Six new calcium metal−organic frameworks [Ca(BDC)(DMF)(H2O)] (1), [Ca(ABDC)(DMF)] (2), [Ca3(BTC)2(DMF)2(H2O)2]·3H2O (3), [Ca(H2dhtp)(DMF)] (4), [Ca(H2dhtp)(DMF)2] (5), and one modification of [Ca(H2dhtp)2(H2O)2] (6), (DMF = N,N-dimethylformamide; BDC = 1,4-benzenedicarboxylate anion; ABDC = 2-aminobenzene-1,4-dicarboxylate anion; BTC = 1,3,5-benzenetricarboxylate anion; H2dhtp = 2,5-dihydroxyterephthalate anion) were synthesized from calcium ions and aromatic carboxylic acids by solvothermal reactions and microwave-assisted solvothermal reactions. The single crystal structure analysis showed that all complexes display three-dimensional structures containing various inorganic motifs with helical or straight one-dimensional inorganic chains (1−3), pentagonal bipyramidal dimers (4 and 6), or discrete octahedra (5) connected through organic linkers and forming DMF- or water-coordinated neutral frameworks. It is also interesting that compounds 1−5 undergo dissolution/reorganization reactions comprising a break and reformation of the Ca−O bond and leading to destruction/construction structural transformations. Compounds 1−5 were further characterized by thermal gravimetric analysis, powder X-ray diffraction, UV−vis, infrared, and PL spectroscopy.
Two new calcium and strontium metal-organic frameworks [Ca(SBA)] (CYCU-1) and [Sr(SBA)] (CYCU-2) were prepared by microwave-assisted reactions. Both rigid frameworks are thermally stable up to about 450 C. As verified by N 2 , CO 2 , and H 2 sorption measurements, the thermally activated CYCU-1 and CYCU-2 exhibit significant microporosity.Porous metal-organic frameworks (MOFs) have attracted much attention because of their various applications in gas storage, separation, catalysis, magnetism, luminescence, and biological drug delivery. [1][2][3][4][5][6][7] Numerous MOFs have been synthesized with various metal ions and organic aromatic carboxylates. The alkaline earth MOFs have been less studied compared with transition or lanthanide metal-based MOFs. Their ionic chemistry in water and their varied coordination numbers make use of these metal ions to generate MOFs with permanently accessible porosity challenging. 8 Only a few results on calcium and strontium MOFs capable of gas sorption have been reported in the literature. 9 Nitrogen gas sorption measurements with microporous type-I isotherms on calcium MOFs (non-heterometallic Ca-MOFs) have not been reported. In this communication, we describe our results on the facile synthesis of two microporous materials, [Ca(SBA)]$0.45H 2 O (CYCU-1 as ) and [Sr(SBA)]$0.2H 2 O (CYCU-2 as ), with microwave irradiation 10 with Ca(II) and Sr(II) ions and 4,4 0 -sulfonyldibenzoate acid (H 2 SBA). ‡ To our knowledge, this work is the first example of the facile synthesis of permanent accessible and porous Ca(II)-MOFs.Single-crystal X-ray diffraction shows that the compounds CYCU-1 as and CYCU-2 as possess similar extended 3D frameworks.x In CYCU-1 as , the asymmetric unit contains one Ca (Sr for CYCU-2 as ) atom, one SBA ligand, and lattice water molecules (Fig. 1a). The Ca (II) and Sr(II) ions are seven-coordinated and bind six oxygen atoms from the carboxylate groups belonging to five SBA ligands and one oxygen from the SO 2 group in the other SBA ligand. The SBA ligand
Six new alkali and alkaline earth metal coordination polymers based on rigid 1,4-naphthalenedicarboxylic acid (H 2 NDA), [Li(HNDA) 5), and [Ba(NDA)(DMF)] ( 6) have been synthesized under solvothermal conditions in order to evaluate the coordination behavior of H 2 NDA towards Li + , Na + , Mg 2+ , Ca 2+ , Sr 2+ , and Ba 2+ ions and the structural features of the resulted polymeric complexes. Their structures were determined by single-crystal X-ray diffraction studies. The coordination number of the metal ions varies from 4 (for Li), 5 (for Na), 6 (for Na and Mg) to 7 (for Ca, Sr, and Ba), while the number of metal ions bound to the ligand ranges from 2 (Li), 4 (Mg), 5 (Ca, Sr, and Ba) to 8 (Na). Compound 1 has a one-dimensional polymeric structure which is further connected by hydrogen bonds to form a supramolecular assembly. Compound 2 is a three-dimensional metal-organic framework (MOF) possessing hexagonal channels which are built up by helical 1D infinite inorganic chains connected with NDA ligands. Interestingly, the porous MOF, 2, exhibited high gas sorption properties for CO 2 over N 2 . Compound 3 has a three-dimensional structure having 1D inorganic chains connected with NDA ligands in two directions to form a cage-like structure.Compounds 4, 5 and 6 are isostructural, having three-dimensional structures in which 1D inorganic chains are connected by NDA to form a 2-nodal 5,5-connected net. In addition, the solid state photoluminescence properties of all the compounds have also been studied.
