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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.

One-pot synthesis of viologen-linked ionic polyacetylenes by catalyst-free quaternization-induced in situ polymerization for efficient heterogeneous catalytic conversion of atmospheric CO2.

Pyridinium-based ionic porous organic polymers (Py-iPOPs) were constructed from newly-designed acetonitrile-functionalized ionic liquids and multi-carbaldehyde monomers by the base-catalyzed Knoevenagel condensation. The obtained Py-iPOPs having in situ formed hydroxide anions and pyridinyl radicals were regarded as efficient metal-free and halogen-free heterogeneous catalysts for atmospheric CO2 fixation under mild conditions.

CH4 storage associated with adsorbed natural gas (ANG) technology is an issue attracting great concern. Following the Advanced Research Project Agency-Energy (ARPA-E) targeted deliverable capacity of 315 cm3·cm−3 (STP), hundreds of thousands of materials have been experimentally or theoretically evaluated, while the best results still show a 35% gap from the target. Moreover, recent theoretical research reveals that the target is beyond the possibility that real materials can be designed. To get rid of the awkward situation, we make attempts on investigating the CH4 delivery performance under other operation conditions. Methods of raising the discharge temperature (to infinite high) or elevating the storage pressure (to 25 MPa) have been proved to show limited effectiveness. In this work, it is found that the ARPA-E target can be achieved by using a decreasing storage temperature strategy. By taking 280 CoRE (computation-ready, experimental) COFs (covalent organic frameworks) as ANG materials, when reduce the storage temperature to 190.6 K, the highest deliverable capacity can reach 392 cm3·cm−3 (STP), and 16.1% CoRE COFs can surpass the target. The target is also achievable when storage at 220 K. Structure performance relationships study shows strong correlation between deliverable capacity and void fraction. Hence, 120 hypothetical COFs are generated to ascertain the optimum void fraction. In addition, the performance of 2D-COFs can be greatly enhanced by increasing the interlayer spacings, e.g. CH4 deliverable capacity (storage at 190.6 K) of ATFG-COF can be improved from 239 to 411 cm3·cm−3 (STP) when interlayer spacing is enlarged to 1.65 nm.

Discovery of remarkable porous materials for CO2 capture from wet flue gas is of great significance to reduce the CO2 emissions, but elucidating the most critical structure features for boosting CO2 capture capabilities remains a great challenge. Here, machine learning assisted computational screening on 516 experimental covalent organic frameworks (COFs) identify the superior secondary building units (SBUs) for wet flue gas separation, which are tetraphenylporphyrin unit in sql-type COFs and functional groups. Accordingly, 1233 COFs are assembled using the superior SBUs. Combined with DFT calculations, the “electron-donating induced vdW interaction” effect is discovered to design better-performing COFs with superior CO2 uptake, which can achieve 4.4 mmol·g-1 with CO2/N2 selectivity of 104.8; while the “electron-withdrawing induced vdW+electrostatic coupling interaction” effect is proposed to design better-performing COFs with superior CO2/N2 selectivity, which can arrive 277.6 with CO2 uptake of 2.2 mmol·g-1, in this case, H2O contributes to improving the CO2/N2 selectivity.

