Porous MIL-101 Research Articles

Ethylenediamine-incorporated MIL-101(Cr)-NH2 metal-organic frameworks for enhanced CO2 adsorption

Ethylenediamine (EA)-incorporated MIL-101(Cr)-NH2 adsorbents were prepared for CO2 adsorption. First, MIL-101(Cr)-NH2 was directly prepared by the solvothermal method, followed by the EA incorporation inside the pores of MIL-101(Cr)-NH2. The prepared samples were characterized by N2 porosimetry, field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrometry, thermogravimetric, and powder X-ray diffraction analyses. The effects of ethylenediamine loading in MIL-101(Cr)-NH2 on the CO2 adsorption capability were systematically investigated. EA-incorporated MIL-101(Cr)-NH2 showed CO2 adsorption capacity of ca. 3.4 mmol/g, which was ∼62% higher than the pristine MIL-101(Cr)-NH2. In addition, the amine-grafted MOF samples showed good regenerability and stability after consecutive adsorption-desorption cycles at ambient conditions. These suggest that introduction of alkylamine molecules into the pores of metal-organic frameworks can be a promising strategy to improve the CO2 soprtion ability of MOFs.

Encapsulation of K6P2W18O62 into magnetic nanoporous Fe3O4/MIL-101 (Fe) for highly enhanced removal of organic dyes

In this work, a magnetic P2W18O62@ Fe3O4/MIL-101 (Fe) nanocomposite as a stable and effective ternary adsorbent was fabricated by the hydrothermal method and utilized for the elimination of organic dyes from aqueous solutions. Characterization of magnetic nanocomposite was accomplished by FT-IR, XRD, SEM, EDX, BET specific surface area, and VSM measurements. The findings demonstrated the prosperous encapsulation of P2W18O62 heteropolyanions within the porous MIL-101(Fe) framework. The encapsulated sample with a less pore volume and surface area compared with the MOF, displayed a considerable diminish in both pore volume and surface area due to the incorporation of huge Dowson-type POM within the cages of MOF. The fabricated nanocomposite was used as an efficient adsorbent for the elimination of cationic dyes (such as rhodamine B and methylene blue) from aqueous solutions. Influencing factors including primary dye concentration, pH, temperature, and adsorbent dose on the adsorption potency of the P2W18O62@ Fe3O4/MIL-101 (Fe) were checked. Adsorption isotherms were investigated by Freundlich and Langmuir models and obtained results confirmed that dyes adsorption pursued the Langmuir model. Moreover, the fabricated nanocomposite had high stability and recoverability without any alter in structure. According to these results, P2W18O62@ Fe3O4/MIL-101 (Fe) can act as a reusable effective adsorbent for the fast elimination of diverse cationic dyes from aqueous solutions.

An organic-inorganic hybrid nanomaterial composed of a Dowson-type (NH4)6P2Mo18O62 heteropolyanion and a metal-organic framework: synthesis, characterization, and application as an effective adsorbent for the removal of organic dyes.

In this work, an inorganic–organic hybrid nanomaterial, P2Mo18/MIL-101(Cr), based on Wells–Dawson-type (NH4)6P2Mo18O62 polyoxometalate (abbreviated as P2Mo18) and the MIL-101(Cr) metal–organic framework was fabricated by the reaction of (NH4)6P2Mo18O62, Cr(NO3)3·9H2O and terephthalic acid under hydrothermal conditions. The as-prepared recyclable nanohybrid was fully characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) equipped with energy dispersive X-ray microanalysis (EDX), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy and Brunauer–Emmett–Teller (BET) specific surface area studies. All the analyses confirmed the successful insertion of P2Mo18O626− heteropolyanion within the cavities of MIL-101(Cr). The encapsulated MIL-101(Cr) showed a considerable decrease in both pore volume and surface area compared with MIL-101(Cr) due to incorporation of the very large Dowson-type polyoxometalate into the three-dimensional porous MIL-101(Cr). The nanohybrid had a specific surface area of 800.42 m2 g−1. The adsorption efficiency of this nanohybrid for removal of methylene blue (MB), rhodamine B (RhB), and methyl orange (MO) from aqueous solutions was evaluated. Surprisingly, the composite not only presented a high adsorption capacity of 312.5 mg g−1 for MB, but also has the ability to rapidly remove 100% MB from a dye solution of 50 mg L−1 within 3 min. These results confirmed that this adsorbent is applicable in a wide pH range of 2–10. The nanohybrid showed rapid and selective adsorption for cationic MB and RhB dyes from MB/MO, MB/RhB, MO/RhB and MB/MO/RhB mixed dye solutions. The equilibrium adsorption data were better fitted by the Langmuir isotherm. Kinetics data indicate that the adsorption of the dye follows a pseudo-second order kinetics model. Also, this material could be effortlessly separated and recycled without any structural modification. Accordingly, it is an efficient adsorbent for removing cationic dyes.

