Nonpolar Gases Research Articles

Molecular Simulation of Gas Solubility in Nitrile Butadiene Rubber.

Molecular simulation is used to compute the solubility of small gases in nitrile butadiene rubber (NBR) with a Widom particle-insertion technique biased by local free volume. The convergence of the method is examined as a function of the number of snapshots upon which the insertions are performed and the number of insertions per snapshot and is compared to the convergence of the unbiased Widom insertion technique. The effect of varying the definition of local free volume is also investigated. The acrylonitrile content of the polymer is altered to examine its influence on the solubility of helium, CO2, and H2O, and the solubilities of polar gases are found to be enhanced relative to those of nonpolar gases, in qualitative agreement with experiment. To probe this phenomenon further, the solubilities are decomposed into contributions from the neighborhoods of different atoms, using a Voronoi cell construction, and a strong bias is found for CO2 and H2O in particular to be situated near nitrogen sites in the elastomer. Temperature is shown to suppress the solubility of CO2 and H2O but to increase that of helium. Increasing pressure is found to suppress the solubility of all gases but at different rates, according to a balance between their molecular sizes and electrostatic interactions with the polymer. These results are relevant to the use of NBR seals at elevated temperatures and pressures, such as in oil and gas wells.

Monte Carlo Simulation of Adsorption of Polar and Nonpolar Gases in (FP)YEu Metal–Organic Framework

This work presents a study on the transferability of simulation parameters and the effect of local composition in a model metal–organic framework (MOF). (FP)YEu MOF was selected as a case study of a model MOF for modeling adsorption of polar gases, such as H2S and H2O, and nonpolar gases, such as CH4, and C2H6, as it is a class of MOF that is relevant for sensor applications but that has not been widely researched. (FP)YEu has two different rare-earth metals, whose distribution is unknown. Results showed that taking interaction parameters from the literature and calculating charges using the Qeq method, the adsorption of nonpolar gases is overestimated, but the adsorption of polar gases is underestimated. Although this could suggest that some pores in the material studied experimentally are inaccessible, care must be taken when using molecular simulations as a predictive tool for different MOF families.

Modifier-assisted differential mobility–tandem mass spectrometry method for detection and quantification of amphetamine-type stimulants in urine

An advantage of differential mobility spectrometry (DMS) is it provides an orthogonal mechanism to mass spectrometry (MS). The DMS-MS/MS detects analytes in the gas phase on the basis of differences in ion mobility in low and high electric fields, which makes DMS-MS/MS an alternative to chromatographic separation-MS. One drawback of DMS is its limited resolution and sensitivity, especially for detecting small molecules when using a nonpolar inert gas as the carrier gas. The present work has evaluated the effects on peak capacity of adding chemical modifiers to inert carrier gases (nitrogen, helium, argon and carbon dioxide). Use of a methanol-helium mixture gave improvements in both separation and sensitivity. Nine structurally similar amphetamine-type stimulants were determined in urine without pretreatment of the samples before analysis. After optimization of carrier gas, nature and concentration of chemical modifier, and DMS temperature, limits of detection ranging from 1.1 to 2.7 ng mL−1, with a linear range of three orders of magnitude (5–5000 ng mL−1) were achieved. Precision was <15% and the accuracy of the quality control samples was 87.6–113.7%. For the quantitation of urine samples from drug abusers, data obtained using DMS-MS/MS showed reasonable agreement (within ±19.5%) with that obtained using LC-MS/MS. The analysis time for DMS-MS/MS was only 1.1 min and a paired sample t-test between the two methods gave a p-value of 0.0894, which indicates that DMS-MS/MS is a reliable method, with comparable precision and sensitivity to LC-MS/MS.

Towards Enhanced Gas Sensor Performance with Fluoropolymer Membranes.

In this paper we report on how to increase the selectivity of gas sensors by using fluoropolymer membranes. The mass transport of polar and non-polar gases through a polymer membrane matrix was studied by systematic selection of polymers with different degrees of fluorination, as well as polymers whose monomers have ether groups (-O-) in addition to fluorine groups (-F). For the study, a set of application-relevant gases including H2, CO, CO2, NO2, methane, ethanol, acetone, and acetaldehyde as well as various concentrations of relative humidity were used. These gases have different functional groups and polarities, yet have a similar kinetic diameter and are therefore typically difficult to separate. The concentrations of the gases were chosen according to international indicative limit values (TWA, STEL). To measure the concentration in the feed and permeate, we used tin-dioxide-based metal oxide gas sensors with palladium catalyst (SnO2:Pd), catalytic sensors (also SnO2:Pd-based) and thermal conductivity sensors. This allows a close examination of the interdependence of diffusion and physicochemical operating principle of the sensor. Our goal is to increase the selectivity of gas sensors by using inexpensive fluoropolymer membranes. The measurements showed that through membranes with low polarity, preferably non-polar gases are transported. Furthermore, the degree of crystallization influences the permeability and selectivity of a polymer membrane. Basically the polar polymers showed a higher permeability to water vapor and polar substances than non-polar polymer membranes.

