Control of interpenetration and gas-sorption properties of metal-organic frameworks by a simple change in ligand design

In metal-organic framework (MOF) chemistry, interpenetration greatly affects the gas-sorption properties. However, there is a lack of a systematic study on how to control the interpenetration and whether the interpenetration enhances gas uptake capacities or not. Herein, we report an example of interpenetration that is simply controlled by the presence of a carbon-carbon double or single bond in identical organic building blocks, and provide a comparison of gas-sorption properties for these similar frameworks, which differ only in their degree of interpenetration. Noninterpenetrated (SNU-70) and doubly interpenetrated (SNU-71) cubic nets were prepared by a solvothermal reaction of [Zn(NO(3))(2)]?6?H(2)O in N,N-diethylformamide (DEF) with 4-(2-carboxyvinyl)benzoic acid and 4-(2-carboxyethyl)benzoic acid, respectively. They have almost-identical structures, but the noninterpenetrated framework has a much bigger pore size (ca. 9.0×9.0 ?) than the interpenetrated framework (ca. 2.5×2.5 ?). Activation of the MOFs by using supercritical CO(2) gave SNU-70' and SNU-71'. The simulation of the PXRD pattern of SNU-71' indicates the rearrangement of the interpenetrated networks on guest removal, which increases pore size. SNU-70' has a Brunauer-Emmett-Teller (BET) surface area of 5290 m(2) g(-1), which is the highest value reported to date for a MOF with a cubic-net structure, whereas SNU-71' has a BET surface area of 1770 m(2) g(-1). In general, noninterpenetrated SNU-70' exhibits much higher gas-adsorption capacities than interpenetrated SNU-71' at high pressures, regardless of the temperature. However, at P<1 atm, the gas-adsorption capacities for N(2) at 77 K and CO(2) at 195 K are higher for noninterpenetrated SNU-70' than for interpenetrated SNU-71', but the capacities for H(2) and CH(4) are the opposite; SNU-71' has higher uptake capacities than SNU-70' due to the higher isosteric heat of gas adsorption that results from the smaller pores. In particular, SNU-70' has exceptionally high H(2) and CO(2) uptake capacities. By using a post-synthetic method, the C?C double bond in SNU-70 was quantitatively brominated at room temperature, and the MOF still showed very high porosity (BET surface area of 2285 m(2) g(-1)).     

Three-bond sugar-base couplings in purine versus pyrimidine nucleosides: a DFT study of Karplus relationships for (3)J(C2/4-H1') and (3)J(C6/8-H1') in DNA

(3)J(C2/4-H1') and (3)J(C6/8-H1') scalar spin-spin coupling constants have been calculated for deoxyadenosine, deoxyguanosine, deoxycytidine, and deoxythymidine as functions of the glycosidic torsion angle chi by means of density functional theory. Except for deoxythymidine, (3)J(C2/4-H1') depends little on the base type. On the contrary, (3)J(C6/8-H1') follows the usual trans to cis ratio ((3)J(C-H(cis)) < (3)J(C-H(trans))) for purine nucleosides, but reveals the opposite relation ((3)J(C-H(cis)) > (3)J(C-H(trans))) for pyrimidine nucleosides. Our results compare well with the experiment for deoxyguanosine and predict a novel trend in the case of pyrimidine bases for which no NMR results are available in the syn region. A breakdown of the key Fermi contact part of (3)J(C6/8-H1') into MO contributions rationalizes this trend in terms of an unusual coupling mechanism in the syn orientation that is very effective for pyrimidine nucleosides and considerably weaker for purine nucleosides.     

