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Understanding CO2 diffusion behavior in functional nanoporous materials is beneficial for improving the CO2 adsorption, separation, and conversion performances. However, it is a great challenge for studying the diffusion process in experiments. Herein, CO2 diffusion in 962 metal–organic frameworks (MOFs) with open Cu sites was systematically investigated by theoretical methods in the combination of molecular dynamic simulations and density functional theory (DFT) calculations. A specific force field was derived from DFT-D2 method combined with Grimme's dispersion-corrected (D2) density functional to well describe the interaction energies between Cu and CO2. It is observed that the suitable topology is conductive to CO2 diffusion, and 2D-MOFs are more flexible in tuning and balancing the CO2 adsorption and diffusion behaviors than 3D-MOFs. In addition, analysis of diffusive trajectories and the residence times on different positions indicate that CO2 diffusion is mainly along with the frameworks in these MOFs, jumping from one strong adsorption site to another. It is also influenced by the electrostatic interaction of the frameworks. Therefore, the obtained information may provide useful guidance for the rational design and synthesis of MOFs with enhanced CO2 diffusion performance for specific applications.

Membrane separation is a high-efficiency, energy-saving, and environment-friendly separation technology. Covalent organic framework (COF)-based mixed-matrix membranes (MMMs) have broad application prospects in gas separation and are expected to provide new solutions for coal-bed methane purification. Herein, a high-throughput screening method is used to calculate and evaluate COF-based MMMs for CH4/N2 separation. General design rules are proposed from thermodynamic and kinetic points of view using the computation-ready, experimental COFs. From our database containing 471671 generated COFs, 5 COF membrane materials were screened with excellent membrane selectivities, which were then used as the filler of MMMs for separation performance evaluation. Among them, BAR-NAP-Benzene_CF3 combined with polydimethylsiloxane and styrene-b-butadiene-b-styrene show high CH4 permeability of 4.43×10–13 mol·m·s–1·Pa–1·m–2 and high CH4/N2 selectivity of 9.54, respectively. The obtained results may provide reasonable information for the design of COF-based membranes for the efficient separation of CH4/N2.

Purification of ethanol from ethanol/water mixtures is important in industrial separation processes, especially for bioethanol fuel purification. In this work, a robust Cu-triazole metal–organic fr...

Oil/organic solvent spills can cause serious threats to environment and ecology, and high efficient oil–water separation has attracted much attention in recent years. Herein, we design a new superhydrophobic ether-based porous organic polymer (E-POP) by the condensation reaction between 4′,4‴,4‴″,4‴‴′’’’’-(ethene-1,1,2,2-tetrayl)­tetrakis­(([1,1′-biphenyl]-4-carbaldehyde)) and pentaerythrotol monomers, and the resulting E-POP-1 exhibits superhydrophobicity on account of abundant ether groups. Meanwhile, the E-POP-1 has a rich porous structure and high stability, which are beneficial to the diffusion of organic solvents or oils, thereby improving adsorption capacity and efficiency. In addition, the E-POP-1 could be successfully coated on the skeleton of PU sponge, and thus, the obtained E-POP-1@PU sponge possesses superhydrophobicity, robust mechanical stability, and hierarchical porous structure. Based on the above, the superhydrophobic E-POP-1@PU sponge can rapidly and selectively adsorb various kinds of oils up to 82 times of its own weight, and the adsorbed oils can be collected by a simple squeezing process. Furthermore, the recovered sponge can maintain high adsorption capacity for oil–water separation even after 100 cycles. More interestingly, the superhydrophobic E-POP-1@PU sponge can continuously adsorb and expulse oils and organic solvents from water surfaces with vacuum assistance. The rapid and efficient adsorption capacity, excellent selectivity, high stability, high elasticity, and renewability make sure that E-POP-1@PU sponge is a promising candidate for large-scale industrial separation of oils/organic solvents and water in corrosive and turbulent conditions.

Cu-BTC is a copper-paddlewheel-based MOF with great potential in gas adsorption and heterogeneous catalysis, but has restricted practical application due to its poor water stability. In this work, ...

Photoreduction of CO2 to CH4, which is an 8-electron photoelectrochemical process, represents one of the most appealing approaches that tackles the global warming challenge and fuel crisis. To achi...

Recovery of propylene from polypropylene (PP) purge stream is of great importance due to both more efficient conversion of the monomers and environmental protection. Herein, eight stable metal–orga...

