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Western Hunan province and its surrounding areas are significant targets for shale gas exploration and development in southern China, where the black shale of the lower Cambrian Niutitang Formation and Wunitang Formation is extensively distributed. Geochemical analysis was conducted on the lower Cambrian black shale from a new exploration well of XAD1 located at the southeast margin of the Yangtze paraplatform, followed by a discussion on gas-bearing properties using molecular dynamics simulation. The geochemical characteristics indicate that the black shale in well XAD1 was primarily deposited in a strongly reducing marine environment, with organic matter predominantly composed of type I kerogen derived from algae. Currently, it has reached a stage of high to over maturity with limited potential for liquid hydrocarbon generation. The recovery of the original hydrocarbon generation potential shows that they are excellent source rocks and have completed the main hydrocarbon generation evolution. Despite the favorable conditions for shale gas formation observed in well XAD1, the low measured gas content within the Niutitang Formation suggests that other geological factors may have contributed to a substantial loss of shale gas. Gas adsorption simulation reveals that the maximum methane adsorption capacity (15.77 m3/t) was achieved by Niutitang shale during the late Silurian period when there was an abundant source of natural gas without any influence from CO2, H2O or other molecules. However, due to a lack of natural gas replenishment and subsequent tectonic uplift and subsidence causing variations in temperature and pressure, the methane adsorption capacity gradually decreased (to 6.56 m3/t). Furthermore, water occurrence within the shale reservoir further reduced the methane adsorption capacity (below 2 m3/t), while tectonic activities exacerbated the loss of shale gas potential within this study area. The findings indicate that the dynamic alteration of gas-bearing properties in shale reservoirs due to tectonic movements is a crucial factor influencing the success rate of shale gas exploration in the study area, provided that there are sufficient gas resources and superior reservoir conditions. [ABSTRACT FROM AUTHOR]

Selective adsorption using nanoporous materials is an efficient strategy for separating gas mixtures. In a nanoporous material, pores can exist in different shapes and can have different degrees of inter-connectivity. In recent studies, both pore connectivity and tortuosity have been found to affect the adsorption and dynamical properties of ethane and CO2 in silicalite differently. Here, using Monte Carlo simulations, we investigate if these two attributes can affect the selective adsorption of one component from a mixture of ethane and CO2 in silicalite. For this, the adsorption of an equimolar mixture of ethane and CO2 is simulated in 12 models of silicalite—SnZm (n, m = 0, 1, 2, 3 or 4; with n and m denoting, respectively, the fraction (out of 4) of straight and zigzag channels of silicalite that are available for adsorption)—differing in degrees of pore connectivity and tortuosity. The adsorption selectivity in this system is found to exhibit a reversal with the adsorption dominated by ethane at low pressures (below ~1 atm) and by CO2 at higher pressures (above ~10 atm). Pore connectivity is found to suppress the selective adsorption of CO2 at higher pressures and also shifts the selectivity reversal to higher pressures. The selectivity reversal results from a competition between the polarizability-affected adsorption at lower pressures and efficient packing at higher pressures. The efficient packing of CO2 is a compounded effect resulting from the larger effective pore volume available for CO2 due to its stronger interaction with the pore surface and smaller molecular volume. CO2 molecules show a preference to adsorb in non-tortuous pores, and this preference is found to be stronger in the presence of ethane. The effects of pore connectivity and tortuosity elucidated here should be applicable to a wide range of natural and engineered nanoporous materials, and this knowledge could be used to identify materials with better capability for separating and storing CO2 based on their pore attributes. [ABSTRACT FROM AUTHOR]

Doping-modified coal samples can effectively enhance the adsorption of CO2. In order to investigate the micro-mechanism of the adsorption of different gases by the synergistic effect of N/S atomic doping and functional groups in coal, the microporous constructed by N/S doping with different functional groups in coal at different temperatures and pressures were investigated based on a series of grand canonical Monte Carlo (GCMC) computational simulations. The adsorption amount, heat of adsorption, diffusion coefficient, interaction energy and relative density distribution of CO2/CH4/N2 by the model. It was found that coal samples with more N-doped carboxyl groups could adsorb CO2 better, and coal samples with more N-doped aliphatic functional groups should be selected for adsorption of CH4 and N2, and the N-COOH system had the most stable adsorption state of CO2, and the amount of N-modified coal samples adsorbed CO2 was higher than that of CH4 and N2 at the adsorption temperature of 293.15 K.The diffusion coefficients of the gas molecules showed an increasing trend with the adsorption temperature, and the relative density distributions of CO2/CH4/N2 in the N-doped micropore model were larger than those in the S-doped system. These noteworthy findings provide a valuable theoretical foundation for the advancement of novel adsorbent materials.

The effective capture of iodine vapour, a potential threat of environment and human health, is crucial for efficiently managing nuclear waste gases. Herein, the adsorption property of iodine vapour on modified activated carbon fibers was investigated using adsorption experiment and simulation methods, to explain the adsorption mechanism at different scales. Preliminary results hint that the ideal adsorbent should have lower density, higher adsorption coefficient and taller poriness, and more pores between 1.6 and 1.9 nm. Compared with KOH modification, microwave modification can effectively improve the performance of activated carbon fibers for capturing iodine vapour. [ABSTRACT FROM AUTHOR]

Porous polymer metal–organic frameworks (MOFs), having the characteristics of large specific surface area, high porosity, and large drug load, are used in the field of medicine. In order to explore the feasibility of MOFs to load drugs, we have made an attempt to analyze the drug loading of MOFs at the molecular level. In order to provide sufficient theoretical support for realistic research, especially in terms of adsorption sites and the adsorption capacity, we selected five MOFs, UiO‐66, UiO‐66‐NH2, UiO‐66‐COOH, UiO‐67, and UiO‐66‐NDC, with bendamustine and 5‐Fluorouracil (5‐FU) as model drugs, and applied Grand Canonical Monte Carlo (GCMC) simulation to calculate the interaction between carrier MOFs and drug molecules, adsorption sites, isothermal adsorption lines and drug loads, and compared them with real experiments. The results showed all five MOFs to have strong interaction with drug molecules, and MOFs after adsorbing drug molecules were thermally stable. The best adsorption effect on bendamustine was found to be of UiO‐66‐COOH, with a drug loading capacity of 20.94 ± 0.99%. The best adsorption effect on 5‐FU was of UiO‐66‐NDC, with a drug loading capacity of 51.23 ± 1.09%. It has been further proven that MOFs have the potential to participate in oral administration as drug carriers, and have broad prospects in the field of biomedical applications. [ABSTRACT FROM AUTHOR]

Selective adsorption using nanoporous materials is an efficient strategy for separating gas mixtures. In a nanoporous material, pores can exist in different shapes and can have different degrees of inter-connectivity. In recent studies, both pore connectivity and tortuosity have been found to affect the adsorption and dynamical properties of ethane and CO2 in silicalite differently. Here, using Monte Carlo simulations, we investigate if these two attributes can affect the selective adsorption of one component from a mixture of ethane and CO2 in silicalite. For this, the adsorption of an equimolar mixture of ethane and CO2 is simulated in 12 models of silicalite—SnZm (n, m = 0, 1, 2, 3 or 4; with n and m denoting, respectively, the fraction (out of 4) of straight and zigzag channels of silicalite that are available for adsorption)—differing in degrees of pore connectivity and tortuosity. The adsorption selectivity in this system is found to exhibit a reversal with the adsorption dominated by ethane at low pressures (below ~1 atm) and by CO2 at higher pressures (above ~10 atm). Pore connectivity is found to suppress the selective adsorption of CO2 at higher pressures and also shifts the selectivity reversal to higher pressures. The selectivity reversal results from a competition between the polarizability-affected adsorption at lower pressures and efficient packing at higher pressures. The efficient packing of CO2 is a compounded effect resulting from the larger effective pore volume available for CO2 due to its stronger interaction with the pore surface and smaller molecular volume. CO2 molecules show a preference to adsorb in non-tortuous pores, and this preference is found to be stronger in the presence of ethane. The effects of pore connectivity and tortuosity elucidated here should be applicable to a wide range of natural and engineered nanoporous materials, and this knowledge could be used to identify materials with better capability for separating and storing CO2 based on their pore attributes.