Promotion of Proton Conductivity by Encapsulation of Metal-Organic Polyhedra in Metal-Organic Frameworks

A Zr-based metal-organic polyhedron (MOP) was self-assembled in a porous MOF host, DUT-68, successfully to synthesize MOP-1@DUT-68. The MOP guest (MOP-1) has a diameter of about 20 Å, larger than that of the square windows (pore sizes of ∼14 Å) of DUT-68 but smaller than that of the rhombicuboctahedral cage (27.7 Å), which means that the migration and leaching of MOP-1 could be effectively prohibited if MOP-1 is encapsulated in the MOF′s cavities. The proton conductivity of MOP-1@DUT-68 is 1.14×10⁻³ S cm⁻¹ (at 80 °C under 98 % relative humidity), which is three orders of magnitude higher than that of DUT-68. Compared with MOP-1⊂DUT-68, which was synthesized by impregnation, MOP-1@DUT-68 is more prone to form faster proton-conduction pathways and thus provides higher proton conductivity.     

Development of mesophase pitch derived mesoporous carbons through a commercially nanosized template

Mesoporous carbons (MCs) with a high surface area (up to 900 m2/g), large pore volume (up to 2.1 cm3/g), high mesopore ratio (94%), and high yield (70%) were successfully prepared from an AR mesophase pitch, using a commercially nanosized silica template. The removal of the template provided some larger mesopores of 25-50 nm (pore I) with a surface area of ca. 300 m2/g, while the successive carbonization opened the closed pores within the carbon body to give smaller mesopores of 2-10 nm (pore II) with a similar surface area. During the carbonization of pitch precursor, the evaporation of volatile components swells the carbon to introduce the second mesopores among the domains and even microdomain units because of their rearrangements and overlappings in the process. The addition of iron salt with the silica template resulted in a remarkable increase of the surface area (ca. 300 m2/g) by introducing mesopores of 3-5 nm. The resultant MCs maintained some graphitizable natures derived from the anisotropic precursor. Their graphitization at 2400 degrees C provided the graphitic structure with large surface areas (270-460 m2/g) and mesoporosity.     

Metal-organic framework from an anthracene derivative containing nanoscopic cages exhibiting high methane uptake

A microporous metal-organic framework, PCN-14, based on an anthracene derivative, 5,5'-(9,10-anthracenediyl)di-isophthalate (H4adip), was synthesized under solvothermal reaction conditions. X-ray single crystal analysis revealed that PCN-14 consists of nanoscopic cages suitable for gas storage. N2-adsorption studies of PCN-14 at 77 K reveal a Langmuir surface area of 2176 m2/g and a pore volume of 0.87 cm3/g. Methane adsorption studies at 290 K and 35 bar show that PCN-14 exhibits an absolute methane-adsorption capacity of 230 v/v, 28% higher than the DOE target (180 v/v) for methane storage.     

活性炭纤维对气相低浓度三氯乙烯的动态吸附

研究了3种不同经表面积活性炭纤维（ACF）对气相低浓度三氯乙烯（TCE）的动态吸附。ACF的比表面积为600m^2/g、1400m^2／g和1600m^2/g，TCE的浓度范围为27mg/m^3-2725mg/m^3。结果表明，比表面积为1400m^2/g和1600m^2/g的ACF对TCE的吸附较好；10％穿透时间的对数与TCE匠对数呈线性关系；穿透时间随温度和湿度的增加而缩短；穿透曲线可以用经验公式拟合。拟合值和实测值吻合良好；ACF吸附是去除气相低浓度TCE的有效方法。     

纳米MoS_2催化剂的合成及其在加氢脱硫反应中的应用

通过羰基钼和升华硫反应制备了晶片层数为3～5,比表面积为71m2/g的纳米MoS2催化剂,并考察了其催化十二硫醇或二苯并噻吩的加氢脱硫活性.结果表明,在3.0MPa初始氢气压力下,该催化剂在200C和280C就可使十二硫醇和二苯并噻吩转化接近100%.     

快速沉淀法制备多孔纳米NiO及其电容性质研究

本文提出一种简单、低成本和无污染的快速沉淀法, 在没有添加任何有机试剂的条件下, 制备了高比表面积并具有良好孔径分布的Ni(OH)2, 于300 ℃下焙烧得到了多孔纳米NiO, 它在2.0 mol/L KOH电解液中的单电极比容量约为255 F/g.     