Rational design of multifunctional radical porous polymers with redox activity for targeted metal-free heterogeneous catalysis is an important research topic. In this work, we reported a new class of phenanthroline-based cationic radical porous hybrid polymers (Phen˙+-PHPs), which were constructed from the Heck reaction between a newly designed dibromo-substituted phenanthroline ionic monomer (iDBPhen) and a rigid building block, octavinylsilsesquioxane (VPOSS). For the first time, the stable phenanthroline-based radical cation was unexpectedly discovered in these polyhedral oligomeric silsesquioxane (POSS)-based porous hybrid polymers, probably undergoing in situ reduction of the dicationic monomer iDBPhen during the alkaline reagent K2CO3-involved Heck reaction. The radical characters of the typical porous polymers Phen˙+-PHP-2 and Phen˙+-PHP-2Br were confirmed from the electron paramagnetic resonance (EPR) spectra and X-ray photoelectron spectra (XPS). The chemical structures and porous geometry were fully characterized by a series of advanced technologies. Surprisingly, the metal-free cationic radical polymer Phen˙+-PHP-2 exhibited high heterogeneous catalytic efficiency in the H2O2-mediated selective oxidation of various sulfides to sulfoxides with high yields under mild conditions, owing to the electron-accepting and redox ability of Phen-based dications and radical cations. Moreover, the extended sample Phen˙+-PHP-2Br prepared by post-treatment of Phen˙+-PHP-2 with aqueous HBr was also employed as a metal-free efficient heterogeneous catalyst in the conversion of CO2 with epoxides into cyclic carbonates under atmospheric pressure and low temperatures. The remarkable catalytic performance in CO2 conversion should be assigned to the synergistic catalysis of POSS-derived Si–OH groups and nucleophilic Br− anions and N active atom-involved Phen cationic radical moieties within Phen˙+-PHP-2Br. These two catalysts can be facilely recovered and reused, also with stable recyclability in the above catalytic reaction systems, achieving the heterogeneous catalytic demands for multipurpose reactions.

In this work, we reported a facile one-pot approach to construct polyhedral oligomeric silsesquioxane (POSS) and imidazolium-based ionic porous hypercrosslinked polymers (denoted as iPHCPs) with multiple active sites towards efficient catalytic conversion of carbon dioxide (CO2) to high value-added cyclic carbonates. The targeted iPHCPs were synthesized from a rigid molecular building block octavinylsilsesquioxane (VPOSS) and a newly-designed phenyl-based imidazolium ionic crosslinker through the AlCl3-catalyzed Friedel–Crafts reaction. The desired multiple active sites come from the mixed anions including free Cl− and Br− anions, and in situ formed Lewis acidic metal–halogen complex anions [AlCl3Br]− within imidazolium moieties and POSS-derived Si–OH groups during the synthetic process. The typical polymer iPHCP-12 possesses a hierarchical micro-/mesoporous structure with a high surface area up to 537 m2 g−1 and shows a fluffy nano-morphology. By virtue of the co-existence of free nucleophilic Cl− and Br− anions, the metal complex anion [AlCl3Br]− with both electrophilic and nucleophilic characters and electrophilic hydrogen bond donor (HBD) Si–OH groups, iPHCP-12 is regarded as an efficient recyclable heterogeneous catalyst for synergistic catalytic conversion of CO2 with various epoxides into cyclic carbonates under mild conditions. The present work provides a succinct one-pot strategy to construct task-specific ionic porous hypercrosslinked polymers from easily available modules for the targeted catalytic applications.

The ability to restrict the shuttle of lithium polysulfide (LiPSn) and improve the utilization efficiency of sulfur represents an important endeavor toward practical application of lithium–sulfur (...

Engineering the structure of core-shell colloidal semiconductor nanoparticles (CSNPs) is attractive due to the potential to enhance photo-induced charge transfer (PICT) and induce favourable optical and electronic properties. Nonetheless, the sensitivity of telluride CSNPs to high temperatures makes it challenging to precisely modulate their surface crystallinity. Herein, we have developed an efficient strategy for synthesising telluride CSNPs with thin amorphous shells using aqueous cation exchange (ACE). By changing the synthesis temperature in the range 40 to 110C, the crystallinity of the CdTe nanoparticles was controllable from perfect crystals with no detectable amorphous shell (c-CdTe) to a core-shell structure with a crystalline CdTe NP core covered by an amorphous shell of tunable thickness up to 7-8nm (c@a-CdTe) . A second ACE step transformed the c@a-CdTe to crystalline CdTe@HgTe core-shell NPs. The c@a-CdTe nanoparticles synthesized at 60C and having a 4-5 nm thick amorphous shell, exhibited the highest surface-enhanced Raman scattering activity with a high enhancement factor around 8.82x10^5, attributed to the coupling between the amorphous shell and the crystalline core., Comment: 15 pages, 5 figures, plus supplementary information

