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Most traditional D2/H2 separation techniques are energy‐intensive with low efficiency. Metal–organic frameworks (MOFs) provide a promising solution for D2/H2 separation due to their excellent chemical and structural characteristics. Here, machine learning‐assisted high‐throughput computational screening was employed to identify the high‐performance MOFs for the dynamic D2/H2 separation. Extensive data analysis reveals that there were two adsorption behaviors in the optimal MOFs, independent adsorption and competitive adsorption, and the independent adsorption was favorable for the preferential adsorption of D2. To quantify these two adsorption behaviors, we introduced and defined overlap degree (OD) and independence degree (ID), and developed a software for the rapid assessment of OD/ID. After batch simulation of the breakthrough curves of 2000 optimal MOFs, ~80% MOFs exhibited independent occupancy, confirming its contribution to good dynamic separation capabilities. This work provides a new idea for designing MOFs with independent adsorption behavior to improve the dynamic separation performance of hydrogen isotopes. [ABSTRACT FROM AUTHOR]

In this work, molecular simulations combined with experimental measurements were conducted to screen candidate metal–organic frameworks (MOFs) for aniline recovery from aqueous solution. The structure–property relationships that can correlate the recovery performance of the MOFs to their physicochemical features were analyzed. The results show that the interplay between the isosteric heat of adsorption of aniline and the free volume of the material is crucial to the aniline recovery capability of MOFs at low concentrations. In contrast, the aniline uptake at high concentrations is dominated by the material's free volume as usually expected. In addition, the requirements of the best MOF candidates for aniline recovery were suggested in this study. Based on the conclusions drawn from the screening route, several novel MOFs were further computationally designed, which possess high aniline uptake within the whole range of concentrations examined. The obtained information may be helpful for in-depth research to broaden the applications of MOFs in mixture separation under liquid phase conditions. [ABSTRACT FROM AUTHOR]

It is of great importance to establish a quantitativestructure–propertyrelationship model that can correlate the separation performance ofMOFs to their physicochemical features. In complement to the existingstudies that screened the separation performance of MOFs from theadsorption selectivity calculated at infinite dilution, this workaims to build a QSPR model that can account for the CO2/N2mixture (15:85) selectivity of an extended seriesof MOFs with a very large chemical and topological diversity underindustrial pressure condition. It was highlighted that the selectivityfor this mixture under such conditions is dominated by the interplayof the difference of the isosteric heats of adsorption between thetwo gases and the porosity of the MOF adsorbents. On the basis ofthe interplay map of both factors that impact the adsorption selectivity,strategies were proposed to efficiently enhance the separation selectivityof MOFs for CO2capture from flue gas. As a typical illustration,it thus leads us to tune a new MOF with outstanding separation performancethat will orientate the synthesis effort to be deployed. [ABSTRACT FROM AUTHOR]

Molecular simulations were performed to study a diverse collection of 105 metal-organic frameworks (MOFs) for their ability to remove CH4 from CH4/H2 mixture. To investigate the practical industrial application in a pressure swing adsorption (PSA) process, working capacity was also considered in addition to selectivity. The results show that MOFs are promising candidate for this separation, which give higher adsorption selectivity with similar working capacity and higher working capacity with similar selectivity than the traditional nanoporous materials such as carbonaceous materials and zeolites. To quantitatively describe the structure-property relationship for CH4/H2 mixture separation in MOFs, a new concept named 'adsorbility' was defined, which shows strong correlation with limiting selectivity, with a correlation coefficient ( r2) of 0.86. This work shows that although MOFs are promising materials for CH4/H2 mixture separation, more investigations that consider both selectivity and working capacity are necessary to screen MOFs in practical PSA application. © 2011 American Institute of Chemical Engineers AIChE J, 2012 [ABSTRACT FROM AUTHOR]

