Computational screening of porous metal‐organic frameworks and zeolites for the removal of SO2 and NOx from flue gases

Sulfur oxides (SO₂) and nitrogen oxides (NO_x) are principal pollutants in the atmosphere due to their harmful impact on human health and environment. We use molecular simulations to study different adsorbents to remove SO₂ and NO_x from flue gases. Twelve representative porous materials were selected as possible candidates, including metal‐organic frameworks, zeolitic imidazolate frameworks, and all‐silica zeolites. Grand canonical Monte Carlo simulations were performed to predict the (mixture) adsorption isotherms to evaluate these selected materials. Both Cu‐BTC and MIL‐47 were identified to perform best for the removal of SO₂ from the flue gases mixture. For the removal of NO_x, Cu‐BTC was shown to be the best adsorbent. Additionally, concerning the simultaneous removal of SO₂, NO_x, and CO₂, Mg‐MOF‐74 gave the best performance. The results and insights obtained may be helpful to the adsorbents selection in the separation of SO₂ and NO_x and carbon capture. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2314–2323, 2014     

Water adsorption in metal–organic frameworks with open‐metal sites

H₂O adsorptions inside porous materials, including silica zeolites, zeolite imidazolate frameworks, and metal–organic frameworks (MOFs) using molecular simulations with different water models are investigated. Due to the existence of coordinately unsaturated metal sites, the predicted adsorption properties in M‐MOF‐74 (M = Mg, Ni, Co, Zn) and Cu‐BTC are found to be greatly sensitive to the adopted H₂O models. Surprisingly, the analysis of the orientations of H₂O minimum energy configuration in these materials show that three‐site H₂O models predict an unusual perpendicular angle of H₂O plane with respect to the Metal‐O₄ plane, whereas those models with more than three sites give a more parallel angle that is in better agreement with the one obtained from density functional theory (DFT) calculations. In addition, the use of these commonly used models estimates the binding energies with the values lower than the ones computed by DFT ranging from 15 to 40%. To correct adsorption energies, simple approach to adjust metal‐O(H₂O) sigma parameters to reproduce the DFT‐calculated binding energies is used. With the refined parameters, the computed water isotherms inside Mg‐MOF‐74 and Cu‐BTC are in reasonable agreement with experimental data, and provide significant improvement compared to the predictions made by the original models. Further, a detailed inspection on the water configurations at higher‐pressure region was also made, and observed that there is an interesting two‐layer water network formed using three‐ and four‐site models. © 2014 American Institute of Chemical Engineers AIChE J, 61: 677–687, 2015     

Bifunctional Metal Organic Framework Catalysts for Multistep Reactions: MOF‐Cu(BTC)‐[Pd] Catalyst for One‐Pot Heteroannulation of Acetylenic Compounds

A bifunctional metal organic framework catalyst containing palladium and copper(II) benzene‐1,3,5‐tricarboxylate – MOF‐Cu(BTC)‐[Pd] – has been prepared. This catalyst enables the performance of the tandem Sonogashira/click reaction starting from 2‐iodobenzylbromide, sodium azide and alkynes to produce 8H‐[1,2,3]triazolo[5,1‐a]isoindoles with good yields under mild reaction conditions.     

Simulation on hydrogen storage properties of metal‐organic frameworks Cu‐BTC at 77–298 K

In recent years, many researchers have studied on the hydrogen storage properties of metal‐organic frameworks (MOFs) by grand canonical Monte Carlo (GCMC) simulation. At present, the GCMC studies of Cu‐BTC (BTC: benzene‐1,3,5‐tricarboxylate) which is a prototypical metal‐organic framework mainly adopt the classical force fields, the simulation temperatures are mainly focus on 298 and 77 K, and most researchers did not consider the effects of quantum effects at low temperature. Therefore, we used the quantum effects to correct the classical force fields and the force fields with more accurate simulation results were used to simulate the hydrogen adsorption performances of Cu‐BTC in the temperature range of 77–298 K and the pressure range of 1–8 MPa at each temperature. The results show that the effects of quantum effects on the hydrogen storage of Cu‐BTC cannot be neglected and the corrected Dreiding force field can simulate hydrogen adsorption performances of Cu‐BTC more accurately at low temperature. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1383–1388, 2018     

Deterioration of metal–organic framework crystal structure during fabrication of poly(l‐lactic acid) mixed‐matrix membranes

