Rational Design of a Multifunctional MOFs for Alkane-Selective Gas Separation.

Fluorous Metal–Organic Frameworks with Unique Cage-in-Cage Structures Featuring Fluorophilic Pore Surfaces for Efficient C ₂ H ₂ /CO ₂ Separation

Adsorption and separation of propane/propylene on various ZIF-8 polymorphs: Insights from GCMC simulations and the ideal adsorbed solution theory (IAST)

Graphyne nanostructure as a potential adsorbent for separation of H2S/CH4 mixture: Combining grand canonical Monte Carlo simulations with ideal adsorbed solution theory

Selective adsorption of CO2 over CH4 and N2 using porous materials is a promising approach for the capture of CO2 and upgrading of natural gas. Herein, we present a combined simulation and experimental study of the adsorption uptakes of CO2, CH4, and N2 in UNT-14, a copper-based metal-organic framework. Grand Canonical Monte Carlo (GCMC) simulations were employed to predict the pure component adsorption isotherms at 273 and 298 K using atomic charges calculated via three different charge methods. Among those, the Mulliken charge set agrees best with the experimental adsorption data. UNT-14 exhibits greater affinity for CO2 as compared to CH4 and N2, revealed by higher Henry's constant (KH) and isosteric heats of adsorption at infinite dilution (Qst0). Density functional theory (DFT) calculation displays a larger binding energy (BE) value for CO2 than for CH4 and N2. Radial distribution function (RDF) analysis reveals that CO2 molecules tend to adsorb preferentially on the peripheral benzene rings, whereas CH4 and N2 molecules tend to adsorb more preferentially on the central benzene ring of the linker. The ideal adsorbed solution theory (IAST) suggests a favorable adsorption selectivity of UNT-14 for equimolar CO2/CH4 and CO2/N2 gas mixtures (for both the experimental and simulated data), demonstrating efficient CO2 capture and natural gas upgrading ability.

Highly efficient separation of CO2/N2 and CO2/CH4 via metal-ion regulation in ultra-microporous metal-organic frameworks

Grand Canonical Monte Carlo (GCMC) simulation combining with the ideal adsorbed Solution Theory (IAST) are employed to study the effect of functionality on the CH4 adsorption property and CO2/CH4 selectivity of modified irmof-3 structures which include a diverse range of functional groups. The result shows that phenyl groups containing nitrogen (e.g. pyrazine, pyridine) and carboxyl group are able to increase the interaction energy between gas and mof, thereby increasing the gas adsorption capacity. In addition, transition metals can significantly enhance the CO2/CH4 selectivity. The straight-chain alkyl group and aniline groups just slightly improve the material property compared to other functional groups. We also note that materials with more than 50 percent of modification do not show a good performance at high pressure range (35–40 atm) due to its low porosity. We herein show that the functionalization of IRMOF-3 can remarkably improve the CH4 uptake and CO2/CH4 separation; particularly, GCMC simulation is demonstrated as a beneficial tool to aid experimental chemists in designing new promising porous materials.

Pressure swing adsorption (PSA) coupling with molecular sieves, especially the Li low silica X (Li‐LSX) zeolite, adsorption technology is widely used in O2 generator instrument under plateau environment. However, the studies of N2 and O2 adsorption and separation properties on zeolite under plateau environment are still obscure to date. In this work, the influence of N2 and O2 adsorptions on the LSX zeolites in harsh plateau environment (3000 ‐ 5000 m) was investigated by Grand Canonical Monte Carlo (GCMC) simulations. Three kinds of LSX zeolites including Li‐LSX, Ag‐LSX and LiCa‐LSX were taken into consideration. The simulation results indicate that the adsorption amount and affinity of both N2 and O2 elevate with the increasing altitude and following the order of Ag‐LSX > Li‐LSX > LiCa‐LSX. The N2 adsorption was dominated over all three LSX zeolites, leaving O2 much easier to permeate through the LSX zeolites. The isosteric adsorption heat and adsorption density results further proved that N2 and O2 have extremely different adsorption strategies. Moreover, the selectivity and separation coefficients based on ideal adsorption solution theory (IAST) were calculated from GCMC simulations, and the results indicate Ag‐LSX has the highest diffusion selectivity and the steadiest diffusion coefficient among the three LSX zeolites. These findings may contribute to the N2/O2 separation molecular sieves for plateau applications by tailoring the LSX zeolite with different extra‐framework cations.

