Kongzhao Su

A porous metal-organic framework with ultrahigh acetylene uptake capacity under ambient conditions

Acetylene, an important petrochemical raw material, is very difficult to store safely under compression because of its highly explosive nature. Here we present a porous metal-organic framework named FJI-H8, with both suitable pore space and rich open metal sites, for efficient storage of acetylene under ambient conditions. Compared with existing reports, FJI-H8 shows a record-high gravimetric acetylene uptake of 224 cm3 (STP) g−1 and the second-highest volumetric uptake of 196 cm3 (STP) cm−3 at 295 K and 1 atm. Increasing the storage temperature to 308 K has only a small effect on its acetylene storage capacity (∼200 cm3 (STP) g−1). Furthermore, FJI-H8 exhibits an excellent repeatability with only 3.8% loss of its acetylene storage capacity after five cycles of adsorption–desorption tests. Grand canonical Monte Carlo simulation reveals that not only open metal sites but also the suitable pore space and geometry play key roles in its remarkable acetylene uptake.

Photophysical studies of europium coordination polymers based on a tetracarboxylate ligand.

Reaction of europium sulfate octahydrate with p-terphenyl-3,3″,5,5″-tetracarboxylic acid (H4ptptc) in a mixed solvent system has afforded three new coordination polymers formulated as {[Eu(ptptc)0.75(H2O)2]·0.5DMF·1.5H2O}n (1), {[Me2H2N]2 [Eu2(ptptc)2(H2O)(DMF)]·1.5DMF·7H2O}n (2), and {[Eu(Hptptc)(H2O)4]·0.5DMF·H2O}n (3). Complex 1 exhibits a three-dimensional (3D) metal-organic framework based on {Eu2(μ2-COO)2(COO)4}n chains, complex 2 shows a 3D metal-organic framework constructed by [Eu2(μ2-COO)2(COO)6](2-) dimetallic subunits, and complex 3 features a 2D layer architecture assembling to 3D framework through π···π interactions. All complexes exhibit the characteristic red luminescence of Eu(III) ion. The triplet state of ligand H4ptptc matches well with the emission level of Eu(III) ion, which allows the preparation of new optical materials with enhanced luminescence properties. The luminescence properties of these complexes are further studied in terms of their emission quantum yields, emission lifetimes, and the radiative/nonradiative rates.

Thiacalix[4]arene-Supported Kite-Like Heterometallic Tetranuclear ZnIILnIII3 (Ln = Gd, Tb, Dy, Ho) Complexes

Four kite-like tetranuclear Zn(II)Ln(III)3 (Ln= Gd 1, Tb 2, Dy 3, Ho 4) clusters supported by p-tert-butylthiacalix[4]arene (H4BTC4A) have been prepared under solvothermal conditions and structurally characterized by single crystal X-ray diffraction and powder X-ray diffraction (PXRD). In the structures of these four complexes, each of them is capped by two tail-to-tail p-tert-butylthiacalix[4]arene molecules to form a bent sandwich-like unit. The photoluminescent analyses reveal that the H4BTC4A is an efficient sensitizer for Tb(3+) ions in 2. The magnetic properties of complexes 1-4 are also investigated, in which complex 3 exhibits slow magnetization relaxation typical for single molecule magnets.

Structural variability, unusual thermochromic luminescence and nitrobenzene sensing properties of five Zn(II) coordination polymers assembled from a terphenyl-hexacarboxylate ligand

Reactions of the terphenyl-hexacarboxylate ligand [1,1′;4′,1′′]terphenyl-3,5,2′,5′,3′′,5′′-hexacarboxylic acid (H6L) with Zn(NO)3 in the mixed solvents under low-temperature solvothermal conditions afforded five new coordination networks, namely, {[Me2NH2]2[Zn5(L)2(H2O)4]·16H2O}n (1), {[Me2NH2][Zn(H3L)(H2O)]·C2H5OH·5H2O}n (2), {[Me2NH2]2[Zn2(L)(H2O)2]·2DMF·2H2O}n (3), {[Zn4(L)(COO)2(DMF)2(H2O)2]·2C2H5OH·2DMF·2H2O}n (4), and {[Zn4(L)(DMF)4(C2H5OH)(H2O)](OH)2·DMF·2H2O}n (5) (DMF = N,N-dimethylformamide). Compounds 1 and 3–5 possess 3D frameworks, while compound 2 exhibits a 2D grid layer network. Photoluminescence properties of these five compounds have been investigated in solid state at room temperature and low temperature. These five compounds exhibit two kinds of emission modes at room temperature, and compounds 3–5 turn out to have interesting responses to temperature. The sensing properties of compound 1 also have been explored, which show high selectivity and sensitivity to trace amounts of nitrobenzene.