Comparisons were made between the samples mechanochemically (MOF-5(M)) and solvothermally (MOF-5(S)) prepared for the development of efficient hydrogen storage medium. Synthesized samples were undergone structural characterization as well as adsorption equilibrium measurements of hydrogen at temperature-pressure range 77 K–87 K and 0.1–10 MPa. Grand Canonical Monte Carlo (GCMC) simulations were further conducted to study the behaviors of hydrogen molecules adsorbed on MOF-5. It shows that, besides the advantage of large scale synthesis and a lower cost, mechanochemical method respectively brings about 207% and 90.5% increments in the specific surface area and the maximum excess adsorption capacity of hydrogen at 77 K within pressure range 0–10 MPa. Results also reveal that the crystal within MOF-5(M) is regular and distributing uniformly with a mean size only one tenth of that of the MOF-5(S); at 77 K within pressure range 0–10 MPa, Toth equation can predict the adsorption equilibrium data of hydrogen on two MOF-5 samples with a mean relative error less than 1.5%. It suggests that MOF-5(M) is more promising for hydrogen storage by adsorption for practical applications. • MOF-5 mechanochemically prepared has a larger specific surface area. • Hydrogen adsorption on mechanochemically and solvothermally prepared samples. • Mechanochemically prepared samples have larger adsorption capacities of hydrogen. • Hydrogen molecules adsorbed on MOF-5 are in a quasi-liquid state. [ABSTRACT FROM AUTHOR]

This study presents a computationally guided approach for selecting covalent organic frameworks (COFs) for the selective detection of the trace ethylene carbonate (EC) vapor, a key indicator of electrolyte leakage from lithium-ion batteries (LIBs). High-throughput screening, employing grand canonical Monte Carlo (GCMC) simulation complemented by density functional theory (DFT) calculations, was used to identify potential COF candidates from the CURATED COF database. Among the screened materials, an imine COF functionalized with quaternary ammonium (QA) groups, named COF-QA-4, exhibited a high adsorption capacity (5.88 mmol/g) and selectivity of EC vapor. DFT analysis revealed strong molecular interactions driven by a partial charge transfer mechanism between EC and the COF-QA-4 framework, underpinning its superior adsorption properties. Experimental validation through chemiresistive gas sensors fabricated with COF-QA-4 demonstrated excellent sensitivity and reversibility to 1.15 ppmv of EC vapor, maintaining consistent performance over three response-recovery cycles. This work highlights the potential of computationally guided material discovery for advancing sensor technologies in LIB safety monitoring.

Identification of high-performing sorbent materials is the key step in developing energy-efficient adsorptive separation processes for ethylene production. In this work, a computational screening of metal-organic frameworks (MOFs) for the purification of ethylene from the ternary ethane/ethylene/acetylene mixture under thermodynamic equilibrium conditions is conducted. Modified evaluation metrics are proposed for an efficient description of the performance of MOFs for the ternary mixture separation. Two different separation schemes are proposed and potential MOF adsorbents are identified accordingly. Finally, the relationships between the MOF structural characteristics and its adsorption properties are discussed, which can provide valuable information for optimal MOF design. [ABSTRACT FROM AUTHOR]

Metal organic framework (MOF) are widely used in adsorption and separation due to their porous nature, high surface area, structural diversity and lower crystal density. Due to their exceptional thermal and chemical stability, Cu-based MOF are considered excellent hydrogen storage materials in the world of MOFs. Efforts to assess the effectiveness of hydrogen storage in MOFs with molecular simulation and theoretical modeling are crucial in identifying the most promising materials before extensive experiments are undertaken. In the current work, hydrogen adsorption in four copper MOFs namely, MOF-199, MOF 399, PCN-6′, and PCN-20 has been analyzed. These MOFs have a similar secondary building unit (SBU) structure, i.e., twisted boracite (tbo) topology. The Grand Canonical Monte Carlo (GCMC) simulation was carried at room temperature (298 K) as well as at cryogenic temperature (77 K) and pressures ranging from 0 to 1 bar and 0–50 bar. These temperatures and pressure were selected to comply with the conditions set by department of energy (DOE) and to perform a comparative study on hydrogen adsorption at two different temperatures. The adsorption isotherm, isosteric heat, and the adsorption sites were analyzed in all the MOFs. The findings revealed that isosteric heat influenced hydrogen uptake at low pressures, while at high pressures, porosity and surface area affected hydrogen storage capacity. PCN-6′ is considered viable material at 298 K and 77 K due to its high hydrogen uptake. [Display omitted] • The hydrogen adsorption capacity of four copper-based Metal-organic frameworks is discussed. • Grand Canonical Monte Carlo simulation is used to determine the adsorption capacities. • Simulation is carried out at ambient and cryogenic temperatures for 0–50 bar pressure. • Isosteric heat affects the adsorption at lower pressure and surface area affects the adsorption at high pressures. • PCN-6′ is considered a viable material at 298 K and 77 K due to its high hydrogen uptake. [ABSTRACT FROM AUTHOR]

A new porous metal-organic framework, [Pb5(OAc)7(nIm)3]n (1), has been successfully synthesized by employing 2-nitroimidazole ligand and Pb2+ ion. 1 contains novel the ribbon-shaped Pb-O SBU and reveals a 2D porous framework with a 1D tubular channel. Due to the existence of the electronegative O atom of nitro group and Lewis acid metal ion in the channel, 1 shows moderate CO2 adsorption uptake of 25.8 cm3 cm− 1 at 298 K and 760 mmHg, and adsorption sites are also confirmed by GCMC simulations. Moreover, the electronic structures and luminescence properties of 1 was investigated. This work displays an effective approach to enrich multifunctional porous Pb-MOFs. [ABSTRACT FROM AUTHOR]

Adsorption of fluids in nanoporous materials is important for several applications including gas storage and catalysis. The pore network in natural, as well as engineered, materials can exhibit different degrees of connectivity between pores. While this might have important implications for the sorption of fluids, the effects of pore connectivity are seldom addressed in the studies of fluid sorption. We have carried out Monte Carlo simulations of the sorption of ethane and CO2 in silicalite, a nanoporous material characterized by sub-nanometer pores of different geometries (straight and zigzag channel like pores), with varied degrees of pore connectivity. The variation in pore connectivity is achieved by selectively blocking some pores by loading them with methane molecules that are treated as a part of the rigid nanoporous matrix in the simulations. Normalized to the pore space available for adsorption, the magnitude of sorption increases with a decrease in pore connectivity. The increased adsorption in the systems where pore connections are removed by blocking them is because of additional, albeit weaker, adsorption sites provided by the blocker molecules. By selectively blocking all straight or zigzag channels, we find differences in the absorption behavior of guest molecules in these channels. [ABSTRACT FROM AUTHOR]