Grand canonical Monte Carlo (GCMC) simulations were used to investigate pore filling and hysteresis in nanoporous metal-organic frameworks (MOFs). Adsorption and desorption isotherms were calculated for argon at 87 K in 1866 MOFs from the CoRE MOF database and for short n-alkanes in selected MOFs, keeping the adsorbent structure rigid. Analysis of the molecular configurations showed two different mechanisms and origins of hysteresis: one involving a transition of the adsorbate arrangement in the pores similar to a gas-to-liquid transition associated with a large change in the loading and one more similar to a liquid-to-solid transition associated with a relatively small change in the loading. Our GCMC simulations in MOFs with diverse pore topologies indicate exceptions to an empirical relationship for the minimum diameter of a cylindrical pore required for hysteresis as a function of the adsorbate diameter and reduced temperature. The simulations reveal some structures where isotherms exhibit two steps in the adsorption branch and only one step in the desorption branch. Hysteresis loops with different numbers of adsorption and desorption steps are not common. To better understand why hysteresis is observed in the GCMC simulations, the concept of the transition probability for observing a step in the adsorption isotherm at a given pressure in a GCMC simulation is introduced. We used two different methods to calculate the transition probabilities and found that these yielded comparable results. The transition probability provides a measure of the length of GCMC simulations to yield reliable results.

Investigation of competitive adsorption is carried out using the Xe–CH4 mixture in zeolite NaA as a model system. The Xen clusters are trapped in the alpha cages of this zeolite for times sufficiently long that it is possible to observe individual peaks in the NMR spectrum for each cluster while the CH4 molecules are in fast exchange between the cages and also with the gas outside. The 129Xe nuclear magnetic resonance spectra of nine samples of varying Xe and CH4 loadings have been observed and analyzed to obtain the 129Xe chemical shifts and the intensities of the peaks which are dependent on the average methane and xenon occupancies. The distributions Pn, the fraction of cages containing n Xe atoms, regardless of the number of CH4 molecules are obtained directly from the relative intensities of the Xen peaks. From the observed 129Xe chemical shift of each Xen peak can be obtained the average number of CH4 molecules in the same cavity as n Xe atoms. Grand canonical Monte Carlo (GCMC) simulations of mixtures of Xe and CH4 in a rigid zeolite NaA lattice provide the detailed distributions and the average cluster shifts, as well as the distributions Pn. The agreement with experiment is reasonably good for all nine samples. The calculated absolute chemical shifts for the Xen peaks in all samples at 300 K range from 80 to 230 ppm and are in good agreement with experiment. We also consider a very simple strictly statistical model of a binary mixture, derived from the hypergeometric distribution, in which the component molecules are distinguishable but equivalent in competition for eight lattice sites per cage under mutual exclusion. The latter simple model provides a limiting case for the distributions, with which both the GCMC simulations and the properties of the actual Xe–CH4 system are compared. The ideal adsorbed solution theory gives a first approximation to the selectivity of the adsorption of the Xe and CH4 from a mixture of gases, but starts to fail at high total pressures, especially at low CH4 mole fraction in the bulk.