Quantitative analysis of COH fluids synthesized at HP–HT conditions: an optimized methodology to measure volatiles in experimental capsules

AbstractThe quantitative assessment of COH fluids is crucial in modeling geological processes. The composition of fluids, and in particular their H2O/CO2 ratio, can influence the melting temperatures, the location of hydration or carbonation reactions, and the solute transport capability in several rock systems. In the scientific literature, COH fluids speciation has been generally assumed on the basis of thermodynamic calculations using equations of state of simple H2O–nonpolar gas systems (e.g., H2O–CO2–CH4). Only few authors dealt with the experimental determination of high‐pressure COH fluid species at different conditions, using diverse experimental and analytical approaches (e.g., piston cylinder + capsule piercing + gas chromatography/mass spectrometry; cold seal + silica glass capsules + Raman). In this contribution, we present a new methodology for the synthesis and the analysis of COH fluids in experimental capsules, which allows the quantitative determination of volatiles in the fluid by means of a capsule‐piercing device connected to a quadrupole mass spectrometer. COH fluids are synthesized starting from oxalic acid dihydrate at P = amb and T = 250°C in single capsules heated in a furnace, and at P = 1 GPa and T = 800°C using a piston‐cylinder apparatus and the double‐capsule technique to control the redox conditions employing the rhenium–rhenium oxide oxygen buffer. A quantitative analysis of H2O, CO2, CH4, CO, H2, O2, and N2 along with associated statistical errors is obtained by linear regression of the m/z data of the sample and of standard gas mixtures of known composition. The estimated uncertainties are typically &lt;1% for H2O and CO2, and &lt;5% for CO. Our results suggest that the COH fluid speciation is preserved during and after quench, as the experimental data closely mimic the thermodynamic model both in terms of bulk composition and fluid speciation.

A new approach for chemical reaction simulation of rarefied gas flow by DSMC method

Present study concerns the development of a new approach for chemical reaction modelling in DSMC technique. The conventional quantum-kinetic (QK) method based on the VHS collision model is usually applied by the DSMC algorithm to simulate chemical reactions in rarefied gas flowfield. In this paper, a modified quantum-kinetic model (MQK) is presented to remove some limitation of the QK chemical model. The MQK method uses the GSS collision model based on the Stockmayer potential function which can capture both the attractive and repulsive intermolecular forces and polarization effect of the molecules in the reactive flow. To investigate the accuracy and capability of the proposed model, firstly, dissociation of the nitrogen (non-polar gas) and water vapour (polar gas) are simulated in a single cell DSMC for equilibrium and non-equilibrium conditions. The results of the MQK are assessed with those of the QK methods, analytical models and experimental data. Secondly, dissociation of these two types of gases is studies in the rarefied gas flowfield along the stagnation line of a typical hypersonic atmospheric blunt body problem. The flowfield properties including the density, velocity, transient, vibrational and total temperature along the stagnation line and surface properties including the surface pressure and heatflux at the stagnation point obtained by the MQK model are compared with results of the QK method and available analytical and experimental data. The results show that the MQK model provides more accurate results when the polarization effects and both the attractive-repulsive intermolecular forces are dominant especially at high temperature. Also, comparison of the computational cost between two models indicates higher efficiency using the proposed method rather than the QK model due to reduction of number of the collision pairs.

Analysis of the state equations of a real gas at high pressures with the virial coefficients obtained from controlled chaotic oscillations

This paper investigates several cubic and non-cubic state equations of real gases at high pressures by using the virial coefficients estimated from chaotic oscillations with a mechanical-thermal device. The mechanical part is formed by a cylinder with a piston whose motion is limited by means of a nonlinear spring, a damper and a nonlinear control force to decouple the mechanical and thermal subsystems. To maintain the gas temperature approximately constant, a linear PI controller and a nonlinear control law which manipulates the flow rate of two heating coils inside the cylinder are added. The stability of the mechanical subsystem is analyzed through the first Lyapunov value, whose harmonic variation leads to chaotic behavior with great pressures and an almost constant temperature. The chaotic simulations for nonpolar gases are treated like experimental data to obtain an arbitrary number of virial coefficients which reproduce the state equation in a prescribed pressure range. The validity of the proposed device has been corroborated by using another alternative route to chaos and calculating the fugacity coefficient. The analytical calculations are in good agreement with the numerical simulations.