The selective adsorption of ethane (C2H6) in the separation process of C2H6 and ethylene (C2H4) is of great importance for obtaining polymer-grade C2H4 in industry, yet it is still challenging task to develop suitable adsorbents with large adsorption capacity, high selectivity and excellent stability for efficient separation of C2H6/C2H4. Herein, carbazole-based covalent trazine frameworks (CTFs) prepared by ionothermal strategy are proposed for C2H6/C2H4 for the first time. By changing the preparation conditions, the obtained CTF-DCTC-500 shows defective ultramicropore structure while CTF-DCTC-400 does not. Compared with CTF-DCTC-400, the introduction of defective ultramicropore in CTF-DCTC-500 not only increases the adsorption capacity of C2H6, but also exhibits obviously C2H6/C2H4 separation behavior. Surprisingly, the adsorption selectivity of C2H6/C2H4 in CTF-DCTC-500 at 298 K and 1 bar is up to 2.08, exceeding all reported COF materials. To the best of our knowledge, this is first reported CTF material with preferential C2H6 adsorption over C2H4. Breakthrough experiments on CTF-DCTC-500 reveal that the polymer-grade C2H4 with 99.95 % purity can be directly obtained from the C2H6/C2H4 mixture in the practical application. Furthermore, CTF-DCTC-500 possesses the high chemical stability and excellent cycling stability and regeneration for C2H6/C2H4 separation, indicating it is a promising material for C2H6/C2H4 separation. This work not only provides a highly stable carbazole-based CTF with high C2H6/C2H4 separation selectivity, but also emphasizes the important role of defective ultramicropore structure on C2H6/C2H4 separation.

Membrane based CO2/CH4 separation is an effective and energy saving way for highly demanded natural gas upgrading. Herein, high-throughput computational screening of covalent organic frameworks (CO...

Poor dispersity of filler particles always limits their application in mixed matrix membranes (MMMs), increasing the difficulties in membrane fabrication and restraining the full exploitation of the intrinsic separation ability of the fillers. Herein, polyethyleneimine (PEI), a functional branched polymer, was covalently bonded on the outer surface of CAU-1 nanoparticles to implement increased colloidal stability and improved CO2 affinity for MMMs preparation. As a result, the dispersity of CAU-1 particles in solvent and MMMs was greatly improved after surface functionalization. Meanwhile, the grafted PEI polymer chains can serve as CO2 carriers simultaneously, which benefits the CO2 transport in MMMs. The prepared MMMs based on modified CAU-1 exhibit largely improved CO2/CH4 separation performance, with a CO2 permeability of 546 Barrer and a CO2/CH4 separation factor of 27.8 at 30 wt% filler loading, showing 165% and 50% increases respectively compared with the pristine polymer membrane. The modification approach presented here is expected to extend the functionality of MOFs and facilitate the development of MMMs.

Porous organic frameworks may be a kind of promising material to address environmental issues such as removing the radioactive vapor wastes in fission as well as coping with organic pollutants of wastewater, due to their excellent porous character and remarkable stability. In this report, a covalent triazine-based framework (CTF-CTTD) with hierarchically porous structure and large pore volume was synthesized via the nitrile trimerization. The CTF-CTTD shows an outstanding adsorption ability for iodine with the uptake value of 387% due to their abundant porosity, triazine units, as well as π–π conjugated structures, which is one of the highest values reported so far for iodine uptake values of solid porous adsorbents. Furthermore, iodine captured in CTF-CTTD can be also released easily from the pore of materials because of the highly porous structure. In addition, CTF-CTTD also presents an excellent adsorptive performance for removing Rhodamine B (RhB) with adsorption capacity of 684.9 mg g–1. These result...

Antibiotic pollutants in wastewater may cause serious damage to the environment and human health. Therefore, it is of vital importance to remove them efficiently from wastewater. In this work, adsorption of cefradine, a typical β-lactam antibiotic, was studied in a stable metal–organic framework (PCN-222). Remarkably, it exhibits an excellent saturated adsorption capacity of 333.33 mg g–1, which is superior to the various reported adsorbents. It is observed that the π–π interaction and electrostatic interaction play essential roles in the adsorption process, leading to PCN-222 as a promising adsorbent of the class of β-lactam antibiotics from water.

