Polar Pore Research Articles

Functionalization of MOFs via a mixed-ligand strategy: enhanced CO2 uptake by pore surface modification

A new Zn(ii) metal-organic framework (MOF) [Me2NH2][Zn2(BDPP)(HTZ)]·4DMF (1) (H4BDPP = 3,5-bis(3,5-dicarboxylphenyl)pyridine, HTZ = 1H-tetrazole) has been constructed under solvothermal conditions by using a mixed-ligand strategy. Structural analysis demonstrates that 1 is a 3D framework based on four kinds of secondary building units (SBUs), which presents a rare structure constructed from quaternary SBUs and shows an uncommon (3,3,4,6)-connected topology. In particular, 1 contains two shapes of 1D open channels with suitable pore sizes, high porosity, and a highly polar pore system decorated with uncoordinated N atoms and carboxylic O atoms, providing a good environment for selective adsorption of CO2. Inspired by the structure of 1 and reticular chemistry, 5-amino-1H-tetrazole (ATZ) was used to replace 1H-tetrazole to enhance CO2 sorption capacity by pore surface modification; as a result, an amino-functionalized MOF, [Me2NH2][Zn2(BDPP)(ATZ)]·4DMF (1-NH2) was successfully built. 1-NH2 exhibits multipoint interactions between the CO2 molecules and the framework, resulting in better CO2 uptake and selectivity for CO2 over CH4 than 1.

A robust microporous ytterbium metal-organic framework with open metal sites for highly selective adsorption of CO2 over CH4

A rare three-dimensional (3D) microporous lanthanide metal–organic framework, {[Yb(BTB)(H2O)](MeOH)2(H2O)}n (1), with 1D nano-sized channels has been constructed by bridging helical chain secondary building units with 1,3,5-Benzenetrisbenzoic acid (H3BTB) ligand. The highly rigid and stable framework contains a 1D triangular channel-type structure with highly polar pore surfaces decorated with abundant open metal sites. The desolvated framework {[Yb(BTB)]}n is found to exhibit permanent porosity with high CO2 storage capacities and significant selective sorption of CO2 over CH4 around room temperature.

Thermal Exfoliation of Layered Metal-Organic Frameworks into Ultrahydrophilic Graphene Stacks and Their Applications in Li-S Batteries.

2D nanocarbon-based materials with controllable pore structures and hydrophilic surface show great potential in electrochemical energy storage systems including lithium sulfur (Li-S) batteries. This paper reports a thermal exfoliation of metal-organic framework crystals with intrinsic 2D structure into multilayer graphene stacks. This family of nanocarbon stacks is composed of well-preserved 2D sheets with highly accessible interlayer macropores, narrowly distributed 7 Å micropores, and ever most polar pore walls. The surface polarity is quantified both by its ultrahigh water vapor uptake of 14.3 mmol g-1 at low relative pressure of P/P0 = 0.4 and ultrafast water wetting capability in less than 10.0 s. Based on the structural merits, this series hydrophilic multilayer graphene stack is showcased as suitable model cathode host for unveiling the challenging surface chemistry issue in Li-S batteries.

Polar Pore Surface Guided Selective CO2 Adsorption in a Prefunctionalized Metal–Organic Framework

Selective CO2 adsorption over other small gases has been realized in an ultra-microporous metal–organic framework (MOF). In the quest of manifesting such selective carbon capture performance, the prefunctionalized linker strategy has been espoused. A new Zn(II)-based three-dimensional, 3-fold interpenetrated metal–organic framework material [Zn(PBDA)(DPNI)]n·xG (PBDA: 4,4′-((2-(tert-butyl)-1,4-phenylene)bis(oxy))dibenzoic acid; DPNI: N,N′-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide; xG: x number of guest species) with unusual rob topology is synthesized following a typical solvothermal synthesis protocol, which gleans a modest CO2-selective adsorption trend over its congener gases (saturation CO2 uptake capacity: 2.39 and 3.44 mmol g–1, at 298 and 273 K; volumetric single component isotherm based separation ratios at 0.2 bar: 189.4 (CO2/N2, 256.5 (CO2/H2), 12.3 (CO2/CH4); at 1 bar: 6.8 (CO2/N2, 17.1 (CO2/H2), 7.1 (CO2/CH4)). The compound also exhibits selective benzene sorption over its aliphatic...

