4-pmntd)(opa) was confirmed through vapor sorption, grand canonical Monte Carlo simulation, and 1H nuclear magnetic resonance spectroscopy. The porous framework was also utilized to create a filtration film using natural rubber, which successfully separated chloroform from water with a minimum test concentration of approximately 1 × 10-6 mol/L and a chloroform purity of 99.2%. [Zn(4-pmntd)(opa)] therefore has significant potential for low-energy separation and recycling of chloroform from water under ambient conditions.

Highly Productive C3H4/C3H6 Trace Separation by a Packing Polymorph of a Layered Hybrid Ultramicroporous Material.

Ultramicroporous materials can be highly effective at trace gas separations when they offer a high density of selective binding sites. Herein, we report that sql-NbOFFIVE-bpe-Cu, a new variant of a previously reported ultramicroporous square lattice, sql, topology material, sql-SIFSIX-bpe-Zn, can exist in two polymorphs. These polymorphs, sql-NbOFFIVE-bpe-Cu-AA (AA) and sql-NbOFFIVE-bpe-Cu-AB (AB), exhibit AAAA and ABAB packing of the sql layers, respectively. Whereas NbOFFIVE-bpe-Cu-AA (AA) is isostructural with sql-SIFSIX-bpe-Zn, each exhibiting intrinsic 1D channels, sql-NbOFFIVE-bpe-Cu-AB (AB) has two types of channels, the intrinsic channels and extrinsic channels between the sql networks. Gas and temperature induced transformations of the two polymorphs of sql-NbOFFIVE-bpe-Cu were investigated by pure gas sorption, single-crystal X-ray diffraction (SCXRD), variable temperature powder X-ray diffraction (VT-PXRD), and synchrotron PXRD. We observed that the extrinsic pore structure of AB resulted in properties with potential for selective C3H4/C3H6 separation. Subsequent dynamic gas breakthrough measurements revealed exceptional experimental C3H4/C3H6 selectivity (270) and a new benchmark for productivity (118 mmol g-1) of polymer grade C3H6 (purity >99.99%) from a 1:99 C3H4/C3H6 mixture. Structural analysis, gas sorption studies, and gas adsorption kinetics enabled us to determine that a binding "sweet spot" for C3H4 in the extrinsic pores is behind the benchmark separation performance. Density-functional theory (DFT) calculations and Canonical Monte Carlo (CMC) simulations provided further insight into the binding sites of C3H4 and C3H6 molecules within these two hybrid ultramicroporous materials, HUMs. These results highlight, to our knowledge for the first time, how pore engineering through the study of packing polymorphism in layered materials can dramatically change the separation performance of a physisorbent.

Crystal Engineering of Ionic Cocrystals Sustained by the Phenol-Phenolate Supramolecular Heterosynthon.

Although crystal engineering strategies are generally well explored in the context of multicomponent crystals (cocrystals) formed by neutral coformers (molecular cocrystals), cocrystals comprised of one or more salts (ionic cocrystals, ICCs) are understudied. We herein address the design, preparation, and structural characterization of ICCs formed by phenolic moieties, a common group in natural products and drug molecules. Organic and inorganic bases were reacted with the following phenolic coformers: phenol, resorcinol, phloroglucinol, 4-methoxyphenol, and 4-isopropylphenol. Nine ICCs were crystallized, each of them sustained by the phenol-phenolate supramolecular heterosynthon (PhOH···PhO-). Such ICCs are of potential utility, and there are numerous examples of phenolic compounds that are biologically active, some of which suffer from low aqueous solubility. The propensity to form ICCs sustained by the PhOH···PhO- supramolecular heterosynthon was evaluated through a combination of Cambridge Structural Database (CSD) mining, structural characterization of nine novel ICCs, and calculation of interaction energies. Our analysis of these 9 ICCs and the 41 relevant entries archived in the CSD revealed that phenol groups can reliably form ICCs through charge-assisted PhOH···PhO- interactions. This conclusion is supported by hydrogen-bond strength calculations derived from CrystalExplorer that reveal the PhOH···PhO- interaction to be around 3 times stronger than the phenol-phenol hydrogen bond. The PhOH···PhO- supramolecular heterosynthon could therefore enable crystal engineering studies of a large number of phenolic pharmaceutical and nutraceutical compounds with their conjugate bases.