Poly(l ‐lactic acid) (PLLA) and metal–organic framework (MOF) mixed‐matrix membranes were prepared by melt extrusion of PLLA with 5% (w/w) of either activated or water‐saturated Cu₃(BTC)₂ (Cu₃(C₉H₃O₆)₂(H₂O)₃·xH₂O, HKUST‐1). The morphology and the stability of injection‐molded samples were evaluated using thermogravimetric analysis, differential scanning calorimetry, gel permeation chromatography, X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The presence of activated and saturated MOF crystals increased the cold crystallization onset temperature as compared to neat PLLA. This can be attributed to the MOF crystals incorporated in the PLLA matrix, which decreased the mobility of PLLA and thus impeded the crystallization process. According to the XRD results, the activated MOF crystals were successfully incorporated into the PLLA matrix without altering the crystal structure of the MOF. Moreover, the findings from permeability and tensile tests as well as SEM imaging indicated good interfacial interactions between PLLA and activated MOF. However, during melt extrusion of PLLA with saturated MOF, water molecules from the saturated MOF altered the MOF crystal structure and contributed to the degradation of the PLLA polymer by reducing its molecular weight by around 21%. © 2013 Society of Chemical Industry     

Matrix effect of mixed‐matrix membrane containing CO2‐selective MOFs

Facilitated mixed‐matrix membranes (MMMs) containing Cu‐metal organic frameworks (Cu‐MOFs) with high CO₂ selectivity on an asymmetric polysulfone support were fabricated and examined the effect of gas separation performance using different matrices. An amorphous poly(2‐ethyl‐2‐oxazoline) (POZ) and semicrystalline poly(amide‐6‐b‐ethylene oxide) (PEBAX^®MH 1657) block copolymer were chosen as the polymeric matrix and the effect of the matrix on CO₂ separation for MMMs containing Cu‐MOFs was investigated. The interaction of CO₂ in different matrix was investigated theoretically using the density functional theory method, and it was found that the amide segment in PEBAX would contribute more to the CO₂ solubility than ether segment. The morphological changes were investigated by differential scanning calorimetry, field emission scanning electron microscope and X‐ray diffractometer. The ideal selectivity of CO₂/N₂ was enhanced significantly with the addition of a Cu‐MOF, and the values are higher in the Cu‐MOF/PEBAX MMM compared with that in a POZ based asymmetric MMM. Improvement in the CO₂/N₂ selectivity of a Cu‐MOF/PEBAX MMM was achieved via facilitated transport by the CO₂‐selective Cu‐MOFs due to both their high adsorption selectivity of CO₂ over N₂ and the decreased crystallinity of PEBAX due to the presence of the Cu‐MOFs, which would provide a synergic effect on the CO₂ separation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42853.     

Metal Organic Frameworks as Solid Acid Catalysts for Acetalization of Aldehydes with Methanol

Room temperature acetalization of aldehydes with methanol has been carried out using metal organic frameworks (MOFs) as solid heterogeneous catalysts. Of the MOFs tested, a copper‐containing MOF [Cu₃(BTC)₂] (BTC=1,3,5‐benzenetricarboxylate) showed better catalytic activity than an iron‐containing MOF [Fe(BTC)] and an aluminium containing MOF [Al₂(BDC)₃] (BDC=1,4‐benzenedicarboxylate). The protocol was validated for a series of aromatic and aliphatic aldehydes and used to protect various aldehydes into commercially important acetals in good yields without the need of water removal. In addition, the reusability and heterogeneity of this catalytic system was demonstrated. The structural stability of MOF was further studied by characterization with powder X‐ray diffraction, Brunauer–Emmett–Teller surface area measurements and Fourier‐transformed infrared spectroscopic analysis of a deactivated catalyst used to convert a large amount of benzaldehyde. The performance of copper MOF as acetalization catalyst compares favourably with those of other conventional homogeneous and heterogeneous catalysts such as zinc chloride, zeolite and clay.     

Dual action bactericides: Quaternary ammonium/N‐halamine‐functionalized cellulose fiber

Bi‐functional antibacterial material was prepared by co‐grafting N‐halamine and quaternary ammonium salt monomers from cellulose fiber. The grafted fiber was characterized by Fourier transform infrared spectra, and X‐ray photoelectron spectra. The N‐halamine derived from the precursor 4‐[(acryloxy)methyl]‐4‐ethyl‐2‐oxazolidinone via chlorination treatment and the oxidative chlorine (Cl⁺) leaching behavior were investigated. The antibacterial activities of singly (only QAs‐functionalized or only Cl⁺‐releasing) and dual (QAs‐functionalized and Cl⁺‐releasing) functional cellulose fibers were tested against Gram‐negative Escherichia coli and Gram‐positive Staphylococcus aureus. Compared to singly functionalized formulations, the bi‐functional cellulose fiber exhibited excellent and rapid bactericidal performance against both E. coli and S. aureus. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40070.     