Crystallography as a Path-Finding Tool to Understand Functionality in Coordination Polymers

Because of their potential applications, coordination polymers (CPs) are at an exalted position in the field of chemical and material science. Porous coordination polymers, popularly known as metal–organic frameworks (MOFs), have large surface area with functional pore environment, permanent porosity, tailorability in pore size, dimension and volume, which make them promising for interesting functionalities. In this review, we show how the mixed-ligand CPs/MOFs are very important in tuning the functionality of such systems and how the X-ray structure illuminates their functionalities. Here, we discuss the application of mixed-ligand functional MOFs for CO2 storage and separation by fine-tuning their pore size and dimension along with their polar pore surfaces using different functional dicarboxylates and N,N′-donor ligands. We also discuss the nature of conductivity and fabrication of Schottky barrier diode for CPs, where free organic ligands are in their pores. In addition, we also present the variation of their interesting chemical reactivity, e.g. framework-assisted in situ redox transformation.

Preinfection process in cocoa fruits by Moniliophthora roreri

Moniliophthora roreri (Cif & Park) (Evans et al 1978) infects cocoa ( Theobroma cacao L) fruits causing great losses. A study was conducted of the pathogen-host relationships on the fruit considering fungal spore distribution, germination, germ tube formation and infection using Scanning Electron Microscopy, Sixty-day-old fruits, inoculated and not inoculated, of cv. Pound-7 (susceptible) and UF-296' (moderately resistant) were collected from two sites of Costa Rica's low humid tropic, La Lola and Turrialba, Conidia were found mostly at the base of trichomes. Spores germinated similarly on both cultivars. Germination occurred through a polar germination pore or alternatively through the lateral spore wall 7-8 hr after inoculation of the fruits. The number of germinated spores was low, Germtube infection of the fruit via stomata was not common, Preliminary evidence suggests infection via direct penetration of epidemal cells and trichomes. Hyphae that emerged from the trichomes spread and infected other sites in the epidermis, including trichomes, stomata, injuries and other epidermal cells, Apressorium-like structures or terminal swellings on germ tubes were observed occassionally.

Separation/purification of ethylene from an acetylene/ethylene mixture in a pillared-layer porous metal-organic framework.

Here we report the synthesis, structure and porous properties of a 3D pillared-layer porous framework of Mn(ii)-Mn(iii), {[Mn3(bipy)3(H2O)4][Mn(CN)6]2·2(bipy)·4H2O}n (1). The guest-removed framework (1a) shows significant uptake of C2H2, whereas it excludes the other two C2 hydrocarbons (C2H4 and C2H6). Furthermore, excellent separation proficiency for C2H2 from a mixture of C2H2 and C2H4 (1 : 99, v/v) is realized in a breakthrough column experiment under ambient conditions.

A microporous MOF with a polar pore surface exhibiting excellent selective adsorption of CO2 from CO2-N2 and CO2-CH4 gas mixtures with high CO2 loading.

A microporous MOF {[Zn(SDB)(L)0.5]·S}n (IITKGP-5) with a polar pore surface has been constructed by the combination of a V-shaped -SO2 functionalized organic linker (H2SDB = 4,4'-sulfonyldibenzoic acid) with an N-rich spacer (L = 2,5-bis(3-pyridyl)-3,4-diaza-2,4-hexadiene), forming a network with sql(2,6L1) topology. IITKGP-5 is characterized by TGA, PXRD and single crystal X-ray diffraction. The framework exhibits lozenge-shaped channels of an approximate size of 4.2 × 5.6 Å2 along the crystallographic b axis with a potential solvent accessible volume of 26%. The activated IITKGP-5a revealed a CO2 uptake capacity of 56.4 and 49 cm3 g-1 at 273 K/1 atm and 295 K/1 atm, respectively. On the contrary, it takes up a much smaller amount of CH4 (17 cm3 g-1 at 273 K and 13.6 cm3 g-1 at 295 K) and N2 (5.5 cm3 g-1 at 273 K; 4 cm3 g-1 at 295 K) under 1 atm pressure exhibiting its potential for a highly selective adsorption of CO2 from flue gas as well as a landfill gas mixture. Based on the ideal adsorbed solution theory (IAST), a CO2/N2 selectivity of 435.5 and a CO2/CH4 selectivity of 151.6 have been realized at 273 K/100 kPa. The values at 295 K are 147.8 for CO2/N2 and 23.8 for CO2/CH4 gas mixtures under 100 kPa. In addition, this MOF nearly approaches the target values proposed for PSA and TSA processes for practical utility exhibiting its prospect for flue gas separation with a CO2 loading capacity of 2.04 mmol g-1.

