Accessible Pore Size Research Articles

Large-Scale Computational Screening-Aided Development of High-Performance Adsorbent for Simultaneous Capture of Aromatic Volatile Organic Compounds.

The development of an efficient adsorbent for the simultaneous capture of large amounts of benzene, toluene, ethylbenzene, and xylene isomers (BTEX) is an important and challenging issue. Here, through a stepwise screening of 10,142 metal-organic framework (MOF) structures from the computation-ready, experimental (CoRE) MOF database, 65 MOFs are proposed as promising adsorbent candidates for BTEX capture by considering the structures with accessible pore sizes for BTEX adsorption, sufficient hydrophobicity, high benzene selectivity (>0.2), and large total BTEX uptake (>3 mmol/g). Among the top-performing MOFs in terms of the BTEXmatrix (total BTEX uptake × benzene selectivity), EGUELUY01 was synthesized, and it exhibited large uptakes (≈5 mmol/g) for all BTEX components at concentrations of 1200-1500 ppm, which are superior to the BTEX uptake of the benchmark adsorbent, activated carbon. Moreover, some structure-property relationships required for BTEX adsorbents are provided through the obtained large-scale simulation data and machine learning analysis. The determined relationships will be useful for the future development of efficient BTEX adsorbents.

Large-pore covalent organic framework as solid phase extraction absorbentforefficientdetermination of polypeptide antibiotics in animal-derived foods

The precise determination of polypeptide antibiotics (PPTs) in foods has been always challenging because of the interference of various endogenous peptides in complex matrix. Herin, a novel large-pore covalent organic framework (TABPT-SPDA-COF) with accessible pore size of 7.9 nm was synthesized as a solid phase extraction (SPE) absorbent for efficiently enriching four PPTs existed in foods originating from animals. The parameters of SPE process were systematically optimized. Subsequently, four PPTs were determined by UHPLC-MS/MS. Under the optimal conditions, TABPT-SPDA-COF shows outstanding enrichment capacity for PPTs in contrast to commercial absorbents ascribed to size selectivity and multiple interaction effects. The method exhibits excellent linear range (0.005–100 ng mL−1), satisfactory limits of detection (0.1 pg mL–1) as well as relative recoveries (86.2–116 %). This work offers a practicable platform to monitor trace PPTs from complex animal-derived foodstuffs.

Molecular Simulations of the Gas Diffusion through the Two-Dimensional Graphyne Membrane

Owing to the unified and tunable pore size, two-dimensional graphyne membranes show excellent performance in the realm of gas transport and separations. The impacts of environmental conditions on the pore size of a porous membrane are ignored in previous studies. Using molecular modeling techniques, we here probe the accessible pore size of the γ-graphyne membrane under various pressure and temperature conditions. First, by assessing the gas permeation through the two-dimensional γ-graphyne membrane at a constant temperature, the accessible pore size of this membrane is shown to be proportional to the driving force—the pressure difference between the two sides of the porous membrane. Such a driving force dependence is found to be well described by a simple asymptotic model. Then, by determining such pressure dependence at two different temperatures, temperature is found to show a weak influence on the accessible pore size. Finally, by considering the binary mixed gases of various mole fractions, the accessible pore size measured using one of the two species is shown to be dependent on its partial pressure difference. These findings for the accessible pore size, which highlight the tunable pore size by altering the driving force, can be expected to provide a practical strategy to rationalize/refine the pore size of the porous membrane for gas transport and separations, especially for two molecules with similar diameters.