Herein, we construct a new series of N-heterocyclic ligand bipyridine-based porous hybrid polymers (denoted Bpy-PHPs) from the Heck reaction of a rigid building unit octavinylsilsesquioxane (VPOSS) and 5,5′-dibromo-2,2′-bipyridine. Surprisingly, the typical sample Bpy-PHP-4 was found to be a metal-/halogen-free heterogeneous catalyst in the cycloaddition reaction of CO2 with a few epoxides under atmospheric pressure. After coordination with ZnBr2, the resultant ZnBr2@Bpy-PHP-4 afforded largely enhanced heterogeneous catalytic activities upon the conversion of carbon dioxide (CO2) and various epoxides into cyclic carbonates without using any co-catalysts under mild conditions. The moderate catalytic activities of Bpy-PHP-4 may be due to the presence of hydrogen bond donors (HBDs), i.e., polyhedral oligomeric silsesquioxane (POSS)-derived Si–OH groups and N active sites from Bpy linkers. In comparison, the high catalytic efficiency of ZnBr2@Bpy-PHP-4 should be attributed to the synergistic catalysis of Si–OH groups, N active atoms, and Bpy-coordinated ZnBr2. Moreover, the catalyst ZnBr2@Bpy-PHP-4 can be easily recovered and reused ten times without any significant loss of catalytic activities. This work affords an efficient metal-based porous hybrid polymer heterogeneous catalyst for the cycloaddition reaction of CO2 and epoxides under mild and co-catalyst-free conditions.

A succinct strategy was demonstrated for constructing a hydroxyl group and imidazolium-bifunctionalized ionic network via a one-pot quaternization. Key to success lies in the rational design of multi-imidazole precursor and hydroxyl-containing counterpart. Unique properties of the resultant ionic network render its high catalytic efficiency toward CO2 fixation under ambient conditions.

In this work, we report a new family of viologen-based ionic porous hybrid polymers (V-iPHPs) with task-specific multiple catalytic active sites toward efficient catalytic fixation of carbon dioxid...

To fabricate high performing ultrathin membranes, the interlayer nanochannel environment, which is hard to be observed and characterized in experiments, plays a key role in membrane performance. In...

A bi-functional cobalt and nitrogen co-doped carbon catalyst was fabricated by calcinating the chelate compound containing citric acid, melamine and CoCl2·6H2O in N2, with the mixed salts of LiCl and KCl as the template. Co and N species are highly dispersed in the target catalyst, which has a high surface area of 1011 m2 g−1. Such structure enables it to efficiently catalyze the direct aerobic oxidative esterification of benzyl alcohol with methanol to the ester of methyl benzoate; meanwhile, it exhibits superior potential ability for the application of oxygen reduction reaction, which is a vital process happening on the cathode of fuel cells and metal-air batteries.

Herein, we construct a new series of N-heterocyclic ligand bipyridine-based porous hybrid polymers (denoted Bpy-PHPs) from the Heck reaction of a rigid building unit octavinylsilsesquioxane (VPOSS) and 5,5'-dibromo-2,2'-bipyridine. Surprisingly, the typical sample Bpy-PHP-4 was found to be a metal-/halogen-free heterogeneous catalyst in the cycloaddition reaction of CO2 with a few epoxides under atmospheric pressure. After coordination with ZnBr2, the resultant ZnBr2@Bpy-PHP-4 afforded largely enhanced heterogeneous catalytic activities upon the conversion of carbon dioxide (CO2) and various epoxides into cyclic carbonates without using any co-catalysts under mild conditions. The moderate catalytic activities of Bpy-PHP-4 may be due to the presence of hydrogen bond donors (HBDs), i.e., polyhedral oligomeric silsesquioxane (POSS)-derived Si-OH groups and N active sites from Bpy linkers. In comparison, the high catalytic efficiency of ZnBr2@Bpy-PHP-4 should be attributed to the synergistic catalysis of Si-OH groups, N active atoms, and Bpy-coordinated ZnBr2. Moreover, the catalyst ZnBr2@Bpy-PHP-4 can be easily recovered and reused ten times without any significant loss of catalytic activities. This work affords an efficient metal-based porous hybrid polymer heterogeneous catalyst for the cycloaddition reaction of CO2 and epoxides under mild and co-catalyst-free conditions.