Well‐dispersed copper nanorods grown on the surface‐functionalized PAN fibers and its antibacterial activity

β‐Cyclodextrins/polyacrylonitrile/copper nanorods (β‐CDs/PAN/CuNRs) composite fibers were fabricated by two steps including the preparation for the β‐CDs/PAN composite fibers by electrospining, and the preparation of the β‐CDs/PAN/CuNRs composite fibers by adsorption and reduction. The β‐CDs/PAN/CuNRs composite fibers were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy respectively. The results indicated that the CuNRs were not only successfully synthesized on the surface of composite fibers but also the CuNRs were distributed without aggregation on the composite fibers. Furthermore, microorganism Escherichia coli had been used to check the antibacterial efficacy of the β‐CDs/PAN/CuNRs composite fibers. Subsequently, antibacterial tests have indicated that the composite fibers have good bactericidal effects. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41011.     

Synthesis and application of cotton‐based chelate fibers grafted with poly(1‐vinyl‐1,2,4‐triazole) side chains

Cotton‐based chelate fibers grafted with poly(1‐vinyl‐1,2,4‐triazole) (PVTAZ) side chains were synthesized facilely by ozone‐induced graft polymerization of 1‐vinyl‐1,2,4‐triazole (VTAZ) monomer onto cotton fibers. The synthesis conditions were optimized to improve the yield and mechanical strength of the products. The obtained cotton‐g‐PVTAZ fibers were characterized and evaluated for batch adsorption of heavy metal ions from aqueous solutions. The maximum adsorption capacity of Ag(I), Pb(II), and Cu(II) on the fibers at pH 6.8 was 522, 330, and 184 mg/g, respectively. At 30% graft yield, the Young's modulus of cotton fiber increased about 26.5%, and its adsorption capacities of Ag(I), Pb(II), and Cu(II) increased about 2.6, 1.9, and 1.4 times, respectively. After washed with 0.1 mol/L HNO₃ solutions, the adsorbed metal ions were eluted, and the regenerated cotton‐g‐PVTAZ fibers could be used repeatedly for water treatment. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41617.     

The Influence of Cu3(BTC)2 metal organic framework on the permeability and perm‐selectivity of PLLA‐MOF mixed matrix membranes

Poly(l ‐lactic acid) (PLLA) ‐ 20% (w/w) and Cu₃(BTC)₂ metal organic framework (MOF) based mixed matrix membranes (MMMs) were fabricated by a vertical corotating twin screw microcompounder followed by an injection molding process. Water vapor, CO_2, O₂, and selected aroma mass transfer properties of PLLA and PLLA MMMs were evaluated. The CO₂/O₂ perm‐selectivity of PLLA (α_CO2/O2) MMMs increased from 7.6 to 10.3 with the incorporation of 20% Cu₃(BTC)₂ MOF. Gravimetric permeability studies of trans‐2‐hexenal performed at 23°C and 50% RH indicated that permeability coefficient of PLLA MMMs increased by around 60% as compared to regular PLLA film. However, no changes in mass transfer rates were observed for acetaldehyde. Furthermore, the thermal processing parameters as well as the presence of MOF did not show any significant effect on the molecular weight of the PLLA matrix nor on the crystalline structure of the Cu₃(BTC)₂ MOF, which was confirmed by both gel permeation chromatography and X‐ray diffraction studies. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42764.     

A novel carbonized polydopamine (C‐PDA) adsorbent with high CO2 adsorption capacity and water vapor resistance

Novel carbonized polydopamine adsorbents (C‐PDAs) with high surface area, high CO₂ adsorption capacity and superior moisture resistance performance were prepared by one‐step synthesis method using polydopamine as carbon precursor at different KOH/C ratios, and then characterized. CO₂ and water vapor adsorption performances of C‐PDAs were examined separately by static adsorption and fixed‐bed experiments. Results showed that BET area and pore volume of C‐PDA‐4 were up to 3342 m²/g and 2.01 cm³/g, respectively. Its CO₂ adsorption capacity reached up to 30.5 mmol/g at 25 bar, much higher than many other adsorbents including metal‐organic frameworks (MOFs). C‐PDAs prepared with high KOH/C ratios had low surface element concentrations of O and N resulting in low surface hydrophilic property. H₂O(g) isotherm of C‐PDA was much lower than those on Mg‐MOF‐74, Cu‐BTC, and MIL‐101(Cr). Fixed‐bed experiments showed that co‐presence of water vapor in feed stream with 30% RH had negligible impact on CO₂ working capacity of C‐PDA. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3730–3738, 2016     

