Search

A Zn(II) coordination polymer (CP), namely, {[Zn(DTPB)]·DMF}n (H2DTPB = 1-(3,5-di(2H-tetrazol-5-yl)phenyl)-1H-benzeimidazole, Zn-DTPB), was assembled from a new tetrazolyl–benzimidazolyl heterotopic triangular ligand. In Zn-DTPB, the tetrazolyl groups connect the Zn(II) ions into a 2D network with a (4·82) topology, and the 2D network is further interconnected by Zn–N bonds between Zn(II) and benzimidazolyl groups to a 3D framework featuring a 4-connected sra topology. The DMF molecules were tightly encapsulated in the framework and could not be released until the framework decomposed. The framework is stable up to 300 °C and can be retained in water for 72 h. The luminescence in the solid-state and in various solvents was investigated, implying that Zn-DTPB can be used to detect acetone and triethylamine (TEA) in water by fluorescence quenching with good sensitivity and selectivity. Moreover, Zn-DTPB exhibited excellent reproducibility in sensing acetone. Mechanistic studies have shown that the fluorescence quenching of acetone and triethylamine is caused by competitive absorption and structural amorphization, respectively. Interestingly, the amorphous product can be transformed into Zn-DTPB crystals through a solvent-media structural transformation process. [ABSTRACT FROM AUTHOR]

For the first time, hierarchical porous amorphous metal–organic frameworks (HP-aMOFs) containing ultramicropores, micropores, and mesopores were synthesized by etching a composite of MOF glass (agZIF-76) and ZnO using ammonia. These materials show potential applications in the adsorption of C2 hydrocarbons. [ABSTRACT FROM AUTHOR]

Although significant progress in the development of functional covalent organic frameworks (COFs) as effective porous adsorbents for capturing radioactive iodine has been achieved, a systematic study on regulating the iodine adsorption performance of COFs by tuning the proportion of monomers is extremely scarce. Herein, a series of two- and three-component β-ketoenamine-linked COFs denoted as NH2-ThX-Mth1−X-Tfp (X = 1, 0.75, 0.50, 0.25, and 0) with different contents of free amino groups have been synthesized by tuning the proportion of three monomers, 2-aminoterephthalohydrazide (NH2-Th), 2,5-bis(2-methylbutoxy) dihydrazide terephthalate (Mth) and 1,3,5-trihydroxy phloroglycerol (Tfp). Then, these NH2-ThX-Mth1−X-Tfp COFs have been utilized as adsorbents for iodine vapour capture. Apparently, owing to the change of the proportion of monomers, the content of amino groups, crystallinity and the specific surface area of the obtained COFs are different, which have remarkable regulation effects on their adsorption performances toward iodine vapour. With the decrease of the content of NH2-Th, the crystallinity and specific surface area of COFs increased gradually. And the adsorption capacities of five NH2-ThX-Mth1−X-Tfp COF materials (X = 1, 0.75, 0.50, 0.25, and 0) were determined to be 1.21, 1.32, 1.55, 2.30 and 1.73 g g−1, respectively. Significantly, the NH2-Th0.25-Mth0.75-Tfp COF containing 25% NH2-Th exhibited the largest adsorption capacity for iodine vapour among the five as-synthesized COFs, and still maintained 70% adsorption capacity after six cycles. Moreover, the iodine adsorption kinetics of NH2-ThX-Mth1−X-Tfp COFs (X = 0, 0.25, 0.50, and 0.75) were consistent with the pseudo-second-order simulations, while that of the NH2-Th-Tfp COF fitted better with the pseudo-first-order simulations. This study uncovered that regulating the COF structures by tuning the proportion of monomers could greatly improve their iodine adsorption performances, which provided a reference for the design and development of new high-performance COF-based absorbents. [ABSTRACT FROM AUTHOR]