Introduction of functionality into a Tb(III)-organic framework via mixed-ligand strategy for selective C2H2 capture and ratiometric Cr(VI) detection

Ideal adsorbed solution theory, two-dimensional equation of state, and molecular simulation for separation of H2/N2/O2/CH4/CO in graphite nanofiber and C60 intercalated graphite

Selective capture of paraffin from olefin that permits one-step purification of olefin is significantly important, yet developing adsorbents with high selectivity and hydrophobicity remains a daunting challenge. Although aromatic environments can enhance paraffin affinity and hydrophobicity through nonpolar interactions, water adsorption still occurs in regions distant from the aromatic rings, as well as in secondary pores that are always overlooked. Herein, we reported an ultramicroporous porous coordination polymer (ZnFPCP) featuring blade-like circular phenyl paraffin nanotraps. As further validated by density functional tight binding (DFTB) calculations, grand canonical Monte Carlo (GCMC) simulations, and in situ Fourier-tansform infrared absorption (FT-IR) analysis, these ultramicroporous paraffin nanotraps created by surrounding benzene rings enhance the paraffin-selective adsorption, and the segmented spaces between adjacent nanotraps in the blade-like structure, combined with hydrophobic petal-like secondary pore channels enclosed by fluorinated functional groups, further mitigate the water co-adsorption. Remarkably, ZnFPCP exhibited outstanding ideal adsorption solution theory (IAST) selectivity (C3H8/C3H6: 2.08, C2H6/C2H4: 2.93) under ambient conditions and record-breaking C3H8/C2H6 uptake at low pressures. Breakthrough experiments demonstrated the excellent performance of ZnFPCP in olefin purification, affording the exceptional productivity of ultra-high purity (99.99%) for C3H6 and C2H4. Robust stability and super hydrophobicity highlight its potential in harsh industrial application scenarios.

Selective capture of paraffin from olefin that permits one‐step purification of olefin is significantly important, yet developing adsorbents with high selectivity and hydrophobicity remains a daunting challenge. Although aromatic environments can enhance paraffin affinity and hydrophobicity through nonpolar interactions, water adsorption still occurs in regions distant from the aromatic rings, as well as in secondary pores that are always overlooked. Herein, we reported an ultramicroporous porous coordination polymer (ZnFPCP) featuring blade‐like circular phenyl paraffin nanotraps. As further validated by density functional tight binding (DFTB) calculations, grand canonical Monte Carlo (GCMC) simulations, and in situ Fourier‐tansform infrared absorption (FT‐IR) analysis, these ultramicroporous paraffin nanotraps created by surrounding benzene rings enhance the paraffin‐selective adsorption, and the segmented spaces between adjacent nanotraps in the blade‐like structure, combined with hydrophobic petal‐like secondary pore channels enclosed by fluorinated functional groups, further mitigate the water co‐adsorption. Remarkably, ZnFPCP exhibited outstanding ideal adsorption solution theory (IAST) selectivity (C3H8/C3H6: 2.08, C2H6/C2H4: 2.93) under ambient conditions and record‐breaking C3H8/C2H6 uptake at low pressures. Breakthrough experiments demonstrated the excellent performance of ZnFPCP in olefin purification, affording the exceptional productivity of ultra‐high purity (99.99%) for C3H6 and C2H4. Robust stability and super hydrophobicity highlight its potential in harsh industrial application scenarios.

In this paper we report the use of Grand Canonical Monte Carlo (GCMC) simulations to characterize the competitive trapping of CO and N2 molecules into clathrates, for various gas compositions in the temperature range from 50 to 150 K. The simulations evidence a preferential trapping of CO with respect to N2. This leads to the formation of clathrates that are preferentially filled with CO at equilibrium, irrespective of the composition of the gas phase, the fugacity, and the temperature. Moreover, the results of the simulations show that the small cages of the clathrate structure are always filled first, independent of either the guest structure or the temperature. This issue has been associated with the rather significant differences in the calculated heats of encapsulation (∼2–3 kJ/mol) between the smallest and the largest cages. In addition, calculations with the simplified ideal adsorbed solution theory (IAST) are developed to allow a comparison with the results arising from the GCMC simulations. Inter...

ReaxFF Grand Canonical Monte Carlo simulation of adsorption and dissociation of oxygen on platinum (111)