Preparation,characterization, and antibacterial activities of quaternarized N‐halamine‐grafted cellulose fibers

A viable method for coating of cellulose fiber with quaternarized N‐halamine is reported in this article. The use of quaternary ammonium salt group in combination with N‐halamine group can reinforce the antibacterial activity. The chemical structure of as‐synthesized N‐halamine precursor 4‐(Bromo‐acetic acid methylester)‐4‐ethyl‐2‐ oxazolidinone (BEO) was characterized by ¹H‐NMR. The cellulose fibers were characterized by Fourier transform infrared spectra and X‐ray photoelectron spectra. The spectra data confirmed that the quaternarized N‐halamine‐grafted cellulose fibers were successfully obtained. The antibacterial properties of functional fibers were challenged with both Gram positive and Gram negative bacteria. The antibacterial tests and showed that the as‐prepared antibacterial cellulose fibers exhibited powerful and rapid bactericidal performance against both Gram negative E. coli and Gram positive S. aureus. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42702.     

Grafting of sulfonated monomer onto an amino‐silane functionalized 2‐aminoterephthalate metal − organic framework via surface‐initiated redox polymerization: proton‐conducting solid electrolytes

A post‐polymerization method for metal–organic frameworks (MOFs) has been developed to produce super‐acidic solid nanoparticles. Thus, the NH₂MIL‐53(Al) MOF was functionalized with (3‐aminopropyl)triethoxysilane (APTES) from amine groups to yield active site anchored MOF nanoparticles. Then, sulfonated polymer/MOF hybrid nanoparticles were prepared by redox polymerization of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (MOF‐g‐PAMPS), initiated onto the surfaces of aminopropyl‐functionalized NH₂MIL‐53(Al) nanoparticles. The synthesis and modification of NH₂MIL‐53(Al) nanoparticles were characterized by Fourier transform infrared (FTIR) spectroscopy and TGA. FTIR and TGA results indicated that APTES modifier agent and AMPS monomer were successfully grafted onto the MOF nanoparticles. The grafting efficiency of PAMPS polymer onto the MOF nanoparticles was estimated from TGA thermograms to be 33%. Also, sulfonated polymer/MOF hybrid nanoparticles showed a proton conductivity as high as 4.9 × 10^?5 S cm^?1. Nitrogen adsorption of modified NH₂MIL‐53(Al) showed also a decrease in pore volume. The morphology and crystalline structure of MOF nanoparticles before and after the modification processes were studied by SEM and XRD, respectively. © 2015 Society of Chemical Industry     

Underlying mechanism of the hydrothermal instability of Cu<Subscript>3</Subscript>(BTC)<Subscript>2</Subscript> metal-organic framework

Water induced decomposition of Cu₃(BTC)₂ (BTC = benzene-1,3,5-tricarboxylate) metal-organic framework (MOF) was studied using dynamic water vapour adsorption. Small-angle X-ray scattering, Fourier transform infrared spectroscopy and differential scanning calorimetry analyses revealed that the underlying mechanism of Cu₃(BTC)₂ MOF decomposition under humid streams is the interpenetration of water molecules into Cu-BTC coordination to displace organic linkers (BTC) from Cu centres.     

Highly antibacterial and toughened polystyrene composites with silver nanoparticles modified tetrapod‐like zinc oxide whiskers

In this work, high‐performance multifunctional composites were obtained by melt blending silver deposited tetrapod‐like zinc oxide whiskers (Ag‐ZnOw) with polystyrene (PS). The chemical, spectroscopic, antibacterial, mechanical, and morphological properties of the PS/Ag‐ZnOw composites were carefully investigated and discussed. The obtained PS/Ag‐ZnOw composites characterized remarkable antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Moreover, it is found that impact strength of the composite increase with increasing nanofiller concentration (up to 0.25 wt %). Morphological characterization of the impact fractured surface of composites revealed that toughening was achieved through uniform filler distribution in the polymer matrix, and anchoring effect was imparted by the tetrapod‐like shape of ZnO whiskers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40900.     