The research on amorphous metal–organic frameworks (aMOFs) is still in its infancy, and designing and constructing aMOFs with functional pores remains a challenge. Two aMOFs based on Co(II) and heterotopic triangular ligands with large conjugated aromatic planes, namely aMOF-1 and aMOF-2, were constructed and characterized by IR, XPS, EA, ICP, XANS and so on. aMOF-1 possesses mesopores, whereas aMOF-2 possesses micropores. The porosity, conjugated aromatic plane and uncoordinated N atoms in the framework allow these aMOFs to adsorb iodine and dyes. The iodine adsorption capacity of aMOF-1 is 3.3 g per g, which is higher than that of aMOF-2 (0.56 g per g), mainly due to the expansion or swelling of aMOF-1 after iodine adsorption. The uptake of cationic dyes by aMOF-2 showed more rapid kinetics and a higher removal rate than that by aMOF-1, mainly due to the difference in the porosity and surface charge. Although the surface charges of aMOF-1 and aMOF-2 are negative, both of them showed significantly faster adsorption kinetics toward anionic dyes, among which methyl orange (MO) and Congo red (CR) can be removed in 5 min. This occurs possibly because the quick adsorption of Na+ ions alters the surface charge of the framework and promotes dye uptake. The adsorption capacities of aMOF-1 for MO and CR reached 921 and 2417 mg g−1, respectively. The correlation data for aMOF-2 are 1042 and 1625 mg g−1, respectively. All adsorption capacities are among the highest compared to many cMOFs. Adsorption in mixed dye solution is found to be charge-dependent, kinetic-dependent, and synergetic in these systems. The porosity, surface charge regulation during adsorption, weak interactions and multiple adsorption processes contribute to the dye adsorption performance. [ABSTRACT FROM AUTHOR]

A metal–organic cage (MOC)-based porous salt composed of cationic Zr-MOC and anionic Cu-MOC was incorporated into SBA-15 nanopores via a two-step impregnation method for the first time. The encapsulated MOC-based porous salt showed improved iodine adsorption capacity when compared with the bulk sample. [ABSTRACT FROM AUTHOR]

Nanotoxicology on plants has raised great concerns about the prevalence of nanoparticles (NPs) in ecosystems, and the most fundamental aspect is to assess the fate of NPs in plants. Nonetheless, the lack of high-sensitivity tracking techniques in vivo constraints intensive research on NP distribution in plants. Herein, we have overcome this limitation by first introducing persistent luminescent nanoparticles (PLNPs) as an imaging probe, which can detect the distribution of NPs in whole plants with high sensitivity by completely eliminating interference from autofluorescence. We synthesized two differently surface-charged PLNPs with excellent biosafety and then exposed these NPs to plants in the hydroponic medium. Persistent luminescence (PersL) images visually showed the disparate accumulation of PLNPs in plants. PersL signals of positively charged PLNPs were observed in the whole exposed portion of the plant roots, while negatively charged PLNPs were mainly in the root collars instead of the exposed portion. With prolonged exposure, the presence of PersL signals in leaves indicated the long-distance translocation of differently charged PLNPs from roots to leaves via hypocotyls. For further confirmation of imaging results, the distribution of NPs in plants was investigated using electron microscopy. Based on their unique optical properties, PLNPs provide a promising strategy for tracking NP's fate in plants. [ABSTRACT FROM AUTHOR]

The stability of Pt nanoparticles on a carbon support is crucial for the lifespan of polymer electrolyte membrane fuel cells as well as other electrocatalysis systems such as electrolyzers. Here we took the approach of utilizing the covalently grafted polyaniline on carbon to stabilize Pt nanoparticles by simultaneously alleviating the particle migration and mitigating the Ostwald ripening, which are two major mechanisms for loss of the catalyst stability. A comprehensive investigation of the stability and performance of Pt catalyst nanoparticles on these supports reveals that the polyaniline can shift the Pt L edge binding energy and the Pt 4f peak energy, leading to the increased redox potential of the Pt nanoparticles and making them more resistant to oxidation. Interestingly, the highest polyaniline density (50 wt%) does not show the best catalyst stability, rather, the second (33 wt%) demonstrates the best catalyst stability among these catalysts. Combining the XPS, XAS and fuel cell stability studies, we concluded that the locations of the Pt nanoparticles over the polyaniline layer on the carbon surface depend on the surface density of the polyaniline over the carbon surface. The Pt nanoparticles in the 50 wt% polyaniline catalyst are wrapped by the polyaniline polymer but do not sit directly on the carbon surface, while Pt nanoparticles in the 33 wt% polyaniline catalyst sit on the carbon surface and are densely surrounded by the polyaniline polymer. The results show that the mass activity loss is 12.5% while the ECSA (electrochemically active surface area) loss is 37.1% after 30k cycles of accelerating stress test for the 33 wt% polyaniline catalyst, far exceeding the DOE 2020 target for MEA (i.e., mass activity loss < 50%, and ECSA loss < 40%). Overall, the polyaniline has a synergistic effect on mitigating the surface migration and slowing down the Ostwald ripening to stabilize the Pt nanoparticles in fuel cells. The novel strategy to stabilize Pt nanoparticles using polyaniline opens a new pathway in the development of highly stable catalysts: relying on the functionalization group on the carbon support, instead of just focusing on the catalyst itself. [ABSTRACT FROM AUTHOR]