A reliable compound-specific nitrogen isotope analysis of amino acids by GC-C-IRMS following derivatisation into N-pivaloyl-iso-propyl (NPIP)esters for high-resolution food webs estimation.

The signatures of natural stable nitrogen isotopic composition (δ(15)N) of individual amino acid (AA) have been confirmed to be a potentially effective tool for elucidating nitrogen cycling and trophic position of various organisms in food webs. In the present study, a two-stage derivatisation approach of esterification followed by acylation was evaluated. The biological samples underwent acid hydrolysis and the released individual AA was derivatived into corresponding N-pivaloyl-isopropyl (NPIP) esters for nitrogen isotopic analysis in gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). Usually, 13 individual AA derivatives were separated with fine baseline resolution based on a nonpolar gas chromatography column (DB-5ms). The minimum sample amount required under the presented conditions is larger than 20ngN on column in order to accurately determine the δ(15)N values. The δ(15)N values determined by GC-C-IRMS with a precision of better than 1‰, were within 1‰ after empirical correction compared to the corresponding measured by element analysis (EA)-IRMS. Bland-Altman plot showed highly consistency of the δ(15)N values determined by the two measurement techniques. Cation-exchange chromatography was applied to remove interfering fraction from the extracts of plant and animal samples and without nitrogen isotope fractionation during the treatment procedure. Moreover, this approach was carried out to estimate the trophic level of various natural organisms in a natural lake environment. Results highly proved that the trophic level estimated via the presented AA method well reflected the actual food web structure in natural environments.

Effect of vibrational degrees of freedom on the heat transfer in polyatomic gases confined between parallel plates

Conductive stationary heat transfer through rarefied nonpolar polyatomic gases, confined between parallel plates maintained at different temperatures, is investigated. It is assumed that gas molecules possess both rotational and vibrational degrees of freedom, described by the classical rigid rotator and quantum harmonic oscillator models, respectively. The flow structure is computed by the Holway kinetic model and the Direct Simulation Monte Carlo method. In both approaches the total collision frequency is computed according to the Inverse Power Law intermolecular potential. Inelastic collisions in DSMC simulations are based on the quantum version of the Borgnakke–Larsen collision model. Results are presented for N2, O2, CO2, CH4 and SF6 representing diatomic as well as linear and nonlinear polyatomic molecules with 1 up to 15 vibrational modes. The translational, rotational, vibrational and total temperatures and heat fluxes are computed in a wide range of the rarefaction parameter and for various ratios of the hot over the cold plate temperatures. Very good agreement, between the Holway and DSMC results is observed as well as with experiments. The effect of the vibrational degrees of freedom is demonstrated. In diatomic gases the vibrational heat flux varies from 5% up to 25% of the total one. Corresponding results in polyatomic gases with a higher number of vibrational modes show that even at low reference temperatures the contribution of the vibrational heat flux may be considerably higher. For example in the case of SF6 at 300K and 500K the vibrational heat flux is about 67% and 76% respectively of the total heat flux. Furthermore, it is numerically proved that the computed solutions are in agreement with the Chapman–Enskog approximation in a central strip of the computational domain even at moderately large values of the rarefaction parameter, as found in previous investigations. This property has been used to compute the gas thermal conductivity predicted by the adopted models.

Thermodynamic trends for the adsorption of non polar gases on activated carbons employing a new adsorption isotherm modelling

In this paper, the author reports a thermodynamic framework for understanding the surface – energy and the surface – structural interaction factors of activated carbons with various non polar adsorbate molecules. For better understanding, the author employs adsorption uptakes data of activated carbons and some non-polar gases such as H2, Ar, N2, CO2, O2 and CH4 to calculate the enthalpy and entropy of adsorption in pressure-temperature-uptake coordinate systems. The RMS errors are calculated with respect to the proposed model and the experimental data. The minimum RMSEs are found as the model fits well with the experimental data. From theoretical observations, the heterogeneity factors (m) are obtained 1 for microporous and 2 for mesoporous activated carbons, and the interactions of non-polar gases on activated carbons are found to be more sensitive to the adsorbent pore geometry and the adsorbate size. It is also established that the enthalpy and entropy of adsorbent – adsorbate system are closely related to the kinetic diameter of adsorbate molecules, and the pore size equivalent to adsorbate kinetic diameter is the key to store more adsorbate at low pressures. For example, the pore width of activated carbon is roughly maintained 3.8Å for more methane storage and 3.3Å for more CO2 captures.