The complexity of secondary building units (SBUs), an indicator that can not only be calculated but also visually estimated, is proposed as a highly indicative predictor of hydrogen storage performance. With optimal pore sizes and void fractions, selecting COFs consisting of simple SBUs greatly improves the probability of top-performing COFs towards the ultimate DOE hydrogen storage target, as an easy principle for experimentalists to select hydrogen adsorbents.

Ionic liquid/metal–organic framework (IL/MOF) composites show great potential in CO2 capture. Here, we report a large-scale computational assembly of 550 357 IL/MOF composites for CO2/CH4 separation by developing a configurational-bias Monte Carlo (CBMC)-based incorporation method rather than applying the long-time Molecular Dynamics (MD) method. The introduction of ILs into MOFs shows both improvement and good balance of selectivity and working capacity. The results show that the high performing IL/MOF composites are mainly the wire-tube type structures originating from 1,3-dimethyl-imidazolium tetrafluoroborate [MMIM][BF4] and MOFs in sql topology with a pore size of ∼9 A, in which ILs are well confined in the MOFs to form the continuous, cation–anion alternately connected electronic nanowires. This work finds that synergistic adsorption sites can be formed in this wire-tube structure with a suitable size, providing useful information that can guide the future design of IL/MOF composites with improved CO2 capture performance.

Mixed matrix membranes (MMMs) have gained great attention for the efficient CO2 removal from raw nature gas or biogas (CO2/CH4 separation) and flue gas (CO2/N2 separation). Nevertheless, the development of high-performance MMMs for industrial applications is largely limited by the lack of suitable porous fillers. Herein, a novel ionic covalent organic polymer (ICOP-1) consisting of gas selective pores and hollow cavities is facilely fabricated using a metal triflate catalyzed condensation reaction. Considering its unique structural properties, ICOP-1 is explored as a novel filler to enhance the gas separation properties of polysulfone (PSf) membranes. Defect-free MMMs are successfully prepared owing to the high polymer–filler affinity originating from the organic nature of these two phases. Besides, the large cavities and size-selective pores of ICOP-1 lead to a simultaneous increase in membrane CO2 permeability and CO2/CH4, CO2/N2 selectivities. With the addition of only 0.5 wt % of ICOP-1 fillers, the a...

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...

CH4 storage associated with adsorbed natural gas technology attracts considerable researches on finding porous materials with remarkable CH4 delivery performance. In this work, we update the online accessible computation-ready, experimental (CoRE) covalent organic frameworks (COFs) database with 280 COFs in 12 topologies. All framework structures are constructed and compiled from the respective experimental studies and are further evaluated for CH4 delivery. The highest deliverable capacity (DC) between 65 and 5.8 bar among the CoRE COFs is 190 v(STP)/v at 298 K achieved by 3D PI-COF-4. Structure–property relationships show that large volumetric surface area generally benefits CH4 delivery. 2D-COFs can also be top performing materials if constructing their pore channels is passable in three dimensions, as the volumetric surface area will be increased accordingly. This idea can be realized by enlarging the interlayer spacings of 2D-COFs. We also evaluate the DC of CoRE COFs under conditions of 233 K, 65 ba...