Lithium-sulfur battery is one of the most prospective chemistries in secondary energy storage field due to its high energy density and theoretical capacity, but the rapid decay of capacity is still a huge challenge. Herein, we reported an ingenious design of nitrogen doped carbon nanofibers with honeycomb-like porous structure for the cathode of lithium-sulfur battery which can effectively suppress the “shuttle effect”. The special porous material with three dimensional (3D) interconnected pore structure is beneficial to enhance the adsorption of lithium polysulfides and accommodate the volume expansion of active materials. In addition, the doped nitrogen can not only improve the conductivity of cathode, but also form a strong interfacial interaction to trap lithium polysulfides. Therefore, the battery with the cathode exhibited a high reversible discharge capacity of 1093.9 mAh g−1 and good capacity retention of 76.0% after 300 cycles at 0.5C rate. After acidification, the cycling performance of the cathode could achieve upon 300 cycles with a very low decay rate of 0.027% at 0.5C.

Probing competent bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) plays a crucial role in the development of energy conversion and storage ...

Efficient capture of nitroimidazole antibiotics from wastewater remains a serious task for public health and environmental protection. In this report, we first propose a strategy of using highly flexible metal–organic framework for dimetridazole (DMZ) capture and excellent performance was achieved. Remarkably, MIL-53(Al) exhibits an excellent saturated adsorption capacity of 467.3 mg g −1 , surpassing all previous reported MOF-based adsorbents and various adsorbent materials like active carbons. Besides, it also shows extremely fast adsorption rate at the initial concentration of 40 mg L −1 . Over 90% of DMZ can be removed within 10 min and the adsorption kinetics will reach equilibrium after 60 min of contact. Moreover, the concrete interaction mechanism between DMZ and MIL-53(Al) was also investigated. The PXRD results show that MIL-53(Al) presents its narrow pore (NP) form in low DMZ concentration. Due to the overlap of potential energy, the van der waals interaction between DMZ and the framework of MIL-53(Al) can be significantly reinforced, leading to strong host–guest interaction and thereby excellent DMZ removal efficiency. As DMZ concentration increasing, the pore structure of MIL-53(Al) was propped open and switched to large pore (LP) form, further promoting its uptake capacity. This flexible adsorbent shows obvious advantage with higher removal efficiency and uptake capacity as compared with its rigid analogical adsorbents of MIL-68(Al) and Al-1,4-NDC. Our work therefore presents an effective adsorbent material for DMZ capture and this strategy of using flexible adsorbents may provide a new perspective for removing other nitroimidazole antibiotics from contaminated water for environmental remediation.

Higher hydrocarbons in natural gas must be removed for safe storage, transport, and application of natural gas. Considering C3H8 and CH4 are nonpolar molecules, electrostatic interactions between C3 and MOFs are relatively weak, while they could be sensitive to the van der Waals interactions. Thus, it is an effective method to greatly enhance the separation performance by improving the van der Waals interactions through tuning the pore size of MOFs. Herein, we synthesized a series of isostructural Zr-MOFs with different pore sizes, and the separation performances of these materials for C3/C1 were systematically studied. The results indicate that pore size plays an important role in the C3 storage and C3/C1 separation in MOFs. Specifically, Zr-BPDC with large surface area and pore volume has the highest C3H8 and C3H6 adsorption capacity (159.2 cc/g and 161.5 cc/g at 298 K 1 bar, respectively), while Zr-FUM with the smallest surface area and pore volume has the highest adsorption heat for C3 as well as C3/C...

Discovering high-performance metal-organic frameworks (MOFs) with open metal sites has become an increasingly hot research topic in the field of safe storage and transportation of acetylene. Following the concept of Materials Genomics proposed recently, a database of 502 experimental MOFs was built by searching the structures deposited in the CSD with the dicopper paddle-wheel node Cu2(COO)4 as the characteristic materials gene. On the basis of the developed ab initio force field, a high-throughput computational screening was conducted to examine the property-performance relationships of MOFs containing Cu-OMS for C2H2 storage at ambient conditions. The optimal ranges of the structural and energetic features for the design of such MOFs were suggested. From our computational screening, three potentially promising MOFs were identified which exhibit a performance outperforming those MOFs reported experimentally so far with record high gravimetric C2H2 uptakes, both in the total and deliverable adsorption capacities. This article is protected by copyright. All rights reserved.

