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CH4/N2 separation is one of the great challenges in gas separation, which is of scientific and practical importance, such as in the upgrading of unconventional natural gas. Unfortunately, the separation performance is still quite low so far mainly due to their very close physical properties. In this work, a high‐throughput computational screening method was performed to develop metal–organic frameworks (MOFs) for efficient CH4/N2 separation. General designing rules as well as the correlation between selectivity and our proposed adsorbility (AD) parameter were obtained by carrying out systematic GCMC simulations of the existing 5109 CoRE MOFs. With the aid of this information, five virtual MOFs were screened out from the large database with 303 991 generated MOFs constructed in our previous work, exhibiting much higher selectivities than all the reported values. Among them, the selectivity of Zn‐PYZ‐BPY‐1 can reach over 29.0, about 2.4 times of the highest value reported in the literature. These results may not only suggest promising candidates for CH4/N2 separation but also provide useful information for large screening of MOFs for other specific separation mixtures. [ABSTRACT FROM AUTHOR]

A diverse set of 46 covalent organic frameworks (COFs) were collected to computationally predict their separation performance for three industrial gas mixtures, CH 4 /H 2 , CO 2 /H 2 and CO 2 /CH 4 , using pressure swing adsorption (PSA) process. The results show that COFs outperform most commonly used zeolites and widely studied metal-organic frameworks (MOFs) in the separation of CH 4 /H 2 , while have a comparable performance in separating CO 2 /H 2 and CO 2 /CH 4 . In addition, microscopic information that is instructive for developing more efficient COFs was obtained by analyzing the relationships between separation performance and framework structures. The results of this work provide useful information that can guide the future design of new COFs with improved performance, as well as demonstrate that COFs are very promising adsorbents in industrial gas separation applications and are worthy of further in-depth study toward practical applications. [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]

Separation zone and shear face generate most turbulence in confluence junctions. Flume experiment studies show the variation of a separation zone from the water surface to the bottom and impacts of the two circulation cells (secondary flow) on the sediment transportation in a confluence zone. The turbulence generated by the shear face is anisotropic, so it needs to be cautious to choose appropriate turbulence models in the simulation of confluence flow. This article utilizes the standard k − ϵ, RNG k − ϵ, and RSM turbulence models to simulate the secondary flow and separation zone in the confluence junction, and a quantificational comparison with the experiment data is provided. [ABSTRACT FROM AUTHOR]

To enhance dispersion and adhesion, functionalized porous metal–organic polyhedrons were incorporated into polysulfone as a filler to obtain mixed-matrix membranes, which exhibit largely improved gas permeability and separation factor simultaneously for CO2–CH4 separation. [ABSTRACT FROM AUTHOR]

In this work, a computation-ready, experimental covalent organic framework (CoRE COF) database that nearly covers all the existing COFs was constructed and provided, which contains 187 COFs with disorder-free and solvent-free structures. Using the CoRE COF database established, structure-property relationships of COFs for Kr/Ar, Xe/Kr and Rn/Xe separations were studied. The conditions of industrial vacuum (VSA) and pressure swing adsorption (PSA) processes were considered in the computation. Qualitative rules of COFs for noble gas separations were clarified, and structural features of COFs with excellent separation performance were summarized and suggested. In addition, COFs with good separation performance were identified from our database for industrial cyclic process. The knowledge obtained in this work may give guidance for experimental efforts in seeking advanced materials for noble gas separation, and the CoRE COF database will facilitate the fundamental research of COFs as well as the development of novel functional materials toward practical applications. [ABSTRACT FROM AUTHOR]

