Zhenxia Chen

A Luminescent Mixed-Lanthanide Metal–Organic Framework Thermometer

A luminescent mixed lanthanide metal-organic framework approach has been realized to explore luminescent thermometers. The targeted self-referencing luminescent thermometer Eu(0.0069)Tb(0.9931)-DMBDC (DMBDC = 2, 5-dimethoxy-1, 4-benzenedicarboxylate) based on two emissions of Tb(3+) at 545 nm and Eu(3+) at 613 nm is not only more robust, reliable, and instantaneous but also has higher sensitivity than the parent MOF Tb-DMBDC based on one emission at a wide range from 10 to 300 K.

Single-molecular artificial transmembrane water channels.

Hydrazide-appended pillar[5]arene derivatives have been synthesized. X-ray crystal structure analysis and (1)H NMR studies revealed that the molecules adopt unique tubular conformations. Inserting the molecules into the lipid membranes of vesicles leads to the transport of water through the channels produced by single molecules, as supported by dynamic light scattering and cryo-SEM experiments. The channels exhibit the transport activity at a very low channel to lipid ratio (0.027 mol %), and a water permeability of 8.6 × 10(-10) cm s(-1) is realized. In addition, like natural water channel proteins, the artificial systems also block the transport of protons.

Selective Artificial Transmembrane Channels for Protons by Formation of Water Wires

Lined up water molecules: Artificial transmembrane channels from pillar[5]arene monomeric and dimeric derivatives have been prepared. Single-channel conductance measurements and isotope effect experiments under acidic conditions showed selective proton transport through the channels, which were mediated by water wires formed in the pillar[5]arene backbones (see picture).

Synthesis of pillar[5]arene dimers and their cooperative binding toward some neutral guests.

Three pillar[5]arene dimers, bridged by a flexible aliphatic chain (H1) or a relatively rigid phenylene unit (H2 and H3), were synthesized, with the possible synthetic strategies being discussed. The dimers could significantly enhance the binding affinities toward neutral model substrates in comparison with monomeric 1,4-dimethoxypillar[5]arene (H4) through the cooperative binding of two pillar[5]arene moieties. The molecular binding ability and selectivity are discussed from the viewpoints of the size/shape-fit concept and multiple recognition mechanism.

Cadmium Imidazolate Frameworks with Polymorphism, High Thermal Stability, and a Large Surface Area

Since the initial inspiration for realizing metal–organic frameworks (MOFs) with zeolitic structures, considerable effort has been made towards novel approaches to construct zeolitic metal–organic frameworks (ZMOFs) by using tetrahedral metal imidazolates. To date, numerous ZMOFs have been synthesized with the motifs of which only those with desired porosity and thermal stability are potentially applicable for gas storage, separation, catalysts, encapsulation of target molecules, etc. For rational synthesis of porous and thermostable ZMOFs with the imidazole ligands, the introduction of smaller substituent groups onto imidazole ring has been found to be a vital strategy, because the groups play not only the role of structure-directing agent (template), but also the sites for functionalizing. Moreover, as an inseparable supporting template, the substituent group can stabilize the imidazolate ZMOFs, however, it also presents an encumbrance that inevitably blocks pores—leading to a reduction of the pore size and surface area. Furthermore, any 2-substituent at the imidazole ring may restrict the flexibility of the M N bond rotation and render the imidazolates either barely to be generated or lacking in framework diversity. For example, the MOFs of metal 2-substituent imidazolates [{M ACHTUNGTRENNUNG(R-im)2}]1 (M= Zn and Co, Rim= 2-substituent imidazolates) have been only prepared for those with R-group to be methyl, ethyl, nitro and carboxaldehyde and each of them has been observed with no more than one MOF structure that exhibits the M N bond 2.05 (and M···M distance 6.0 ). On the supposition that the M N bond (and M···M distance) could be expanded (Scheme 1), the lack of framework diversity from a 2-sub-

Selective and effective binding of pillar[5,6]arenes toward secondary ammonium salts with a weakly coordinating counteranion.

The selective and effective binding of secondary ammoniums with a weakly coordinating tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF) counteranion by per-ethylated pillar[5,6]arenes is reported. The construction of a first pillararene-based self-sorting system consisting of two wheels and two axles is also described.

Heterolytic Cleavage of Dihydrogen by “Frustrated Lewis Pairs” Comprising Bis(2,4,6‐tris(trifluoromethyl)phenyl)borane and Amines: Stepwise versus Concerted Mechanism

Recently, the chemistry of “frustrated Lewis pairs” (FLPs), which was introduced by the research groups of Stephan and Erker, has received considerable attention. 2] One of the most remarkable applications of FLPs is in the heterolytic activation of H2 without the involvement of transition-metals. A variety of FLP systems have been shown to activate H2 under mild conditions, and have been applied as catalysts in metal-free hydrogenation reactions. By analogy to the transition metal chemistry, it was originally proposed by Stephan and co-workers that the activation of H2 is a stepwise process, in which H2 is initially activated by the Lewis acid, followed by proton transfer to the Lewis base (Scheme 1).

Silica‐Templated Synthesis of Ordered Mesoporous Tungsten Carbide/Graphitic Carbon Composites with Nanocrystalline Walls and High Surface Areas via a Temperature‐Programmed Carburization Route

Ordered mesostructured tungsten carbide and graphitic carbon composites (WC/C) with nanocrystalline walls are fabricated for the first time by a temperature-programmed carburization approach with phosphotungstic acid (PTA) as a precursor and mesoporous silica materials as hard templates. The mesostructure, crystal phase, and amount of deposited graphitic carbon can be conveniently tuned by controlling the silica template (SBA-15 or KIT-6), carburizing temperature (700-1000 degrees C), the PTA-loading amount, and the carburizing atmosphere (CH(4) or a CH(4)/H(2) mixture). A high level of deposited carbon is favorable for connecting and stabilizing the WC nanocrystallites to achieve high mesostructural regularity, as well as promoting the carburization reaction. Meanwhile, large pore sizes and high mesoporosity of the silica templates can promote WC-phase formation. These novel, ordered, mesoporous WC/C nanocomposites with high surface areas (74-169 m(2) g(-1)), large pore volumes (0.14-0.17 cm(3) g(-1)), narrow pore-size distributions (centered at about 3 nm), and very good oxidation resistance (up to 750 degrees C) have potential applications in fuel-cell catalysts and nanodevices.

Crystal transformation synthesis of a highly stable phosphonate MOF for selective adsorption of CO2

A 2D phosphonate MOF {[Ni(Hptz)2]·7H2O}n (H2ptz = 4-(1,2,4-triazol-4-yl)phenylphosphonic acid) (2) is obtained through crystal transformation from a trinuclear compound [Ni3(Hptz)6·(H2O)6]·9H2O (1). Studies of chemical stability show that 2 retains its crystallinity in boiling water and organic solvents. 2 also exhibits high adsorption capacity for CO2 (80 cm3(STP) g−1) and selective separation of CO2 over N2.

Controllable one-step synthesis of spirocycles, polycycles, and di- and tetrahydronaphthalenes from aryl-substituted propargylic alcohols.

A novel, convenient, and efficient method has been developed for selective synthesis of spirocycle, polycycle, and di- and tetrahydronaphthalene systems from aryl-substituted propargylic alcohols by FeCl3- or TsOH-catalyzed multiple activations of unsaturated C-C bonds and C-H bonds.