A new layer-stacked porous framework showing sorption selectivity for CO2 and luminescence.

A new metal-organic framework, [Zn3(μ3-OH)(tzba)2(bpy)(H2O)]OH·DMF (1), was solvothermally synthesized by employing tetrazolate-carboxylate 4-(1H-tetrazol-5-yl) benzoic acid (H2tzba) linker and 2,2'-bipyridine (bpy) chelating coligand. 1 contains novel Zn6(μ3-OH)2(μ2-H2O)2(COO)4(N4C)2 hexanuclear clusters and reveals a three-dimensional (3D) microporous supramolecular framework based on the stacked 2D layers. The highly polar pores cause not only strong affinity towards CO2 molecules but also a significant selective adsorption of CO2 over CH4. Meanwhile, the multiple binding sites for CO2 in the framework were determined by Grand Canonical Monte Carlo (GCMC) simulations. 1 also shows strong blue luminescence from ligand-to-metal charge transfer (LMCT).

Tunable Porosity and Polarity of the Polar Hyper-Cross-Linked Resins and the Enhanced Adsorption toward Phenol

The synthesis of hyper-cross-linked resins with tunable porosity and polarity remains a challenge. Herein, we employed an interpenetration reaction, Friedel–Crafts reaction, and amination reaction, and we synthesized a series of polar hyper-cross-linked resins. We found that the porosity and polarity of these resins could be effectively tuned by the interpenetrating polymer networks (IPNs) technology and the Friedel–Crafts reaction. These resins possessed moderate Brunauer–Emmett–Teller (BET) surface area and pore volume, decent polarity, and excellent pore structure, endowing them with efficient adsorption toward phenol. Particularly, the adsorption was very fast: 38 min was sufficient to reach equilibrium, suggesting that these polar hyper-cross-linked resins were potential candidates for the adsorptive removal of phenol.

Superior capacitive performance of reduced graphene hydrogels via dimethyl ketoxime

Three-dimensional (3D) reduced graphene hydrogels (RGHs) have been prepared by using dimethyl ketoxime as reducing agents in aqueous solution of graphene oxide (GO) with ammonia. The structure and surface chemistry were analyzed by scanning electron microscopy, Raman, X-ray diffraction, and X-ray photoelectron spectroscopy. The capacitive performance of the RGHs materials are studied in 6M KOH electrolyte. Benefitting from the 3D porous structures and heteroatom-doped polar pore surface, the as-prepared RGHs materials exhibit high specific capacitances up to 159.8, 215.1 and 163.4Fg−1 at 1Ag−1 for RGHs-1, RGHs-2 and RGHs-5, respectively. More importantly, the materials can maintain high capacitances of 95.6, 155.2 and 118.9Fg−1 at a very high current density of 20Ag−1, the retention rates are 59.8, 72.2 and 72.8% for RGHs-1, RGHs-2 and RGHs-5, respectively.