Abstract: In this work a hierarchical multiscale approach combining grand canonical Monte Carlo simulation and density functional theory calculation was performed to study the effect of the chemical properties of nine organic linkers on CO2/CH4 mixture separation in metal–organic frameworks (MOFs). The computational results show that the organic linkers decorated with the electron-donating groups can strengthen the distribution of the electrostatic field in the pores of MOFs, and greatly enhance the adsorption selectivity of CO2/CH4 mixture in MOFs. This enhancement becomes stronger with the increase of the electron-donating ability of groups. In addition, this work also demonstrates that the negative steric hindrance effects on the separation behavior should be considered when the organic linkers are modified with multiple substitutions in designing new materials. The knowledge obtained is expected to provide useful information for tailoring the electrostatic properties of MOFs for separation of various gas mixture systems of practical importance. [Copyright &y& Elsevier]

Quantitative structure–property relationship (QSPR) model has demonstrated that CO 2 /N 2 adsorptive selectivity of MOFs is dependent on Δ Q st 0 / φ (Δ Q st 0 is the difference of the isosteric heat of adsorption between the two gases and φ is the porosity of the MOF). Under the guidance of this model, three functionalized MOFs were designed by introducing double –NO 2 , –NH 2 , or –SO 3 H groups into each ligand of a platform MOF, [Zr 6 O 4 (OH) 8 (NDC) 6 ] n (Zr-NDC, NDC 2− = naphthalene-2,6-dicarboxylate). Molecular simulations were firstly applied to predict the gas adsorption properties of these materials, which show that CO 2 adsorption and separation capability can be greatly improved through incorporating these functional groups. Two analogues, [Zr 6 (O) 4 (OH) 8 (NDC-2NO 2 ) 6 ] n (Zr-NDC-2NO 2 ) and [Zr 6 (O) 4 (OH) 8 (NDC-2SO 3 H) 6 ] n (Zr-NDC-2SO 3 H) were then synthesized by using ligands 4,8-dinitronaphthalene-2,6-dicarboxylic acid (H 2 NDC-2NO 2 ) and 4,8-disulfonaphthalene-2,6-dicarboxylatlic acid (H 2 NDC-2SO 3 H), and checked experimentally for their CO 2 capture abilities. Compared with Zr-NDC, Zr-NDC-2NO 2 and Zr-NDC-2SO 3 H exhibit obviously enhanced CO 2 adsorption capacity and separation selectivity over N 2 , notwithstanding their pore sizes are reduced because of adding functional groups. Particularly, grafting two –SO 3 H groups in each ligand has led to a double gravimetric and triple volumetric increase of CO 2 adsorption capacity and a very high CO 2 /N 2 separation selectivity in Zr-NDC-2SO 3 H. Usually, the more functional groups in pores of a MOF are, the better their efficiency is. In these functionalized MOFs, the density of the functional groups is quite high, thus a huge impact on the gas adsorption property was achieved. These results also suggest that the QSPR model is a useful tool in designing MOFs with high performances for CO 2 capture. [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]

Abstract: Volatile sulfur compounds (VSCs) are the main source for malodor from composting plants. In this study, the VSCs generated from composting of 15–80mm municipal solid waste (T0), kitchen waste (T1) and kitchen waste mixed dry cornstalks (T2) were measured in 60L reactors with forced aeration for a period of 30days. The VSCs detected in all treatments were hydrogen sulfide (H2S), methyl mercaptan (MM), dimethyl sulfide (DMS), carbon bisulfide (CS2) and dimethyl disulfide (DMDS). Over 90% of the VSCs emissions occurred during the first 15days, and reached their peak values at days 4–7. The emission profiles of five VSCs species were significantly correlated with internal materials temperature and outlet O2 concentration (p <0.05). Total emissions of the VSCs were 216.1, 379.3 and 126.0mgkg−1 (dry matter) for T0, T1 and T2, respectively. Among the five VSCs, H2S was the most abundant compound with 39.0–43.0% of total VSCs released. Composting of kitchen waste from separate collection posed a negative influence on the VSC and leachate production because of its high moisture content. An addition of dry cornstalks at a mixing ratio of 4:1 (wet weight) could significantly reduce the VSCs emissions and avoid leachate. Compared to pure kitchen waste, VSCs were reduced 66.8%. [Copyright &y& Elsevier]