Converting a Non-Porous Rare-Earth Metal-Organic Framework into a Porous Yttrium-Based NH2UiO-66 Network via a Linker Exchange Approach.

The solvent-assisted linker exchange (SALE) method was used to produce amino-functionalized yttrium-based UiO-66 [NH2UiO-66(Y)], which is not obtainable via a direct synthetic method. Remarkably, SALE not only produced relatively highly porous NH2UiO-66(Y) from completely non-porous 3,3-bpdc-Y but also changed the network topology from 8-connected bcu in 3,3-bpdc-Y to 12-connected fcu in NH2UiO-66(Y). Based on our knowledge, this is one of the rare cases where SALE changes the whole network topology of the resulting metal-organic framework. NH2UiO-66(Y) also showed promising ability for selective detection of Cu2+ at a low concentration.

In Situ Transformation of Metal-Organic Frameworks into Hollow Nickel-Cobalt Double Hydroxide Arrays for Efficient Water Oxidation.

Developing earth-abundant electrocatalysts for efficient oxygen evolution reaction (OER) is of paramount significance for electrochemical water splitting. Herein, an efficient in situ etching-deposition growth strategy is employed to transform pristine two-dimensional (2D) Co-metal-organic frameworks into hollow Ni/Co double hydroxide arrays (denoted as Ni/Co-DH), which not only yields a larger surface area and exposes more active sites but also decreases the activation energy to the OER. With structural and compositional benefits, the Ni/Co-DH exhibits high performance with an overpotential of 229 mV at 10 mA cm-2 and exceptional long-term stability of over 90 h in 1 M KOH medium for OER, comparable to most non-noble oxygen evolution catalysts reported so far. In addition, a two-electrode Ni/Co-DH∥Pt/C electrolyzer also requires a considerably low voltage of 1.58 V at 10 mA cm-2 for overall water splitting. This study affords a rational strategy to develop water-alkali electrolyzers with great complexity for large-scale water-splitting systems.

Drug Delivery Using Hydrophilic Metal-Organic Frameworks (MOFs): Effect of Structure Properties of MOFs on Biological Behavior of Carriers.

To study the influence of pore structural properties of metal-organic frameworks (MOFs) on drug adsorption and delivery, we synthesized two MOF termed TMU-6(RL1) {[Zn(oba)(RL1)0.5]n·(DMF)1.5} and TMU-21(RL2) {[Zn(oba)(RL2)0.5]n·(DMF)1.5} with amine basic N-donor pillars containing phenyl or naphthyl cores with various hydrophilic properties around the main center of the reaction. TG, IR, XPS, and PXRD analyses were used to extensively characterize the MOFs. The synthesized carriers showed high adsorption efficiency, stability, and controlled release. As an anticancer drug, Nimesulide (Nim) was adsorbed to MOFs using multiple adsorption mechanisms, such as Hostπ-πGuest interaction and HostN-H···OGuest hydrogen bonds. Moreover, Hirshfeld surface analysis showed when the benzene core was replaced with the naphthalene core, the percentage of intermolecular interactions of π···π and N···H by amine sites in TMU-21(RL2) decreased compared with TMU-6(RL1), while the percentage of these interactions with guest molecules increased. The results showed that changes in the hydrophobicity/hydrophilicity properties of MOFs would alter their ability to adsorb Nim in the pore of the frameworks. In vitro anticancer studies also showed that the cytotoxicity of Nim in MOFs@Nim composites against human cervical cancer cell line (HeLa cells) and human colon cancer cell line (HT-29 cells) is much higher than that of free Nim. Generally, based on the results, it can be said that the biological behavior of carriers can be regulated by adjusting the structure properties of MOFs.

Highly Sensitive Colorimetric Naked-Eye Detection of HgII Using a Sacrificial Metal-Organic Framework.

This study has developed a specific, easy, and novel approach to designing a sacrificial metal-organic framework (MOF) that can detect and measure the amount of Hg2+ in aqueous and nonaqueous solutions using the naked eye. The functionalized [Zn(oba)(RL3)0.5]n·1.5DMF (TMU-59) provides the ability of simple visual assessment or colorimetric readout without sophisticated analytical equipment. Because of the special interaction with Hg2+, degradation of the structure of this unique MOF causes the solution to change color from colorless to a pink that is easily recognizable to the naked eye. The presence of a methyl group plays a major role in naked-eye detection by a qualitative sensor. Furthermore, this qualitative sensor data for the production of a simple, instant, and portable red, green, and blue (RGB)-based quantitative sensor were used to determine the concentration of Hg2+ in different specimens. As a turn-off fluorescence sensor, this unique structure is also capable of detecting Hg2+ at very low concentrations (the limit of detection is 0.16 ppb). To the best of our knowledge, TMU-59 is the first MOF-based naked-eye sensor that can successfully and specifically display the presence of Hg2+ through a major color change.