Activated polyaniline-based carbon nanoparticles for high performance supercapacitors

Polyaniline (PANI) nanoparticles have been prepared by disperse polymerization of aniline in the presence of poly(4-styrenesulfonate). The PANI nanoparticles are further subjected to pyrolysis treatment and chemical-activation to prepare the activated nitrogen-doped carbon nanoparticles (APCNs). The porosity, structure and nitrogen-doped surface chemistry are analyzed by a varies of means, such as scanning electron microscopy, transition electron microscopy, N2 sorption, X-ray diffraction and X-ray photoelectron spectroscopy. The capacitive performance of the APCNs materials are test in 6M KOH electrolyte. Benefitting from the abundant micropores with short length, large specific surface area, hierarchical porosity and heteroatom-doped polar pore surface, the APCNs materials exhibit v exhibit very high specific capacitance up to 341Fg−1, remarkable power capability and excellent long-term cyclic stability (96.6% after 10 000 cycles). At 40Ag−1, APCN-2 carbon shows a capacitance of 164Fg−1, responding to a high energy and power densities of 5.7Whkg−1 and 10 000Wkg−1.

A new porous MOF with two uncommon metal-carboxylate-pyrazolate clusters and high CO2/N2 selectivity.

By a less-exploited strategy, a stable framework was constructed by using 4,4'-biphenyldicarboxylic acid (H2bpdc) and methyl-functionalized 3,3',5,5'-tetramethyl-4,4'-bipyrazole (H2bpz) coligands, revealing a new (6,8)-connected net based on two extremely rare trinuclear and tetranuclear metal-carboxylate-pyrazolate clusters. The framework is very porous and possesses not only high CO2 loadings but also very high CO2/N2 selectivities at 308 and 313 K because of the polar pore surface decorated by clusters, pyrazolyl units, and confined cages with methyl groups dangling. Importantly, GCMC simulation identified two favorable CO2 sorption sites located sequentially near Co3(pz)3 and Co3(CO2)2(pz) motifs of the tetranuclear cluster, and the multipoint framework-CO2 interactions were distinguished. The framework also displays remarkable stability toward water and organic solvents.

A triazine–resorcinol based porous polymer with polar pores and exceptional surface hydrophobicity showing CO2 uptake under humid conditions

Phenol functionalized pores in an ultra-microporous triazine–resorcinol polymer provides exceptional surface hydrophobicity and polarizing character favoring adsorption of CO2 under humidity.

The Persistence of Apparent Non-Magnetostatic Equilibrium in NOAA 11035

AbstractNOAA 11035 was a highly sheared active region that appeared in December 2009 early in the new activity cycle. The leading polarity sunspot developed a highly unusual feature in its penumbra, an opposite polarity pore with a strong magnetic field in excess of 3500 G along one edge, which persisted for several days during the evolution of the region. This region was well observed by both space- and ground-based observatories, including Hinode, FIRS, TRACE, and SOHO. These observations, which span wavelength and atmospheric regimes, provide a complete picture of this unusual feature which may constitute a force-free magnetic field in the photosphere which is produced by the reconnection of magnetic loops low in the solar atmosphere.

Amide Functionalized Microporous Organic Polymer (Am-MOP) for Selective CO2 Sorption and Catalysis

We report the design and synthesis of an amide functionalized microporous organic polymer (Am-MOP) prepared from trimesic acid and p-phenylenediamine using thionyl chloride as a reagent. Polar amide (-CONH-) functional groups act as a linking unit between the node and spacer and constitute the pore wall of the continuous polymeric network. The strong covalent bonds between the building blocks (trimesic acid and p-phenylenediamine) through amide bond linkages provide high thermal and chemical stability to Am-MOP. The presence of a highly polar pore surface allows selective CO2 uptake at 195 K over other gases such as N2, Ar, and O2. The CO2 molecule interacts with amide functional groups via Lewis acid-base type interactions as demonstrated through DFT calculations. Furthermore, for the first time Am-MOP with basic functional groups has been exploited for the Knoevenagel condensation reaction between aldehydes and active methylene compounds. Availability of a large number of catalytic sites per volume and confined microporosity gives enhanced catalytic efficiency and high selectivity for small substrate molecules.