The globally increasing concentrations of greenhouse gases in atmosphere after combustion of coal- or petroleum-based fuels give rise to tremendous interest in searching for porous materials to efficiently capture carbon dioxide (CO2) and store methane (CH4), where the latter is a kind of clean energy source with abundant reserves and lower CO2 emission. Hundreds of thousands of porous materials can be enrolled on the candidate list, but how to quickly identify the really promising ones, or even evolve materials (namely, rational design high-performing candidates) based on the large database of present porous materials? In this context, high-throughput computational techniques, which have emerged in the past few years as powerful tools, make the targets of fast evaluation of adsorbents and evolving materials for CO2 capture and CH4 storage feasible. This review provides an overview of the recent computational efforts on such related topics and discusses the further development in this field. Keywords: High-throughput computation, Screening and design, Nanoporous materials, CO2 capture, CH4 storage.

Benzaldehyde is an important chemical intermediate, and its production via the oxidation of benzyl alcohol with O2 is highly pursued as an alternative for the existing industrial process to meet the demand of green chemistry. Most of the reported catalytic systems are dependent on the noble/toxic metal catalysts. Herein, a biomass carbon catalyst doped with P and N heteroatoms is prepared by calcinating the phosphoric acid-treated N-containing biomass of soybean flour in N2. In the absence of solvent or additive, the obtained P,N co-doped carbon catalyst exhibits a remarkable catalytic activity for oxidation of benzyl alcohol to benzaldehyde with air (99.4% yield, TOF = 62.1 × 10-4 mol BAD/(g catalyst × h reaction time)). The present turnover frequency surpasses all the previously reported ones of similar metal-free carbon catalysts for this reaction. The N co-doping facilitates the P doping into the carbon matrix, favors the formation the catalytic active species and has a remarkable electronic effect on them, which are identified via experiments and DFT calculations.

POSS and viologen-linked porous cationic frameworks (V-PCIF-X, X = Cl, Br) are constructed via the Zincke reaction between octa(aminophenyl)silsesquioxane and viologen linkers. The typical V-PCIF-Br has a high surface area with abundant ionic sites, micro-/mesopores and Si–OH groups, serving as an efficient porous adsorbent and metal-free catalyst for simultaneous CO2 capture and conversion.

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.

A succinct strategy was demonstrated for constructing a hydroxyl group and imidazolium-bifunctionalized ionic network via a one-pot quaternization. Key to success lies in the rational design of multi-imidazole precursor and hydroxyl-containing counterpart. Unique properties of the resultant ionic network render its high catalytic efficiency toward CO2 fixation under ambient conditions.

Covalent organic frameworks (COFs) are a promising category of porous materials possessing extensive chemical tunability, high porosity, ordered arrangements at a molecular level, and considerable chemical stability. Despite these advantages, the application of COFs as membrane materials for gas separation is limited by their relatively large pore apertures (typically >0.5 nm), which exceed the sieving requirements for most gases whose kinetic diameters are less than 0.4 nm. Herein, we report the fabrication of ultrathin two-dimensional (2D) membranes through layer-by-layer (LbL) assembly of two kinds of ionic covalent organic nanosheets (iCONs) with different pore sizes and opposite charges. Because of the staggered packing of iCONs with strong electrostatic interactions, the resultant membranes exhibit features of reduced aperture size, optimized stacking pattern, and compact dense structure without sacrificing thickness control, which are suitable for molecular sieving gas separation. One of the hybrid membranes, TpEBr@TpPa-SO3Na with a thickness of 41 nm, shows a H2 permeance of 2566 gas permeation units (GPUs) and a H2/CO2 separation factor of 22.6 at 423 K, surpassing the recent Robeson upper bound along with long-term hydrothermal stability. This strategy provides not only a high-performance H2 separation membrane candidate but also an inspiration for pore engineering of COF or 2D porous polymer membranes.