Production of demineralised high quality hierarchical activated carbon from lignite and determination of adsorption performance using methylene blue and p-nitrophenol: The role of surface functionality, accessible pore size and surface area

In the adsorption process, the surface area, pore and particle size distribution and the chemical structure of the solid and the type of adsorbent are of vital importance. Activated carbon (AC) is a very good adsorbent material and its cost is highly dependent on the starting material and production method. The pore size and functional structure of the surface depend on the amount of activation chemical used. Hierarchical ACs were produced from lignite by loading two different amounts of KOH. The impregnation ratio (KOH/lignite) was chosen as 1/1 and 3/1 and the produced ACs were labelled as AC1 and AC3. The surface areas of AC1 and AC3 were determined as 1321.3 and 2421.3 m2/g, and the total pore volumes were 1.079 and 1.425 cm3/g. Methylene blue (MB) and p-nitrophenol (p-NP) were used to determine the adsorption performance of the produced ACs. The adsorption data were evaluated in terms of the Langmuir and Freundlich models. The amounts of MB and p-NP adsorbed on the surface were calculated in mg/g, total and accessible surface area in mg/m2. It was determined that the MB and p-NP adsorbed to the AC1 sample were higher than the AC3 sample per m2 of population. Molecular orientation is possible depending on the solid surface functionality and chemical structure of the molecule to be adsorbed. It was concluded that in addition to the large surface area, the pore width that can be entered and the functional structure of the surface are very significant factors in the adsorption processes.

Potentiality of the porous geopolymer sphere in adsorption of Pb (II) from aqueous solutions: Behaviors and mechanisms

In this study, a porous geopolymer sphere (PGS) was developed that comprised a mixture of coal gasification fly ash, steel slag, metakaolin and an alkaline activator (SiO 2 /Na 2 O molar ratio = 1.33) (44.89 wt%, 20.10 wt%, 2.01 wt% and 33 wt%) using an 8.5 wt% hydrogen peroxide foaming agent. The micro characteristics of the PGS were tested using X-ray CT, BET, XRD, and FT-TR. The mechanism to Pb adsorption was revealed via adsorption isotherm, adsorption kinetics, thermodynamics, and adsorbent characterization. Results indicated that the PGS was a mesoporous structure (the most accessible pore sizes was 9.31 nm) and the main crystalline phases in the PGS were ZK-5 zeolite, vaterite, calcium silicate, and wustite. Batch experiments showed that the adsorption of Pb by the PGS was best described by pseudo-second-order kinetics and the Langmuir isotherm model, indicating that the adsorption process was dominated by chemical adsorption. Moreover, the maximum adsorption capacity of the PGS could reach 59.31 mg/g. The mechanism of Pb(II) adsorption using the PGS mainly involves: (1) ion exchange, (2) a complexation reaction between Pb and the PGS, (3) lattice immobilization of Pb and in the ZK-5 zeolite and zeolite-like phase, (4) physical adsorption by the PGS.

Pyrene-based covalent organic framework for selective enrichment of hydrophobic peptides with simultaneous proteins exclusion

Owing to the desirable structures, covalent organic frameworks (COFs) have emerged as promising porous crystalline materials in bioanalytical and biomedical science. However, the application of their merits for analysis of hydrophobic peptides in complicated bio-samples has not been well investigated, possibly due to challenges in developing materials with high-specific binding effect of target peptides and accurate controllable pore-size for high selectivity. In this study, we proposed the size-exclusive peptide enrichment with Azo-COF constructed from 1,3,6,8-tetrabromopyrene (TBPy) building block and p-azoaniline linking units. The as-synthesized sieve-like COFs show high surface area together with accessible nanometer pore size (∼2.5 nm). With these advantages, specific enrichment of hydrophobic peptides using Azo-COF can be achieved by simply packing them in a 100 μL Axygen pipette tip. A maximum capacity of 36 mg g−1 for FGFGF was obtained, which is more than a magnitude order larger than those of hydrophilic peptides. Furthermore, this method was successfully applied in analysis of hydrophobic peptides in tryptic digest of proteins and real human serum samples, indicating that the proposed method is promising for high-selective peptides enrichment from complex biological samples, and is of great value for further application of the functional materials in bioanalysis.

