Hai-Hua Wang

Trinuclear-based Copper(I) Pyrazolate Polymers: Effect of Trimer π-Acid···Halide/Pseudohalide Interactions on the Supramolecular Structure and Phosphorescence

Under different situations, solvothermal reactions of 3,5-diethyl-4-(4-pyridyl)-pyrazole (HL) with CuX or CuX(2) (X = Cl, Br, I, and SCN) afforded five copper(I) coordination polymers, {CuX[CuL](3)·solvent}(n) (X = Cl, 1; Br, 2; I, 3; X = SCN and solvent = MeCN, 4) and {Cu(2)I(2)[CuL](3)}(n) (5). X-ray diffraction analyses show that all the complexes have trinuclear [CuL](3) (referred as Cu(3)) secondary building units featuring planar nine-membered Cu(3)N(6) metallocycles with three peripheral pyridyl groups as connectors, which are further linked by CuX or Cu(2)X(2) motifs to generate single- or double-strand chains. Interestingly, the Cu(I) atoms within the Cu(3) units in 1-5 behave as coordinatively unsaturated π-acid centers to contact soft halide/pseudohalide X atoms of CuX and Cu(2)X(2) motifs, which lead to novel sandwich substructures of [(Cu(3))(Cu(2)X(2))(Cu(3))] (X = Br, I, and SCN) in 2-4. In addition, both the π-acid [Cu(3)]···X contacts and intertrimer Cu···Cu interactions contribute to the one-dimensional (1D) double-strand and 2D/3D supramolecular structures of 1-5. All of these complexes exhibit high thermostability and bright solid-state phosphorescence upon exposure to UV radiation at room temperature. The emissions arise from the mixtures of metal-centered charge transfer, metal to ligand charge transfer, and halide-to-ligand charge transfer excited states, and can be tuned by intermolecular π-acid [Cu(3)]···halide/pseudohalide contacts.

A Cationic MOF with High Uptake and Selectivity for CO2 due to Multiple CO2 -Philic Sites.

The reaction of N-rich pyrazinyl triazolyl carboxyl ligand 3-(4-carboxylbenzene)-5-(2-pyrazinyl)-1H-1,2,4-triazole (H2 cbptz) with MnCl2 afforded 3D cationic metal-organic framework (MOF) [Mn2 (Hcbptz)2 (Cl)(H2 O)]Cl⋅DMF⋅0.5 CH3 CN (1), which has an unusual (3,4)-connected 3,4T1 topology and 1D channels composed of cavities. MOF 1 has a very polar framework that contains exposed metal sites, uncoordinated N atoms, narrow channels, and Cl(-) basic sites, which lead to not only high CO2 uptake, but also remarkably selective adsorption of CO2 over N2 and CH4 at 298-333 K. The multiple CO2 -philic sites were identified by grand canonical Monte Carlo simulations. Moreover, 1 shows excellent stability in natural air environment. These advantages make 1 a very promising candidate in post-combustion CO2 capture, natural-gas upgrading, and landfill gas-purification processes.

Porous MOF with Highly Efficient Selectivity and Chemical Conversion for CO2

A new Co(II)-based MOF, {[Co2(tzpa)(OH)(H2O)2]·DMF}n (1) (H3tzpa = 5-(4-(tetrazol-5-yl)phenyl)isophthalic acid), was constructed by employing a tetrazolyl-carboxyl ligand H3tzpa. 1 possesses 1D tubular channels that are decorated by μ3-OH groups, uncoordinated carboxylate O atoms, and open metal centers generated by the removal of coordinated water molecules, leading to high CO2 adsorption capacity and significantly selective capture for CO2 over CH4 and CO in the temperature range of 298-333 K. Moreover, 1 shows the chemical stability in acidic and basic aqueous solutions. Grand canonical Monte Carlo simulations identified multiple CO2-philic sites in 1. In addition, the activated 1 as the heterogeneous Lewis and Brønsted acid bifunctional catalyst facilitates the chemical fixation of CO2 coupling with epoxides into cyclic carbonates under ambient conditions.

An Uncommon Carboxyl‐Decorated MOF with Selective Gas Adsorption and Catalytic Conversion of CO2

A new three-dimensional (3D) framework, [Ni(btzip)(H2 btzip)]⋅2 DMF⋅2 H2 O (1) (H2 btzip=4,6-bis(triazol-1-yl)isophthalic acid) as an acidic heterogeneous catalyst was constructed by the reaction of nickel wire and a triazolyl-carboxyl linker. Framework 1 possesses intersected 2D channels decorated by free COOH groups and uncoordinated triazolyl N atoms, leading to not only high CO2 and C2 H6 adsorption capacity but also significant selective capture for CO2 and C2 H6 over CH4 and CO in 273-333 K. Moreover, 1 reveals chemical stability toward water. Grand Canonical Monte Carlo simulations confirmed the multiple CO2 - and C2 H6 -philic sites. As a result of the presence of accessible Brønsted acidic COOH groups in the channels, the activated framework demonstrates highly efficient catalytic activity in the cycloaddition reaction of CO2 with propylene oxide/4-chloromethyl-1,3-dioxolan-2-one/3-butoxy-1,2-epoxypropane into cyclic carbonates.

A Pb2+-based coordination polymer with 5-(1H-tetrazol-5-yl)isophthalic acid ligand: structure and photoluminescence

Abstract A coordination polymer, [Pb2(OH)(tzia)]·2H2O (1), has been prepared by solvothermal reaction of 5-(1H-tetrazol-5-yl)isophthalic acid (H3tzia) and Pb(NO3)2. The polymer 1 is based on an unprecedented centrosymmetric tetranuclear [Pb4(OH)2(COO)4(ttaz)2] cluster linked by a multidentate tzia ligand, affording a 2-D 3,6-connected kgd layer. The adjacent layers are further jointed by Pb⋯O interactions to form a 3-D supramolecular framework with a rare (3,8)-connected tfz-d; UO3 topology. Photoluminescent properties of H3tzia, 1, and 1-desolvated have been further investigated, and it was interesting to find that 1-desolvated due to the removal of lattice water molecules reveals stronger photoluminescence than 1.

Five transition metal coordination polymers driven by a semirigid trifunctional nicotinic acid ligand: selective adsorption and magnetic properties

Five coordination polymers, {[Co3(L)2(H2O)2]·4H2O} (1), {[Cd3(L)2(NMP)2]} (2), {[Cu(HL)]·NMP} (3), {[Cd(HL)(2,2′-bipy)]} (4) and {[Co(HL)(4,4′-bipy)(H2O)2]} (5) with different dimensional structures, have been solvothermally synthesized from a trifunctional N,O-building block, 5-(3,4-dicarboxylphenoxy)nicotinic acid (H3L) that combines three distinct types of functional groups (COOH, N-pyridyl, and O-ether), and an auxiliary co-ligand, 2,2′-bipy or 4,4′-bipy (2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine). H3L contains three different types of functionalities and has eight potential coordination sites, which results in diverse coordination patterns and different dimensionalities depending on the reaction conditions. Complexes 1–3 display 2D layer structures with 1D channels, 4 shows a 2D + 2D → 2D interpenetrated wavy structure, while 5 exhibits a 1D chain structure. 1 demonstrates an effective storage capacity for CO2 as well as high selectivity for CO2 over CH4 under ambient conditions. The magnetic properties revealed antiferromagnetic behaviors for complexes 1, 3 and 5. Also, the alternating-current susceptibility of 5 displays slow magnetic relaxation, showing interesting magnetic behavior with an effective energy barrier of 8.98 K.