In this work, we report a series of crystalline viologen-based porous ionic polymers (denoted VIP-X, X = Cl or Br), that have

Effective capture of radioactive iodic contaminants from nuclear wastes is of great importance for public safety as well as the secure utility of nuclear energy. In this work, a computational study was performed to systematically evaluate the performance of 187 experimentally reported covalent organic frameworks (COFs) for gaseous I2 and CH3I adsorption under real industrial conditions. The results show that 3D-COFs present better performance than 2D-COFs for both I2 and CH3I adsorption. 3D-Py-COF was identified with the highest I2 uptake of 16.7 g g−1, outperforming the adsorbents reported to date. In addition, based on the obtained structure–property relationships, a new 3D-COF with an even higher I2 uptake of 19.9 g g−1 was designed. For CH3I adsorption, the pore morphology plays an important role, and 3D-COFs with ctn topology having a pore size of around 9 A show superiority compared with other COFs. COF-103 was identified as the best material with a CH3I uptake of 2.8 g g−1, which is much higher than those of traditional adsorbents like activated carbons, alumina and zeolites.

POSS and viologen-linked porous cationic frameworks (V-PCIF-X, X = Cl, Br) are constructed via the Zincke reaction between octa(aminophenyl)silsesquioxane and viologen linkers. The typical V-PCIF-Br has a high surface area with abundant ionic sites, micro-/mesopores and Si-OH groups, serving as an efficient porous adsorbent and metal-free catalyst for simultaneous CO2 capture and conversion.

Energy-efficient and environmentally friendly separation processes are highly required in various industries, for which membrane-based separation technology is considered to be one of the most promising solutions. However, the development of membranes with efficient separation performances still remains a great challenge. Herein, a graphene oxide (GO)-assisted layer-by-layer restacking method was proposed to fabricate ultrathin covalent organic framework membranes for gas separation. The abundant functional groups in GO can improve the interactions, acting as “magnetic sheets”, to implement the up-down restacking of two dimensional (2D) covalent triazine-based framework-1 (CTF-1) nanosheets on the support, leading to the formation of continuous and dense ultrathin membranes with tunable thickness (100 nm, 210 nm, and 290 nm) by simple vacuum filtration of different amounts of dispersion liquid. Different numbers of nanosheets are restacked in these membranes, resulting in narrow interlayer passages that can exert an effect on the selective permeation of gas molecules with a tunable separation performance. As a demonstrative example, an efficient separation performance of H2 from CO2 was obtained with very high permeance for H2 (1.7 × 10−6 mol m−2 s−1 Pa−1) as well as a competitive selectivity. This method may also be applied to the development of ultrathin membranes from nanosheets of other materials.

Ultrathin films have the intrinsic feature to show high flux, which may become ideal membranes if they are fabricated to also have high selectivity. 2D covalent organic frameworks (COFs) are a class of crystalline materials with well-defined layered porous structures. Utilizing this feature, 2D-COF nanosheets can be stacked into few-layered ultrathin membranes, and thus the newly formed interlayer flow passages can be regulated to tune their separation properties, making them potential candidates for high-performance membranes. In this work, a series of few-layered 2D-COF membranes were constructed to explore their capability for gas separation as well as the underlying gas transport mechanisms by taking CO2/N2 separation as an example. The results showed that various few-layered 2D-COF membranes can be fabricated to show very different separation performances, from nonselective to highly selective, and even to the molecular sieving level. Furthermore, it was revealed that the energetic microenvironment around the narrow interlayer passages plays a crucial role, and introduction of interacting surfaces to generate van der Waals potential sites near these passages by tuning stacking modes can achieve few-layered membranes with both high CO2 flux and high CO2/N2 selectivity, leading to their separation performance far above the Robeson's upper bound. The mechanisms revealed and the design strategies proposed in this work may provide useful guidance for preparing ultrathin membranes with outstanding performance for gas separation.