Capture of radioactive barium from nuclear wastewater is of great importance for environmental protection. Here, [Zr6(OH)10.8(SO4)3.6(BDC-NH2)3(H2O)7.4]·nH2O (Zr-BDC-NH2-SO4) was selected as an adsorbent for its high content of sulfate group, which is a strong barium-chelating group, and its binding sites are fully exposed. Zr-BDC-NH2-SO4 exhibits high adsorption capacity of 181.8 mg g–1, which is higher than those of most reported adsorbents, and showed excellent high selectivity even when the concentrations of background metal ions are 10 times of Ba2+. The breakthrough study showed good adsorption performance with fast kinetics and low outlet concentration. In addition, the great stability of Zr-BDC-NH2-SO4 under γ radiation has been confirmed, making it possible to be applied in real nuclear wastewater treatment. Moreover, the adsorption of Ba2+ is irreversible and therefore it could avoid secondary pollution. Overall, this work provides a stable, efficiency adsorbent for removing radioactive barium f...

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.

Developing advanced filtration membrane with high flux, good solute rejection and excellent antifouling performance is highly demanded. Hydrophilic graphene oxide (GO) nanosheets are attractive fillers for the preparation of composite membranes for water purification. However, strategies that can fully exploit the advantages and remedy the drawbacks of GO nanosheets are still needed. In this work, UiO-66 was specifically anchored to the GO layers as a porous modifier. The incorporated UiO-66 can effectively prevent the GO layers from stacking and introduce unique properties into the composite (UiO-66@GO). A series of novel composite membranes were prepared with the obtained UiO-66@GO composite and polyethersulfone (PES). As a result, the prepared composite membranes (UiO-66@GO/PES) exhibit high hydrophilicity and water purification performance. Especially, the water flux of composite membrane with 3.0 wt% UiO-66@GO loading shows an increase of 351% and 78% respectively in comparison with that of the PES and GO/PES membranes. Moreover, the UiO-66@GO/PES membranes exhibit good solute rejection and impressive antifouling performance, which is appealing for the application of industrial water purification.

Rational structure designs of cathodes with high electrical conductivity and strong interface adsorption to lithium polysulfide are a huge requirement for lithium sulfur (Li-S) battery. Herein, we report a multifunctional pomegranate-like porous carbon nanofibers with LaF3 doped (La@PCNFs) by electro-blowing spinning technique and subsequent one-step carbonization process for high stability Li-S battery. Interestingly, a number of hollow and mesoporous carbon grains with high graphitization evenly and densely grow inside the macroporous carbon skeleton, which can construct a fast and hierarchical transfer channel and largely enrich the exposed active sites. More importantly, the polar interfaces decorated with active ionic C-F and LaF3 nanocrystal have strong trapping to the lithium polysulfide during cycles. Therefore, the La@PCNFs cathode exhibits a high discharge capacity of 640 mAh·g−1 and a low average capacity decay of 0.05 % during 1000 cycles at 5 C, which will shed some lights on the development of other biomimetic materials for various energy conversion and storage systems.

Although Li incorporation into adsorbent has been considered as an efficient method to enhance the selectivity for CO2 capture, the reported results are not desired. Herein, we proposed a dual-Li+ sites synergistic strategy to boost CO2 affinity and selectivity. The synergistic dual-Li+ sites in MOF are constructed by incorporating polyacrylic acid (PAA) with rich flexible carboxyl sites into stable UiO-66 framework, followed by neutralization with LiOH solution. Interestingly, 0.1 M Li+@PAA@UiO-66 composites exhibit steep absorption isotherm at low pressure range, which has never been observed in any other Li doped adsorbent, suggesting ultrahigh CO2 affinity. Meanwhile, 0.1 M Li+@PAA@UiO-66 composites show very high selectivity for CO2 over N2 or CH4 (6341 and 1904 at 298 K, respectively) at zero coverage, surpassing all the reported Li doped adsorbents. The DFT calculations reveal that synergistic dual-Li+ sites show much stronger interactions with CO2 than that of traditional single Li+ site. This work not only proposes a strategy of constructing synergistic dual-Li+ sites in MOF to boost CO2 adsorption and separation, but also provides a promising CO2 adsorbent with high efficiency, high water stability and recyclability, low cost and commercially available raw materials, as well as simple and feasible preparation process.

For ammonia (NH3), 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 NH3 adsorption capacity using the ionic liquids (ILs) and stable metal–organic frameworks (MOFs). The obtained [BOHmim][Zn2Cl5]@MIL-101(Cr) exhibits a record NH3 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 NH3 conditions and the excellent NH3 adsorption capacity can be well maintained (23.55 mmol/g) in a 20% NH3 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 NH3 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.

