No abstract

The insufficient catalytic stability of Cu-based catalysts is still its bottleneck in industrial application, and it is widely studied how to synthesize highly stable Cu-based catalysts. Herein, we have developed a MOF-derived preparation of robust Cu/SiO 2 catalyst for the efficient hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). The sol−gel method was used to in situ load the HKUST-1 into SiO 2 support with only a copper loading of 7.83%. The advantages of MOF-derived Cu/SiO 2 catalyst are that copper species could escape from severe coating by silica matrix and expose more active sites with small particles sizes (4.2 nm). Furthermore, it is inclined to generate more stable Cu 2 O reduced from Cu−O−Si units by using MOF as precursor. As a result, more than 95.0% selectivity of EG with a long lifetime of 220 h was achieved over the Cu/SiO 2 -MOF catalyst. On the contrary, when using the copper nitrate as the copper precursor, the prepared Cu/SiO 2 -CN catalyst with similar copper loading exhibited much lower catalytic activity because that copper species were encapsulated into SiO 2 network and difficult to be available for reactants. Therefore, using MOF as copper precursor solves the problem of high-dispersed copper species but inactive by coating with SiO 2 matrix.

Two 3D Zn(II) and Pb(II) isophthalates, [Zn(ip)]n (1) and [Pb4(mu4-O)(ip)3(H2O)]n (2) (H2ip = isophthalic acid), have been prepared under hydro(solvo)thermal conditions and characterized by single-crystal X-ray diffraction. The two complexes crystallize in different space groups (P4(3)2(1)2 for 1 and P2(1)/c for 2) and have different bridging modes of the ip ligand. The 3D framework of 1 is constructed by the interconnection of ZnO4 polyhedra via ip ligands, which represents a chiral net with PtS-type topology. In contrast, complex 2 is formed by the combination of Pb4O-cluster secondary building units and has a novel (3.4.5)(3(2).4(5).5(6).6(7).7(2)) topology, which is the first ever example of a (3,7)-connected net. Complex 1 displays a second harmonic generation efficiency of about 1.5 times that of KH2PO4. Optical properties and thermal stabilities of the two complexes have been studied. Additionally, the calculations of band structure and density of states of 1 have also been performed with the density functional theory method.

Nine members of a new anions-controlled Cd(II)-guanazole (3,5-diamino-1,2,4-triazole=Hdatrz) hybrid family, that is, [Cd3(datrz)6(H2O)2] (1), [Cd3(datrz)4F2] (2), [Cd5(datrz)4Cl4(OH)2] (3), [Cd5(datrz)4Br4(OH)2] (4), [Cd3(datrz)2(SO3)2].(H2O) (5), [Cd3(datrz)2(O2CMe)4] (6), [Cd(datrz)(O2CEt)] (7), [Cd(Hdatrz)(O2CtBu)2] (8), and [Cd(Hdatrz)2(H2Edta)] (9) have been synthesized by exploiting hydrothermal reactions of guanazole with suitable cadmium salts under appropriate reaction conditions. With effective control of inorganic or organic anions, the coordination diversity of the guanazole ligand in 1-9 manifests an unprecedented enrichment with five bridging modes varying from bidentate to quadridentate, two of which are first reported. Compound 1 is the first reported three-dimensional chiral complex constructed from the guanazole ligand which adopts a novel N1, N2, amino N-bridging mode. Halogen anions F-, Cl-, and Br- controlled compounds 2-4 are all three-dimensional, with their guanazole ligands possessing another novel quadridentate bridging mode. Sulfite anions controlled compound 5 displays a three-dimensional network with peculiar cage-like hexnuclear cadmium clusters. As for organic anions, low dimensional structures have been found for alkylcarboxylate anions MeCO2-, EtCO2-, and tBuCO2- controlled compounds 6, 7, and 8 (two-dimensional) and for H2Edta2- controlled compound 9 (zero-dimensional), and their guanazole ligands manifest low coordination numbers as well. These hybrid materials also present interesting structure-induced physical properties. The chiral compound 1 exhibits the second-order nonlinear optical properties at room temperature. Compounds 2-9 except 6 all exhibit photoluminescence of blue fluorescent emissions in the solid state at ambient temperature, which may be assigned to the intraligand pi-pi* transitions. Some structure related red or blue emission shifts have been investigated. Thermal studies show that most compounds of this study possess a high thermal stability.