Optimized Extraction of cAMP From Jujube by Ultra-High Pressure Technology and the Anti-allergic Effect for Peanut Allergy Mouse.

Jujube contains abundant cyclic adenosine monophosphate (cAMP). In contrast, the extraction technology of cAMP from jujube is still to be explored. In this study, the ultra-high pressure extraction (UHPE) conditions for obtaining the maximum cAMP yield from jujube were optimized. Orthogonal array design (OAD) was applied to evaluate the effects of three variables (pressure, pressure-holding time, and liquid-to-solid ratio) by UHPE on cAMP yield. The results showed that the optimal cAMP yield (1223.2 µg/g) was derived at 300 MPa, 20 min duration, and a liquid-to-solid ratio of 2.5 ml/g. In addition, as an important functional ingredient in jujube, cAMP has potential anti-allergic effect. To develop the functional characteristics of jujube, the effect of cAMP was characterized in vivo with the Balb/c mouse model of peanut allergy, which was established by subcutaneous injection of crude peanut protein extract (PN). The results showed that treatment with cAMP in PN-sensitized mice suppressed the lesions in jejunal tissues and allergic symptoms and restored spleen index. Meanwhile, cAMP treatment reduced serum levels of specific immunoglobulin E (IgE), histamine, as well as interleukin-4 (IL-4) and stimulated the secretion of tumor necrosis factor-α (TNF-α), whereas the serum levels of interleukin-10 (IL-10) were not affected. Our results suggested that cAMP has an anti-allergic effect in PN-sensitized mice.

Allantoin-functionalized silk fibroin/sodium alginate transparent scaffold for cutaneous wound healing.

In clinical application, it's highly desirable for developing bio-functionalized cutaneous scaffold with transparent features for convenient observation, excellent biocompatibility, and high efficiency for promoting wound repair. Herein, allantoin-functionalized composite hydrogel was developed by coupling silk fibroin (SF) and sodium alginate (SA) for treatment of cutaneous wounds. The prepared allantoin-functionalized SF-SA composite scaffolds (AFAS) exhibited excellent mechanical properties, especially featured by similar ultimate tensile strength (UTS) and elongation at breaking to human skin. Besides, the solvent-casting method guaranteed the AFAS to obtain highly transparent properties with sufficient moisture permeability and excellent adhesion in wet state. In vitro cellular experiments demonstrated excellent biocompatibility of the scaffold that attachment and proliferation of NIH-3T3 fibroblast cells was promoted in the presence of AFAS. Furthermore, the scaffolds exhibited efficient hemostatic property, based on rat hepatic hemorrhage model. In a cutaneous excisional mouse wound model, the AFAS significantly improved the wound closure rate, compared with pure SF-SA scaffolds and blank control. Moreover, the histomorphological assessments showed that AFAS facilitated the integrity of skin and wound healing process by enhancing collagen deposition, re-epithelialization and vascularization at wound site. The results demonstrate that the novel allantoin-functionalized SF/SA transparent hydrogel has great potential for clinical treatment of cutaneous wound.

Benchmark Acetylene Binding Affinity and Separation through Induced Fit in a Flexible Hybrid Ultramicroporous Material.