Abstract: Grand canonical Monte Carlo simulations were conducted to systematically evaluate the adsorption separation of three binary mixtures, CO2/CO, C2H4/CO2, and C2H4/C2H6, in a metal-organic framework Cu-BTC at room temperature. The simulated results showed that Cu-BTC could be potentially used for the purification of carbon monoxide, capture of carbon dioxide and separation of olefin/paraffin. The topology structure of the side pockets in Cu-BTC caused the selective adsorption behaviors between gas components, and its effects were more evident at low adsorption loadings. The results also provided qualitative guidelines for the synthesis and design of new MOFs for applications in mixture separations. [Copyright &y& Elsevier]

The ligand functionalization effect on the CO2/CH4separation performance of the MOF type UiO-66(Zr) was explored computationally. The –SO3H and –CO2H functionalized forms show the highest selectivity, good working capacity and medium ranged CO2adsorption enthalpy that make these materials very promising for physisorption-based processes. [ABSTRACT FROM AUTHOR]

Molecular simulations were performed to investigate the performance of 151 metal–organic frameworks (MOFs) with large chemical and topological diversity on CO 2 /CH 4 separation via temperature swing adsorption (TSA) process. The thermal regeneration energy was adopted in this work as an evaluation criterion and combined with other three commonly used ones (CO 2 working capacity, adsorption selectivity and regenerability) to explore the structure–property relationships for the separation of the target system. The results show that the four evaluation criteria exhibit intimate correlations with the difference of adsorbility ( Δ A D ) of adsorbates but with non-concerted changing tendency. With a certain range of this parameter, it can be used as a good indicator for the preliminary screening of MOFs and the tailoring of new materials. Furthermore, from the structural database considered in current study, Cu-TDPAT with strong CO 2 adsorption sites was found to possess the best performance by taking the thermal and water-stable properties into account. [ABSTRACT FROM AUTHOR]

Classically, stable covalent bonding cannot occur between heavy metal cations and clay surface O atoms. However, the classical theory ignores the effect of the electric field arising from clay surface charges on the orbitals of surface O atoms. This article studies the adsorption behavior of heavy metal cations (Pb2+, Cd2+, Cu2+, and Zn2+) on charged montmorillonite surfaces from a new theoretical foundation based on the quantum mechanics analysis of surface O atoms in this electric field, which reveals that polarization-induced covalent bonding is a strong adsorption force. The strength of polarization-induced covalent bonding can be controlled by regulating the energy of the lone-pair electrons of surface O atoms, which depends on solution pH, electrolyte type, electrolyte concentration, temperature or dielectric constant of medium, etc. The mathematic relationship between the energy of lone-pair electrons of surface O atoms and electric field arising from surface charges was established through quantum mechanics analysis; and correspondingly the mathematical relationship between the polarization-induced covalent bonding energy and surface potential also was established for different heavy metal cations. The finding of the new adsorption force will have important impact on both theoretical research and removal/deactivation approaches of heavy metal cations. [Display omitted] • Polarization induced covalent bonding has been found in heavy metal adsorption. • Electrostatic and the covalent bonding forces jointly drive the adsorption. • The energies from the two forces have been quantitatively distinguished. • The polarization induced covalent bonding energy is lower than that of a classic one. • The covalent bonding energy can be adjusted and controlled. [ABSTRACT FROM AUTHOR]

[BOHmim][Zn 2 Cl 5 @MIL-101(Cr) exhibits high NH 3 adsorption capacities. • · A stable IL@MOF composite with multiple adsorption sites was prepared for efficient ammonia capture. • · The composite exhibits a high NH 3 uptake of 24.12 mmol/g. • · The NH 3 uptake can be maintained in a 20% NH 3 solution steam atmosphere. For ammonia (NH 3), a kind of vital pollutant and raw chemical material, it is of great importance to develop materials with high stability and efficient capture performance from dry and humid atmosphere. Herein, a new IL@MOF composite was designed to enhance the NH 3 adsorption capacity using the ionic liquids (ILs) and stable metal–organic frameworks (MOFs). The obtained [BOHmim][Zn 2 Cl 5 @MIL-101(Cr) exhibits a record NH 3 uptake of 24.12 mmol/g among the reported porous materials at 298 K and 1 bar, more than twice that of MIL-101(Cr) (8.92 mmol/g). More importantly, the composite is stable under the humid NH 3 conditions and the excellent NH 3 adsorption capacity can be well maintained (23.55 mmol/g) in a 20% NH 3 solution (approaching the saturated ammonia solution) steam atmosphere with good regenerability. The mechanism reveals that the metal center and hydroxyl-functionalized alkyl chain of IL confined in the framework of MOF provide multiple adsorption sites and large free volume for NH 3 capture. Moreover, the adsorbed water molecules can act as the additional adsorption sites, contributing to the excellent adsorption capacity in humid conditions. This work provides a general way to develop adsorbents for the capture of corrosive gases in combination of the advantages of IL and MOFs. [ABSTRACT FROM AUTHOR]