Controllable fabrication of cuprous sites in confined spaces for efficient adsorptive desulfurization

Cu+ modified materials have important research significance for deep desulfurization of fuels by π-complexation adsorption. Up to now, it is still challenging to design green and mild conditioned strategy for fabricating high yield of Cu+ sites. Here, we have developed a new strategy, one-step double solvents method (OSDS), which can realize fabricating high yield (~100%) of Cu+ sites. Compared with traditional two-step methods including introduction of Cu2+ precursor and conversion to Cu+ such as wet impregnation method and liquid-phase reduction method, this preparation strategy make sure that all the introduced Cu2+ was confined in MIL-101(Cr) pores and the conversion of Cu2+ to Cu+ took place in that confined spaces as well. Besides, OSDS strategy can only performed at room temperature (25 °C) which is time- and energy-efficient process considering the harsh condition of high-temperature autoreduction method. The resulting material exhibits excellent adsorption and reusability performance for deep desulfurization due to the balanced synergistic effect of suitable Cu+ sites and pores of MIL-101(Cr).

A green synthesized recyclable ZnO/MIL-101(Fe) for Rhodamine B dye removal via adsorption and photo-degradation under UV and visible light irradiation

ABSTRACT Metal–organic frameworks (MOFs) have recently debuted as participants and solid supports in catalysts for environmental application in water treatment. Visible light active nanocomposites; ZnO/MIL-101(Fe); were synthesized via a hydrothermal method by loading ZnO; prepared by a green method; on a porous MIL-101(Fe) to be used as a heterogeneous catalyst for Rhodamine B dye (RhB) degradation as a model pollutant. The effect of adding acetic acid during the preparation of MIL-101(Fe) was studied; [A] used for the samples prepared by acetic acid. The prepared catalysts were characterized by XPS, XRD, zeta potential, TGA, FTIR, N2 adsorption–desorption measurements, SEM, EDX, elemental mapping, TEM, and UV–VIS diffuse reflectance spectroscopy. The loading of ZnO on MIL-101(Fe) decreased the band gap from 3.2 eV for ZnO to be 2.85 eV for ZnO/MIL-101(Fe)[A], this low band gap explaining the obtained high activity under visible light irradiation. The mechanism of the photocatalytic degradation of RhB was investigated by introducing different scavengers to compete for the possible reactive species involved in the degradation process. The trapping experiments indicated that h+ and •OH have a vital role in the RhB degradation. The reusability of MIL-101(Fe) was also investigated after three runs. Thus, the synthesized ZnO/MIL-101(Fe)[A] could be used as an alternative catalyst for the photocatalytic degradation of coloured wastewater as it can successfully degrade 97.1% of Rhodamine B (10 mg/L) with high reaction rate (k = 0.0339 min−1) under visible light irradiation for 300 min using 0.5 g/L of the catalyst. The as-prepared ZnO/MIL-101(Fe) and ZnO/MIL-101(Fe)[A] have competitive photocatalytic dye degradation activity.

Construction of a voltammetric sensor based on MIL-101 hollow cages for electrocatalytic oxidation and sensitive determination of nitrofurazone

Antibiotic pollution as a hot issue of global concern is extraordinarily sought after due to the deleterious consequences on ecosystems and human health from the excessive utilization and deficient management. Achieving determination of antibiotics residues in food is greatly crucial but remains challenging. In this work, a rational strategy was employed to fabricate chromium (III) terephthalate MOF (MIL-101) hierarchical hollow cages through crystal growth and subsequent acid etching processes. The material has been characterized using several characterizations such as scanning electron microscopy, transmission electron microscopy, and X-ray powder diffraction, showing the porous MIL-101 microspheres were made of large inner cavity and single-crystalline shell. An electrochemical sensor based on the hollow MIL-101 was then developed for the determination of nitrofurazone (NFZ). Electrochemical measurements indicate that the hollow MIL-101 has highly electrocatalytic activity and excellent voltammetric response towards the NFZ oxidation, exhibiting as a wide linear range of 0.030–55μM and a low detection limit of 10nM (S/N=3). Moreover, detection of NFZ in food samples was carried out by standard addition method. Acceptable result with recovery of 93.2–103% was obtained for six parallel measurements. Our work provides a promising strategy to construct electrochemical sensors with extended applicability for analysis in complex food matrices.

Control of pore chemistry in metal-organic frameworks for selective uranium extraction from seawater

Abstract Extracting uranium from seawater is of great importance for the sustainable development of nuclear energy. A central problem is to develop high-performance adsorbents to allow for efficient and selective recovery of uranium from seawater. Since the adsorption properties are strongly dependent on the functional groups and the architectures of the adsorbents, one option is to bond effectively functional groups onto high-surface-area materials. Here we report the first synthesis of amidoxime functionalized metal-organic frameworks MIL-101-OA, exhibiting excellent adsorption performance arising from the large surface areas of the metal-organic frameworks (MIL-101) and the high affinity of the amidoxime towards uranyl. The MIL-101-OA was synthesized via grafting of acrylonitrile onto the pores of MIL-101 followed by its conversion to amidoxime functionalities. The MIL-101-OA demonstrated excellent uranium adsorption capacities of 321 mg g −1 in simulated seawater and 4.6 mg g −1 in real seawater, which are competitive with the currently state-of-the-art uranium adsorbent.