Constrained by the unsatisfactory physical adsorption capacity and the low carbon yield from chemical activation, practical utilization of carbon materials for CO 2 capture and separation (CCS) remains a huge challenge. Herein, we proposed a novel in-situ activation methodology to prepare a category of porous carbon monoliths in which the potassium ion activation sites are evenly introduced through acid-base reaction, contributing to the high carbon yield, abundant ultramicropores as well as rich nitrogen content. Tested at adsorption temperatures of 0, 25 and 40 °C, the as-prepared carbon monoliths display remarkable static CO 2 uptake (7.1, 5.0 and 3.7 mmol/g, respectively) and excellent selective adsorption ability in dynamic breakthrough experiment with a binary mixture of CO 2 /N 2 (68, 63 and 67, respectively). Along with the experiments, the CO 2 adsorption mechanism was determined by calculating the adsorption density and adsorption energy on slit pore with various pore sizes and surface functionalities using grand canonical Monte Carlo (GCMC) simulation. The narrow micropores can significantly and effectively increase the CO 2 adsorption capacity, while the functional groups played the second role. [Display omitted] [ABSTRACT FROM AUTHOR]

The microscopic mechanism of the competitive adsorption of CH 4 , CO 2 and N 2 in coal is the theoretical basis for enhancing coal seam gas recovery by injecting CO 2 (CO 2 -ECBM). Based on this principle, this work used Grand Canonical Monte Carlo and Molecular Dynamics to investigate the microscopic adsorption mechanism of single, binary, and ternary component gases in Wiser bituminous coal molecules. The adsorption mechanism was explored by changing gas composition and concentration. The comparison of adsorption separation coefficients suggested that CO 2 had the highest adsorption capacity, whereas N 2 had the lowest capacity. When the CO 2 concentration in the gas mixture was high, the adsorption amount was large and the adsorption separation coefficient was small. This finding indicated that high concentrations of CO 2 had negative effects on competitive adsorption. Energy changes were also evaluated. The potential energy between CO 2 and the framework was the strongest among the two other gases. The inhibition of CH 4 adsorption intensified with decreasing molar fraction of CO 2. This phenomenon was explained from the perspective of heat of adsorption. As the molar fraction of CO 2 in the adsorption system decreased, the heat of the isotherm adsorption increased. Meanwhile, the adsorption system became unstable and the capacity of CH 4 adsorption on the framework weakened. Results provide a theoretical basis for the use of CO 2 -ECBM. [Display omitted] • Molecular simulation was carried out to study the microscopic adsorption mechanism of single- and multi-gases in bituminous coal. • The greater the content of strongly adsorbed gas, the weaker the gas adsorption selectivity. • Van der Waals and electrostatic energy are the main potential energy affecting gas adsorption in coal molecules. • The energy distribution of different types and contents of gas in the adsorption system is analyzed. • Clarified the linear relationship between the heat of adsorption and the amount of adsorption. [ABSTRACT FROM AUTHOR]

Based on a new semi-rigid tridentate azole ligand, a porous metal–organic framework (MOF), {[Ni3(tmpa)2(bdc)3]·6DMF}n (1) (tmpa = tris(4-(2-methylimidazolyl)phenyl)amine, H2bdc = 1,4-benzenedicarboxylic acid) was synthesized and characterized. 1 possessing a twofold interpenetrating 3D brick-wall framework shows significant selectivity for CO2 over CH4 together with N2 and strong affinity towards CO2 due to its polar and narrow pores. Meanwhile, sorption binding sites for CO2 in 1 were determined by Grand Canonical Monte Carlo (GCMC) simulations. [ABSTRACT FROM AUTHOR]

The hydrogen uptake of a novel type of cup-stacked carbon nanotubes (CSCNTs) are investigated by the Grand Canonical Monte Carlo simulation at 298 K and 1–10 MPa. The differences of the hydrogen storage behaviors between the truncated cone of CSCNTs and the cylinder of carbon nanotubes (CNTs) are studied. The effects of apex angle and interlayer distance of the truncated cone are also considered. The simulated results show that the hydrogen uptake of the truncated cone is higher than that of the cylinder. Compared with the cylinder, the adsorbed hydrogen molecules of the truncated cone can distribute uniformly. With the decrease of apex angle, the C–H interaction becomes stronger and then the hydrogen uptake increases. CSCNTs with the interlayer distance of 7 Å have the optimum hydrogen uptake. The excessively large interlayer distance will weaken the C–H interaction and result in the decrease of hydrogen uptake. • Hydrogen molecules can be absorbed on the truncated cone uniformly. • Hydrogen uptake of the truncated cone is larger than that of the cylinder. • Truncated cone with apex angle of 19.2° has maximum hydrogen uptake. • Interlayer distance of 7 Å is optimum for the hydrogen storage of CSCNTs. [ABSTRACT FROM AUTHOR]

In order to study differences in the methane adsorption characteristics of coal pores of different metamorphic degrees, 4 nm pore structure models based on three typical coal structure models with different metamorphic degrees were constructed. Based on the molecular mechanics and dynamics theory, the adsorption characteristics of methane in different coal rank pores were simulated by the grand canonical Monte Carlo (GCMC) and molecular dynamics methods. The isothermal adsorption curve, Van der Waals energy, concentration distribution, and diffusion coefficient of methane under different conditions were analyzed and calculated. The results showed that at the same pore size, the adsorption capacity of CH4 is positively correlated with pressure and metamorphic degree of coal, and the adsorption capacity of CH4 in high metamorphic coal is more affected by temperature. The relative concentration of CH4 in high-order coal pores is low, and the relative concentration at higher temperature and pressure conditions is high. The CH4 diffusion coefficient in high-rank coal is low, corresponding to the strong Van der Waals interaction between CH4 and coal. The research results are of great significance for further exploration of the interaction mechanism between CH4 and coal with different metamorphic degrees and can provide theoretical support for the selection of gas extraction parameters.

Adsorption of fluids in nanoporous materials is important for several applications including gas storage and catalysis. The pore network in natural, as well as engineered, materials can exhibit different degrees of connectivity between pores. While this might have important implications for the sorption of fluids, the effects of pore connectivity are seldom addressed in the studies of fluid sorption. We have carried out Monte Carlo simulations of the sorption of ethane and CO2 in silicalite, a nanoporous material characterized by sub-nanometer pores of different geometries (straight and zigzag channel like pores), with varied degrees of pore connectivity. The variation in pore connectivity is achieved by selectively blocking some pores by loading them with methane molecules that are treated as a part of the rigid nanoporous matrix in the simulations. Normalized to the pore space available for adsorption, the magnitude of sorption increases with a decrease in pore connectivity. The increased adsorption in the systems where pore connections are removed by blocking them is because of additional, albeit weaker, adsorption sites provided by the blocker molecules. By selectively blocking all straight or zigzag channels, we find differences in the absorption behavior of guest molecules in these channels.