Adsorptive denitrogenation (ADN) was carried out by adsorption of indole (IND) and quinoline (QUI) over metal–organic frameworks (MOFs) including acidic UiO-66—SO3H for the first time. The adsorbed amount of IND increased with increasing content of —SO3H in UiO-66. The favorable effect of the —SO3H group on the adsorptive removal of IND could be explained by hydrogen bonding between the O of —SO3H and the H of IND, which was firmly supported by the adsorption of pyrrole and methylpyrrole and by theoretical calculations. The application of an —SO3H group in the adsorptive removal of neutral IND is meaningful since neutral nitrogen-containing compounds are not easy to remove and since UiO-66—SO3H is reusable after simple washing with ethanol. The expected increase in QUI adsorption (due to acid–base interaction) with acidic —SO3H was observed when QUI was present at low concentrations (

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.

A diverse set of 46 covalent organic frameworks (COFs) were collected to computationally predict their separation performance for three industrial gas mixtures, CH4/H2, CO2/H2 and CO2/CH4, 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 CH4/H2, while have a comparable performance in separating CO2/H2 and CO2/CH4. 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.

Exploitation of new metal–organic framework (MOF) materials with high surface areas has been attracting great attention in related research communities due to their broad potential applications. In this work, a new Zr(IV)-based MOF, [Zr{sub 6}O{sub 4}(OH){sub 4}(eddb){sub 6}] (BUT-30, H{sub 2}eddb=4,4′-(ethyne-1,2-diyl)dibenzoic acid) has been solvothermally synthesized, characterized, and explored for gases and dyes adsorptions. Single-crystal X-ray diffraction analysis demonstrates a three-dimensional cubic framework structure of this MOF, in which each Zr{sub 6}O{sub 4}(OH){sub 4} building unit is linked by 12 linear eddb ligands. BUT-30 has been found stable up to 400 °C and has a Brunauer–Emmett–Teller (BET) surface area as high as 3940.6 m{sup 2} g{sup −1} (based on the N{sub 2} adsorption at 77 K) and total pore volume of 1.55 cm{sup 3} g{sup −1}. It is more interesting that this MOF exhibits stepwise adsorption behaviors for Ar, N{sub 2}, and CO{sub 2} at low temperatures, and selective uptakes towards different ionic dyes. - Graphical abstract: A new Zr(IV)-based MOF with high surface area has been synthesized and structurally characterized, which shows stepwise gas adsorption at low temperature and selective dye uptake from solution. - Highlights: • A new Zr-based MOF was synthesized and structurally characterized. • This MOFmore » shows a higher surface area compared with its analogous UiO-67 and 68. • This MOF shows a rare stepwise adsorption towards light gases at low temperature. • This MOF performs selective uptakes towards cationic dyes over anionic ones. • Using triple-bond spacer is confirmed feasible in enhancing MOF surface areas.« less

The adsorptive removal of organoarsenic compounds such as p-arsanilic acid (ASA) and roxarsone (ROX) from water using metal-organic frameworks (MOFs) has been investigated for the first time. A MOF, iron benzenetricarboxylate (also called MIL-100-Fe) exhibits a much higher adsorption capacity for ASA and ROX than activated carbon, zeolite (HY), goethite, and other MOFs. The adsorption of ASA and ROX over MIL-100-Fe is also much more rapid than that over activated carbon. Moreover, the used MIL-100-Fe can be recycled by simply washing with acidic ethanol. Therefore, it is determined that a MOF such as MIL-100-Fe can be used to remove organoarsenic compounds from contaminated water because of its high adsorption capacity, rapid adsorption, and ready regeneration. Moreover, only one of three analogous MIL-100 species (MIL-100-Fe, rather than MIL-100-Al or MIL-100-Cr) can effectively remove the organoarsenic compounds. This selective and high adsorption over MIL-100-Fe, different from other analogous MIL-100 species, can be explained (through calculations) by the facile desorption of water from MIL-100-Fe as well as the large (absolute value) replacement energy (difference between the adsorption energies of the organoarsenic compounds and water) exhibited by MIL-100-Fe. A plausible adsorption/desorption mechanism is proposed based on the surface charge of the MOFs, FTIR results, calculations, and the reactivation results with respect to the solvents used in the experiments.