Acyclic pore model and its applications in imbibition efficiency calculation

The classical pore structure conceptual model, such as a bundle of capillaries and lattice model is challenged for applicability in unconventional reservoirs, due to the micro/nano pore scale in unconventional reservoirs, with most of them below 100nm. Meanwhile, it is important to obtain an accurate evaluation of imbibition efficiency in unconventional reservoirs since imbibition is the main method for sweeping oil in matrix. This paper improves the acyclic pore model which is more practical for unconventional reservoirs. An imbibition efficiency calculation method is proposed, the effects of bifurcation number, pore throat radii corresponding to a mercury saturation of 50% (r50) and wettability is studied. The mechanism about how the pore structure affects imbibition performance is revealed. Results show that the increment of bifurcation number can decelerate the imbibition time in the branch level with smaller diameter, enlarges the imbibition accessible pore size as well. As r50 and hydrophilic saturation increase, wetting fluid volume imbibed and driving force for imbibition is also enhanced, which results in an improvement of imbibition efficiency.

Screening of zeolites for H2S adsorption in mixed gases: GCMC and DFT simulations

Zeolites with high Si/Al ratio are widely used in industrial desulfurization process because of their stability and hydrophobicity as adsorbents. However, the method to design a practical zeolites and the kinetics of competitive adsorption in multicomponent systems still remain to be studied. The adsorption capacity of H2S in 36 all-silica zeolites with different accessible area and pore size was calculated by the Grand Canonical Monte Carlo (GCMC) method. Identical method was used to simulate the adsorption behavior of H2S in the 5 widely used all-silica zeolites (CHA, BEA, MFI, LTA, FAU). Further, the adsorption properties of H2S in metal-modified SSZ was investigated using the Density Functional Theory (DFT) method. The simulation results display that the zeolites with a pore size of 7–9 Å and a higher accessible area tend to exhibit efficient adsorption at 313 K and atmospheric pressure. For pure H2S component, CHA adsorbs most H2S molecules at atmospheric pressure while FAU are more attractive for removal of H2S at saturation pressure. FAU shows a strong preferential adsorption on H2S in the presence of CO, CO2, H2O and N2. In addition, the Co-SSZ obtained by doping Co on CHA is the most promising adsorbent in this research.

Mineralogy, microfabric and pore evolution in late-middle Ordovician mudstone of the Utica/Point Pleasant sub-basin of Ohio, West Virginia, and Pennsylvania

The Utica/Point Pleasant Formations comprise a major unconventional gas resource in the Appalachian Basin. Core samples from several boreholes in Ohio, West Virginia and Pennsylvania were studied to determine mineralogy, microtexture/microfabric, accessible pore surface area, porosity and pore size distribution as a function of maturity in the Utica/Point Pleasant sub-basin. This effort compares shallower, generally more phyllosilicate-rich Utica intervals with deeper, more carbonate-rich Point Pleasant intervals, the latter representative of horizons currently targeted for gas recovery. The Point Pleasant Formation contains mostly calcite (in the form of fossil tests, grains, and cements), distributed within alternating carbonate- and phyllosilicate-rich matrix laminae, as well as coarse-grained fossil-rich laminae. In both Utica and Point Pleasant core samples, the greatest mercury-accessible connected porosity measurements are associated with the highest maturity samples, an observation that is particularly pronounced for the Point Pleasant. More detailed vertical sampling and analysis of core from a well in Harrison County, Ohio (a region that has experienced copious shale gas production) shows that surface area, pore volume and pore connectivity increase locally in target horizons identified for gas recovery. Observations suggest that optimal mixtures and arrangements of minerals and organic matter, as well as increasing maturity, contribute to forming this productive carbonate-rich unconventional resource. In particular, early diagenetic calcite and quartz cement and increasing quantities of silt-sized particles are associated with higher measured connected porosities, while later-stage matrix dolomitization and recrystallization of fossil laminae tend to occlude the pore network.

Design of Graphene/Ionic Liquid Composites for Carbon Capture.