Two Cu(I) coordination polymers (CPs), namely, [CuI(DBPT)(H2O)]n (HDBPT = 3,5-di((1H-benzeimidazol-yl)phenyl)-2H-tetrazole, CP 1) and [CuI(DBPT)·DMF]n (CP 2), were constructed based on a new N-containing heterotopic triangular ligand. CP 1 is a 2D network consisting of binuclear secondary building units (SBUs). The 2D layers are connected by strong hydrogen bonds to form a 3D supramolecular framework. CP 2 possesses a 3D framework based on binuclear SBUs and features a (3,6)-connected rtl topology. Both CP 1 and CP 2 have high stability in water in the pH range from 3–13 and exhibit energy band gaps of 2.70 and 2.79 eV, respectively, which indicate their possibility in visible-light-driven photocatalysis. The photocatalytic results show that both CP 1 and CP 2 display good activity for MLB degradation in the presence of H2O2 as an oxidant under visible light irradiation. A mechanistic investigation indicated that the photogenerated holes trapped by Cu(I) generate Cu(II). Cu(II) may be involved in a Fenton-like CuI/CuII redox reaction to generate ˙OH. Thus, holes and ˙OH contribute to the degradation of MLB. In addition, the degradation product of MLB was further studied by LC-MS, which indicates that MLB is almost degraded to small molecules. [ABSTRACT FROM AUTHOR]

By virtue of visible light absorption ability, the energy band structure and electronic affinity of covalent organic frameworks (COFs) can be easily tuned at the molecular level, making them attractive photocatalysts for metal-free organic transformation. However, the relationship between the electronic structure and photocatalytic properties of COFs is still vague. In this study, we developed a bottom-up strategy to construct three triazine-based COFs with different electronic structures through introducing various building blocks. The photocatalytic oxidation of sulfides to sulfoxides showed that electron-deficient COF afforded higher conversion and selectivity than that of electron-rich or neutral structures, which due to the electron-deficient triazine-based COF can not only facilitate the generation and separation of charge, but also enrich the photocatalytic active sites. This result was further confirmed by photoelectrochemical measurements and theoretical calculations. This work lights up the design and application of high-efficient metal-free photocatalysts by modulation of electronic structures. [ABSTRACT FROM AUTHOR]

Two amorphous metal–organic frameworks (aMOFs) were obtained from crystalline Co-MOF (SCNU-Z6) via temperature-induced (aT-SCNU-Z6) and water-immersed (aW-SCNU-Z6) approaches. They exhibited high iodine uptake, with the adsorption capacities of aT-SCNU-Z6 and aW-SCNU-Z6 reaching 2.05 and 5.04 g g−1, respectively. This work is the first report of iodine uptake by aMOFs. [ABSTRACT FROM AUTHOR]

