Adsorption Of H2O Vapor Research Articles

Design, Preparation, and High Intrinsic Proton Conductivity of Two Highly Stable Hydrazone-Linked Covalent Organic Frameworks.

Assembling crystalline materials with high stability and high proton conductivity as a potential alternative to the Nafion membrane is a challenging topic in the field of energy materials. Herein, we concentrated on the creation and preparation of hydrazone-linked COFs with super-high stability to explore their proton conduction. Fortunately, two hydrazone-linked COFs, TpBth and TaBth, were solvothermally prepared by using benzene-1,3,5-tricarbohydrazide (Bth), 2,4,6-trihydroxy-benzene-1,3,5-tricarbaldehyde (Tp), and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (Ta) as monomers. Their structures were simulated by Material Studio 8.0 software and confirmed by the PXRD pattern, demonstrating a two-dimensional framework with AA packing. The presence of a large number of carbonyl groups as well as -NH-NH2- groups on the backbone is responsible for their super-high water stability as well as high water absorption capacity. AC impedance tests demonstrated a positive correlation between the water-assisted proton conductivity (σ) of the two COFs and the temperature and humidity. Under 100 °C/98% RH, the highest σ values of TpBth and TaBth can reach 2.11 × 10-4 and 0.62 × 10-5 S·cm-1, which are among the high σ values of the reported COFs. Their proton-conductive mechanisms were highlighted by structural analyses as well as N2 and H2O vapor adsorption data and activation energy values. Our systematic research affords ideas for the synthesis of proton-conducting COFs with high σ values.

A thermal-stable praseodymium(III) metal-organic framework from a naphthyl acylthiourea-carboxylate ligand: Synthesis, crystal structure and proton conductive properties

Compared with other traditional proton-conducting materials, the structures of metal-organic frameworks (MOFs) are more advantageous in terms of designability and tunability. Considering the strong and flexible coordination ability of carboxylate-based thiourea ligands, we synthesized a [3-(naphthalene-2-carbonyl)-thioureido]-acetic acid (H3L) ligand, and successfully obtained {[Pr(H2L)2(NO3)(H2O)2]·2H2O·MeOH}n (1). 1 is a 1D framework, in which the Pr(III) atoms are bridged by carboxyl oxygen, and then form a three-dimensional solid-state structure under the action of intermolecular hydrogen bonds and π-π stacking interactions. AC impedance measurements uncover that proton conductivity (σ) of 1 has a significant positive temperature and humidity dependence. The σ of MOF 1 can attain 3.41 ​× ​10−4 ​S/cm under 100 ​°C and 98% RH. In addition, the proton-conductive mechanism was discussed based on the structural analysis, H2O vapor adsorption curve and the activation energies evaluated by fitting the Arrhenius equation.

Vapor sorption behavior in heptazine-based MOF featuring a brick-shaped framework

A new porous MOF, [Mg1.5(HTB)2]·2Me2NH2·3DMF·12MeOH, (1) (HTB ​= ​s-heptazine tribenzoate) was successfully synthesized by employing a π-conjugated organic ligand possessing a brick-shaped framework. The activated 1a was investigated as an adsorbent towards a series of vapors (H2O, MeOH, EtOH, n-PrOH and CH2Cl2). The H2O vapor adsorption capacity of 1a can reach 533.9 ​cm3 ​g−1. Interesting, the absorption isotherm of MeOH shows an obvious stepwise sorption phenomenon with the saturated adsorption capacity of 300.8 ​cm3 ​g−1, whereas the bulker EtOH, n-PrOH and CH2Cl2 present hardly any uptakes. Moreover, the IAST selectivities of equimolar H2O/MeOH and H2O/EtOH vapor mixtures was calculated, GCMC simulations were performed to locate the framework-vapor binding sites.

Two stable phenyl acyl thiourea carboxylate-based MOFs: Syntheses, crystal structures and proton conductive properties

The phenyl-substituted acylthiourea-carboxylic acid ligand has several coordination sites and strong coordination ability. The MOFs constructed by these ligands are flexible and stable, which is very beneficial to the study of proton conductivity. In this paper, we designed and synthesized two MOFs, [Mn(H2BBT)2(H2O)2]n (H3BBT = N-benzoyl-N′-(4-benzoxy)thiourea) (1), and [Cd(H2BBT)2]n (2) by the solvent evaporation method. Their molecular structures were characterized by single-crystal X-ray diffraction. The high water and chemical stability of the two MOFs were confirmed by X-ray powder diffraction. The AC impedance spectra of them show that the proton conductivity increases with the increase in temperature and humidity. The best proton conductivities of 1 and 2 are 1.69 ​× ​10-5 and 1.79 ​× ​10-4 ​S ​cm-1 under 98% RH and 100 ​°C, respectively. The proton conduction mechanisms of the two MOFs were highlighted based on the calculated activation energy, structural characteristics, N2 and H2O vapor adsorption determinations, and so on.