The hydro(solvo)thermal reactions of Pb(OAc)(2).3H(2)O with the aromatic carboxylic ligands 1,3,5-benzenetricarboxylic and 1,4-, 1,2-, and 1,3-benzenedicarboxylic acids (1,3,5-H(3)BTC; 1,4-, 1,2-, and 1,3-H(2)BDC) have yielded a family of inorganic-organic framework materials: [Pb(2)(1,3,5-BTC)(mu(3)-OH)(H(2)O)](n) (Iota), [NaPb(1,3,5-BTC)(H(2)O)](n) (IotaIota), [Pb(1,4-BDC)](n) (IotaIotaIota), [Pb(5)(1,2-BDC)(4)(OAc)(2)](n) (IV), and {[Pb(5)(1,3-BDC)(5)(H(2)O)(2)](2).H(2)O}(n) (V). These complexes have been characterized by means of single-crystal X-ray diffraction, X-ray powder diffraction, thermogravimetric analysis-mass spectrometry, and photoluminescence spectra. They are all three-dimensional structures except for two-dimensional IV. Topology analysis reveals that complexes I an V represent rare (4,8)-connected flu and (3,4)-connected zeolite-like nets, respectively. The five complexes exhibit diverse inorganic connectivity, including a 0D Pb(4)O(16) cluster for I, a 1D Pb-O-Pb chain for II, a 2D Pb-O-Pb network for III and IV, and an unprecedented 3D Pb-O-Pb framework for V. And the diversity in inorganic arrays leads to differences in luminescent properties of these complexes.

A systematic investigation on the Ag/bpy/(H)dpa family represents seven Ag(I) supramolecular compounds with distinct structural features, Ag2(bpy)0.5(dpa) (1), Ag2(bpy)1.5(dpa)(H2O) (2), Ag(bpy)0.5(Hdpa) (3), α-[Ag(bpy)]·(Hdpa) (4), β-[Ag(bpy)]·(Hdpa) (5), [Ag(bpy)]2·(dpa)·6(H2O) (6), and [Ag(bpy)]4·(dpa)·2(NO3)·6(H2O) (7) (H2dpa = 1,1′-biphenyl-2,2′-dicarboxylic acid, bpy = 4,4′-bipyridine). Of particular interest about this work is that supramolecular isomerism is observed between compounds 4 and 5. Single-crystal X-ray structural analysis reveals the structural diversity of the formed products. Compounds 1−5 are extended from various one-dimensional (1D) chain substructures. Three distinct 1D chains exist in 1−3: one 1D chain of {Ag2(dpa)} exists in compound 1, one supramolecular chain of tetranuclear {Ag2(dpa)(H2O)}2 subunits linked by Ag···Ag interactions (argentophilic interactions) and hydrogen bonding interactions is observed in 2, and one 1D alternate chain of eight-membered {Ag2(Hdpa)2} ring bridged by bpy is present in 3. However, two different 1D supramolecular double chains of [Ag(bpy)(Hdpa)] are found in 4 and 5, which are sustained by the combination of weak Ag···O interactions, π−π stacking interactions, and argentophilic interactions in 4 while only by π−π stacking interactions in 5. These 1D chain substructures are further threaded into a 2D covalent layer bridged by bpy (1) or 2D (3 and 4)/3D (2 and 5) supramolecular architectures with the help of supramolecular driving forces in different ways. In contrast to compounds 1−5, compounds 6 and 7 are based upon 2D supramolecular substructures of [Ag(bpy)]2·(dpa) and {[Ag(bpy)]4·(dpa)·(H2O)} n 2n+, respectively. The most striking feature of 6 is that a quasi-1D water aggregate is confined in the 1D channel of the 3D porous interdigitated host framework. Greatly different from compound 6, compound 7 is a nitrate-templated 3D supramolecular framework constructed from a positively charged layer substructure through versatile hydrogen bonds. The diversity of the product structures illustrates that controlled synthesis by adjusting the molar ratio of precursors or the pH value of the solution is a facile and effective approach to further design and construct novel supramolecular assemblies with distinct structural features. Moreover, the thermal dynamic properties and fluorescent properties of all compounds except 1 are also investigated.

A new hybrid system of cadmium(II) polymers has been synthesized by using 1H-1,2,4-triazole-3-thiol (HtrzSH) and cadmium salts, affording six novel luminescent complexes, that is, [Cd(H2trzS)2Cl2] (1), [Cd(HtrzS)Br] (2), [Cd(HtrzS)I] (3), [Cd2(HtrzS)2(SO4)] (4), [Cd(H2trzS)(H2Edta)]·(H2O) (5), and [Cd(trzS)2] (6). In these materials, owing to the effective inducement of inorganic or organic anions, coordination versatility of the HtrzSH ligand manifests as many as six bridging modes (type A−F), and five of them (type B−F) are first reported. The structure of complex 1 is a one-dimensional chain constructed from the neutral monodentate and bidentate H2trzS ligand (type A−B), whereas two-dimensional complexes 2−3 and the three-dimensional complex 4 possess the deprotonated tridentate to quadridentate HtrzS ligands (type C−E). Zero-dimensional complex 5 and peristyle-like three-dimensional complex 6 are synthesized by means of organic anions, and in the latter complex a bideprotonated quadridentate trzS ligand is presented (type F). All complexes exhibit strong photoluminescence with fluorescent emissions varying from blue to orange in the solid state. Some structure related red or blue emission shifts compared to the free ligand are studied, as well as several advantageous structural factors to obtain longer fluorescence lifetime. X-ray powder diffraction and thermal studies are used to investigate the bulk properties of these compounds.

Aggregation-induced emission (AIE) has been identified and studied based on a bulky π-conjugated ligand (H2IDPA) with Zn/CdII metals.