Pyridine (Py) was adsorbed over metal–organic frameworks (MOFs) (UiO-66 and UiO-66-NH2 with different incorporated amino group content) in both vapor and liquid phases to understand the interactions between the basic adsorbate Py and a basic or neutral adsorbent. Py was adsorbed more favorably over UiO-66-NH2 than over the pristine UiO-66. Not only the adsorbed amount of Py but also adsorption kinetics increased with increasing amino group content in UiO-66s, showing that amino groups in the MOFs benefit the adsorption of Py in both vapor and liquid phases. To understand the favorable interaction between Py and basic UiO-66, calculations were also carried out. The results, including calculations, suggested that hydrogen bonding is important for improving the adsorption of Py over UiO-66s. However, the expected repulsive interaction between basic Py and amino groups of UiO-66-NH2 was not observed. Therefore, it is vital that specific interaction mechanisms should be considered in order to understand select...

With the aid of multi-scale computational methods, a diverse set of 46 covalent organic frameworks (COFs), covering the most typical COFs synthesized to date, were collected to study the structure–property relationship of COFs for CO2 capture. For this purpose, CO2 capture from postcombustion gas (CO2–N2 mixture) under industrial vacuum swing adsorption (VSA) conditions was considered as an example. This work shows that adsorption selectivity, CO2 working capacity and the sorbent selection parameter of COFs all exhibit strong correlation with the difference in the adsorbility of adsorbates (ΔAD), highlighting that realization of large ΔAD can be regarded as an important starting point for designing COFs with improved separation performance. Furthermore, it was revealed that the separation performance of 2D-layered COFs can be greatly enhanced by generating “splint effects”, which can be achieved through structural realignment to form slit-like pores with suitable size in the structures. Such “splint effects” in 2D-COFs can find their similar counterpart of “catenation effects” in 3D-COFs or MOFs. On the basis of these observations, a new design strategy was proposed to strengthen the separation performance of COFs. It could be expected that the information obtained in this work not only will enrich the knowledge of the structure–property relationship of COFs for separation, but also will largely facilitate their future applications to the fields related to energy and environmental science, such as natural gas purification, CO2, NOx and SOx capture, etc.

Metal-organic frameworks (MOFs) have recently emerged as a new type of nanoporous materials with tailorable structures and functions. Usually, MOFs have uniform pores smaller than 2 nm in size, limiting their practical applications in some cases. Although a few approaches have been adopted to prepare MOFs with larger pores, it is still challenging to synthesize hierarchical-pore MOFs (H-MOFs) with high structural controllability and good stability. Here we demonstrate a facile and versatile method, an in situ self-assembly template strategy for fabricating stable H-MOFs, in which multi-scale soluble and/or acid-sensitive metal-organic assembly (MOA) fragments form during the reactions between metal ions and organic ligands (to construct MOFs), and act as removable dynamic chemical templates. This general strategy was successfully used to prepare various H-MOFs that show rich porous properties and potential applications, such as in large molecule adsorption. Notably, the mesopore sizes of the H-MOFs can be tuned by varying the amount of templates., The synthesis of porous materials with hierarchically-sized pores is an attractive target for a variety of applications. Here, the authors employ in situ generated metal-organic assemblies as metal-organic framework templates which, upon removal, yield single mesoporous-microporous materials.

International audience; MIL-100(Fe) shows large adsorption uptakes for both MO and MB, whileMIL-100(Cr) can selectively adsorbMB from aMO-MB mixture. This work demonstrates that MOFs are promising adsorbents for dye capture and highlights that framework metal ion replacement is an efficient way to tailor MOFs for different applications in liquid separation.