Radioactive iodine is a major nuclear waste, and its capture and immobilization are highly desirable. Herein, a new Ni(II) metal–organic framework based on a newly designed imidazole–tetrazole heterotopic tripodal ligand, namely, SCNU-Z5, was constructed and applied to the capture of iodine from solution and the vapor phase. SCNU-Z5 has an interesting high-connectivity chiral framework with 1D helical channels. The combination of 1D channels and two other crossed 1D channels resulted in a porous framework with N,N-dimethylacetamide (DMAc) guest molecules. The guest molecules were exchanged by iodine molecules present in cyclohexane, water and vapor, with maximum adsorption capacities of 442, 352, and 1680 mg g−1, respectively. Mechanism studies showed that iodine adsorption was attributed to the charge transfer between iodine molecules and the framework and the interaction of iodine molecules themselves. Interestingly, the adsorption of iodine molecules led to amorphization of the framework, and I2 was buried and fixed stably inside the framework, thus providing a new strategy for stable immobilization of iodine in MOFs. [ABSTRACT FROM AUTHOR]

The increasing demand for freshwater and the intensification of environment pollution have driven the exploration of high-performance photothermal conversion materials for solar-driven interfacial evaporation (SIE) to produce fresh water. However, the preparation of photothermal conversion materials with high mechanical strength, low cost and sustainability is still a challenge. Herein, an aligned attapulgite-based aerogel with high content of attapulgite (ATP) and high mechanical strength was prepared by chemically/physically cross-linking nano-fibrillated cellulose (NFC), polyvinyl alcohol (PVA) and glutaraldehyde (GA). The resulting ATP-based aerogels were characterized by SEM, N2-adsorption/desorption, axial compression experiment, thermal conductivity test and UV-vis-NIR spectroscopy. The results show that the as-prepared ATP-based aerogels exhibit a three-dimensional macroporous structure, high mechanical strength, low thermal conductivity and excellent light absorption ability. As a solar steam generator, the desired aerogel not only possesses a high energy conversion efficiency of 87.6% in pure water, but also shows highly efficient and stable evaporation performance in harsh environments, such as high-concentration brine water, acid solution, alkali solution, and hot water. In addition, it also exhibits superiorities such as a flexible tunable structure and scalable preparation due to the combination of material selection and rational design. This work provides an insight for the rational design of photothermal conversion materials, showing potential applications in high brine water and harsh environment desalination. [ABSTRACT FROM AUTHOR]

Metal nanoparticles are easily deactivated by migration–aggregation in combustion. Encapsulated nanoparticles are one of the tools for coping with the stability challenges of metal nanoparticles. The self-assembly details of aluminum nanoparticles (ANPs) encapsulated into carbon nanotubes (CNTs) were demonstrated by molecular dynamics simulations. The simulation results show that ANPs can completely self-roll into CNTs to form a stable core–shell structure by inertial force and van der Waals force. Inside the tubes, ANPs move toward the cap at a velocity of 2.27 Å ps−1. However, it increases to 3.17 Å ps−1 when near the cap of CNTs. The initiation of the ANPs' oxidation and degradation can be effectively checked by coating CNTs. The diffusion of the Al atoms in the encapsulated ANPs occurred earlier than their oxidation in combustion, verified by using ReaxFF molecular dynamics simulations. The morphological evolutions of the nanostructures in the initial combustion of the encapsulated ANPs are predicted. The interplay between the encapsulated ANPs' responses and external stimuli is classified into core–shell separation, shell damage, and core–shell burst, which provides insights into the oxidation mechanism of encapsulated nanoparticles. [ABSTRACT FROM AUTHOR]

Since Fe(III) ions are of importance in biological systems, the development of new sensors for detecting Fe(III) with excellent selectivity and low detection limit is desirable. Herein, a new stable hydrazone-linked covalent organic framework (COF), namely, Tfpa–Mth COF, was synthesized by the Schiff-base condensation reaction between tris(4-formylphenyl) amine (Tfpa) and a chiral hydrazide precursor (Mth). The ethanol-dispersed Tfpa–Mth COF can be used as a fluorescence sensor for the detection of Fe(III) ions, showing high selectivity and low detection limit (64 nM). Moreover, a novel COF-based quartz crystal microbalance (QCM) sensor has been fabricated by the in situ growth of the Tfpa–Mth COF on an amino-modified QCM chip. Such a COF-based QCM sensor, with a uniform surface and thickness of the Tfpa–Mth COF film on the surface, is able to monitor Fe(III) ions in real-time with high selectivity. The recognition process, as a result of Fe(III) immobilization on the Tfpa–Mth COF framework, is further verified by zeta potential measurements and X-ray photoelectron spectroscopy. To the best of our knowledge, this represents the first report on the development of COF-based QCM sensors for metal ion detection. Exploration of the COF-based QCM sensor in our work demonstrates the new pathway for the selective detection of metal ions. [ABSTRACT FROM AUTHOR]