Gas‐permeation performance of metal organic framework/polyimide mixed‐matrix membranes and additional explanation from the particle size angle

With MOFs of Cu₃(BTC)₂ and ZIF‐8 as the dispersed phases and four polyimides with CO₂ permeabilities ranging from 1.36 to 564 barrer as the continuous phase, the influence of metal organic frameworks on the gas‐separation properties of mixed‐matrix membranes (MMMs) was investigated. The results show that the gas permeabilities of all of the prepared MMMs greatly increased and even largely exceeded the predicted value of the Bruggeman model; for example, with the same Cu₃(BTC)₂ loading of 21.3 vol %, the O₂ permeability increase rate of our prepared Cu₃(BTC)₂/Matrimide 5218‐20 MMMs was 2.26 times, whereas that predicted by the Bruggeman model was only 1.05 times. In addition, when the gas permeability of the polymeric phase was far lower than the dispersed phase of ZIF‐8 or Cu₃(BTC)₂ compared with ZIF‐8, which had a particle size (R) around 150 nm, Cu₃(BTC)₂ of 5–15 µm showed a little better enhancing effect on the gas‐permeation performance of the MMMs. In addition to the properties of the dispersed and continuous phases, we speculated that the ratio between R of the dispersed phase to the membrane thickness (L) played an important role for MMMs; the larger R/L was, the greater the gas permeability of the MMMs was. This speculation was initially evidenced by the ZIF‐8/ODPA/TMPDA‐20 MMMs with different Ls. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45728.     

Fabrication of homochiral metal‐organic framework membrane for enantioseparation of racemic diols

Chiral metal‐organic frameworks (MOFs) used to discriminate chiral enantiomers are of great practical significance. In this study, a novel homochiral [Ni₂(L‐asp)₂(bipy)] membrane was fabricated on a porous ceramic support and used for enantioselective separation of racemic diols. High‐energy ball milling was applied to decrease the size of MOF crystals to achieve homogeneous seed suspensions. A high‐quality homochiral membrane was obtained after optimizing the preparation process. Under the concentration‐driven permeation process, racemic 2‐methyl‐2,4‐pentanediol (MPD) was readily separated by the as‐prepared membrane. At 30°C, an enantiomeric excess value of 35.5 ± 2.5% was obtained at a feed concentration of 1.0 mmol L^?1. The chiral separation of racemic MPD via the membrane followed a preferential sorption mechanism. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4364–4372, 2013     

ZIF‐8 SURMOF Membranes Synthesized by Au‐Assisted Liquid Phase Epitaxy for Application in Gas Separation

Metal‐organic frameworks (MOFs) exhibit a huge potential for gas separation. ZIF‐8 is an interesting candidate due to its high thermal stability and its pore properties. By liquid phase epitaxy, the growth of the highly oriented surface‐anchored MOF ZIF‐8 on non‐porous and porous surfaces has been proven. The preparation of monolithic ZIF‐8 thin films supported by porous α‐Al₂O₃ substrates modified by a thin layer of Au is investigated. The layer‐by‐layer deposition process accomplished via a dipping procedure results in the formation of defect‐ or crack‐free membranes, preliminary characterized by the determination of ethane and ethene permeance.     

Development of a cashew nut shell liquid (CNSL)‐based polymer for antibacterial activity

A biobased polymer derived from cashew nut shell liquid (CNSL) as a renewable resource was investigated for use as an antibacterial material. CNSL is a mixture of aromatics containing cardanol as the main component and cardol and 2‐methylcardol as minor components. CNSL composition analyses showed that the minor components (i.e., cardol and 2‐methylcardol) in CNSL had higher contents of unsaturated structures than cardanol. These higher unsaturated contents promoted the thermal polymerization in the preparation of an epoxy CNSL prepolymer (ECNP). The biobased polymer film was fabricated by the reaction of amine compounds and ECNP without any organic solvent. The ECNP film took less than 2.0 h to reach a hardened dry condition at room temperature because of the crosslinking reaction between epoxy and amine groups. The antibacterial activities of the biobased polymer against Escherichia coli and Staphylococcus aureus were evaluated. CNSL showed antibacterial activity against S. aureus, whereas epoxy CNSL and ECNP alone showed no significant antibacterial activity against E. coli or S. aureus. This indicated that the antibacterial activity was based on the phenolic and catechol hydroxyl groups of CNSL. In addition, a biobased polymer film derived from CNSL and diamine showed antibacterial activity against both E. coli and S. aureus, even with alcohol conditioning. This suggested that the antibacterial activity was certainly fixed in the structure of the ECNP‐based polymers after the standard antisepsis treatment in medical facilities. Therefore, this biobased polymer could be useful in antibacterial materials as a coating and resin for health care applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42725.