Preparation of defect-free and optimized thin film nanocomposite (TFN) membranes is an effective way to enhance the process of organic solvent nanofiltration. However, it still remains a great challenge due to poor filler particle dispersibility in organic phase and compatible issue between fillers and polymers. Aiming at these difficulties, UiO-66-NH2 nanoparticles were surface modified with long alkyl chains and used in the preparation of TFN membranes. As a result, defect-free TFN membranes with ultrathin MOF@polyamide layer were successfully prepared benefited from the improved particle dispersibility in n-hexane. Significant enhancement was found in methanol permeance after nanoparticle incorporation, without comprising the tetracycline rejection evidently. Especially, the novel TFN membrane prepared with organic phase solution containing 0.15% (w/v) modified UiO-66-NH2 nanoparticles showed a superior methanol permeance of 20 L·m−2·h−1·bar−1 and a tetracycline rejection of about 99%, which is appealing to the application in pharmaceutical industry for example. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1303–1312, 2017

By taking desulfurization of liquid fuels as a demonstrative example, a bottom-up selection was performed to find the metal-organic frameworks (MOF)-type adsorbents with highly efficient adsorption performance of large molecules. Through carefully analyzing the adsorption mechanism for typical S-heterocyclic compounds like dibenzothiophene (DBT), PCN-10 was selected in consideration of the simultaneous inclusion of several kinds of interactions in the framework. Experimental results demonstrate that this MOF exhibits extraordinary high DBT adsorption capacity (75.24 mg S g−1), showing record uptake among all the reported porous materials for the removal of thiophenicsulfur from fuels (below 1000 ppmwS), to the best of our knowledge. Moreover, the removal rate for the low sulfur concentration (50 ppmwS) can reach beyond 99%. This strategy can be conveniently extended to the screening and design of MOFs for the efficient removal of other important large guest molecules. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4491–4496, 2016

In this work, ZIF-9 membranes were successfully synthesized using temperature-switching synthesis method. Compared with the conventional hydrothermal synthesis at a constant temperature, this method could promote the growth of crystals on the support. Scanning electron microscopy (SEM) demonstrated that the obtained membranes had continuous and well-intergrown layer with a denser surface and better crystal size uniformity. As a result, gas separation performance was enhanced. It is also found that the properties of membrane can remain almost stable at a relatively broad range of operating temperature and transmembrane pressure drop, which is beneficial for the practical operation of membrane in the separation process. More importantly, this synthesis strategy can be conveniently extended to the preparation of other MOF membranes with improved performance.

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.

Quantitative structure–property relationship (QSPR) model has demonstrated that CO2/N2 adsorptive selectivity of MOFs is dependent on ΔQst0/φ (ΔQst0 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 –NO2, –NH2, or –SO3H groups into each ligand of a platform MOF, [Zr6O4(OH)8(NDC)6]n (Zr-NDC, NDC2− = naphthalene-2,6-dicarboxylate). Molecular simulations were firstly applied to predict the gas adsorption properties of these materials, which show that CO2 adsorption and separation capability can be greatly improved through incorporating these functional groups. Two analogues, [Zr6(O)4(OH)8(NDC-2NO2)6]n (Zr-NDC-2NO2) and [Zr6(O)4(OH)8(NDC-2SO3H)6]n (Zr-NDC-2SO3H) were then synthesized by using ligands 4,8-dinitronaphthalene-2,6-dicarboxylic acid (H2NDC-2NO2) and 4,8-disulfonaphthalene-2,6-dicarboxylatlic acid (H2NDC-2SO3H), and checked experimentally for their CO2 capture abilities. Compared with Zr-NDC, Zr-NDC-2NO2 and Zr-NDC-2SO3H exhibit obviously enhanced CO2 adsorption capacity and separation selectivity over N2, notwithstanding their pore sizes are reduced because of adding functional groups. Particularly, grafting two –SO3H groups in each ligand has led to a double gravimetric and triple volumetric increase of CO2 adsorption capacity and a very high CO2/N2 separation selectivity in Zr-NDC-2SO3H. 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 CO2 capture.