Pore size is a crucial factor impacting gas separation in porous separation materials, but how to control the pore size to optimize the separation performance remains a challenge. Here, we propose a design of graphene/ionic liquid composites with tunable slit pore sizes, where cations and anions of ionic liquids are intercalated between graphene layers. By varying the sizes of the ions, we show from first-principles density functional theory calculations that the accessible pore size can be tuned from 3.4 to 6.0 Å. Grand canonical Monte Carlo simulations of gas sorption find that the composite materials possess high CO2 uptake at room temperature and 1 bar (up to ∼8.5 mmol/g). Further simulations of the sorption of gas mixtures reveal that high CO2/N2 and CO2/CH4 adsorption selectivities can be obtained when the accessible pore size is <5 Å. This work suggests a new strategy to achieve tunable pore sizes via the graphene/IL composites for highly selective CO2/N2 and CO2/CH4 adsorption.

Characterisation of the absolute accessible volume of porous materials

We presented a new characterization method for surface area, pore volume and pore size distribution of a solid based on the recently proposed concept of absolute accessible volume (Prasetyo et al. 2018). This method provides a coherent framework to characterize nanoporous atomic models. It gives an advantage over earlier methods in the sense that the accessible properties, volume, surface area and pore size distribution, follow a single set of rules that are based on the energy of interaction between a molecular probe and the solid. The derived parameters result in the Henry constant and the differential heat of adsorption approaching zero at extremely high temperatures as physically demanded, and we illustrated this new method with a range of porous solids.

Effects of elevated temperature on the tensile properties of NS-modified self-consolidating engineered cementitious composites and property optimization using response surface methodology (RSM)

Abstract This paper discusses the influence of elevated temperature on the tensile properties (tensile strength, tensile strain, and energy absorption) and microstructure of nano-silica-modified self-consolidating engineered cementitious composites (NS-modified SC-ECC) mixtures. Response surface methodology (RSM) was utilized to develop a design matrix and predictive models and to perform multi-objective optimization for a matrix of mixtures prepared with polyvinyl alcohol (PVA) fiber at 0.5%, 1%, 1.5%, and 2% volume fractions and NS at 0%, 1%, 2%, 3%, and 4% of the weight of cementitious materials at temperatures of 23 °C, 100 °C, 200 °C, 300 °C, and 400 °C. To investigate the influence of elevated temperature on the certain characteristics of NS-modified SC-ECC mixtures, residual compressive strength, tensile properties, and microstructure properties were assessed at elevated temperatures of up to 400 °C for 1 h. Microstructure was examined using scanning electron microscopy before and after the mixtures had been exposed to elevated temperatures; accessible porosity and pore size distribution with cumulative pore volume were measured using mercury intrusion porosity (MIP) to validate the behaviors of the tensile properties and compressive strength of NS-modified SC-ECC mixtures. The results show that the tensile properties of the NS-modified SC-ECC mixtures improve due to pozzolanic reactivity of NS by utilizing the calcium hydroxide (CH) released from cement hydration to produce more calcium-silicate-hydrate (C-S-H) gel, which refines the fiber-matrix and aggregates-matrix interfacial transition zones (ITZ). The pozzolanic reactivity is further facilitated by temperature curing to produce more C-S-H gel, improving the fiber-matrix interactions at elevated temperatures of up to 200 °C. The PVA fiber improves the elevated temperature behavior of the mixtures and prevents explosive spalling behavior even after the incorporation of 2% NS with a PVA fiber volume of up to 2%. The responses considered in the RSM were tensile strength, tensile strain, and energy absorption. The established models showed high degrees of correlation between the responses and independent variables. Optimized tensile properties could be achieved at 2% PVA fiber volume, 1.3% NS, and a temperature of 125.7 °C. The measured absolute deviations (error) between the experimental data and the theoretical (predicted) models’ results for tensile strength, tensile strain, and energy absorption were 2.83%, 4.4%, and 1.68%, respectively.