Understanding the effects of pore size on shale gas adsorption behavior is necessary for accurate evaluation of adsorbed gas content under geological conditions. Shale is a porous medium, and the pore structure of the shale reservoir is complicated, with a wide distribution of aperture sizes. Critical parameters for investigating pore size effects on shale gas adsorption behavior were determined, using Grand Canonical Monte Carlo (GCMC) simulations, and the shale gas occurrence state in varying sized kerogen pores was documented, by linking GCMC simulations to the experimental pore size distribution. It was found that using the excess adsorption estimation, in terms of per unit surface area (PUSA), which was obtained from the free gas density calculated by using the GCMC method in a bulk simulation cell, and then derived from the free volume probed by the methane, was a reasonable way of demonstrating pore size effects on shale gas adsorption behavior. The distribution profiles of both the gas density and the interaction energy, rather than their average values, could be used to reflect this pore size effect objectively. Gas density in the adsorption phase rose non-monotonically with reducing pore size, under the combined influence of the interactions' overlapping effects and the limited pore space, and the overlapping threshold was determined to be 1.24 nm for the experiments. The gas in the pores that were smaller than the overlapping threshold, which was difficult to desorb under geological pressures, accounted for approximately 40.53% of the total adsorbed gas in the kerogen. The adsorbed gas in the kerogen lay mainly (84.97%) in smaller pores (<5 nm), while the free gas was mainly located (77.70%) in larger pores (>5 nm). • Overlapping threshold (OT) is 1.8 nm for simulations and 1.24 nm for experiments. • In small pores (OT), pore size no longer affects the adsorption of shale gas. • Adsorbed gas mainly lies in pores with the size smaller than 5 nm. [ABSTRACT FROM AUTHOR]

• Flue gas adsorption on MCM-41 was simulated by GCMC method. • Simulated pure gas isotherm was in reasonable agreement with experimental data. • Selectivity of CO 2 /N 2 was computed for pure gases and in binary mixture. • Effect of impurity on CO 2 /N 2 selectivity was studied in ternary mixtures by GCMC. • Adsorption mechanism was investigated by isosteric heat of adsorption. Pure CO 2 and N 2 adsorption isotherms on MCM-41 were simulated by Grand Canonical Monte Carlo method. The results showed a reasonable agreement with literature reported data. The CO 2 /N 2 selectivity was determined for the pure phase and binary mixture. Nevertheless, competitive adsorption improved the selectivity but decreased adsorption amount of each gas. The effect of impurity on CO 2 /N 2 selectivity was also simulated in a ternary mixture in the presence of water, NO 2 , and SO 2 molecules. Also, an isosteric heat calculation and radial distribution function analysis were performed to prove that the water molecules interact more with MCM-41 than other gases. [ABSTRACT FROM AUTHOR]

Abstract Accurate characterization of methane absolute adsorption in shale nanoporous media is of great importance to the gas-in-place (GIP) estimation and well productivity. Because experimental measurement can only provide the excess adsorption, the absolute adsorption is generally converted from the excess adsorption based on the single-layer adsorption model. However, it is well known that shale has a widespread pore size distribution (PSD), ranging from sub 2-nm to hundreds of nanometers. In micropores (<2 nm), methane may have layering structures, which deviates from the commonly used adsorption model. Thus, it is necessary to take into account the varying methane adsorption behavior in micropores and mesopores and consider the PSD effect to obtain the absolute adsorption from the experimentally measured excess adsorption. In this work, we propose a number of artificially generated PSDs and study methane adsorption in each nanopore by using grand canonical Monte Carlo (GCMC) simulations. By coupling GCMC simulations and varying PSDs, we effectively model methane adsorption in nanoporous media. Based on the varying density profiles in different nanopores obtained from GCMC, we propose the corresponding methane adsorption model in each nanopore, which is applied in Ono-Kondo (OK) lattice model. By fitting the excess adsorption in nanoporous media and explicitly considering the PSD, OK model can readily obtain the absolute adsorption. In order to validate our model, 1000 sets of randomly generated PSDs are used. We find that our proposed OK model has an excellent agreement with GCMC simulation, while the commonly used method to convert the excess adsorption to the absolute adsorption without considering the PSD shows noticeable deviations. Moreover, the optimized constant adsorbed phase densities are very different from the commonly used values as 424 kg/m3 and 373 kg/m3. Our work proposes a simple, efficient and accurate empirical model to obtain the absolute adsorption in nanoporous media. This work should provide important insights into accurate characterization methane absolute adsorption and the gas-in-place estimation in shale. [ABSTRACT FROM AUTHOR]

Abstract By utilizing the 1,3,5-benzenetricarboxylic acid (H 3 btc) and the N-rich melamine (ma) as the co-ligands, a new microporous cluster-based metal-organic framework [Cu 3 (btc) 2 (ma)(H 2 O) 2 ](DMA) 4 (1) containing open metal sites and uncoordinated nitrogen atoms on the internal surface was solvothermally synthesized. The single crystal X-ray study reveals that compound 1 is built up from the {Cu 3 (ma)(COO) 6 (H 2 O) 2 } cluster-based secondary building unit (SBU) and incorporates two types of polyhedral cages in the framework, which results in 1D nanosized channels along the c axis. More importantly, the activated compound 1 exhibits not only high uptake capacity for CO 2 molecules at room temperature but also a significant selective adsorption of CO 2 over CH 4 , which may be ascribed to the proper-sized pores with high density of open metal sites as well as the amine and triazine decorated pore surroundings. Meanwhile, the Grand Canonical Monte Carlo (GCMC) simulations on CO 2 adsorption of compound 1 demonstrate that the both of the open metal sites and melamine backbone play key roles in the CO 2 binding. Graphical abstract A new cluster-based microporous metal-organic framework containing open metal sites and uncoordinated nitrogen atoms on the internal surface was solvothermally synthesized. The activated compound 1 not only exhibits high uptake capacity for CO 2 molecules at room temperature but also a significant selective adsorption of CO 2 over CH 4 at room temperature, which may be ascribed to the proper-sized pores with high density of open metal sites as well as the amine and triazine decorated pore surroundings as revealed via the GCMC simulations. Unlabelled Image Highlights • A new porous mixed-ligand Cu(II)-organic framework has been synthesized. • It is composed of polyhedral cages and nano-sized 1D channels. • It exhibits high uptake capacity for CO 2 and a significant selective adsorption of CO 2 over CH 4 at room temperature. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen storage capacity (HSC) of multilayer graphitic carbon nitride, d -g-C 3 N 4 (d is interlayer spacing), and its palladium nanocomposite, d -Pd@g-C 3 N 4 , were investigated using multiscale computational techniques including quantum mechanics calculations and grand canonical Monte Carlo (GCMC) simulation. According to the results, the volumetric HSC of 8-g-C 3 N 4 and 8-Pd@g-C 3 N 4 can reach to DOE target of 30 gH 2 /L at 177 K, 5.7 MPa, and 177 K, 4.0 MPa, respectively. The gravimetric HSC of 10-g-C 3 N 4 and 12-Pd@g-C 3 N 4 meet the DOE target of 4.5 wt% at 150 K, 3.5 MPa, and 125 K, 4.0 MPa, respectively. The incorporation of Pd atoms enhances the delivery volumetric HSC of 6-, 8-, 10-, and 12-g-C 3 N 4 by 49, 55, 129, and 146%, respectively at 177 K and 0.5 MPa. On the other hand, the incorporation of Pd atoms has a negative effect on the delivery gravimetric HSC of 6- and 8-g-C 3 N 4 and positive effect for 10- and 12-g-C 3 N 4. The estimated isostric heat, Q st , of adsorption is 5.5–8.5 kJ/mol. The maximum value of Q st for both nanoadsorbents belong to those with d = 8 Å. The structure of adsorbates and possibility of multilayer adsorption occurrence were also investigated using pair correlation functions and density profiles. Highlights • Volumetric HSC of 8-g-C 3 N 4 reached to DOE target of 30 gH 2 /L at 177 K, 5.7 MPa. • Volumetric HSC of 8-Pd@g-C 3 N 4 reached to DOE target of 30 gH 2 /L at 177 K, 4.0 MPa. • Gravimetric HSC of 10-g-C 3 N 4 met DOE target of 4.5 wt% at 150 K, 3.5 MPa. • Gravimetric HSC of 12-Pd@g-C 3 N 4 met DOE target of 4.5 wt% at 125 K, 4.0 MPa. • Pd atoms significantly enhance the delivery volumetric HSC of g-C 3 N 4. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two-stage adsorption in CSPM explored for efficient heat storage. • Salt SrCl 2 acts as moisture pump and MOF acts as a water reservoir. • Grand Canonical Monte Carlo (GCMC) simulation confirms the two-stage mechanism. • Experimental and simulation results support the two-stage sorption process. The 'two-stage adsorption mechanism' within different Composite salt porous matrix (CSPM) materials is studied for the enhancement in water sorption performance and heat storage capacities of thermochemical heat storage materials. Several Metal-Organic Frameworks (MOFs) in combination with SrCl 2 were selected as examples to study the mechanism. The simulation and experimental results indicate that within this two-stage adsorption mechanism, SrCl 2 salts function as 'moisture pumps,' rapidly capturing water from ambient and increasing humidity levels inside MOF pores, while MOFs act as 'water reservoirs,' efficiently storing water within a short timeframe. Grand Canonical Monte Carlo (GCMC) simulation confirms the two-stage sorption process, demonstrating that salts within the MOFs exhibit a stronger affinity for water molecules and the impregnation of salt in MOF composites results in additional water sorption in MOF pores, therefore enhanced water sorption performance of the composites. Experimental results also reveal that composites exhibit enhanced water sorption as the result of the two-stage adsorption, with SrCl 2 @MIL-101(Cr) showing the highest sorption enhancement, reaching 0.825 g/g within 120 min. The two-stage adsorption not only enables rapid sorption but also achieves remarkable heat storage enthalpy, where SrCl 2 @MIL-101(Cr) reaches 1462 kJ/kg with lower dehydration temperatures. Experimental results also demonstrated that the composites have a lower desorption temperature in comparison with their single components, which may be related to the two-stage desorption facilitated by the impregnated salt. The two-stage adsorption mechanism demonstrated in this study offers valuable insights for the design and optimization of porous matrices of composites for advanced thermochemical heat storage applications. [ABSTRACT FROM AUTHOR]

