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     

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     

Antibacterial activity against Escherichia coli of Cu‐BTC (MOF‐199) metal‐organic framework immobilized onto cellulosic fibers

A strong antimicrobial activity against Escherichia coli of Cu‐BTC metal‐organic frameworks immobilized over cellulosic fibers is hereby reported. The in situ synthesis of Cu‐BTC metal‐organic frameworks, aka MOF‐199 or HKUST‐1, onto cellulosic substrates was carried out by exposing carboxymethylated cellulosic substrates to Cu(OAC)₂, 1,3,5‐benzenetricarboxylic acid and triethylamine solutions following a very specific order. Using an in vitro model, in accordance to ASTM E2149‐13a, we observed that the cellulose‐MOF system was able to completely eliminate the growth of E. coli on agar plates and liquid cultures. The antibacterial activity of the comprising components of MOF‐199 and the cellulosic substrate was also evaluated and determined to be negligible. Since the method used to synthesize MOF‐199 crystals provides a strong bond between the crystals and the cellulosic substrates, the crystals not detach from the anionic cellulosic fibers allowing the modified textile to be washed and reused hence opening a new avenue to fabricate antibacterial clinical fabrics. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40815.     

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     

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.     

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.     

Electrochemical synthesis,characterization and application of a microstructure Cu<Subscript>3</Subscript>(BTC)<Subscript>2</Subscript> metal organic framework for CO<Subscript>2</Subscript> and CH<Subscript>4</Subscript> separation

The electrochemical route is a promising and environmentally friendly technique for fabrication of metal organic frameworks (MOFs) due to mild synthesis condition, short time for crystal growth and ease of scale up. A microstructure Cu₃(BTC)₂ MOF was synthesized through electrochemical path and successfully employed for CO₂ and CH₄ adsorption. Characterization and structural investigation of the MOF was carried out by XRD, FE-SEM, TGA, FTIR and BET analyses. The highest amount of carbon dioxide and methane sorption was 26.89 and 6.63 wt%, respectively, at 298 K. The heat of adsorption for CO₂ decreased monotonically, while an opposite trend was observed for CH₄. The results also revealed that the selectivity of the developed MOF towards CO₂ over CH₄ enhanced with increase of pressure and composition of carbon dioxide component as predicted by the ideal adsorption solution theory (IAST). The regeneration of as-synthesized MOF was also studied in six consecutive cycles and no considerable reduction in CO₂ adsorption capacity was observed.     

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     

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.     

A Computational Study of the Adsorptive Removal of H<Subscript>2</Subscript>S by MOF-199

Metal–organic framework material MOF-199 is a new type of adsorption material for removal toxic H₂S. In this work, the effects of temperature and pressure on the performance of H₂S adsorption in MOF-199 were studied by using the grand canonical Monte Carlo (GCMC) simulation; the interaction mechanism between framework atoms of MOF-199 and guest H₂S molecules were further discussed through density functional theory (DFT) calculations. It is found that the MOF-199 adsorption capacity towards H₂S decreases with increasing temperature and increases with increasing pressure. At low pressures, the frameworks containing the binding sites of copper dimers and trimesic acid are the main factor affecting the adsorption performance of MOF-199. While at high pressures, the free volume of MOF-199 contributes to the adsorption capacity as well. The adsorptive interactions between H₂S and the organic ligand are weak (>??14.469 kJ/mol). When H₂S adsorption on the Cu–Cu bridge, the binding energies of the modes where hydrogen is put inward of the copper dimer are generally smaller than that where hydrogen is outward, whereas the adsorption on the top of copper ion shows the smallest BEs value (<??50 kJ/mol) due to its tendency of forming a saturated six-coordinated configuration.     

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.     

Tuning the Performance of Ni‐Based Catalyst by Doping Coinage Metal on Steam Reforming of Methane and Carbon‐Tolerance

Density functional theory (DFT) calculations are employed to investigate the key reactions in steam reforming of methane (SRM) on Ni‐based bimetallic surface alloys, including the dissociation of CH₄ and H₂O, the oxidation of CH by oxygen atom to form formyl (CHO), and the dehydrogenation of CHO to form carbon monoxide (CO). The aim of this investigation is to hunt for an optimal catalyst for SRM, which can inhibit carbon formation while maintaining high activity to the SRM. Coinage metal impurity (Au, Ag, and Cu) doped Ni catalysts have been proven to inhibit carbon deposition. In this work, we focus on investigating the doping effects on some leading processes in SRM. It is found that the coinage metal doping has a little effect on the two‐step dissociation of H₂O, which has a linear correlation between the dissociation barriers and the OH–H coadsorption energies. In addition, the dehydrogenation of CHO is kinetically favorable on all alloy surfaces. However, for the CH oxidation to CHO, only the Ni–Cu surface remains high activity. These results suggest that Ni–Cu bimetallic material is an excellent active carbon‐tolerance SRM catalyst for solid‐oxide fuel cells.     