Structural changes at the active site of an enzyme induced by binding to a substrate molecule can result in enhanced activity in biological systems. Herein, we report that the new hybrid ultramicroporous material sql-SIFSIX-bpe-Zn exhibits an induced fit binding mechanism when exposed to acetylene, C2 H2 . The resulting phase change affords exceptionally strong C2 H2 binding that in turn enables highly selective C2 H2 /C2 H4 and C2 H2 /CO2 separation demonstrated by dynamic breakthrough experiments. sql-SIFSIX-bpe-Zn was observed to exhibit at least four phases: as-synthesised (α); activated (ß); and C2 H2 induced phases (ß' and γ). sql-SIFSIX-bpe-Zn-ß exhibited strong affinity for C2 H2 at ambient conditions as demonstrated by benchmark isosteric heat of adsorption (Qst ) of 67.5 kJ mol-1 validated through in situ pressure gradient differential scanning calorimetry (PG-DSC). Further, in situ characterisation and DFT calculations provide insight into the mechanism of the C2 H2 induced fit transformation, binding positions and the nature of host-guest and guest-guest interactions.

Proinflammatory S100A9 Regulates Differentiation and Aggregation of Neural Stem Cells.

Inflammation is the primary pathological feature of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease. Proinflammatory molecules (e.g., S100A9) play important roles during the progression of the diseases by regulating behavior and fate of multiple cell types in the nervous system. Our earlier studies reveal that S100A9 is toxic to neurons, and its interaction with Aß peptides leads to the formation of large nontoxic amyloidogenic aggregates, suggesting a protective role of coaggregation with Aß amyloids. We herein demonstrate that S100A9 interacts with neural stem cells (NSCs) and causes NSC differentiation. In the brain of transgenic AD mouse models, we found large quantities of proinflammatory S100A9, which colocalizes with the differentiated NSCs. NSC sphere formation, which is a representative character of NSC stemness, is also substantially inhibited by S100A9. These results suggest that S100A9 is a representative marker for the inflammatory conditions in AD, and it promotes NSC differentiation. Intriguingly, in contrast to the death of both stem and differentiated NSCs caused by high S100A9 doses, S100A9 at a moderate concentration is toxic only to the early differentiated NSCs but not the stem cells. We therefore postulate that, at the early stage of AD, the expression of S100A9 leads to NSC differentiation, which remedies the neuron damage. The application of drugs, which help maintain NSC stemness (e.g., the platelet-derived growth factor, PDGF), may help overcome the acute inflammatory conditions and improve the efficacy of NSC transplantation therapy.

A rapid, high-volume cervical screening project using self-sampling and isothermal PCR HPV testing.

OBJECTIVE: Rapid, high-volume screening programs are needed as part of cervical cancer prevention in China. METHODS: In a 5-day screening project in Inner Mongolia, 3345 women volunteered following a community awareness campaign, and self-swabbed to permit rapid HPV testing. Two AmpFire™ HPV detection systems (Atila Biosystems) were sufficient to provide pooled 15-HPV type data within an hour. HPV+ patients had same-day digital colposcopy (DC) performed by 1 of 6 physicians, using the EVA™ system (MobileODT). Digital images were obtained and, after biopsy of suspected lesions for later confirmatory diagnosis, women were treated immediately based on colposcopic impression. Suspected low- grade lesions were offered treatment with thermal ablation (Wisap), and suspected high-grade lesions were treated with LLETZ. RESULTS: Of 3345 women screened, 624 (18.7%) were HPV+. Of these, 88.5% HPV+ women underwent same-day colposcopy and 78 were treated. Later consensus histology results obtained on 197 women indicated 20 CIN2+, of whom 15 were detected and treated/referred at screening (10 by thermal ablation, 4 by LLETZ, 1 by referral). CONCLUSIONS: Global control of cervical cancer will require both vaccination and screening of a huge number of women. This study illustrates a cervical screening strategy that can be used to screen-and-treat large numbers of women. HPV self-sampling facilitates high-volume screening. Specimens can be tested rapidly, promoting minimal loss-to-follow-up. Specifically, the AmpFire™ system used in this study is highly portable, simple, rapid (92 specimens per 65 min per unit), and economical. Visual triage can be performed on HPV+ women with a portable digital colposcope that provides magnification, lighting, and a recorded image. Diagnosis and appropriate treatment remain the most subjective elements. The digital image is under study for deep-learning based automated evaluation that could assist the management decision, either by itself or combined with HPV typing.