Selective Synthesis and Characterization of Single Walled Carbon Nanotubes (11, 8)

Single walled carbon nanotubes (SWCNTs) are attractive in the nanotechnology industry where they find applications in the field of pharmacy and medicine due to high surface area capable of transporting drugs and vaccines to active sites; for fabrication of energy storing devices due to excellent electrical conductivity and accessible pore sizes; in transport for the fabrication of strong and lightweight vehicle and aircraft parts and in composite materials to enhance physical and chemical properties such as toughness, durability, conductivity and strength. The most efficient and cost effective method of obtaining these precious materials is the Chemical Vapour Deposition (CVD), however, obtaining SWCNTs of desired electronic type via this method, has remained a global challenge for over 20 years. This has limited the availability of these products in the global research and technological industries, contributing to the problem of lack of raw materials to sustain them. In this report, metallic SWCNTs (11, 8) are selectively synthesized via chemical vapor deposition (CVD) method, by the pyrolysis of C₆H₁₄/N₂ feedstock on Fe₂O₃/Al₂O₃ catalyst matrix. Catalyst design and preparation was achieved by correlating the numerical magnitudes of chiral index (n, m) of the desired SWCNTs with mole fractions of metal/support, respectively. Field emission scanning electron microscopy analysis reveals densely entangled tubular bundles, while high resolution transmission electron microscopy confirms rigid arrangements of SWCNTs in the bundles. Values of the radial breathing modes, diameter and energy band gaps of the sample obtained from Raman analysis conforms to that of SWCNTs (11, 8), established via Extended Tight Binding (ETB) model. Outcome of this report suggested that our catalyst design and preparation may help alleviate the stated global challenge.

Hierarchical porous carbon materials from nanosized metal-organic complex for high-performance symmetrical supercapacitor

The accessible surface area, conductivity, and pore size determine the capacitive properties of carbon-based materials. In this work, hierarchical nanoporous carbon (NPC) materials with a large specific surface area, high conductivity, and suitable pore size are prepared from nanoscaled Al-based metal-organic complex (Al-MOC) by annealing. The annealing temperature has a profound influence on the morphology of the NPC materials which in turn impact the electrochemical performance. Compared to annealing at a low temperature, an interconnected structure is formed at an annealing temperature exceeding 950 °C to produce a larger accessible surface area. Owing to the interconnected structure and high conductivity, sample NPC-950 with the two-electrode configuration has the highest specific capacitance and the best stability. The specific capacitances are 298 Fg-1 at a scanning rate of 1 mVs-1 in symmetrical supercapacitor device. These values are the largest values reported from ultrapure carbon-based EDLCs in an aqueous electrolyte so far. Furthermore, 96.73% of the capacity is retained after 5000 cycles in 1 M H2SO4 electrolyte. In an organic electrolyte, the supercapacitor cells composed of NPC produce an energy density of 43 Wh kg−1. The NPC materials with large specific capacity and excellent stability produced by the simple and cost effective technique have large potential in supercapacitors.

Preparation and Properties of Magnetic Hematite Core/Alumina Shell Nanospheres

Magnetic core/alumina shell (MFeCA) structured nanospheres were obtained from a hematite core/alumina precursor shell (HFeCAP) nanosphere precursor. A uniform alumina layer was coated on the surface of -Fe2O3 by the self-assembly of a stearic acid/alumina isopropoxide complex. Hematite cores of the nanospheres were then reduced under H2/N2 gas flow to produce the MFeCA nanospheres. Transmission electron microscopy images showed that the products possessed a distinct core-shell structure. N2 sorption measurements showed that the uniform accessible pore size was 5.2 nm. The surface area was 140m2/g and pore volume were 0.22 cm3/g. Saturation magnetization values indicated the product had a high degree of magnetization (50.2 emu/g).