Porous crystal derived from a tricarboxylate linker with two distinct binding motifs

The use of a reduced symmetry organic linker for the preparation of porous coordination polymers is demonstrated. The solvothermal reaction of the unsymmetrically substituted biaryl compound biphenyl-3,4',5-tricarboxylic acid with Cu(II) ions produces a [3,4,6]-connected coordination polymer exhibiting very high porosity and surface area (SLangmuir = 3100 m2/g). A striking feature of the structure is its incorporation, in a single material, of both the ubiquitous dinuclear Cu(II) paddlewheel motif and the rarely observed trinuclear Cu(II) cluster. Saturation H2 uptake, measured at 77 K, shows an excess gravimetric uptake of 5.7 wt % at 45 bar with a steep rise at low pressures.     

The infrared and Raman spectra of trans- and cis-tetrachloro-tetramethylbicyclopropylidene

The title compounds trans- and cis-2,2,2',2'-tetrachloro-3,3,3',3'-tetramethyl-bicyclopopylidene were synthesized, and their infrared and Raman spectra were recorded. Non-coincidence between the IR and Raman bands of the trans compound suggested C(2h) symmetry and a planar ring system. In the cis compound most of the IR and Raman bands coincided and a C(2v) symmetry seems likely. The exocyclic CC double bond gave rise to a medium/weak Raman band at 1,847 cm(-1) in the trans compound. In the cis derivative IR and Raman bands both at 1,825 cm(-1) were observed. From similarities with related molecules, the ring breathing, the antisymmetric ring stretch, the CCl(2) out-of-phase and in-phase stretch and the out-of-plane ring bending modes have been tentatively assigned for the trans and cis compounds.     

Characterization of the surface interacting ability of carbon black by means of electron paramagnetic resonance analysis of adsorbed Cu2+, supported by surface analysis and atomic absorption

Electron paramagnetic resonance (EPR) has been used to investigate the adsorption capability and the surface interacting ability towards Cu(II) solutions (CuCl2, Cu(NO3)2, CuSO4 in water or ethanol) of various carbon blacks, both graphitized and ungraphitized, selected on the basis of the surface area, namely, Carbograph1 (area = 100 m2/g), Carbograph4 (area = 210 m2/g), and Carbograph5 (area = 560 m2/g), which were indicated as C1g, C4g, C5g (g = graphitized), and C1ng, C4ng, C5ng (ng = ungraphitized). The EPR analysis was supported by surface analysis, for evaluating the surface area, the pore volume and the porosity, and by atomic absorption to obtain the adsorbed Cu(II) amounts. Graphitization provokes a decrease in surface area, but C1g, at low surface area, showed a unexpected increase of the adsorption ability ascribed to the formation of new surface porosity closed by graphite layers. The carbon samples showed a broad unresolved EPR signal due to mobile unpaired electrons in the carbon matrix. Graphitized samples presented a narrower signal than ungraphitized samples, which increases in width with the increase in surface area (with the exception of C5ng due to the high exposition of the wide surface to oxydizing external agents) and upon prolonged thermal treatment. The signal intensity of the carbon paramagnetic centers decreases upon Cu(II) adsorption. Computer aided analysis of the EPR spectra of the solids after Cu(II) adsorption allowed to extract structural information on the Cu-surface site complexes. The Cu2+ ions coordinated with surface polar sites, mainly oxygenated. Adsorption depends on the different Cu(II) salts, caused by the salt solubility and the interacting ability of the counter-ion. In several cases the solutions concentrated in the carbon porosity leading to precipitation of the salt. Ethanol solutions are more adsorbed at the carbon surface than water solutions; Cu(II) partially retains its solvation shell and partially presents electron transfer to the carbon surface. Adsorption is favored to ungraphitized carbons with respect to the graphitized ones due to both the higher surface area, and the higher hydrophilicity of the surface. In summary, these carbon powders, widely used for chromatographic applications, show an adsorption capability towards Cu(II) solutions higher than expected due to both a definite porosity, and the presence of polar groups which are not eliminated with chemical surface treatments.     