Adsorption of Cu2+ ions with poly(N‐isopropylacrylamide‐co‐methacrylic acid) micro/nanoparticles

Chelation efficiency of stimuli‐responsive poly(N‐iospropylacrylamide‐co‐methyacrylic acid) (PNIPAAm‐MAA) nanoparticles with Cu²⁺ ions from CuSO₄·5H₂O solution and from wood treated with copper‐based preservatives was studied. It was shown that particle size played a very important role in the adsorption process. The nano‐scale particles showed much improved Cu ion adsorption efficiency, compared with the micro hydrogels. The amount of Cu ion adsorption increased with increase of MAA ratio in copolymers and adsorption efficiency decreased with increased particle size. Furthermore, the adsorption amount varied with adsorption temperature at temperatures both below and above the corresponding low critical solution temperature (LCST). The high adsorption efficiency of Cu ions by PNIPAAm‐MAA polymer particles provides an effective technique for recovering metal ions (e.g., Cu²⁺) from wood treated with metal‐based preservatives. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Facile and Large-Scale Syntheses of Nanocrystal Rare Earth Metal–Organic Frameworks at Room Temperature and Their Photoluminescence Properties

The treatment of Ln(NO₃)₃·6H₂O (Ln?=?La, Ce, Eu, Gd, Dy) with 1,3,5-benzenetricarboxylic acid (H₃BTC) in a water–ethanol solution facilely yields crystal nanorods of rare earth metal–organic frameworks (MOFs) at room temperature. Electron micrographs show that the nanorods are 50–200?nm in width, 50–100?nm in thickness and 1–2?μm in length. All the crystal nanorods have the same Ln(BTC)(H₂O)₆ structure as identified by power X-ray diffraction, elemental analysis, thermogravimetric and Fourier transform infrared analysis. The optical properties of all the compounds are recorded; and, the nanoscale MOFs (NMOFs) with Eu³⁺ and Dy³⁺ show excellent photoluminescence.     

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.     

Electrochemical Synthesis of Cu (II) Coordination Polymer Coatings Based on 2,2′-Thiodiacetic Acid and 1,2,4,5-Benzenetetracarboxylate

Electrochemical synthesis of coordination polymers of Cu(II), [Cu(TDA)]_n and [Cu₂(BTC)(H₂O)₆?6H₂O]_n in which H₂TDA is 2,2′-thiodiacetic acid and BTC stands for 1,2,4,5-benzenetetracarboxylate was carried out by the electrochemical oxidation of Cu anode in the presence of H₂TDA (a flexible ligand), and 1,2,4,5-benzentetracarboxylic acid (H₄BTC) (a rigid ligand) in aqueous solutions. The structure of coordination polymers were characterized by scanning electron microscopy, X-ray powder diffraction, elemental analysis, thermal gravimetric and differential thermal analyses. The crystal structure of the compounds consists of one-dimensional cubical crystal polymeric units of [Cu(TDA)]_n and [Cu₂(BTC)(H₂O)₆?6H₂O]_n. Furthermore, the coordination number of Cu (II) ions in synthesized coordination polymers to be found five. The main advantages of electrosynthesis are the minor synthesis time, the milder conditions and the facile synthesis of coordination polymer coatings.     

Performance study of modified ZSM‐5 as support for bimetallic chromium–copper catalysts for VOC combustion

The catalytic performance of bimetallic chromium–copper supported over untreated ZSM‐5 (Cr? Cu/Z), ZSM‐5 treated with silicon tetrachloride (Cr–Cu/SiCl₄‐Z) and ZSM‐5 treated with steam (Cr–Cu/H₂O‐Z) is reported. The activity is based on the combustion of ethyl ethanoate and benzene at a feed concentration of 2000 ppm and a gas hourly space velocity (GHSV) of 32 000 h^?1. Due to higher reactivity and larger molecular size compared with that of water molecules, SiCl₄ reacted at the external surface of ZSM‐5 crystals. Cr–Cu/SiCl₄‐Z and Cr–Cu/H₂O‐Z both gave slightly lower conversion and carbon dioxide yield compared with Cr–Cu/Z. This was attributed to larger active metal crystallites formed in the mesopores and narrowing pore mouth and pore intersection by extraframework species. Cr–Cu/SiCl₄‐Z and Cr–Cu/H₂O‐Z both had reduced concentration and strength of acid sites, thus making them less susceptible to deactivation by coking. The coke accumulated by these two catalysts was relatively softer and more easily decomposed in oxygen during catalyst regeneration. Copyright © 2004 Society of Chemical Industry     

A novel 3D zinc metal–organic framework based on the tetrazole-containing ligand and tricarboxylic acid

A novel zinc metal–organic framework (MOF) with the combination of 5,5′-(1,4-phenylene)bis(1H-tetrazole) (H₂BDT) and 1,3,5-benzenetricarboxylic acid (H₃BTC) as the mixed ligands, namely [Me₂NH₂]₄Zn₂(BDT)(BTC)₂ 2DMF (1), has been solvothermally synthesized and characterized. Single-crystal X-ray analysis reveals that the structure of 1 features a pillared-layered three-dimensional (3D) anionic framework of [Zn₂(BTC)₂(BDT)]_n⁴ⁿ⁻. The luminescent property studies indicated that 1 might be a potential blue-light material. It was found that the introduction of H₃BTC could exhibit an obvious influence on the luminescence of 1, which can help us in better designing luminescent MOF materials.     

Confining organic cations in metal organic framework allows molecular level regulation of CO2 capture

High tunability of both ionic liquids (ILs) and metal organic frameworks (MOFs) enables great opportunity in the rational designation of IL/MOF composites for physical adsorption and separation. Traditionally, cations and anions of ILs as an entirety are combined with MOFs either inside or outside the microchannels. Herein, organic cations of ILs were confined into Cu-BTC and the champion adsorbent is obtained by using 1-propionic acid-3-vinylimidazole bromide as the precursor with a moderate loading amount, exhibiting higher CO₂ uptakes of 8/5 mmol g⁻¹ than Cu-BTC (6.0/3.5 mmol g⁻¹) at 273/298 K and 100 kPa, associating with significantly improved CO₂/N₂(CH₄) selectivities. The organic cations are interacted with two adjacent CuII₂(CRO₂)₂ paddle wheel units of Cu-BTC, expanding the Cu O bond to strengthen the CO₂ affinity of open Cu sites and also serving as an additive CO₂ adsorptive site. The promotion of CO₂ capture ability is further reflected in the dynamic column breakthrough experiment.