Optimal Size of a Cylindrical Pore for Post-Combustion CO2 Capture

Pore size is an essential factor in controlling gas sorption in porous separation media. Overlap of the potential energy surface (PES) of CO2 interacting with a cylindrical pore wall can be used to tune gas sorption inside a porous material, but how such overlap can benefit post-combustion CO2 capture has not been fully addressed from a computational perspective. Here we use van der Waals density functional (vdW-DF) theory to assess the overlap of PES of CO2 inside cylindrical pores as represented by carbon nanotubes (CNTs) of different diameters. Then we employ grand-canonical Monte Carlo simulations to obtain the adsorption capacity and selectivity of a CO2/N2 mixture with a CO2 partial pressure of 0.15 atm at room temperature. We find that the maximum PES overlap and maximum amount of CO2 adsorbed are both achieved at a CNT diameter or cylindrical pore size of 7.8 A, which corresponds to an accessible pore size of 4.4 A. Further investigation of N2 adsorption corroborates the idea of PES overlap. GCMC ...

Fabrication of autofluorescent porous silica nanoparticles for redox-responsive drug release

Porous silica nanoparticles were prepared by emulsion-condensation route. The silica nanoparticles with diameter of 50nm have both accessible center-radial large pore channels (19.9nm) and small pore size of 3.5nm. The hierarchical porous structure endows them large pore volume for loading drugs and sustained release property. The silica nanoparticles were further modified with glucose-oxidized glutathione. The formulated Schiff base and disulfide bonds render the silica nanoparticles auto-fluorescent and redox-responsive properties. The cleavage of disulfide bonds caused by reactive thiols facilitates aminomethylbenzoic acid (AMA) release. The release of drug leads to the loss of fluorescence, which would be used to monitor the drug delivery and carrier distribution.

Fe3O4@mZnO nanoparticles as magnetic and microwave responsive drug carriers

Mesoporous and core–shell structure nanomaterials have attracted great attention owing to their unique characteristics and promising applications in drug delivery, and water treatment. In this paper, Fe3O4@mZnO (m was short for mesoporous) core–shell structured nanoparticles with magnetic, microwave to heat responsive properties and high specific surface area (93 m2 g−1) were synthesized by a simple template-free homogeneous precipitation method. The nanoparticles not only has the large accessible pore size (6.7 nm) for the physical adsorption of drug molecules and showed both strong magnetic and unique microwave to heat responsive properties, which may lead to development of nanoparticles with great potential for applications in drug targeting, chemo- and microwave-thermal combination therapy and water treatment.

Synthesis of magnetical microspheres with tunable large pore mesostructures

The synthesis of core–shell structured magnetic mesoporous silica particles with large pore sizes through a recently developed oil–water biphase stratification coating strategy was reported. The obtained nanoparticles exhibited spherical morphology, high surface area (347–430 m2 g−1) and easily accessible large pore size. Significantly, the pore size of the silica shells can be finely controlled to range from 5.1 to 8.4 nm through tuning the coating conditions, including reaction temperature and the concentration of silica source in the upper oil phase. Such material might have great promising applications in drug delivery, catalysis and purification of water, etc.

Effect of pore texture on performance of activated carbon supercapacitor electrodes derived from olive pits

Activated carbon electrodes for electrochemical capacitors have been prepared by the chemical activation of a natural renewable and by-product material precursor – olive pits – from the olive oil production industry. The careful adjustment of the synthesis conditions has allowed synthesizing a series of microporous carbon electrodes with an optimized microporosity, enabling a gravimetric and volumetric capacitance in basic aqueous medium up to 260Fg−1 and 140Fcm−3, respectively, with good rate capability. A relation amongst capacitance, specific surface area, accessible average pore size and effective dielectric permittivity has been established, demonstrating that there is not just a single parameter decisively impacting the capacitance value. The collective analysis of experimental data suggests that solvation imposes an optimum pore size for each ion with regard to rate capability: moderate solvation contributes to enhancing capacitance in pores slightly exceeding solvated ion size while excessive solvation deteriorates the high-rate response of supercapacitor electrodes having pores much wider than ion size.