Sorption behaviour in a unique 3,12-connected zinc–organic framework with 2.4 nm cages

A polyhedral metal–organic framework (FJI-2) has been synthesized based on rare hexanuclear zinc clusters, which comprises 2.4 nm double-walled octahedral cages topologically featuring a new 3,12-connected structure. FJI-2 has a good H2 uptake capacity of 149.7 cm3 g−1 (1.34 wt %) at 77 K and 1.0 bar, and the IAST calculation predicts highly selective adsorption of CO2 over N2 and CH4.

Stepwise construction of extra-large heterometallic calixarene-based cages.

Utilizing presynthesized large Na2Ni12Ln2 clusters (Ln = Dy and Tb) supported by calixarene as molecular building blocks (MBBs), we have obtained a series of cationic trigonal prismatic heterometallic organic nanocages (HMONCs) with tunable sizes through a stepwise method. Specially, in each structure of the HMONCs, three linear dicarboxylate linkers substitute the peripheral coordinated acetate ligands of two Na2Ni12Ln2 clusters to form an unprecedented Na4Ni24Ln4 HMONC through a M2L3 condensation. Moreover, magnetic study reveals that the Na2Ni12Dy2 core retains its slow magnetic relaxation behavior. Gas sorption behaviors of these HMONCs were also studied. To the best of our knowledge, these HMONCs built from large heterotrimetallic Na2Ni12Ln2 MBBs, which are based on smaller Ni4-calix ones, have not been reported in any other cages to date. In addition, this research also provides a new strategy for the design and construction of HMONCs with predictable structures and functional properties.

Open Pentameric Calixarene Nanocage

A novel open helmetlike coordination cage has been synthesized based on Co4-calixarene shuttlecock-like secondary building units and in situ generated phosphate anions, where the opening of the cage comprises a large 16-membered ring. The above unprecedented Co20 nanocage presents the first pentameric calixarene coordination compound. Sorption behavior and magnetic properties are also investigated.

Increase in pore size and gas uptake capacity in indium-organic framework materials

We herein report the synthesis and characterization of a new charged metal-organic framework, [Et2NH2][In(BPTC)] (InOF-2) (InOF = indium-organic framework; BPTC = biphenyl-3,3′,5,5′-tetracarboxylate), featuring an unc-type topology. Interestingly, InOF-2 undergoes a distinct porosity transition on going from a typical reversible type-I N2 isotherm to a type-IV N2 isotherm with a hysteresis loop when employing thermal treatment. A Li+-exchanged material [Li0.9(H3O)0.1][In(BPTC)] (InOF-2-Li+) is obtained using an ion-exchange method with BET surface areas estimated to be 1494 m2 g−1, and 867 m2 g−1 for InOF-2, indicating that the N2 adsorption capacity of InOF-2-Li+ significantly increases by ca. 72.3%. Meanwhile, H2 adsorption measurements show a corresponding improvement in H2 storage capacity (ca. 70.6%) on going from InOF-2 (1.14 wt%) to desolvated InOF-2-Li+ (1.95 wt%) at 1.0 bar and 77 K, which is comparable to the calculated increase in BET surface area. A similar improvement is also confirmed in other single gas adsorption measurements, including CH4 and CO2. Overall, the performance characteristics of InOF-2 and InOF-2-Li+ indicate these two materials to be unprecedented examples for the charged metal-organic frameworks to improve their gas storage capacity with both the thermal treatment and cation-exchange method, showing promise for more applications in producing more porous metal-organic frameworks.