Tetrahedral Geometry Induction of Stable Ag-Ti Nanoclusters by Flexible Trifurcate TiL3 Metalloligand.

A series of increasingly large silver nanoclusters with a varied combination of Archimedean and/or Platonic solid arrangements was constructed using a flexible trifurcate TiL3 (L = Salicylic acid or 5-fluorosalicylic acid) metalloligand: Ag4@Ag4@Ti4 (PTC-85), Ag12@Ti4 (PTC-86), Ag4@Ag6@Ag12@Ti4 (PTC-87), Ag6@Ag24@Ag12@Ti4 (PTC-88), and Ag12@Ag24@Ti4 (PTC-89). The silver nanoclusters are each capped by four TiL3 moieties, thereby forming {Ti4} supertetrahedra with average edge lengths ranging from ∼8.12 Å to ∼17.37 Å. Such {Ti4} moieties further induce the tetrahedral geometry of the encapsulated silver nanoclusters. These atomically precise metallic clusters were found to be ultrastable with respect to air for several months, and to water for more than 3 days, due to the stabilizing effects of the TiL3 metalloligand. Moreover, the obtained clusters exhibit nonlinear optical (NLO) effects in optical limiting tests and also temperature-dependent photoluminescent properties. This work provides an interesting metalloligand method not only to induce the spatial growth of metallic clusters to achieve highly symmetric structures, but also to enhance their stability which is crucial for future application.

Reversible Switching between Nonporous and Porous Phases of a New SIFSIX Coordination Network Induced by a Flexible Linker Ligand.

Closed-to-open structural transformations in flexible coordination networks are of potential utility in gas storage and separation. Herein, we report the first example of a flexible SiF62--pillared square grid material, [Cu(SiF6)(L)2]n (L = 1,4-bis(1-imidazolyl)benzene), SIFSIX-23-Cu. SIFSIX-23-Cu exhibits reversible switching between nonporous (ß1) and several porous (α, γ1, γ2, and γ3) phases triggered by exposure to N2, CO2, or H2O. In addition, heating ß1 to 433 K resulted in irreversible transformation to a closed polymorph, ß2. Single-crystal X-ray diffraction studies revealed that the phase transformations are enabled by rotation and geometrical contortion of L. Density functional theory calculations indicated that L exhibits a low barrier to rotation (as low as 8 kJmol-1) and a rather flat energy surface. In situ neutron powder diffraction studies provided further insight into these sorbate-induced phase changes. SIFSIX-23-Cu combines stability in water for over a year, high CO2 uptake (ca. 216 cm3/g at 195 K), and good thermal stability.

Selective Adsorption of Water, Methanol, and Ethanol by Naphthalene Diimide-Based Coordination Polymers with Constructed Open Cu2+ Metal Sites and Separation of Ethanol/Acetonitrile.

The selective separation of ethanol/acetonitrile by porous materials has rarely been observed owing to their similar physicochemical properties. In this work, we report a new coordination network, [Cu2(4-pmntd)2(opd)2](4-pmntd = N,N'-bis(4-pyridymethy)naphthalene diimide, opd = disodium 1,2-benzenedicarboxylate), which exhibits selective separation of ethanol over acetonitrile. The weak coordination bonds formed by unsaturated Cu2+ sites and hydroxyl groups are the key to such performance.

Control of bulk homochirality and proton conductivity in isostructural chiral metal-organic frameworks.

We have demonstrated for the first time that isostructural homochiral metal-organic frameworks (MOFs) can be synthesized directly from chiral ligands and indirectly from achiral ligands via spontaneous resolution combined with cooperative chirality induction, respectively. Moreover, the usage of different ligands leads to distinct proton conduction behaviors.