Sorption and Diffusion of Water Vapor and Carbon Dioxide in Sulfonated Polyaniline as Chemical Sensing Materials.

A hybrid quantum mechanics (QM)/molecular dynamics (MD) simulation is performed to investigate the effect of an ionizable group (–SO3−Na+) on polyaniline as gas sensing materials. Polymers considered for this work include emeraldine base of polyaniline (EB-PANI) and its derivatives (Na-SPANI (I), (II) and (III)) whose rings are partly monosubstituted by –SO3−Na+. The hybrid simulation results show that the adsorption energy, Mulliken charge and band gap of analytes (CO2 and H2O) in polyaniline are relatively sensitive to the position and the amounts of –SO3−Na+, and these parameters would affect the sensitivity of Na-SPANI/EB-PANI towards CO2. The sensitivity of Na-SPANI (III)/EB-PANI towards CO2 can be greatly improved by two orders of magnitude, which is in agreement with the experimental study. In addition, we also demonstrate that introducing –SO3−Na+ groups at the rings can notably affect the gas transport properties of polyaniline. Comparative studies indicate that the effect of ionizable group on polyaniline as gas sensing materials for the polar gas molecule (H2O) is more significant than that for the nonpolar gas molecule (CO2). These findings contribute in the functionalization-induced variations of the material properties of polyaniline for CO2 sensing and the design of new polyaniline with desired sensing properties.

Fully Atomistic Simulations of the Ionic Liquid Crystal [C16mim][NO3]: Orientational Order Parameters and Voids Distribution.

We present a fully atomistic molecular dynamics simulation of the smectic phase of the ionic liquid crystal (ILC) 1-hexadecyl-3-methylimidazolium nitrate, [C16MIm][NO3]. We have characterized the structure of the phase by means of a set of radial distribution functions resolved along the director and in the plane of the smectic layers. The results obtained allow us to discuss the similarities in the microscopic structure of ionic liquids (ILs) and ILCs. In addition to this, we have calculated the orientational order parameters, S, of the methylene groups of the alkyl chain and compared them with the results obtained for phospholipidic membranes from (2)H NMR experiments. We also discuss the orientational order parameters of the imidazolium ring. Finally, we analyze the distribution of voids in the ILC phase. We have found that voids of considerable volume to host a nonpolar gas, e.g. xenon, are localized in the hydrophobic layers and almost absent in the ionic layers.

B40 fullerene as a highly sensitive molecular device for NH3 detection at low bias: a first-principles study

The adsorption of small molecules (NH3, N2, H2 and CH4) on all-boron fullerene B40 is investigated by density functional theory (DFT) and the non-equilibrium Green’s function (NEGF) for its potential application in the field of single-molecular gas sensors. The high adsorption energies (−1.09 to −0.75 eV) of NH3 on different adsorption sites of the B40 surface indicate that NH3 strongly chemisorbs to B40. The charge transfer induced by the NH3 adsorption results in a modification of the density of states (DOS) of B40 near the Fermi level, and therefore changes its electronic transport properties. For all possible adsorption sites, the adsorption of NH3 exclusively leads to a decrease of the conductance of B40. Taking into consideration that the non-polar gas molecules (e.g. N2, H2 and CH4) are only physisorbed and show negligible effect on the conductance properties of B40, we would expect that B40 can be used as a single-molecular gas sensor to distinguish NH3 from non-polar gas molecules at low bias.

Organic Membranes for Selectivity Enhancement of Metal Oxide Gas Sensors

We present the characterization of organic polyolefin and thermoplastic membranes for the enhancement of the selectivity of metal oxide (MOX) gas sensors. The experimental study is done based on theoretical considerations of the membrane characteristics. Through a broad screening of dense symmetric homo- and copolymers with different functional groups, the intrinsic properties such as the mobility or the transport of gases through the matrix were examined in detail. A subset of application-relevant gases was chosen for the experimental part of the study: H2, CH4, CO, CO2, NO2, ethanol, acetone, acetaldehyde, and water vapor. The gases have similar kinetic diameters and are therefore difficult to separate but have different functional groups and polarity. The concentration of the gases was based on the international indicative limit values (TWA, STEL). From the results, a simple relationship was to be found to estimate the permeability of various polar and nonpolar gases through gas permeation (GP) membranes. We used a broadband metal oxide gas sensor with a sensitive layer made of tin oxide with palladium catalyst (SnO2:Pd). Our aim was to develop a low-cost symmetrical dense polymer membrane to selectively detect gases with a MOX sensor.