A metal–organic framework (MOF), namely SCNU-Z3, based on an imidazole-tetrazole tripodal ligand and Mn(II), has been constructed. It exhibits a porous 3D framework composed of truncated octahedron cage subunits. Unexpected ligand-induced missing metal-ion defects were observed in the framework. In addition, the application of SCNU-Z3 in a supercapacitor was performed. [ABSTRACT FROM AUTHOR]

The development of a robust and efficient stationary phase for chromatographic biopharmaceutical purification is of prime importance but remains challenging. Herein, we have developed a series of protein A-mesoporous silica composites for the first time by covalently coupling protein A with the tagged carbonyl imidazole moieties in the column, which constitutes a facile and efficient route for the preparation of protein A immunoaffinity materials. The resultant composites are employed as the stationary phase for chromatographic purification of immunoglobulin G (IgG). The effect of silica's pore size and coupled protein A on the antibody purification is systematically investigated. When the pore size of silica increased from 100 to 1000 Å, the amount of coupled protein A decreased, and the surface coverage on the silica significantly improved, accompanied by an increase in the amount of purified rabbit IgG. With an increasing coupled protein A, the surface coverage increased at first and decreased subsequently, which shows a similar trend to the amount of purified IgG and specific activity. When practically implemented for purifying several immunoglobulins that are central for commercial ELISA Kits, the protein A-mesoporous silica composite exhibited superior performance compared to the GE-Mabselcetxtra rProtein A column, particularly in the purification of immunoglobulin M (IgM), which cannot be realized by the GE-Mabselcetxtra rProtein A column. This study sheds new light on the rational development of protein-affinity chromatography for biopharmaceutical purification. [ABSTRACT FROM AUTHOR]

A new strategy of using a MOF as an effective amplifier in a QCM miRNA sensor was presented based on the selective interaction between a MOF (UiO-66) with different zeta potentials and different miRNAs. The signal can be significantly enhanced, which leads to significantly improved performance in miRNA detection. [ABSTRACT FROM AUTHOR]

A 2D imine-linked COF with a hitherto unreported htb type topology was synthesized from a linear diamine linker and a judiciously designed tetra-aldehyde building block. This work opens the door to the development of COFs with unprecedented topologies and may broaden the scope of COF functional materials by pore size and pore surface engineering. [ABSTRACT FROM AUTHOR]

To explore the influence of in situ hydrolysis reaction on the assembly of coordination polymers (CPs), seven new CPs based on in situ formed 3,5-di(1H-1,2,4-triazol-1-yl)benzoic acid (HDTBA) from two different precursors, 3,5-di(1H-1,2,4-triazol-1-yl)benzonitrile (DTBN) and 5-(3,5-di(1H-1,2,4-triazol-1-yl)phenyl)-2H-tetrazole (HDTPT), were constructed. When DTBN is used as a precursor, four CPs, namely, [Zn(DTBA)2]n (1), [Cd(DTBA)2]n (2 and 3), and {[Cd(DTBA)2]·H2O}n (4), were obtained under hydrothermal conditions. Compound 1 is a nested double layer structure based on (6,3) networks. Compounds 2 and 3 are supramolecular isomers which were synthesized from Cd(NO3)2·6H2O and Cd(ClO4)2·6H2O, respectively. Compound 2 displays a 3D framework with a two-folded interpenetrating bimodal (3,6)-connected rtl network topology, while compound 3 possesses a 2D network with a CdI2-type network topology. Compound 4 presents a 3D framework that can be denoted as a new (3,5)-connected topological net with point symbol of {4·6·8}{4·64·85}. When HDTPT was used as a precursor under similar conditions, three CPs, namely, Zn(DTBA)NO3]n (5), [Zn(DTBA)Cl]n (6) and {[Cd(DTBA)(NO3)(H2O)]·H2O}n (7), were obtained. Compound 5 is a 2D network with a (4·82) topology, while compounds 6–7 are 2D networks with the same (6,3) network topology. Interestingly, anion…π interaction between inorganic anions and triazolyl ring can be observed and plays an important role in connecting the 2D layer into 3D supramolecular frameworks in 5–7. The results show that the in situ hydrolysis reactions affect the assembly processes significantly. The in situ reactions regulate the structure via changing the concentration (but not the total amount) of HDTBA during the assembly process, which in turn regulates the coordination competition between HDTBA and inorganic anions, thus generating different structures. Furthermore, their solid-state fluorescent properties were investigated at room temperature. [ABSTRACT FROM AUTHOR]