Atmospheric water harvesting on MIL-100(Fe) upon a cyclic adsorption process

The main objective of this study was the design of an efficient adsorptive process to extract water from thin air, based on MIL-100(Fe), which is a promising material in water adsorption-related processes. Indeed, equilibrium and dynamic studies were performed to evaluate the suitability of this adsorbent. CO2, N2, and O2 adsorption equilibrium isotherms were measured at three different temperatures, and CO2 was the gas that presented a higher affinity towards MIL-100(Fe). H2O adsorption equilibrium isotherms follow a Type VI isotherm, showing two steps (0.21 < P/Po < 0.30 and 0.36 < P/Po < 0.40) attributed to the presence of two different cavities (25 and 29 Å) on its structure. The obtained data were regressed against adsorption equilibrium isotherm models (Langmuir model, Dual Ising-Single Langmuir model, and Polanyi's potential theory). The H2O adsorption dynamic behavior was in agreement with the expected from the H2O vapor adsorption equilibrium isotherms. Furthermore, the dynamic adsorption behavior of water adsorption in fixed-bed experiments was well predicted by the developed model. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) analysis revealed a high regeneration capability during the adsorption/desorption cycles. Additionally, the structure remains stable during the water vapor contact and after exposure at different temperatures. Temperature Swing Adsorption (TSA) process, with a column volume of 0.35 m3, allowed maximum H2O productivity of 86.8 l·day−1 for MIL-100(Fe).

High Proton Conduction in Two Highly Water-Stable Lanthanide Coordination Polymers from a Triazole Multicarboxylate Ligand.

Two lanthanide coordination polymers (CPs) {[Er(Hmtbd)(H2mtbd)(H2O)3]·2H2O}n (1) and [Yb(Hmtbd)(H2mtbd)(H2O)3]n (2) carrying an N-heterocyclic carboxylate ligand 5-(3-methylformate-1H-1,2,4-triazole-1-methyl)benzen-1,3-dicarboxylate (H3mtbd) were prepared under solvothermal conditions. The single-crystal X-ray diffraction data demonstrate that 1 and 2 are isostructural and display 1D chain structure. Alternating current (AC) impedance measurements illustrate that the highest proton conductivities of 1 and 2 can attain 5.09 × 10-3 and 3.09 × 10-3 S·cm-1 at 100 °C and 98% relative humidity (RH), respectively. The value of 1 exceeds those of most reported lanthanide-based crystalline materials and ranks second among the described Er-CPs under similar conditions, whereas the value for 2 is the highest proton conductivity among the previous Yb-CPs. Coupled with the structural analyses of the two CPs and H2O vapor adsorption, the calculated Ea values help to deduce their proton conductive mechanisms. Notably, the N-heterocyclic units (triazole), carboxyl, and hydrogen-bonding network all play key roles in the proton-transfer process. The prominent proton conductive abilities of both CPs show great promise as efficient proton conductors.

A Series of Metal–Organic Frameworks: Syntheses, Structures and Luminescent Detection, Gas Adsorption, Magnetic Properties

Six metal–organic frameworks of [Cd2(L)2(mmpa)2]·6H2O (1), [Mn2(L)2(mmpa)2]·L·2H2O (2), [Zn(L)(NO2 mbda)]·H2O (3), [Cu(L)(NO2 mbda)] (4), [Co3(L)2(BTC)2(H2O)4]·H2O (5), and [Co3(L)2(OBTC)2(H2O)2] (6) were prepared based on different metal salts and the mixed ligands including the N-heterocyclic 1-(4-(1H-imidazol-5-yl)phenyl)-1H-1,2,4-triazole (L) ligand and auxiliary carboxylic acids of 5-methylisophthalic acid (H2 mmpa), 5-nitroisophthalic acid (H2NO2 mbda), trimesuc acid (H3BTC), and 1,2,3-benzenetricarboxylic acid (H3OBTC). MOFs 1 and 2 are isomorphous and isostructural, and both are binodal 4-connected CdS network based on Cd2(COO)2 binuclear secondary building unit (SBU). Compound 3 is a 2D → 3D “polycatenated network” because of its mutual interpenetration between two-dimensional (2D) corrugated (4, 4) layers, while 4 is a sql network on the basis of binuclear [Cu2(COO)2] SBUs. Compound 5 is a trinodal (3, 4)-connected rare nor-3,4-C2/m 3-fold interpenetrated net, while 6 is a 4-connected 3D frl/Ferey ladder net based on L and two isomers of benzenetricarboxylic acids. Photoluminescent properties were determined for the corresponding d10 MOFs. Microporous crystalline material 1 can selectively sense nitroaromatic compounds by fluorescence quenching and show a rare luminescent sensing property for Ag+ ions in H2O solution. Also, the activated microporous material 1 can selectively adsorb CO2 over N2 and undergo H2O vapor adsorption. Furthermore, magnetostructural analyses have also shown that MOFs 2, 4, 5, and 6 consisting of the paramagnetic ions Mn(II), Cu(II)/Co(II), and carboxylate or N-heterocyclic organic molecules exhibit meaningful magnetic-exchange coupling properties.