In this work, UiO-66 with defects was successfully prepared by a synthesis strategy of using benzoic acid as a modulator and postsynthetic acid treatment. The defective frameworks can be confirmed by N 2 adsorption–desorption analysis and 1 H NMR. It is observed that this strategy can effectively enlarge the surface area and pore volume of stable UiO-66 through the removal of coordinated benzoate ligands. The resulting defective UiO-66 shows high BET surface area and total pore volume (1890 m 2 /g and 0.88 cm 3 /g), which are both larger than those of defect-free sample (1200 m 2 /g and 0.49 cm 3 /g) as well as all the reported UiO-66s with defects so far to the best of our knowledge. This MOF exhibits significantly improved capture ability (366 mg/g) toward Safranine T (ST) compared with the defect-free UiO-66 (39 mg/g) and most of reported adsorbents. Meanwhile, it also shows high selectivity for ST over Crystal Violet (CV) due to the size-exclusion effect constructed from the defects in the framework. The results show that this work provides a promising strategy to rationally design novel MOFs for separating large molecules. [ABSTRACT FROM AUTHOR]

Experimentalmeasurements have been combined with molecular simulationsto investigate the adsorption and separation of aniline/phenol mixturesfrom aqueous solutions by the aluminum terephthalate MIL-53. The resultsshow that the framework flexibility of this material plays a crucialrole in the adsorption process and thus can greatly enhance the separationof the aniline/phenol mixture from their solutions. Compared withthe conventional adsorbents, MIL-53(Al) shows the best performancefor such systems of interest, from the points of view of both theadsorption capacities and the selectivities for aniline. The findingsobtained in this work may facilitate more investigations in connectionwith the application of flexiblenanoporous materials for the separation of organic compounds fromliquid-phase environments. [ABSTRACT FROM AUTHOR]

Highlights: [•] Stability of MOFs in fluoride solution is controlled by the cooperative effects. [•] MOFs are promising adsorbents for defluoridation. [•] UiO-66(Zr) has a high adsorption capacity of 41.36mgg−1. [•] Increasing the number of –OH group may improve the defluoridation performance. . [ABSTRACT FROM AUTHOR]

Abstract: The adsorption of n-hexane and n-nonane in MIL-53(Cr) and MIL-47(V) was first investigated by gravimetric measurements. While MIL-53(Cr) exhibits a sub-step during the sorption process induced by the breathing ability of this solid, the adsorption isotherm for MIL-47(V) is of type I. This different shape of the so-obtained isotherms was then interpretated in light of complementary experimental tools including thermogravimetry and X-ray thermodiffraction. We thus evidenced the occurrence of different structures in presence of n-hexane or n-nonane in the case of MIL-53(Cr) identified as the narrow pore (NP) phase and large pore (LP) phase. One noticed the existence of a swollen NP form which spans in a broad range of temperature. A computational assisted structure determination allowed us to elucidate the structures for both NP and LP forms in presence of each investigated alkane. From these structures, the adsorption enthalpies of n-alkanes over MIL-53(Cr) have been computed. It was shown that the NP phase leads to higher enthalpy of adsorption as compared to the LP phase which is related to a higher degree of confinement. [ABSTRACT FROM AUTHOR]