Conformational Exploration of Enflurane in Solution and in a Biological Environment.

Enflurane is a fluorinated volatile anesthetic, whose bioactive conformation is not known. Actually, a few studies have reported on the conformations of enflurane in nonpolar solution and gas phase. The present computational and spectroscopic (infrared and NMR) work shows that three pairs of isoenergetic conformers take place in the gas phase, neat liquid, polar, and nonpolar solutions. According to docking studies, a single conformation is largely preferred over its isoenergetic isomers to complex with the active site of Integrin LFA-1 enzyme (PDB code: 3F78 ), where the widely used anesthetic isoflurane (a constitutional isomer of enflurane) is known to bind. Weak hydrogen bonding from an electrostatic interaction between the CHF2 hydrogen and the central CF2 fluorines was not found to rule the conformational isomerism of enflurane. Moreover, intramolecular interactions based on steric, electrostatic, and hyperconjugative effects usually invoked to describe the anomeric effect are not responsible for the possible bioactive conformation of enflurane, which is rather governed by the enzyme induced fit.

Thermodynamic and Structural Evidence for Reduced Hydrogen Bonding among Water Molecules near Small Hydrophobic Solutes.

The structure of water molecules near a hydrophobic solute remains elusive despite a long history of scrutiny. Here, we re-examine the subtle issue by a combination of thermodynamic analysis for Henry's constants of several nonpolar gases over a broad range of temperatures and molecular dynamic simulations for the water structure in the hydration shell using several popular semiempirical models of liquid water. Both the structural and thermodynamic data indicate that hydrophobic hydration reduces the degree of the hydrogen bonding among water molecules, and the effect becomes more prominent at high temperatures. Hydrogen-bond formation is slightly hindered near a hydrophobic solute due to the restriction of the degree of freedom for water molecules in the solvation shell, and the confinement effect becomes more significant as temperature increases. Reduction in the extent of hydrogen bonding is fully consistent with a positive contribution of a small hydrophobic solute to the solution heat capacity. As predicted by the scaled-particle theory, both Henry's constants and simulation results suggest that the hydration entropy is determined primarily by cavity formation in liquid water, with its magnitude rising with the solute size but declining with temperature.

Identification of chemical warfare agents from vapor samples using a field-portable capillary gas chromatography/membrane-interfaced electron ionization quadrupole mass spectrometry instrument with Tri-Bed concentrator

A field-portable gas chromatograph–mass spectrometer (Hapsite ER system) was evaluated for the detection of chemical warfare agents (CWAs) in the vapor phase. The system consisted of Tri-Bed concentrator gas sampler (trapping time: 3s−1min), a nonpolar low thermal-mass capillary gas chromatography column capable of raising temperatures up to 200°C, a hydrophobic membrane-interfaced electron ionization quadrupole mass spectrometer evacuated by a non-evaporative getter pump for data acquisition, and a personal computer for data analysis. Sample vapors containing as little as 22μg sarin (GB), 100μg soman (GD), 210μg tabun (GA), 55μg cyclohexylsarin (GF), 4.8μg sulfur mustard, 390μg nitrogen mustard 1, 140μg of nitrogen mustard 2, 130μg nitrogen mustard 3, 120μg of 2-chloroacetophenone and 990μg of chloropicrin per cubic meter could be confirmed after Tri-Bed micro-concentration (for 1min) and automated AMDIS search within 12min. Using manual deconvolution by background subtraction of neighboring regions on the extracted ion chromatograms, the above-mentioned CWAs could be confirmed at lower concentration levels. The memory effects were also examined and we found that blister agents showed significantly more carry-over than nerve agents. Gasoline vapor was found to interfere with the detection of GB and GD, raising the concentration limits for confirmation in the presence of gasoline by both AMDIS search and manual deconvolution; however, GA and GF were not subject to interference by gasoline. Lewisite 1, and o-chlorobenzylidene malononitrile could also be confirmed by gas chromatography, but it was hard to quantify them. Vapors of phosgene, chlorine, and cyanogen chloride could be confirmed by direct mass spectrometric detection at concentration levels higher than 2, 140, and 10mg/m3 respectively, by bypassing the micro-concentration trap and gas chromatographic separation.