A nearly isosteric photosensitive amide-backbone substitution allows enzyme activity switching in ribonuclease s

psi[CS-NH]4-RNase S, a site specific modified version of RNase S obtained by thioxylation (O/S exchange) at the Ala4-Ala5- peptide bond, was used to evaluate the impact of protein backbone photoswitching on bioactivity. psi[CS-NH](4)-RNase S was yielded by recombination of the S-protein and the respective chemically synthesized thioxylated S-peptide derivative. Comparison with RNase S revealed similar thermodynamic stability of the complex and an unperturbed enzymatic activity toward cytidine 2',3'-cyclic monophosphate (cCMP). Reversible photoisomerization with a highly increased cis/trans isomer ratio of the thioxopeptide bond of psi[CS-NH](4)-RNase S in the photostationary state occurred under UV irradiation conditions (254 nm). The slow thermal reisomerization (t(1/2) = 180 s) permitted us to determine the enzymatic activity of cis psi[CS-NH](4)-RNase S by measurement of initial rates of cCMP hydrolysis. Despite thermodynamic stability of cis psi[CS-NH](4)-RNase S, its enzymatic activity is completely abolished but recovers after reisomerization. We conclude that the thioxopeptide bond modified polypeptide backbone represents a versatile probe for site-directed photoswitching of proteins.     

Electrochemical polymerization of acetylene on a surface of platinum

Polyacetylene (PA) deposited on a platinum surface is synthesized by electrochemical polymerization of acetylene in a cell with platinum strip as cathode, nickel strip as anode, and nickel bromide in acetonitrile as electrolyte. The electrolytic solution is presaturated with acetylene. The PA so produced has a granular morphology and high surface area (79 m²/g), and is insoluble. Polymerization at lower temperature gives higher content in cis units. It has the same chemical structure as that produced using the Shirakawa method as examined by elemental analysis, infrared spectroscopy, x-ray diffraction, and differential scanning calorimetry.     

高比表面积VPO催化剂的制备及其性质研究

利用有机相制备VPO催化剂,在制备过程中加入聚乙二醇(PEG)作为分散剂可有效提高VPO催化剂的比表面积。实验中采用两种不同分子量的聚乙二醇(PEG 6000和PEG 10000),所得VPO催化剂的比表面积分别为52与54m²/g,而不加聚乙二醇的VPO催化剂其比表面积仅为19m²/g.XRD,XPS及FTIR的结果表明,催化剂的主要晶相均为(VO)₂P₂O₇,但两类催化剂的微观结构有所不同。正丁烷选择氧化生成马来酐的催化反应结果表明,385℃时加聚乙二醇制备的VPO催化剂其丁烷的转化率为84%～86%.马来酸酐的选择性为78%,而不加聚乙二醇制备的VPO催化剂其转化率和选择性均为71%.     

Synthesis of high surface area Al-containing mesoporous silica from calcined and acid leached kaolinites as the precursors

Al-containing mesoporous silicas were synthesized by hydrothermal treatment of microporous silica prepared by selectively acid leached metakaolinites with Si/Al = 3.9-92.5 mixed with a surfactant of cetyltrimethylammonium bromide (CTABr). The specific surface area of the products increased with higher surfactant/microporous silica (surf/Si) ratio and Si/Al ratio of the microporous silica, reaching about 1400 m2/g at CTABr/Si 0.1 and Si/Al 40. The XRD patterns of these products show a hexagonal (100) peak with the lattice parameter a0=4.2-4.3 nm and the N2 adsorption isotherms show steep increase of adsorption between relative pressure of 0.3 and 0.4. Hexagonal mesoporous microstructure is observed by high resolution TEM. The pore size distributions of the products show a sharp peak at 2.8 nm by the BJH method. The high specific surface area of the present mesoporous samples is attributed to the lower matrix density and surface roughness of mesopore wall. The highest specific surface area of the products reached up to 1420 m2/g and this value is apparently higher than those reported in hexagonal mesoporous silicas. A unique microporous structure of the starting material is thought to be related to achieve such a high specific surface area of the products.     