Ultrahigh Proton Conduction in Two Highly Stable Ferrocenyl Carboxylate Frameworks

Nowadays, although research of proton conductive materials has been extended from traditional sulfonated polymers to novel crystalline solid materials such as MOFs, COFs, and HOFs, research on crystalline ferrocene-based carboxylate materials is very limited. Herein, we selected two hydrogen-bonded and π-π interactions-supported ferrocenyl carboxylate frameworks (FCFs), [FcCO(CH2)2COOH] (FCF 1) and [FcCOOH] (FCF 2) (Fc = (η5-C5H5)Fe(η5-C5H4)) to fully investigate their water-mediated proton conduction. Their excellent thermal, water, and chemical stabilities were confirmed by the means of thermogravimetric analyses, PXRD, and SEM determinations. The two FCFs indicate temperature- and humidity-dependent proton conductive features. Intriguingly, their ultrahigh proton conductivities are 1.17 × 10-1 and 1.01 × 10-2 S/cm, respectively, under 100 °C and 98% RH, which not only are comparable to the commercial Nafion membranes but also rank among the highest performing MOFs, HOFs, and COFs ever described. On the basis of the structural analysis, calculated Ea value, H2O vapor adsorption, PXRD, and SEM measurements, reasonable conduction mechanisms are highlighted. Our research provides a novel inspiration for finding new high proton conducting crystalline solid materials. Importantly, the outstanding conducting performance of 1 and 2 suggests their, hopefully, potential in fuel cells and related electrochemical fields.

An unsymmetrical tritopic pyrazole carboxylate ligand based porous Cd(II) MOF sensor for acetone molecule

A Cd(II) based novel 3D porous MOF, {[Cd4(L)4(NO3)3(H2O)3]∙8DMF∙H2O∙NO3}n (1) (where, L = 4-(3,5-di(pyridin-4-yl)-1H-pyrazol-1-yl)benzoic acid) is reported. Compound 1 features open N sites and 6,3 connected net with ant/anatase topology having nano sized cavities in the 2D sheet structure which are masked by the adjacent layers stacked in a slipped manner in 3D packing. The open voids in 1 are occupied by DMF and water solvent molecules that constitute 46% of the total volume of crystal. Compound 1 exhibits selective H2O vapor adsorption over methanol and ethanol solvents. Its solid state luminescent property demonstrates that it can selectively detect acetone molecules on the basis of fluorescence quenching mechanism among several other solvent molecules.

Organic template-free synthesis of high-quality CHA type zeolite membranes for carbon dioxide separation

Microporous chabazite (CHA) zeolite is very promising for CO2 capture because of its appropriate pores with molecular dimensions for the preferential adsorption of CO2 molecules. Herein, CHA type zeolite particles and membranes were prepared by using a seeded growth method in the absence of an organic structure directing agent (OSDA) or template. After substantial effort to find appropriate and reliable conditions for obtaining continuous CHA type zeolite membranes, it was recognized that the formation of these membranes is a highly sensitive function of the Si/Al ratio in the synthetic precursor. Using the appropriate Si/Al ratio of ~50, OSDA-free CHA type zeolite membranes were manufactured with high reproducibility. The resulting OSDA-free CHA type zeolite membranes showed maximum CO2/N2 and CO2/CH4 separation factors of ~12.5 ± 3.8 and ~28.8 ± 6.9, respectively, with a moderate CO2 permeance of ~1 × 10−7molm−2s−1Pa−1. Notably, under more realistic wet conditions (i.e., in the presence of H2O vapor), the separation performance at temperatures above 75°C was comparable to that obtained under dry conditions, although permeation was hindered below 50°C, apparently due to the strong adsorption of H2O vapor.