Effect of hydrostatic pressure on gas solubilization in micelles.

Molecular dynamics simulations of anionic sodium decylsulfate and nonionic pentaethylene glycol monodecyl ether micelles in water have been performed to examine the impact of hydrostatic pressure on argon solubilization as a function of pressure. The potential-of-mean force between the micelles and argon demonstrates that nonpolar gases are attracted to the interiors of both micelles. The affinity of argon for micelle interiors, however, decreases with increasing pressure as a result of the comparatively higher molar volume of argon inside assemblies. We evaluate solubility enhancement coefficients, which describe the drop in the solute chemical potential as a function of the micellized surfactant concentration, to quantify the impact of micellization on gas solubilization. While argon is similarly attracted to the hydrophobic cores of both micelles, the gas is more effectively sequestered within nonionic micelles compared with anionic micelles as a result of salting out by charged head groups and accompanying counterions. The solubility enhancement coefficients of both micelles decrease with increasing pressure, reflecting the changing forces observed in the potentials-of-mean force. An analytical liquid drop model is proposed to describe the pressure dependence of argon solubilization within micelles that captures the simulation solubility enhancement coefficients after fitting an effective micelle radius for each surfactant.

Climatology and variability of trace gases in extratropical double‐tropopause regions from MLS, HIRDLS, and ACE‐FTS measurements

AbstractUpper tropospheric and lower stratospheric measurements from the Aura Microwave Limb Sounder (MLS), the Aura High Resolution Dynamics Limb Sounder (HIRDLS), and the Atmospheric Chemistry Experiment‐Fourier transform spectrometer (ACE‐FTS) are used to present the first global climatological comparison of extratropical, nonpolar trace gas distributions in double‐tropopause (DT) and single‐tropopause (ST) regions. Stratospheric tracers, O3, HNO3, and HCl, have lower mixing ratios ∼2–8 km above the primary (lowermost) tropopause in DT than in ST regions in all seasons, with maximum Northern Hemisphere (NH) differences near 50% in winter and 30% in summer. Southern Hemisphere winter differences are somewhat smaller, but summer differences are similar in the two hemispheres. H2O in DT regions of both hemispheres shows strong negative anomalies in November through February and positive anomalies in July through October, reflecting the strong seasonal cycle in H2O near the tropical tropopause. CO and other tropospheric tracers examined have higher DT than ST values 2–7 km above the primary tropopause, with the largest differences in winter. Large DT‐ST differences extend to high NH latitudes in fall and winter, with longitudinal maxima in regions associated with enhanced wave activity and subtropical jet variations. Results for O3 and HNO3 agree closely between MLS and HIRDLS, and differences from ACE‐FTS are consistent with its sparse and irregular midlatitude sampling. Consistent signatures in climatological trace gas fields provide strong evidence that transport from the tropical upper troposphere into the layer between double tropopauses is an important pathway for stratosphere‐troposphere exchange.

Molybdenum disulfide as a highly efficient adsorbent for non-polar gases.

Molybdenum disulfide (MoS2), a kind of graphene-like, two-dimensional material, has attracted great interest because of its unique properties and potential applications in electronics and sensors. In this paper, first-principle calculations and grand canonical Monte Carlo (GCMC) simulations are performed and used to show that the MoS2 layer is efficient at absorbing non-polar gases. Compared with the popular gas sorbents (metal organic frameworks and carbon-based materials), MoS2 has additional advantages, including large surface to volume ratio and tunable properties. The non-polar gas [carbon dioxide (CO2) and methane (CH4)] adsorption on the MoS2 layer with and without vacancies has been systematically studied. The perfect MoS2 shows little or no adsorption for CO2 and CH4 molecules, but the MoS2 with a single S vacancy and double S vacancies exhibits an excellent adsorption ability for CO2 and CH4 gases. The adsorption energies were 65 kJ mol(-1) for CO2 and 47 kJ mol(-1) for CH4 (van der Waals-D2), respectively. An orbital coupling between the p orbital of the CO2 (or CH4) molecule and the d orbital of the Mo atom was observed. GCMC simulation results show that MoS2 with a single S vacancy could absorb 42.1 wt% of CO2 and 37.6 wt% of CH4 under a pressure of 80 bar at room temperature. The results given in this paper indicate that monolayer MoS2 with defects is a highly efficient absorbent for non-polar gases.