A systematic computational study was performed in this work to investigate the dispersion behaviors of ionic liquids (ILs) in metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) as well as the separation performance of the resulting composites for CO 2 /CH 4 and CO 2 /N 2 mixtures. Five MOFs and eight COFs with diverse pore structures and chemical properties were selected as the supporters for 1-n-butyl-3-methy limidazolium thiocyanate [BMIM][SCN]. The results show that stronger Coulombic interactions contributed from the frameworks of MOFs can lead to better dispersion of the IL molecules in their pores compared with COFs. The gas separation performance can be significantly enhanced by introducing [BMIM][SCN] into MOFs and COFs, and MOFs can be considered as better support materials for ILs. Better dispersion of the IL in a given support material will induce greater enhancement on the separation performance of the composite, and such phenomenon is more evident for CO 2 /CH 4 mixture compared with the CO 2 /N 2 system. The IL molecules are more inclined to aggregate in the 2D-COFs and MOFs with 1D pore structures. However, they are more dispersive in the materials with 3D pore structures as the supporters, leading to a more evident improvement on the separation performance. This work also shows that using the materials containing strong adsorption sites like coordinatively unsaturated metal sites as the supporters for ILs cannot achieve significant enhancement on the gas separation performance of the composites.

Three new isostructural luminescent complexes [(CH3)2NH2]2[Eu6(μ3-OH)8(BDC-NH2)6(H2O)6], [(CH3)2NH2]2[Eu6(μ3-OH)8(BDC-F)6(H2O)6] and [(CH3)2NH2]2[Eu6(μ3-OH)8(BDC-NO2)6(H2O)6] have been synthesized based on [(CH3)2NH2]2[Eu6(μ3-OH)8(1,4-NDC)6(H2O)6] under solvothermal conditions. In addition, these Eu-MOFs possess tuned intrinsic luminescence properties and detection capacities for different analytes, such as Cr2O72−, acetone and Fe3+. Here, these Eu-MOFs display distinct intrinsic luminescence properties because of the synergistic effect of donor groups and nonradiative vibrations, which are reflected in the lifetime, fluorescence quantum yield and emission intensity. Meanwhile, the detection experiments show that the one with the higher fluorescence quantum yield displays much more sensitive and efficient detection capacities for different kinds of analytes. Overall, this work indicated that tuning functional groups is vital to gain Eu-MOFs with good intrinsic luminescence properties, and make the detection capacities more sensitive and efficient.

A series of CNT@MIL-68(Al) composites with different carbon nanotubes (CNTs) loadings have been synthesized and characterized by SEM, TEM, PXRD, FT-IR, TGA, and N2 adsorption. As evidenced from SEM and TEM images, the incorporation of CNTs can result in better dispersity of MIL-68(Al) in composites and smaller particle size than pure MIL-68(Al). Adding appropriate amounts of CNTs increases both the BET surface areas and the total volume of small micorpores (

A computational study was firstly performed in this work to examine the applicability of an acid-functionalized metal-organic framework (MOF), UiO-66(Zr)-(COOH) 2 , in membrane-based H 2 S/CH 4 separation. The results show that this MOF could be potentially interesting when being used as the pure membrane material for the separation of the mixture with low H 2 S concentration. Further, the performance of 10 different mixed matrix membranes (MMMs) on the basis of the MOF was predicted by combing the molecular simulation data and the Maxwell permeation model. The results indicate that using this MOF as filler particles in MMMs can significantly enhance the permeation performance of pure polymers. The findings obtained in this work may be helpful in facilitating the application of this promising MOF for practical desulfurization process of fuel gas.

Water stable Zr-based metal–organic frameworks (MOFs) with different functional groups were used for selective removal of Cu2+ over Ni2+ from aqueous solution. Due to the unique chelation effect of two carboxyl groups on the adjacent organic ligand as well as the Jahn–Teller effect, UiO-66(Zr)–2COOH exhibits the highest selectivity (up to about 27) for Cu2+/Ni2+ in aqueous solution among the reported adsorbents as far as we know. In addition, the removal process is fast with less than 60 min for equilibration, and the stability and regenerability are good. These results may be helpful not only for the efficient treatment of wastewater containing heavy transition metal ions, but also for metal enrichment and recycling.

The current inefficient separation of O2 from air is an important industrial problem. Metal–organic frameworks containing coordinatively unsaturated metal sites (CUS) have emerged as competitive new adsorbents for such targets. In this study, dispersion-corrected density functional theory calculations were performed to investigate the influence of framework metal ions on the adsorption behavior of O2 in M3(BTC)2-type materials (M = Cr, Mn, Fe, Co, Ni and Cu; BTC = 1,3,5-benzenetricarboxylate acid). The results show that Ni3(BTC)2 can be potentially considered as promising oxygen adsorbent with relatively easier deoxygenation than Cr3(BTC)2. The magnitude of charge transfer from the CUS to O2 molecule was found to have a significant impact on the interaction energies of O2 with M3(BTC)2 except for the Cu version. Furthermore, it was revealed that the origin of the difference in the charge transfer can be attributed to the different electronegativity of the metals.