• A new metal-organic framework was prepared. • It showed discriminating sorption performance toward C 2 H 2 over CO 2. • The sorption mechanism was studied via GCMC simulations. Acetylene is an important industrial material for the production of acetaldehyde, acetic acid, benzene, synthetic rubber, synthetic fiber, etc., and its separation from the gas mixtures of C 2 H 2 /CO 2 is of great importance but a challenging task due to their similar physical properties and molecular sizes. In this study, taking the advantage of open-donor sites on the pore surface as the nano-traps for C 2 H 2 molecules, a new microporous metal-organic framework (MOF) formulated as {[C o 3 (OH) 2 (HCOO) 2 (CPT) 2 ](NMF) 2 (MeOH) 3 (H 2 O)} n (1 , NMF = N - methylformamide) has been prepared by virtue of a bifunctional organic ligand 4-(4H-1,2,4-triazol-4-yl)benzoic acid (HCPT), which showed discriminating sorption performance toward C 2 H 2 (113 cm3/g at 298 K and 1 bar) over CO 2 (33 cm3/g) under the same conditions. The different sorption behavior of {[C o 3 (OH) 2 (HCOO) 2 (CPT) 2 ]} n between C 2 H 2 and CO 2 results in a high uptake ration (3.4:1) and IAST selectivity (13) at 298 K and 1 bar. Furthermore, the force-field based grand canonical Monte Carlo (GCMC) simulation results demonstrate that the large electronegativity and polarizability of open O donor sites on the pore surface contribute to its high C 2 H 2 /CO 2 separation performance, leading to its more favorable C 2 H 2 uptakes than CO 2. A new microporous metal-organic framework has been prepared by virtue of a bifunctional organic ligand 4-(4H-1,2,4-triazol-4-yl)benzoic acid, which showed discriminating sorption performance toward C 2 H 2 over CO 2 under the same conditions. The different sorption behavior of {[C o 3 (OH) 2 (HCOO) 2 (CPT) 2 ]} n between C 2 H 2 and CO 2 results in a high uptake ration (3.4:1) and IAST selectivity (13) at 298 K and 1 bar. Furthermore, the force-field based grand canonical Monte Carlo (GCMC) simulation results demonstrate that the large electronegativity and polarizability of open O donor sites on the pore surface contribute to its high C 2 H 2 /CO 2 separation performance. [Display omitted] [ABSTRACT FROM AUTHOR]

Doping-modified coal samples can effectively enhance the adsorption of CO 2. In order to investigate the micro-mechanism of the adsorption of different gases by the synergistic effect of N/S atomic doping and functional groups in coal, the microporous constructed by N/S doping with different functional groups in coal at different temperatures and pressures were investigated based on a series of grand canonical Monte Carlo (GCMC) computational simulations. The adsorption amount, heat of adsorption, diffusion coefficient, interaction energy and relative density distribution of CO 2 /CH 4 /N 2 by the model. It was found that coal samples with more N-doped carboxyl groups could adsorb CO 2 better, and coal samples with more N-doped aliphatic functional groups should be selected for adsorption of CH 4 and N 2 , and the N-COOH system had the most stable adsorption state of CO 2 , and the amount of N-modified coal samples adsorbed CO 2 was higher than that of CH 4 and N 2 at the adsorption temperature of 293.15 K.The diffusion coefficients of the gas molecules showed an increasing trend with the adsorption temperature, and the relative density distributions of CO 2 /CH 4 /N 2 in the N-doped micropore model were larger than those in the S-doped system. These noteworthy findings provide a valuable theoretical foundation for the advancement of novel adsorbent materials. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of different trinuclear precursors and 5-(pyridin-4-yl)isophthalic acid (H 2 L) successfully led to four anionic ant topological MOFs as Fe 3- x M x (μ 3 -OH)(CH 3 COO) 2 (L) 2 ·(DMA + )·DMF [M = Mn(II), Fe(II), Co(II), x = 0, 1, 2 and 3], namely, NJTU-Bai79 [NJTU-Bai = Nanjing Tech University Bai's group, Mn 3 (μ 3 -OH)], NJTU-Bai80 [Fe 2 Mn(μ 3 -OH)], NJTU-Bai81 [Fe 3 (μ 3 -OH)], and NJTU-Bai82 [Fe 2 Co(μ 3 -OH)], which possess the narrow pores (2.5-6.0 Å). NJTU-Bai80-82 is able to be tuned to the neutral derivatives [NJTU-Bai80-82(-ox), ox = oxidized] with M 2+ ions oxidized to M 3+ ones in the air and the OH - ions coordinated on M 3+ ions. Very interestingly, selective CO 2 /N 2 adsorptions of NJTU-Bai80-82(-ox) are significantly enhanced with the CO 2 adsorption uptakes more than about 6 times that of NJTU-Bai79. GCMC simulations further revealed that neutral NJTU-Bai80-82(-ox) supplies more open frameworks around the -CH 3 groups at separate spaces to the CO 2 gas molecules with relatively more pores available to them after the removal of counterions. For the first time, finely tuning metal ion valences of metal clusters of ionic MOFs and making them from electrostatic to neutral were adopted for greatly improving their CO 2 capture properties, and it would provide another promising strategy for the exploration of high-performance CO 2 capture materials.