A variety of nanocarriers have been designed to deliver photosensitizers (PSs) and promote the clinical applications of photodynamic therapy (PDT). However, most of them suffer from insufficient loading capability, premature leakage, and/or unstable therapeutic efficacy. Herein, we constructed a novel nanocomposite (TGP@MOS) with a benzene-bridged mesoporous organosilica shell and a triangular gold nanoprism core. The TGP@MOS could load model PS molecules, zinc phthalocyanine (ZnPc), with high loading capacity (11.8 wt%) and minimal premature leakage (only 2.6% after incubation in PBS with 10% FBS for 60 h) viaπ–π stacking interactions and hydrophobic interactions. We demonstrated that the obtained TGP@MOS–ZnPc could realize timely coordinated photodynamic/photothermal therapy upon single irradiation, and thus stabilize and maximize the therapeutic efficacy of phototherapy both in vitro and in vivo. Other advantages of TGP@MOS-ZnPc include excellent water solubility, stability, hemocompatibility and biocompatibility. [ABSTRACT FROM AUTHOR]

Nanoparticles (NPs) functionalized with targeting ligands have shown promise, but are still limited by their nonspecific uptake by certain healthy tissues and cells that express low or even comparable levels of receptors. To increase their accumulation at tumor sites while decreasing the unintended toxicity, a possible solution is the involvement of two separate tumor-specific ligands in the localization. In this study, a dual tumor-targeting drug-loaded NP system was self-assembled by the amphiphilic conjugate of methotrexate–hyaluronic acid–octadecylamine (MTX–HA–OCA) with curcumin (CUR) encapsulated within the hydrophobic core (designated as MTX–HA–OCA/CUR NPs). The advantages of this nanosystem are that the anticancer drug MTX can be utilized as a tumor-targeting ligand toward folate receptors due to its structural similarity to folic acid (FA), and HA can serve as another tumor-targeting ligand toward CD44 receptors. The MTX–HA–OCA/CUR NPs are ∼70 nm in diameter and have sustained/controlled drug release behavior. An in vitro cellular uptake and competition inhibition study exhibited that MTX–HA–OCA/CUR NPs could significantly enhance the internalization efficiency in HeLa cells via folate/CD44 receptor-mediated endocytosis as compared to HA–OCA/CUR NPs. More importantly, the in vitro cytotoxicity of MTX–HA–OCA/CUR NPs was significantly enhanced as compared to those of the HA–OCA/CUR NPs, both free drugs, and individual free drug. Furthermore, the real-time in vivo and ex vivo fluorescence imaging of HeLa tumor-bearing mice showed that MTX–HA–OCA/CUR NPs could more efficiently enhance their accumulation and improve the penetration at the tumor site as compared to HA–OCA/CUR NPs. Therefore, these dually folate/CD44 receptor-targeted self-assembled HA NPs for the co-delivery of both anticancer drugs might provide a promising strategy for dual-targeted combination cancer therapy. [ABSTRACT FROM AUTHOR]