New 3D Porous Silver Nanopolycluster as a Highly Effective Supercapacitor Electrode: Synthesis and Study of the Optical and Electrochemical Properties.

A high-nucleus silver nanopolycluster as a new type of silver-based polymer supercapacitor (SSc) by a simple and single-step synthesis process was designed and synthesized. The structural, optical, and electrochemical properties of SSc-2 were determined. This highly stable conductive 3D nanopolycluster shows great cycling stability, large capacity, and high energy density without any modification or doping process and so acts as an excellent SSc (412 F g-1 at 1.5 A g-1). In addition, there was a stable cycling performance (94% capacitance) following 7000 cycles at 3 A g-1 current density. The presence of fluorinated groups, 3D expansion of high-nucleus metallic clusters, and porosity are the advantages of SSc-2 that lead to stability, conductivity, and high capacity, respectively. These results lead to the development of a novel kind of SSc by overcoming the low conductivity and limited capacity challenges without any modification.

All-Carboxylate-Protected Superatomic Silver Nanocluster with an Unprecedented Rhombohedral Ag8 Core.

We report the synthesis and structure of the first all-carboxylate-protected superatomic silver nanocluster. It was prepared by heating a dimethylformamide solution of perfluoroglutaric acid and AgNO3 under alkaline conditions, yielding a single crystal of [(CH3)2NH2]6[Ag8(pfga)6]. The [Ag8(pfga)6]6- cluster has a rhombohedral Ag86+ core, with each of its faces protected by one dianionic perfluoroglutarate (pfga) ligand. Electronic-structure analysis from density functional theory confirms the stability of this two-electron cluster due to the shell closing of the superatomic orbital in the (1S)2 configuration and explains the optical absorption of the cluster in the visible region as the transition from 1S to 1P orbital. The [Ag8(pfga)6]6- cluster emits bright green-yellow light in THF solution and bright orange light in the solid state. This work opens the door to using the widely available carboxylic acids to synthesize atomically precise Ag clusters of attractive properties.

Comparative Study of the Supercapacitive Performance of Three Ferrocene-Based Structures: Targeted Design of a Conductive Ferrocene-Functionalized Coordination Polymer as a Supercapacitor Electrode.

As redox-active based supercapacitors are known as highly desirable next-generation supercapacitor electrodes, the targeted design of two ferrocene-functionalized (Fc(COOH)2 ) clusters based on coinage metals, [(PPh3 )2 AgO2 CFcCO2 Ag(PPh3 )2 ]2 ⋅7 CH3 OH (SC1 : super capacitor) and [(PPh3 )3 CuO2 CFcCO2 Cu(PPh3 )3 ]⋅3 CH3 OH (SC2 ), is reported. Both structures are fully characterized by various techniques. The structures are utilized as energy storage electrode materials, giving 130 F g-1 and 210 F g-1 specific capacitance at 1.5 A g-1 in Na2 SO4 electrolyte, respectively. The obtained results show that the presence of CuI instead of AgI improves the supercapacitive performance of the cluster. Further, to improve the conductivity, the PSC2 ([(PPh3 )2 CuO2 CFcCO2 ]∞ ), a polymeric structure of SC2 , was synthesized and used as an energy storage electrode. PSC2 displays high conductivity and gives 455 F g-1 capacitance at 3 A g-1 . The PSC2 as a supercapacitor electrode presents a high power density (2416 W kg-1 ), high energy density (161 Wh kg-1 ), and long cycle life over 4000 cycles (93 %). These results could lead to the amplification of high-performance supercapacitors in new areas to develop real applications and stimulate the use of the targeted design of coordination polymers without hybridization or compositions with additive materials.

Size-Selective Urea-Containing Metal-Organic Frameworks as Receptors for Anions.