Abstract Understanding the adsorption mechanisms of different gas molecules on various minerals is crucial for accurately modelling shale gas adsorption behaviors and for objectively evaluating adsorbed gas contents under geological conditions. We simulated the adsorption behaviors of CH 4 , CO 2 and N 2 on both organic matter and inorganic minerals at 60 °C and 90 °C over a range of pressures up to 50 MPa by using the Grand Canonical Monte Carlo (GCMC) method. It has been found that both the comprehensive effect of the adsorption sites with differential adsorption capacity and the distribution density of the adsorption sites on the organic matter and inorganic mineral surfaces control the adsorption capacity in terms of per unit surface area of minerals. For individual minerals with a certain adsorption capacity in terms of per unit surface area, the specific surface area of individual minerals is the critical factor that determines the adsorption capacity in terms of per unit mass of the minerals. The interaction among gas molecules also affects the adsorption behavior slightly. We further compared the adsorption capacity among various gas molecules on both organic matter and inorganic minerals by inspecting the strength and distribution density of the adsorption sites on mineral surfaces, the specific surface area of the minerals and the interaction strength among gas molecules. These investigations allowed us to identify the key factors controlling shale gas adsorption mechanisms on different minerals, which provide some helpful insights for both of the exploration and the development of shale gas. Highlights • Both strength and density of adsorption sites control adsorption capacity of mineral surface. • Strengths of adsorption sites on clay surface are different, but similar on kerogen surface. • Specific surface area is one of the main factors controls adsorption behaviors. • Density of adsorption sites and specific surface area of kerogen are larger than that of clay. • Interactions among gas molecules also affect the adsorption behaviors. [ABSTRACT FROM AUTHOR]

The adsorption performances of chloroform (TCM), carbon disulfide (CDS), and acetone (CP) were investigated and compared over self-prepared coconut shell-derived carbon (CDC) to study the adsorption behavior and mechanism of heteroatom (Cl, S, O)-containing volatile organic compounds (VOCs). The result indicates that the adsorption capacity of three typical VOCs obeys the sequence: TCM (361 mg/g) > CDS (194 mg/g) > CP (37 mg/g). However, desorption experiments show that adsorption intensity follows the order: CDS (165 °C) > TCM (147 °C) > CP (130 °C). The influence of surface oxygen-containing functional groups over CDC on adsorption performance was also studied by temperature programmed desorption (TPD) and in situ DRIFT spectra. It is implied that carbonyl in lactone and benzoquinonyl of CDC could affect VOC adsorption intensity by conjugation effect. Furthermore, adsorption isotherms of three VOCs were obtained through Grand Canonical Monte Carlo (GCMC) simulation and then fitted by classical isothermal models. Furthermore, the total adsorption potentials are calculated by potential theory, and the result follows the order: TCM (− 2.18 kJ/mol) > CDS (− 2.1 kJ/mol) > CP (− 1.5 kJ/mol). It is believed that the effect of magnetic susceptibility (χ) is more crucial than polarizability (∂) and the distance r between the interacting molecules for the potential difference. [ABSTRACT FROM AUTHOR]

In the last three decades, the air pollution is the main problem to affecthumanhealth and the environment in China and its contaminants include SO2, NH3, H2S,NO2,NOand CO. In thiswork,we employed grand canonical Monte Carlo simulations to investigate the adsorption capability of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) for these toxic gases. Eighty-nine MOFs and COFs were studied, and top-10 adsorption materials were screened for each toxic gas at room temperature.Dependence of the adsorption performance on the geometry and constructed element of MOFs/COFs was determined and the adsorption conditions were optimised. The open metal sites have mainly influenced the adsorption of NH3, H2S, NO2 and NO. Especially, the X-DOBDC and XMOF- 74 (X = Mg, Co, Ni, Zn) series of materials containing open metal sites are all best performance for adsorption of NH3 to illustrate the importance of electrostatic interaction. Our simulation results also showed that ZnBDC and IRMOF-13 are good candidates to capture the toxic gases NH3, H2S, NO2, NO and CO. This work provides important insights in screening MOF and COF materials with satisfactory performance for toxic gas removal. [ABSTRACT FROM AUTHOR]

Understanding the adsorption behaviors of supercritical fluid in confined space is pivotal for coupling the supercritical technology and the membrane separation technology. Based on grand canonical Monte Carlo simulations, the adsorption behaviors of a Lennard-Jones (LJ) fluid in slit-like pores at reduced temperatures over the critical temperature, T c *  = 1.312, are investigated; and impacts of the wall-fluid interactions, the pore width, and the temperature are taken into account. It is found that even if under supercritical conditions, the LJ fluid can undergo a “vapor-liquid phase transition” in confined space, i.e. , the adsorption density undergoes a sudden increase with the bulk density. A greater wall-fluid attractive potential, a smaller pore width, and a lower temperature will bring about a stronger confinement effect. Besides, the adsorption pressure reaches a local minimum when the bulk density equals to a certain value, independent of the wall-fluid potential or pore width. The insights in this work have both practical and theoretical significances. [ABSTRACT FROM AUTHOR]

Metal-organic framework material MOF-199 is a new type of adsorption material for removal toxic H2S. In this work, the effects of temperature and pressure on the performance of H2S adsorption in MOF-199 were studied by using the grand canonical Monte Carlo (GCMC) simulation; the interaction mechanism between framework atoms of MOF-199 and guest H2S molecules were further discussed through density functional theory (DFT) calculations. It is found that the MOF-199 adsorption capacity towards H2S decreases with increasing temperature and increases with increasing pressure. At low pressures, the frameworks containing the binding sites of copper dimers and trimesic acid are the main factor affecting the adsorption performance of MOF-199. While at high pressures, the free volume of MOF-199 contributes to the adsorption capacity as well. The adsorptive interactions between H2S and the organic ligand are weak (>− 14.469 kJ/mol). When H2S adsorption on the Cu-Cu bridge, the binding energies of the modes where hydrogen is put inward of the copper dimer are generally smaller than that where hydrogen is outward, whereas the adsorption on the top of copper ion shows the smallest BEs value (<− 50 kJ/mol) due to its tendency of forming a saturated six-coordinated configuration. [ABSTRACT FROM AUTHOR]