A series of metal coordination polymers, [Li 2 (OBA)] (1), [Na 2 (OBA) 7), and [Sr(OBA)(H 2 O)] (8) (H 2 OBA = 4,49-oxybisbenzoic acid), was synthesized from alkali and alkaline-earth metal salts and 4,49-oxybisbenzoic acid by solvothermal reactions. Single crystal X-ray structure analysis revealed that compounds 1-5 and 7-8 are three-dimensional while complex 6 has a layered structure. The inorganic motifs, ranging from discrete octahedra (6), edge-sharing octahedral dimers ( 7), and straight one-dimensional inorganic chains (1 and 8) to two-dimensional inorganic layers (2-5), are connected through organic linkers and thus form neutral networks. High thermal stabilities were observed for compounds 1, 2, 6, 7, and 8 up to approximately 500 uC. Electrochemical measurements of 1 revealed a stabilized reversible capacity of approximately 100 mAh g 21 after more than 30 charge/discharge cycles.
Computational protein design methods have enabled the design of novel protein structures, but they are often still limited to small proteins and symmetric systems. To expand the size of designable proteins while controlling the overall structure, we developed Elfin, a genetic algorithm for the design of novel proteins with custom shapes using structural building blocks derived from experimentally verified repeat proteins. By combining building blocks with compatible interfaces, it is possible to rapidly build non-symmetric large structures (>1000 amino acids) that match three-dimensional geometric descriptions provided by the user. A run time of about 20min on a laptop computer for a 3000 amino acid structure makes Elfin accessible to users with limited computational resources. Protein structures with controlled geometry will allow the systematic study of the effect of spatial arrangement of enzymes and signaling molecules, and provide new scaffolds for functional nanomaterials.
A series
of four new metal–organic frameworks, [Na2(SBA)]
(1 or CYCU-6), [K8(H2O)2(SBA)4(DMF)] (2), [Rb2(SBA)] (3), and [Cs(H2O)(HSBA)]·DMF
(4), have been constructed under solvothermal conditions
by using 4,4′-sulfonyldibenzoic acid (H2SBA) as
ligand. The structure of the complexes has been determined by single-crystal
X-ray diffraction analysis and further characterized by elemental
analyses, reflectance UV–vis, and IR spectra, powder X-ray
diffraction (PXRD), and thermogravimetric analysis (TGA). The single
crystal X-ray structural studies showed that all the complexes display
three-dimensional (3D) structures containing inorganic motifs with
one-dimensional chains connected through organic linkers and forming
3D networks. Among the four complexes, the Na(I) complex (1) displays very high thermal stability, which was inferred from TGA
and PXRD results. Moreover, the solid state luminescent properties
of the new complexes have been investigated at room temperature. In
addition, the gas sorption properties of 1 toward nitrogen,
hydrogen, carbon dioxide, and methane are reported.
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