Anion recognition by neutral hosts that function in aqueous solution is an emerging area of interest in supramolecular chemistry. The design of neutral architectures for anion recognition still remains a challenge. Among neutral anion receptor systems, urea and its derivatives are considered as "privileged groups" in supramolecular anion recognition, since they have two proximate polarized N-H bonds exploitable for anion recognition. Despite promising advancements in urea-based structures, the strong hydrogen bond drives detrimental self-association. Therefore, immobilizing urea fragments onto the rigid structures of a metal-organic framework (MOF) would prevent this self-association and promote hydrogen-bond-accepting substrate recognition. With this aim, we have synthesized two new urea-containing metal-organic frameworks, namely [Zn(bpdc)(L2)]n·nDMF (TMU-67) and [Zn2(bdc)2(L2)2]n·2nDMF (TMU-68) (bpdc = biphenyl-4,4'-dicarboxylate; bdc = terephthalate; L2 = 1,3-bis(pyridin-4-yl)urea), and we have assessed their recognition ability toward different anions in water. The two MOFs show good water stability and anion affinity, with a particular selectivity toward dihydrogen arsenate for TMU-67 and toward fluoride for TMU-68. Crystal structure characterizations reveal 3-fold and 2-fold interpenetrated 3D networks for TMU-67 and TMU-68, respectively, where all single interpenetrated networks are hydrogen bonded to each other in both cases. Despite the absence of self-quenching, the N-H urea bonds are tightly hydrogen bonded to the oxygen atoms of the dicarboxylate ligands and cannot be directly involved in the recognition process. The good performance in anion sensing and selectivity of the two MOFs can be ascribed to the network interpenetration that, shaping the void, creates monodimensional channels, decorated by exposed oxygen atom sites selective for arsenate sensing in TMU-67 and isolated cavities, covered by phenyl groups selective for fluoride recognition in TMU-68.

Hexavalent Octahedral Template: A Neutral High-Nucleus Silver Alkynyl Nanocluster Emitting Infrared Light.

The first silver nanocluster with an octahedral template of TeO66- was synthesized as a neutral 36-nucleus nanocluster, and its structure was demonstrated using single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, electrospray ionization mass spectrometry, and X-ray photoelectron spectroscopy. The peripheral ligands of the cagelike skeleton of the nanocluster are CF3COO- and tBuC≡C-. During the synthesis, the TeO66- template arranged the nanocluster, and a 36-nucleus nanocluster was formed. The effect of the template nature was displayed on the structural features of the nanocluster in comparison with an 8-nucleus cluster, with the same synthesis conditions. The photoluminescence and UV-vis absorption analyses of the nanocluster were also investigated. The nanocluster displayed near-infrared luminescence emission at 690 nm.

Investigation of the Effect of a Mixed-Ligand on the Accommodation of a Templating Molecule into the Structure of High-Nucleus Silver Clusters.

Advancement of the synthesis and control of the self-assembly process of new high-nucleus silver clusters with desired structures is important for both the material sciences and the many applications. Herein, three new silver clusters, 20-, 22-, and 8-nucleus, based on alkynyl ligands were constructed and their structures were confirmed by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analyses, and Fourier-transform infrared spectroscopy (FT-IR). For the first time, the trivalent tetrahedron anion of AsO43-, as a template, and the surface ligand of Ph2PO2H, with new coordination modes, were employed in preparation of the silver clusters. The role of surface ligands and template anions in the size and structure of the clusters was investigated. The presence of the template in the structure of the clusters led to the formation of the high-nucleus clusters. Also, in this report, it was shown that the participation of the template in the assembly of a cluster can be controlled by the surface ligands. UV-vis absorption and luminescent properties of the clusters and the thermal stability of the 8-nucleus cluster were also studied.

Trivalent Tetrahedral Anion Template: A 26-Nucleus Silver Alkynyl Cluster Encapsulating Vanadate.

In order to study the charge effect on the formation of an anion-templated silver cluster, a trivalent tetrahedral anion was incorporated into the silver assembly. A 26-nuclear silver cluster was prepared, and its structure was confirmed by single-crystal X-ray diffraction. Also, the resulting structure was characterized by powder X-ray diffraction data. Its light absorption and photoluminescent properties were studied by solid-state UV diffuse-reflectance and fluorescence spectroscopy. Compared with the other reported silver clusters with tetrahedral anion templates, the more negative VO43- anion led to the formation of a bigger silver cluster. Also, the supramolecular motif O-H(CH3OH)···O(trifluoroacetate) was confirmed on the cluster surface for the first time.

Helical Polyisocyanopeptides as Lyotropic Liquid Crystals for Measuring Residual Dipolar Couplings.

Residual dipolar couplings (RDC) emerged to be an important structural parameter for organic and biomolecules. Herein, a new helical polyisocyanopeptide (l,l-PIAF-OBn) that forms lyotropic liquid crystals (LLC) in CDCl3 is proposed as a novel weakly orienting medium for acquiring residual dipolar couplings (RDCs) of organic molecules. We demonstrate its application for the structural elucidation of strychnine and triptolide.