Gas Storage in a Partially Fluorinated Highly Stable Three-Dimensional Porous Metal–Organic Framework

A partially fluorinated linear rigid linker, 2,2'-bis-trifluoromethyl-biphenyl-4,4'-dicarboxylic acid (H2bfbpdc), has been synthesized. This linker forms a porous three-dimensional (3D) metal-organic framework, {[Zn4O(bfbpdc)3(bpy)0.5(H2O)]·(3DMF)(H2O)}n (1), in the presence of the colinker 4,4'-bipyridine (bpy) and Zn(NO3)2·6H2O under solvothermal condition. Single crystal X-ray analysis shows that 1 contains a 3D channel structure with highly polar pore surfaces decorated with pendant trifluoromethyl groups of bfbpdc(2-) linker. Thermogravimetric analysis (TGA) and variable temperature powder X-ray diffraction (VTPXRD) exhibit high thermal stability of the framework. The solvent molecules present in the voids can be removed by heating, maintaining the integrity of the structure to afford a porous framework. Gas (N2, H2, CH4, and CO2) and water adsorption studies were performed on this framework.

Three new solvent-directed 3D lead(ii)–MOFs displaying the unique properties of luminescence and selective CO2 sorption

Three new solvent-directed three-dimensional (3D) lead(II) coordination polymers, [Pb2(L)2]n (1), [Pb3(L)3]n (2) and [Pb(L)]·H2O (3) [H3L = 2-(pyridine-2-yl)-1H-imidazole-4,5-dicarboxylic acid], have been synthesized solvothermally. As influenced by different solvent systems, compounds 1 and 3 exhibit varying architectures from a multi-nodal 3,3,4,4-connected to a uninodal 3-connected net, while 2 with helices represents a binodal 3,4-connected topological net. Moreover, 3 possesses a micropore which is decorated with pyridyl systems and uncoordinated carboxylate oxygen atoms. In addition, the small-sized and highly polar pores enable 3 to attract CO2 strongly, leading to a high sorption heat for CO2 and significant selectivity for CO2 over H2 and N2 at 293 K. The luminescent behaviors and emissive lifetimes of 1-3 are also discussed.

Relating pore hydrophilicity with vapour adsorption capacity in a series of amino acid based metal organic frameworks

A new Zn based porous homochiral metal–organic framework, ThrZnOAc, belonging to unh topology, has been synthesized using pyridyl functionalized threonine and Zn(OAc)2 as the metal precursor. Stepwise substitution of the homochiral MOF backbone by simply changing the sidearm of the amino acids (isopropyl in the case of valine, methyl in alanine and hydroxyethyl in threonine) resulted in increased water adsorption in ThrZnOAc compared to the previously reported ValZnOAc/AlaZnOAc. Extensive solvent sorption isotherms (water, methanol, isopropanol and toluene) have been carried out, which revealed high solvophilic interaction with polar solvents in ThrZnOAc due to the polar pore [2-hydroxyethyl {–CH(OH)CH3} sidearm of the amino acid], which is not prominent in the corresponding valine/alanine counterparts. The aforementioned functionalization in a series of isostructural amino acid based MOFs with the only difference being in the sidearm and their emergence as enhanced solvophilic materials is unprecedented in the MOF literature.

High cadence spectropolarimetry of moving magnetic features observed around a pore

Moving magnetic features (MMFs) are small-size magnetic elements that are seen to stream out from sunspots, generally during their decay phase. Several observational results presented in the literature suggest them to be closely related to magnetic filaments that extend from the penumbra of the parent spot. Nevertheless, few observations of MMFs streaming out from spots without penumbra have been reported. The literature still lacks of analyses of the physical properties of these features. We investigate physical properties of monopolar MMFs observed around a small pore that had developed penumbra in the days preceding our observations and compare our results with those reported in the literature for features observed around sunspots. We analyzed NOAA 11005 during its decay phase with data acquired at the Dunn Solar Telescope in the FeI 617.3$ nm and the CaII 854.2$ nm spectral lines with IBIS, and in the G-band. The field of view showed monopolar MMFs of both polarities streaming out from the leading negative polarity pore of the observed active region. Combining different analyses of the data, we investigated the temporal evolution of the relevant physical quantities associated with the MMFs as well as the photospheric and chromospheric signatures of these features. We show that the characteristics of the investigated MMFs agree with those reported in the literature for MMFs that stream out from spots with penumbrae. Moreover, observations of at least two of the observed features suggest them to be manifestations of emerging magnetic arches.