Molecular diffusion is commonly found to slow down with increasing molecular size. Deviations from this pattern occur in some host materials with pore sizes approaching the diameters of the guest molecules. A variety of theoretical models have been suggested to explain deviations from this pattern, but robust experimental data are scarcely available. Here, we present such data, obtained by monitoring the chain length dependence of the uptake of n-alkanes in the zeolitic imidazolate framework ZIF-4. A monotonic decrease in diffusivity from ethane to n-butane was observed, followed by an increase for n-pentane, and another decrease for n-hexane. This observation was confirmed by uptake measurements with n-butane/n-pentane mixtures, which yield faster uptake of n-pentane. Further evidence is provided by the observation of overshooting effects, i.e., by transient n-pentane concentrations exceeding the (eventually attained) equilibrium value. Accompanying grand canonical Monte Carlo simulations reveal, for the larger n-alkanes, significant differences between the adsorbed and gas phase molecular configurations, indicating strong confinement effects within ZIF-4, which, with increasing chain length, may be expected to give rise to configurational shifts facilitating molecular propagation at particular chain lengths. [ABSTRACT FROM AUTHOR]

A model based on the Generalized van der Waals partition function is derived to predict the adsorption of square-well fluid in slit pores of any size, the walls of which also have square-well potential. The space inside the pore is divided into several regions based on the extent of the attractive regions generated by the walls. Closed-form expressions of the chemical potentials of the confined fluid in different regions in the pore are obtained. The densities of fluid in different regions are calculated by equalizing the chemical potentials of fluid in those regions to that of the bulk phase. To examine the accuracy of the model, the Grand Canonical Monte Carlo (GCMC) simulation is also conducted. We find that the model well captures the effects of the bulk conditions and the properties of adsorbate and pore on the density of adsorbate in the pore. The model is also shown to be able to predict the adsorption of real gases in various activated carbons. [ABSTRACT FROM AUTHOR]

A good consistence between the grand canonical Monte Carlo (GCMC) simulation results and the adsorption experimental measurements is an important precondition to reveal the shale gas adsorption mechanisms by the GCMC method. To better link the simulations and the experiments, we investigated the expression of the excess adsorption amount and the reasonability of selecting the critical parameters by performing the GCMC simulations of CH 4 in the Na-Montmorillonite simulation cell with the pore size of 4 nm at the temperature of 90 °C under varying pressures. It is found that the excess adsorption amount in the nanopore in the simulations and between the simulations and the experiments are comparable by expressing it in per unit surface area of the adsorbent. The accessible volume probed by the corresponding gas molecule is the theoretical value of the free volume, and the determination of the bulk gas density from the GCMC method, which keeps the same method with the calculation of the absolute loading number of gas molecules, will eliminate the system error. We expect the findings are useful in the further investigation on the shale gas adsorption mechanisms by combing the GCMC simulations and the adsorption experiments. [ABSTRACT FROM AUTHOR]

To explore the adsorption and separation properties of CO2 in a novel material consisting of a series of polyoxometalates (POMs) impregnated within supramolecular porous catenane (shorted as SPC), grand canonical Monte Carlo (GCMC) simulations and ab initio calculations were used. GCMC simulations showed this impregnation can enhance CO2/CH4 (or CO2/N2) selectivity almost 30 times compared to the bare SPC due to the strong interaction of CO2 with the nPOMs@SPC structures. And, the loading of CO2 inhibits the adsorption of CH4 (or N2) as CO2 occupying the preferred adsorption sites. Furthermore, the effect of number, mass, and volume of POMs inserted in SPC on CO2/CH4 (or CO2/N2) selectivity over large pressure range was investigated in detail. Additionally, the accurate ab initio calculations further confirmed our GCMC simulations. As a result, the proposed nPOMs@SPC structures are promising candidates for CO2/N2 and CO2/CH4 separations. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

[Display omitted] • We believe that four aspects of this manuscript will make it interesting to general readers of your journal: • The occupancy isotherms of three mixed systems with different compositions are studied by using GCMC + MD method. • The thermodynamics calculation is employed to explore the phase equilibria of hydrates in two-component gas. • The abundance ratio of mixed gas CO 2 + X varies with the mole fractions of impurity gases and pressure. • HBGS technology can effectively separate mixed gas CO 2 + X was elucidated. As a remedy for air pollution caused by flue gas, Hydrate Based Gas Separation (HBGS) technology is under development. Among many issues in HBGS, the prediction for the adsorption and dissociation conditions of hydrate and the impact from mixed gas on the formation of carbon dioxide hydrate are crucial to understand the sequestration and separation of CO 2. In this work, the occupancy isotherms of the mixed systems of CO 2 + H 2 S, CO 2 + SO 2 and CO 2 + N 2 O with different mole fractions of H 2 S, SO 2 and N 2 O in sI and sII hydrates are examined. The results show that X (H 2 S, SO 2 and N 2 O) in flue gases can increase the absorption of mixed gas; CO 2 + H 2 S in the sI and sII hydrates can be categorized as the one-site Langmuir type. The calculated abundance ratio of CO 2 to X vary with the mole fraction of impurity gas and pressure, which provide the prerequisite information for prediction of gas recovery yield at different conditions during the CO 2 + X gas separate process. The phase equilibria of clathrate hydrates of mixed gases are predicted and the hydration numbers are determined. The results show that the dissociation pressure of mixed hydrates decreases as the impurity gas mole fraction increases, indicating that SO 2 , H 2 S and N 2 O gases can all promote the formation of CO 2 hydrate. Additionally, inspection indicates that the mixed flue gas can be efficiently separate by clathrate hydrate. [ABSTRACT FROM AUTHOR]

• Microstructures of the outcrop/core kerogen were systematically characterized. • Differences in chemical structure between the outcrop/core kerogen were identified. • Realistic 2D/3D molecular models of the outcrop/core kerogen were constructed. • Validity of the proposed molecular models was verified by gravimetric adsorption. • Effect of the kerogen microstructure on CH 4 adsorption behavior was investigated. It has been known that adsorbed gas, mainly CH 4 , serves as the dominant source of shale gas yield in the middle and later stages of reservoir exploitation. Therefore, it is of great significance to study the microstructure of kerogen (organic matter rich in shale) and its effect on CH 4 adsorption characteristics. In this paper, for the first time, a comparative study was conducted to experimentally characterize the microstructure of both outcrop and core kerogen samples from Longmaxi Shale, Sichuan Basin, SW China, using 13C NMR, FTIR, and XPS. Great differences in the chemical structure such as carbon skeleton (e.g. , aromaticity, aliphatic branch) and heteroatoms (e.g. , distribution and proportion of various types of functional groups) between the two kerogen samples have been identified. Molecular models of the outcrop and core kerogen samples were constructed based on the experimental data, that is, C 237 H 219 O 21 N 5 S 4 for the former and C 239 H 175 O 27 N 5 S 4 for the latter. CH 4 adsorption isotherms obtained from gravimetric adsorption test and molecular simulation using proposed kerogen molecular models are in reasonable agreement with each other, especially at low-pressure range. Interestingly, the adsorption capacity of CH 4 in the core sample is found higher than that in the outcrop sample under the same condition, indicating the effect of kerogen microstructure on CH 4 adsorption behavior. As a result, to precisely evaluate the adsorbed gas content in shale gas reservoirs, it is strongly recommended to use a core sample rather than an outcrop sample. [ABSTRACT FROM AUTHOR]