An Alignment Medium for Measuring Residual Dipolar Couplings in Pure DMSO: Liquid Crystals from Graphene Oxide Grafted with Polymer Brushes.

Residual dipolar couplings (RDCs) have attracted attention in light of their great impact on the structural elucidation of organic molecules. However, the effectiveness of RDC measurements is limited by the shortage of alignment media compatible with widely used organic solvents, such as DMSO. Herein, we present the first liquid crystal (LC) based alignment medium that is compatible with pure DMSO, thus enabling RDC measurements of polar and intermediate polarity molecules. The liquid crystals were obtained by grafting polymer brushes onto graphene oxide (GO) using free radical polymerization. The resulting new medium offers several advantages, such as absence of background signals, narrow line shapes, and tunable alignment. Importantly, this medium is compatible with π-conjugated molecules. Moreover, sonication-induced fragmentation can reduce the size of GO sheets. The resulting anisotropic medium has moderate alignment strength, which is a prerequisite for an accurate RDC measurement.

Palladium-catalyzed cyanation of aryl halides with CuSCN.

A palladium-catalyzed cyanation of aryl halides and borons has been developed by employing cuprous thiocyanate as a safe cyanide source. This protocol avoids the use of a highly toxic cyanide source, providing aromatic nitriles in moderate to good yields with good functional tolerance.

Interfacial engineering of heterostructured Fe-Ni3S2/Ni(OH)2 nanosheets with tailored d-band center for enhanced oxygen evolution catalysis.

Hydrogen production by electrochemical water splitting suffers from high kinetic barriers in the anodic oxygen evolution reaction (OER), which limits the overall efficiency. Herein, we report a structural and electronic engineering strategy by integrating self-standing Fe-doped Ni3S2 (denoted by Fe-Ni3S2) nanosheet arrays with Ni(OH)2 subunits to form heterostructured Fe-Ni3S2/Ni(OH)2 on a Ni Foam substrate. The strong electronic interaction between the Fe-Ni3S2 and Ni(OH)2 constituents contributes abundant catalytic sites and ensures high electron transfer. Moreover, the combined experimental and theoretical study revealed that the coupling of Ni(OH)2 onto the Fe-Ni3S2 is favorable for lowering the activation energy of water oxidation for favorable OER kinetics and upshifting the Ni d-band center to facilitate the adsorption of O-containing intermediates. Consequently, the optimized Fe-Ni3S2/Ni(OH)2 hybrid catalyst exhibits excellent OER performance in alkaline electrolytes with an ultralow overpotential of 202 mV at 10 mA cm-2, a small Tafel slope of 50.6 mV dec-1, and long-term durability under high current density (0.25 A cm-2) for up to 60 h without significant deactivation. Moreover, a two-electrode Fe-Ni3S2/Ni(OH)2||Pt/C electrolyzer requires only a low voltage of 1.54 V at 10 mA cm-2 for overall water splitting. This study emphasizes the importance of interface and surface engineering in achieving highly efficient electrocatalysts.

Reuse of Predesigned Dual-Functional Metal Organic Frameworks (DF-MOFs) after Heavy Metal Removal.

Designing porous and functionalized adsorbents and achieving high efficiency in heavy metals removal from wastewater is in the spotlight of environmental science. On the other hand, upon removal, adsorbents are still highly hazardous requiring that great care be taken in its packaging, transporting and storing. A fundamental route in the synthesis of functional extended structures is the ability to combine different chemical entities in a controlled way in order to achieve high performance. Herein, we report the systematic design of dual-functionalized metal organic framework (TMU-81) by incorporating sulfonyl and amide groups for the removal of Cd(II), Cu(II) and Cr(II) ions from simulated aqueous solutions. TMU-81 showed significant enhancement in heavy metals uptake suggesting that the strong host - guest interactions between cations and the donor sites play a major role in adsorption process. The maximum adsorption capacity for Cd2+ was 526 mg/g which is among the highest values reported for similar MOFs and other porous materials. The good performance in uptake and selectivity of TMU-81 can be attributed to the network structure that shaping the void, create mono-dimensional channels, decorated by exposed oxygen atom sites selective for Cadmium ion. Environmental "compatibility" of a treated MOFs was studied in order to evaluate its possible recycling as a new template for different applications by using pyrolysis method. Engineering of the pore surface provides a potential for MOF with a hybrid interface to act as a versatile tool for the design of multifunctional nanoparticles to meet specific application requirements.