Zr-based MOFs usually feature exceptionally high thermal and chemical stability, which suggests that composites of noble metals and Zr-based MOFs could have wide industrial applications. In this work, we report the synthesis and characterization of Pd nanoparticles (of three different loadings: 0.3%, 0.5% and 1.0%) supported on micro-crystal DUT-67 MOFs. Via SEM, TEM and XPS characterization methods, it was found that the Pd nanoparticles were well dispersed on the interface of the MOF micro-crystals, with a diameter of 3.5 nm, and both the dangling organic groups and the cavities of the MOFs play important roles. Furthermore, PXRD, IR, TGA and N2 adsorption measurements confirmed that the composites are very robust. Studies on the catalytic properties indicated that they have good catalytic performance with a conversion of 99% and selectivity of 89% in the Suzuki coupling reaction. By a series of explorations, we found the best catalytic conditions are an ethanol–water mixed solvent as the medium, K2CO3 as the base and a temperature of 70 °C. Moreover, good catalytic properties were also shown for the hydrogenation of nitrobenzene, where the optimum temperature was 60 °C, and a conversion of 99% and selectivity of 99% were achieved.

Metal–organic frameworks (MOFs) have exhibited promising applications in gas and liquid separation. As a subclass of MOFs, zeolitic imidazolate frameworks (ZIFs) are attracting more and more interest because of their unique thermal and chemical stability. One of the representative ZIFs, ZIF-7, has super-hydrophobic pores, making it a perfect filler in polymer membranes for recovering acetone from fermentation broths. In this study, mixed matrix membranes (MMMs) based on ZIF-7 and polydimethylsiloxane (PDMS) were prepared, which display improved acetone–water total flux and separation factors simultaneously compared with a pure PDMS membrane. The separation factor can reach up to 39.1 with a high flux of 1236.8 g m−2 h−1 at 333 K, which is the highest value among those reported up to now to the best of our knowledge.

A cheap and biocompatible metal–organic framework MIL-88B(Fe) (MIL = Material Institut Lavoisier) was synthesized and incorporated into Matrimid® 5218 to fabricate mixed-matrix membranes (MMMs) for gas separation. Separation performances of the MIL-88B(Fe)/Matrimid MMMs were tested for the single gas permeation of H2 and CH4 as well as the mixture gas separation of an equimolar binary H2–CH4 mixture. Due to the molecular sieving effect, the incorporation of MIL-88B(Fe) can enhance H2 permeability but hinder the transport of CH4 in MIL-88B(Fe)/Matrimid MMMs, thus resulting in enhanced separation selectivity of H2–CH4. At 298 K and ΔP = 3.0 bar, compared with those of a pure polymeric membrane, the H2 permeability and H2–CH4 mixture separation factor of MMMs with a MIL-88B(Fe) loading of 10% increased by 16% and 66%, respectively. In addition, the operation temperature has a significantly positive effect on the separation of a H2–CH4 mixture.

In this work, a series of metal–organic frameworks (MOFs) are systematically screened for the capture of nitrobenzene (NB) from water for the first time. The results show that the adsorption capacities of two aluminum-based MOFs, CAU-1 and MIL-68(Al), can reach around 970 ± 10 and 1130 ± 10 mg g − 1 respectively, which are much higher than the experimental values of other porous materials reported so far. The μ 2 -OH in Al–O–Al units of Al-MOFs may play a key role in the adsorption process of NB. Langmuir isotherm was found to be suitable for depicting the NB adsorption process on these two MOFs, and the adsorption kinetics appropriately matched the pseudo-second-order model. Moreover, the Weber–Morris intraparticle diffusion model demonstrates that intraparticle diffusion is not the only rate-limiting step, and film diffusion also plays an important role in the adsorption for NB on MOFs. In addition, the regeneration of CAU-1 and MIL-68(Al) could be fully achieved using methanol without secondary pollution. These results indicate that MOFs are promising adsorbents for efficient capture of NB from waste water, and further in-depth investigations deserve to be performed.