Study on the response of InAs nanowire transistors to H2O and NO2

Through studying the transfer curve of field effect transistors (FETs) and the current response at various gate voltages, we observe that the adsorption of H2O vapor and NO2 introduce opposite effect to the performance of InAs nanowire (NW) FETs compared with that in the vacuum. Although the hysteresis in the transfer curve increases in both the gases, the threshold voltage shifts negatively in H2O vapor and positively in NO2/N2 gas due to the different response mechanisms. The transconductance and the field-effect mobility of the devices do not change in H2O for both the gate voltage sweeping directions and in NO2/N2 for forward sweeping compared with that in the vacuum, probably due to the InOx layer covering the InAs NW. Importantly, current response to H2O and NO2 can be modulated by the gate voltage. Analysis suggests that the effect of H2O adsorption is to increase electron density, while the effect of NO2 adsorption is to decrease the electron density in the channel.

Truncated fractal modeling of H2O-vapor adsorption isotherms

Adsorbent–adsorbate interaction in fractal surfaces is complicated but important in soil science. The main objectives of the present work were (i) to test a truncated version of the Frankel–Halsey–Hill (FHH) model with experimental H2O-vapor adsorption data, (ii) to describe, analytically, the space filling of H2O-vapor as a function of the fractal dimension and (iii) to search for potential relationships between fractal parameters and different available soil physical and chemical attributes. We used 48 H2O-vapor adsorption isotherm data sets corresponding to light, medium and heavy alluvial soils. The truncated model fitted experimental data quite well (R2>0.98 in most cases) within the entire data range. Surface fractal dimensions (Ds) ranged from 2.18 to 2.97. This allowed us to estimate a lower bound for water adsorption while a new estimate of monolayer capacity was also considered. The surface filling was larger for higher Ds values. Model parameters correlated positively with CEC, specific surface area, clay and sand fractions. All the Ds values estimated from the truncated model were larger than those computed from its classical fractal FHH counterpart. This could mean that, while the classical FHH model is sensitive to the multilayer geometry, our truncated FHH version could be related to the monolayer geometry and the adsorbent fractal surface.

Investigation of the dynamics of the adsorption of water vapors by synthetic zeolites

1. A universal bench setup for fundamental investigations of the dynamics of adsorption in a stationary layer of sorbent for various real adsorbent-adsorbate systems was designed and constructed. With negligible modifications in the design, the setup can be converted to a system of operation with a moving or pseudoliquefied layer of sorbent. 2. The characteristic features of this setup in comparison with analogous ones are: the possibility of conducting the experiments on the same vibration-compacted layer of charge of the sorbent and of obtaining five effluent curves in this case, corresponding to different lengths of the layer of charge of the sorbent; regeneration of the adsorbent directly in the adsorber itself; automation of the recordings of the experimental results. 3. The dynamics of the adsorption of H2O vapor in a stationary layer of granulated synthetic NaA zeolite at rates of gas flow from 0.1 to 5.0 liters/min·cm2, input concentration of H2O vapor from 0.1 to 3.2 g/m3, temperature of gas flow from 20.0 to 100.0°, and sensitivity of the analyzer of water vapor 0.1 mg/m3, was investigated on the setup.

ChemInform Abstract: VARIATIONS OF HEAT OF IMMERSION OF FERRIC OXYHYDROXIDES IN WATER WITH STRUCTURAL CHANGES BY HEATING

AbstractDie Beziehung zwischen der Oberflächenaktivität von 04‐, β‐ und 7‐FeOOH und seinen Strukturänderungen beim Erhitzen wird durch Bestimmung der lmmersionswärmen in Wasser sowie der Adsorption von Wasserdampf untersucht.

Variations of Heat of Immersion of Ferric Oxyhydroxides in Water with Structural Changes by Heating

Abstract The relationship between the activity of ferric oxyhydroxides (α-, β-, and γ-FeOOH) and structural changes has been investigated by determining the heat of immersion in H2O and H2O vapor adsorption. For each ferric oxyhydroxide, the monolayer capacity of H2O adsorption and the heat of immersion decreased with the progress of transformation into α-Fe2O3. Above the transformation temperature the heat of immersion increased with the outgassing temperature. The heat of immersion of α-Fe2O3 obtained by outgassing each ferric oxyhydroxide at 400 and 500 °C increased with the accompanying increase in crystallite size. β-FeOOH showed higher heat of immersion and larger monolayer capacity per unit surface area than other ferric oxyhydroxides. It is presumed that the higher heat of immersion and larger monolayer capacity observed for β-FeOOH are ascribed to micropores in β-FeOOH crystals produced by the removal of molecular water originally contained.