Phenolic nitroaromatics detection by fluorinated metal-organic frameworks: Barrier elimination for selective sensing of specific group of nitroaromatics.

Many piesce of research have been performed to detect nitroaromatic-compounds (NACs) by metal-organic frameworks (MOFs). Despite extensive studies, there are still significant challenges like selective detection of specific NAC group in presence of other NACs. Here, we have integrated two functionalization strategies through decoration of pore-walls of the MOFs with trifluoromethyl groups and extension in π-conjugated system. Based on this idea, trifluoromethyl TMU-44 (with the formula [Zn2(hfipbb)2(L1)]n.DMF, H2hfipbb = 4,4'-(hexafluoroisopropylidene) bis(benzoic acid), L1 = N,N'-bis-pyridin-4-ylmethylene-benzene-1,4-diamine) and TMU-45 (with formula [Zn2(hfipbb)2(L2)]n.DMF, L2 = N,N'-bis-pyridin-4-ylmethylene-naphthalene-1,5-diamine) frameworks have been synthesized. The aromatic skeleton of TMU-44 is based on phenyl rings while TMU-45 aromatic skeleton is extended by replacement of phenyl with naphthyl core. Measurements reveal that these MOFs are highly sensitive to phenolic NACs especially 2,4,6-trinitrophenol (TNP) with high quenching efficiency of 90% for TMU-44 (KSV = 10,652 M-1, LOD = 6.9 ppm) and 99% for TMU-45 (KSV = 34,741 M-1, LOD = 2.07 ppm). The proposed detection mechanism can be associated with hydrogen bonding between OH group of phenolic NACs and trifluoromethyl groups of TMU-MOFs as well as π(rich)∙∙∙π(deficient) interaction between π-conjugated backbone of TMU-frameworks and π-deficient ring of NACs.

Stable supercapacitor electrode based on two-dimensional high nucleus silver nano-clusters as a green energy source.

Atomically precise silver nanoclusters (Ag-NCs) are known as a hot research area owing to their brilliant features and they have attracted an immense amount of research attention over the last year. There is a lack of sufficient understanding about the Ag-NC synthesis mechanisms that result in optimal silver nanoclusters with an appropriate size, shape, and morphology. In addition, the coexisting flexible coordination of silver ions, the argentophilic interactions, and coordination bonds result in a high level of sophistication in the self-assembly process. Furthermore, the expansion of clusters by the organic ligand to form a high dimensional structure could be very interesting and useful for novel applications in particular. In this study, a novel two-dimensional 14-nucleus silver poly-cluster was designed and synthesized by the combination of two synthetic methods. The high nucleus silver cluster units are connected together via tetradecafluoroazelaic acid (CF2) and this leads to the high stability of the polymer. This highly stable conductive poly-cluster, with bridging groups of difluoromethylene, displays a high energy density (372 F g-1 at 4.5 A g-1), excellent cycling stability, and great capacity. This nanocluster shows a high power density and long cycle life over 6000 cycles (95%) and can also tolerate a wide range of scan rates (5 mV s-1 to 1 V s-1), meaning it could act as a green energy source.

Base-mediated cascade amidination/N-alkylation of amines by alcohols.

A base-mediated cascade amidination/N-alkylation reaction of amines by alcohols has been developed. For the first time, nitriles have been identified as an efficient and benign water acceptor reagent in N-alkylation. Notably, the procedure tolerates a series of functional groups, such as methoxyl, halo, vinyl and hetero groups, providing a convenient method to construct different substituted diamino compounds, 15N labeled amine and could be scaled up to 1 mol scale offering 138.7 g of the desired product in good yield in one-pot. Mechanistic studies provided strong evidence for the amidination of amines with nitriles facilitated by t-BuOK.

A practical base mediated synthesis of 1,2,4-triazoles enabled by a deamination annulation strategy.

A rapid and efficient base mediated synthesis of 1,3,5-trisubstituted 1,2,4-triazoles has been developed using the annulation of nitriles with hydrazines, which can be expanded to a wide range of triazoles in good to excellent yields. Ammonia gas is liberated during the reaction, and halo and hetero functional groups as well as free hydroxyl and amino groups are tolerated in this transformation. A variety of alkyl and aryl-substituted nitriles can be functionalized with aromatic and aliphatic hydrazines employing this procedure. This finding provides a practical and useful strategy for the synthesis of various 15N-labeled 1,2,4-triazole derivatives, and two types of mGlu5 receptor pharmaceuticals can be easily assembled in a one-pot manner.