Five novel Zn(II)/Cd(II) coordination polymers based on bis(pyrazinyl)-triazole and varied polycarboxylates: syntheses, topologies and photoluminescence

Five novel Zn(II)/Cd(II) coordination polymers (CPs) based on the V-shaped ligand 1H-3,5-bis(pyrazinyl)-1,2,4-triazole (Hbpt) and different polycarboxylates, {[Cd(bpt)(H2O)]·ClO4·H2O} (1), {[Cd4(bpt)2(suc)2.5(OH)]·3H2O} (2), {[Cd4(bpt)3(1,3-bdc)2.5]·4H2O} (3), {[Cd9(bpt)6(1,4-bdc)6(H2O)2]·4H2O} (4) and {[Zn2(bpt)(H3bhc)(H2O)6]·H2O} (5) (H2suc = succinic acid, 1,3-H2bdc = isophthalic acid, 1,4-H2bdc = terephthalic acid, H6bhc = benzene-1,2,3,4,5,6-hexacarboxylic acid), have been successfully synthesized. Their structures have been characterized using single-crystal X-ray crystallography, powder X-ray diffraction (PXRD) analyses, elemental analyses, IR spectroscopy, and thermogravimetric analyses (TGA). Complex 1 bears a two-dimensional (2D) layered (3,3) network, which is further extended into the resulting three-dimensional (3D) supramolecular architecture via π⋯π stacking interactions between the terminal pyrazine groups of bpt− ligands. In 2, Cd(II) ions and bpt− ligands construct a 2D Cd-bpt layer and two 1D zigzag chains, which are further connected by suc2− ligands to form a 2D + 1D → 3D (4,5)-connected framework. Complex 3 contains two kinds of grids, and their alternating arrangement gives a final complicated 3,4,5-connected network with a stoichiometry of (3-c)6(4-c)9(5-c)2. In 4, the bpt− ligands act as tetradentate ones to connect neighbouring Cd(II) ions into an infinite 1D Cd-bpt chain. The completely deprotonated 1,4-bdc2− ligands further link the adjacent Cd-bpt chains to generate a novel 3,4,6-connected 3D topological network with (3-c)2(4-c)14(6-c). Complex 5 displays an infinite 1D coordination chain. There are strong π⋯π stacking interactions between adjacent chains in 5 with a centroid–centroid distance of 3.860 A and 3.862 A, resulting in a 3D supramolecular structure. The results show that Hbpt can act as a versatile building block for the construction of various coordination polymers. Moreover, the fluorescence properties of 1–5 in the solid state have also been investigated.

Diverse architectures and luminescence properties of two novel copper(I) coordination polymers assembled from 2,6-bis[3-(pyrid-4-yl)-1,2,4-triazolyl]pyridine ligands

Two attractive Cu(I) coordination polymers with unique structures, namely, {[Cu8(bptp)4]·6H2O} (1) and {[Cu5(bptp)2(CN)]·2H2O} (2), have been successfully synthesized based on a V-shaped multidentate N-containing ligand 2,6-bis[3-(pyrid-4-yl)-1,2,4-triazolyl]pyridine (H2bptp). The structural analysis reveals that complex 1 displays a Cu8 cluster-based infinite 1D ladder chain, in which each H2bptp ligand links four or five Cu(I) ions through nitrogen atoms of pyridine/triazole groups. Complex 2 features an unusual (3,4,5)-connected 3D topological network with the Schlafli symbol (42·54·63·7)(42·63·7)(5·6·8)(5·62·7·82), which has not been reported before. The structural and dimensional diversity of the two complexes indicates that H2bptp exhibits strong coordination ability and diverse coordination modes. It is worth mentioning that the Cu⋯Cu distances in 1 and 2 are shorter than the sum of the van der Waals radii of copper(I) (2.80 A), implying the metal–metal bonding interactions. What is more, the solid-state luminescence bands of 1 and 2 have also been investigated between 298 and 10 K. Interestingly, the low-energy emission bands of 1 and 2 exhibit yellow/orange-red luminescence, and their intensities increase gradually upon cooling.