Two new imidazole-based dicarboxylate ligands, which are 2-(pyridin-4-ylmethyl)-1H-imidazole-4,5-dicarboxylic acid (H3pPyMIDC) and 2-(pyridin-3-ylmethyl)-1H-imidazole-4,5-dicarboxylic acid (H3mPyMIDC), have been designed and successfully synthesized. Both these multidentate ligands are then used to react with different kinds of alkaline earth metal ions under solvothermal conditions, leading to the construction of a series of new coordination polymers (CPs), namely, [Ba(μ5-HpPyMIDC)(H2O)]n (1), [Sr(μ5-HpPyMIDC)(H2O)]n (2), [Ca2(μ4-HpPyMIDC)2(H2O)2]n (3), {[Ca2(μ3-HpPyMIDC)(μ4-HpPyMIDC)(H2O)2]·H2O}n (4), [Ba(μ5-HmPyMIDC)(H2O)]n (5), {[Mg10(μ3-mPyMIDC)3(μ4-mPyMIDC)3(H2O)21]·SO4·12H2O}n (6) and {[Sr(μ2-H2mPyMIDC)2(DMF)2]n·H2O}n (7). Compounds 1 and 2 are isostructural, exhibiting two-dimensional (2D) network structures with a hexagonal honeycomb (6,3) topology if the corresponding metal ions are seen as 3-connected nodes. Compound 3 displays another type of 2D network, which is built by the connection of μ4-HpPyMIDC ligands and Ca(ii) centres. Compound 4 is a binodal (3,4)-connected 3D framework with the Schläfli symbol of (6·82)(65·8). The 2D structure of compound 5 is similar to those of compounds 1 and 2, although different kinds of ligands are employed. Compound 6 exhibits an interesting 3D framework with a pcu topology by considering each unusual heptanuclear magnesium cluster as a 6-connected node. In compound 7, connection of μ2-H2mPyMIDC ligands with Sr(ii) ions results in the formation of an uncommon 3D chiral framework containing two different types of 1D helical chains. The present results reveal that both these new imidazole-based dicarboxylate ligands containing flexible pyridinylmethyl groups show versatile coordination abilities and are good candidates for fabricating new CPs. Moreover, the thermogravimetric and solid-state luminescence properties of all the compounds have also been studied. [ABSTRACT FROM AUTHOR]