[Display omitted] • Design high thermally and chemically stable Ni2+-MOF; • Multi accessible adsorption sites with good gas uptake capacity; • Favorable selectivity for binary mixtures by breakthrough experiments; • The synergistic host–guest interactions confirmed by GCMC simulation. Metal-organic frameworks (MOFs), a type of designable porous materials, are effectively employed to realize light hydrocarbons storage and separation in favor of energy conservation and environmental protection, superior to traditional separation technology. Significantly, a novel MOF, Ni 2 (L) 2 (HCOO) 2 ·4H 2 O (1) has been constructed from a bifunctional group ligand of 3-hydroxy-4-(4 H -1,2,4-triazol-4-yl) benzoic acid ligand (HL). MOF 1 possesses stable porous structure with narrow channels functionalized with multiple accessible adsorption sites of hydroxy group, carboxyl oxygen atoms from the L− and HCOO−, exhibiting a well trade-off between good capacity and selectivity for light hydrocarbons. The single-component sorption isotherm results of Ni2+ based MOF not only shows good gas sorption capacity for light hydrocarbons of C 2 H 2 , C 2 H 6 , C 2 H 4 , C 3 H 8 , and greenhouse gas CO 2 , especially remarkable uptake for C 2 H 2 (122.0 cm3 g−1 at ambient condition), but also favorable selectivity for binary mixtures of C 2 H 2 /CH 4 , C 2 H 6 /CH 4 , C 3 H 8 /CH 4 , C 2 H 4 /CH 4 , C 2 H 2 /C 2 H 4 as well as C 3 H 8 /C 2 H 6 /CH 4 ternary mixture, as confirmed by ideal adsorbed solution theory (IAST) calculations, and dynamic breakthrough experiment. Grand canonical Monte Carlo (GCMC) simulation reveals the multiple synergism of accessible adsorption sites including functional OH groups, carboxylate groups, HCOO− and π···π stacking interaction between guest molecules and host-pore are crucial to contribute selective gas adsorption of light hydrocarbons. [ABSTRACT FROM AUTHOR]

• ANF aerogel frameworks were constructed as MOF carrier and gas transfer channel. • HKUST-1 was synthesized onto the ANFs to develop hierarchical porous structure. • HKUST-1 aerogel showed a high CO 2 level adsorption capacity of 7.29 mmol/g. • HKUST-1 aerogel had a high CO 2 capture selectivity (39 for CO 2 /N 2 and 42 for CO 2 /O 2). • The dynamic adsorption process of CO 2 molecules was proved by GCMC simulation. Sustainable low-carbon economy has attracted global attention, and the development of advanced CO 2 capture technology has become an important undertaking. Metal organic frameworks (MOFs) featured with high specific surface area and large porosity have held the promise for CO 2 adsorption, but the micron scale make them difficult to handle, leading to easily be blown away, pipeline blockage, and the decline of adsorption capacity. Here, we demonstrate a novel strategy to develop a nanoporous HKUST-1 aerogel with hierarchical pore structure by combining HKUST-1 and aramid nanofiber for promoting CO 2 adsorption. The resultant HKUST-1 aerogel has a low density of 5.86 mg/cm3, high specific surface area of 636.62 m2g−1, and hierarchical porosity of 99.33 %. The meso-/macropores of HKUST-1 aerogel can act as gas transfer channels to facilitate the transport CO 2 into the HKUST-1, and the micropores of HKUST-1 provide active sites for CO 2 adsorption. Benefitting from the synergistic effect of the hierarchical pore structure, the HKUST-1 aerogel demonstrates high CO 2 adsorption capacity of 7.29 mmol/g, and high adsorption selectivity of 39 for CO 2 /N 2 and 42 for CO 2 /O 2. This novel design may provide a reliable theoretical and experimental basis for the development of MOF aerogel as CO 2 adsorbent candidate for environmental purification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metal-organic frameworks were computationally screened for acetylene separation. • Anion-pillared metal–organic frameworks perform well for acetylene separation. • Non-interpenetrated materials can efficiently separate acetylene from CH 4 or CO 2. • Machine-learning models could identify top materials for acetylene separation. Acetylene is a crucial chemical feedstock that can be efficiently purified from CH 4 and CO 2 through adsorption-based separation methods. Combining advantages of organic and inorganic chemistry, metal–organic frameworks (MOFs) provide high separation performances in adsorption processes. In this work, anion-pillared (AP) MOFs were computationally investigated for C 2 H 2 /CH 4 and C 2 H 2 /CO 2 separations using Grand Canonical Monte Carlo (GCMC) simulations. Results of molecular simulations were used to compute selectivity, working capacity and regenerability, which were then combined to identify the top adsorbents and their structural features for C 2 H 2 /CH 4 and C 2 H 2 /CO 2 separations. The best adsorbents were computed to have C 2 H 2 selectivities, working capacities, regenerabilities of 25.5–30.6 (6.1–7.3), 5.6–6 (4.9–5.8) mol/kg, 81.3–83 % (81.2–85.5 %) for C 2 H 2 /CH 4 (C 2 H 2 /CO 2) separation, respectively. We then developed machine learning (ML) models to accurately predict C 2 H 2 , CH 4 , and CO 2 adsorption amounts in AP-MOFs for equimolar C 2 H 2 /CH 4 and C 2 H 2 /CO 2 mixtures by using pore-limiting diameter, surface area, isosteric heat of adsorption as the input features. ML-predicted gas adsorption amounts, separation performance metrics and adsorbent rankings were found to be in good agreement with those directly obtained from GCMC simulations. Therefore, ML models that we developed can be used to accurately and quickly screen large number of AP-MOFs and related materials to identify the top performing materials for C 2 H 2 /CH 4 and C 2 H 2 /CO 2 separations. [ABSTRACT FROM AUTHOR]

Simulations of adsorption isotherms for simple gases in homogeneous slit pores with two open ends often show hysteresis, between condensation and evaporation branches. The hysteresis may result either, from the difference in the curvature of the interface separating the adsorbed and gas phases, or from molecular restructuring when the adsorbate is densely packed. The order–disorder transition that occurs in the second case, has also been observed experimentally for adsorption on a graphite surface, and is supported by molecular simulation (Duval and Thomy, 1975; Ustinov and Do, 2012). In this paper we report a comprehensive set of GCMC simulations designed to explore the effects of pore size and temperature on the hysteresis loop induced by adsorbate restructuring. We report isotherms, isosteric heats, and microscopic analyses of the local density distribution, and the 2D and 3D radial density distributions. Local compressibilities reinforce the supposition that adsorbate restructuring is the origin of the ordering hysteresis. [ABSTRACT FROM AUTHOR]

By combining experiment with molecular simulation, the CO 2 sorption performance of a 2D honeycomb layered coordination polymer, {[Zn 2 (bpydb) 2 (H 2 O) 2 ](DMA) 3 (H 2 O)} n ( 1 ) (bpydb = 4,4′-(4,4′-bipyridine-2,6-diyl) dibenzoate) was systematically investigated. The desolvated 1 not only shows high CO 2 capacity (72.5 cm 3 /g at 273 K and 42.9 cm 3 /g at 298 K) with a moderate high zero-coverage adsorption enthalpy (29.7 kJ/mol), but also exhibits excellent CO 2 /N 2 selectivity around room temperature. To better understand the adsorption behaviors and adsorption sites for CO 2 in 1 , GCMC simulations were carried out, which indicate that the open metal sites between two adjacent layers account for the high CO 2 sorption capacity and strong CO 2 binding ability. Moreover, the thermal stability of 1 was further confirmed by the TGA and VT-PXRD, which indicate that 1 could be thermally stable up to 400 °C. [ABSTRACT FROM AUTHOR]