Kinetics and Mechanism of Dechlorination of o-Chlorophenol by Nanoscale Pd／Fe

IntroductionTherehasbeenagrowinginterestintheuseofzero valentironforthetreatmentofchlorinatedor ganiccompounds(COCs)inwaterandgroundwater .Thestudieshavebeenfocusedonsuchcompoundsascarbontetrachloride ,trichloroethene ,pesticidesandtherelatedcompounds[1— 7] .Whenironisincontactwithalessreductivemetalsuchaspalladiumwhosecomplexhasbeenusedtohydrogenatenitroben zene[8] ,themetalcouplecanformgalvaniccells .ThisledtothediscoveryofaPd/Febimetalliccomplexofwhichpalladiumservesasacatalystandironasa…     

Surface area determination of a polystyrene-divinylbenzene chromatographic packing material via ionic amphiphile adsorption from aqueous mobile phases and application of Gouy-Chapman theory

A method for the determination of the chromatographically accessible area of a reversed-phase column similar to the method of H?gglund and St?hlberg [J. Chromatogr. A 761 (1997) 13] is applied to a column containing a polystyrene-divinylbenzene resin. Its theoretical basis is Gouy-Chapman theory in combination with an electrostatically modified linear adsorption isotherm. The surface area value determined for the resin, 96 m2/g, is much less than the reported surface area value, 400 m2/g, determined by N2 sorptometry and application of Branauer-Emmett-Teller (BET) theory. The method also provides a value for the number of moles of native anionic sites present on the column.     

木素磺酸离子交换树脂的改性

本文对木素磺酸阳离子交换树脂进行改性，使比表面积提高了四倍多。改性后的树脂有较好的表面性能，且原料廉价，合成工艺简单，有希望用作废水生物处理的载体。     

Porous metal-organic framework based on mu4-oxo tetrazinc clusters: sorption and guest-dependent luminescent properties

A three-dimensional, highly porous metal-organic framework [Zn 4O(bdc)(bpz) 2].4DMF.6H 2O ( 1) (bdc = 1,4-benzenedicarboxylate, bpz = 3,3',5,5'-tetramethyl-4,4'-bipyrazolate) constructed by Zn 4O clusters with bdc and bpz linkers, has been prepared and structurally characterized. The N 2 sorption measurements reveal that 1 exhibits high porosity with a Langmuir surface area of 1908 m (2)/g and a pore volume of 0.58 cm (3)/g. Compound 1 features hydrophobic channels with a free passage of approximately 8.2 A defined by the methyl groups from bpz, and it exhibits nice sorption capability for benzene and toluene and interesting two-step sorption behavior for methanol. Meanwhile, 1 also exhibits interesting guest-dependent luminescent properties.     

Synthesis of titanium dioxide nanoparticles with mesoporous anatase wall and high photocatalytic activity

Mesoporous titanium dioxide nanosized powder with high specific surface area and anatase wall was synthesized via hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as surfactant-directing agent and pore-forming agent. The resulting materials were characterized by XRD, nitrogen adsorption, FESEM, TEM, and FT-IR spectroscopy. The as-synthesized mesoporous TiO2 nanoparticles have mean diameter of 17.6 nm with mean pore size of 2.1 nm. The specific surface area of the as-synthesized mesoporous nanosized TiO2 exceeded 430 m2/g and that of the samples after calcination at 600 degrees C still have 221.9 m2/g. The mesoporous TiO2 nanoparticles show significant activities on the oxidation of Rhodamine B (RB). The large surface area, small crystalline size, and well-crystallized anatase mesostructure can explain the high photocatalytic activity of mesoporous TiO2 nanoparticles calcined at 400 degrees C.