Six new d–f heterometallic Ln(iii)–Zn(ii) coordination polymers (CPs), namely, {[EuZn(NIPH)1.5(INC)(H2O)(OH)]·0.5H2O}n (1), [LnZn(NIPH)2(INC)(H2O)]n [Ln = Eu (2), Tb (3)], [EuZn2(NIPH)2.5(INC)2]n (4) and [LnZn(NIPH)2(NC)(H2O)]n [Ln = Eu (5), Tb (6)] [H2NIPH = 5-nitroisophthalate, HINC = isonicotinate, and HNC = nicotinate], were obtained under hydrothermal conditions. All the compounds are based on well-defined heterometallic secondary building units (SBUs). Compound 1 is a 3D network with pcu topology, which was generated from tetragonal tetranuclear heterometallic [Eu2Zn2(NIPH)4(INC)2(OH)2] SBUs connected by NIPH2− and INC− ligands. Compounds 2 and 3 are isostructural and exhibit 3D heterometallic frameworks with bcu topology constructed by the linkage of 2D layers containing linear tetranuclear heterometallic [Eu2Zn2(NIPH)6(INC)2] SBUs and INC− anions. Compound 4 possesses 7-connected 3D frameworks with the Schläfli symbol of (33·411·56·6) constructed by the interconnection of linear trinuclear heterometallic [EuZn2(NIPH)4(INC)4] SBUs, NIPH2− ligands and INC− anions. In compounds 5 and 6, 3D networks are formed through the linkage among linear tetranuclear [Ln2Zn2(NIPH)8(NC)2] SBUs, NIPH2− ligands and NC− anions. All the compounds represent examples of 3D lanthanide–transition heterometallic–organic coordination polymers with two types of metal ions and two organic carboxylates. Furthermore, their solid-state fluorescence properties have been investigated at room temperature. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of 2,3,5,6-tetra(2-pyridyl)pyrazine (tppz) and sodium azide with different cadmium salts including CdCl2·2.5H2O, Cd(NO3)2 and Cd(CH3COO)2·2H2O at 80 °C produce three new coordination polymers, namely, {[Cd2(N3)2(tppz)Cl2]·2H2O}n (1), [Cd2(N3)2(tppz)(NO3)2]n (2) and {[Cd2(N3)2(tppz)(CH3COO)2]·2H2O}n (3), respectively. Single-crystal X-ray diffraction analysis reveals that the anions of the Cd(ii) salts all participate in coordination in compounds 1–3. Compound 1 features an infinite one-dimensional (1D) chain with loops-and-rods topology, compound 2 exhibits a 1D ladder-like chain, while compound 3 possesses a 2D honeycomb-like network structure with (6,3) topology. The low-dimensional structures of compounds 1–3 are further stabilized by diverse supramolecular interactions such as hydrogen bonds and π…π stacking. Interestingly, when the temperature is increased to 100 °C, similar reactions of tppz and sodium azide ligands with CdCl2·2.5H2O, Cd(NO3)2 and Cd(CH3COO)2·2H2O lead to three other novel 3D Cd(ii) coordination polymers formulated as [Cd3(N3)6(tppz)]n (4), {[Cd2(N3)2(tppz)(NO3)2]·MeOH}n (5) and [Cd4(N3)6(tppz)(CH3COO)2]n (6), respectively. The anions of the Cd(ii) salts again take part in coordination in compounds 5 and 6 but disappear in the final structure of 4. Compound 4 displays a rare sxd-type 3D framework with the Schläfli symbol of (33·46·55·6) if each V-shaped trinuclear [Cd3(μ1,1-N3)4] secondary building unit (SBU) is regarded as a 6-connected node. In compound 5, both the Cd1 and Cd2 atoms serve as 3-connected nodes to construct an uncommon binodal (3,3)-connected 3D framework with (6·102)(62·10) topology. Compound 6 contains another type of V-shaped trinuclear [Cd3(μ1,1-N3)2(μ3-CH3COO)] SBU, which acts as a 7-connected node to fabricate a unique uninodal 7-connected 3D framework with a completely new topology of (36·42·510·63). The present results reveal that both anions and temperature play essential roles in the structural and topological diversity of such six new Cd(ii) coordination polymers. Moreover, the IR spectra, thermogravimetric analysis curves, and solid-state luminescence properties of all the compounds have been also investigated. Compared with the free tppz ligand, compounds 1–6 exhibit superior luminescence properties with largely enhanced emission, indicating that they may be good candidates for optical materials. [ABSTRACT FROM AUTHOR]

In this article, the reaction mechanisms of H2S + 3O2 formation by the HO2 + HS reaction without and with catalyst X (X = H2O, (H2O)2 and (H2O)3) have been investigated theoretically at the CCSD(T)/6-311++G(3df,2pd)//B3LYP/6-311+G(2df,2p) level of theory, coupled with rate constant calculations by using conventional transition state theory. Our results show that in the presence of catalyst X (X = H2O, (H2O)2 and (H2O)3) into the channel of H2S + 3O2 formation, the reactions between the SH radical and HO2…(H2O)n (n = 1–3) complexes are more favorable than the corresponding reactions of the HO2 radical with HS…(H2O)n (n = 1–3) complexes due to the lower barrier of the former reactions and the higher concentrations of HO2…(H2O)n (n = 1–3) complexes. Meanwhile, the catalytic effect of water, water dimers and water trimers is mainly taken from the contribution of a single water vapor molecule, since the total effective rate constant of HO2…H2O + HS and H2O…HO2 + HS reactions was, respectively, larger by 7–9 and 9–12 orders of magnitude than that of SH + HO2…(H2O)2 and SH + HO2…(H2O)3 reactions. Besides, the enhancement factor of water vapor is only 0.37% at 240 K, while at high temperatures, such as 425 K, the positive water vapor effect is enhanced up to 38.00%, indicating that at high temperatures the positive water effect is obvious under atmospheric conditions. Overall, these results show how water and water clusters catalyze the gas phase reactions under atmospheric conditions. [ABSTRACT FROM AUTHOR]