Composite salt in MIL-101(Cr) with high water uptake and fast adsorption kinetics for adsorption heat pumps

Abstract Owing to the features of S-shape water sorption isotherm and low desorption temperature, MIL-101(Cr) has been considered as up-and-coming adsorbent for adsorption heat pumps (AHPs). In order to improve water vapor uptake at the low relative pressure (P/P0 ≤ 0.3) for AHPs, a new type of solid adsorbent was fabricated by impregnating porous MIL-101(Cr) with the aqueous solution of hygroscopic salt such as CaCl2 and LiCl. The effect of impregnation salt concentration on hygroscopicity of composite salt-MIL-101(Cr) was discussed. The crystalline phase, pore structure, morphology and the composition of the composites were characterized by X-ray diffraction, pore size analysis, Scanning Electron Microscopy and Energy Dispersive Spectrometry. And their adsorption and desorption performances were evaluated. The experimental results indicated that the composites obtained by dipping MIL-101(Cr) with the solution of 25% CaCl2 and 15% LiCl, exhibited excellent adsorption capacities and fast adsorption rates. Their amounts adsorbed at P/P0 of 0.3 reached 0.44, 0.45 g/g, respectively, which were much higher than the pristine MIL-101(Cr). Additionally, fifty separate adsorption/desorption cycles suggested that the composite had excellent reversibility. All the results indicated that the novel composite salt-MIL-101(Cr) are expected to be a promising candidate for AHPs.

WO3 in suit embed into MIL-101 for enhancement charge carrier separation of photocatalyst

Compositing nanoparticles photo-catalyst with enormous surface areas metal–organic framework (MOF) will greatly improve photocatalytic performances. Herein, WO3 nanoparticles are partly embedded into pores of MIL-101 or only supported on the outside of representative MIL-101, which were defined as embedded structure WO3@MIL-101@WO3 and coating structure WO3&MIL-101 respectively. Different pH, concentration and loading percentage were researched. XRD, TEM and BET were carried to analyze the composites. Compared with the pristine WO3, all WO3 loaded MOF nanocomposites exhibited remarkable enhancing for the efficiency of photocatalytic degradation methylene blue under visible light. Their activity of the same loading percentage WO3 in embedded structure and coating structure have increased for 9 and 3 times respectively compared with pure WO3. The WO3@MIL-101@WO3 has 3 times higher efficiency than WO3&MIL-101, because the shorter electron-transport distance can make a contribution to electron–hole separation. The further mechanism involved has been investigated by radical quantify experiment, XPS and photoluminescence spectroscopy.

Dawson-Type Polyoxometalate Incorporated into Nanoporous MIL-101(Cr): Preparation, Characterization and Application for Ultrafast Removal of Organic Dyes

In this work, Dawson-type K6P2W18O62 polyoxometalate salt (abbreviated as P2W18) was successfully encapsulated into mesoporous MIL-101(Cr) metal organic framework. The as-prepared P2W18@MIL-101(Cr) nanohybrid was characterized by FT-IR spectroscopy, XRD, Raman spectroscopy, EDX, SEM, zeta potential measurements and BET surface area. The results demonstrated the successful loading of K6P2W18O62 (~36 wt.%) into porous MIL-101(Cr) framework. Compared with the pristine MIL-101(Cr), the encapsulated sample demonstrated a significant decrease in both surface area and pore volume owing to the insertion of large Dowson-type POM into the cages of MOF. The resulting P2W18@MIL-101(Cr) was applied as a new adsorbent to remove methylene blue (MB), Rhodamine B (RhB) and methyl orange (MO) organic dyes from aqueous solutions. The effect of effective parameters such as adsorbent dosage, dye concentration, pH, and the temperature was studied on the dye removal process. Furthermore, the selective adsorption of the nanohybrid was investigated towards MB/MO, MB/RhB, MO/RhB and MB/MO/RhB mixed dye solutions. The nanohybrid showed rapid and selective adsorption for cationic MB and RhB dyes from mixed dye solutions. The results indicated that the dye adsorption followed Langmuir isotherm. The thermodynamic data showed that the adsorption is an endothermic process. This nanohybrid can function as a recyclable efficien adsorbent for the rapid removal of various cationic textile dyes from aqueous solutions.

Effective Removal of Antibacterial Drugs from Aqueous Solutions Using Porous Metal–Organic Frameworks

Effective removal of antibacterial drugs attracts more and more attentions with the rapid development of pharmacy industry, while still facing large challenge in removal efficiency to date. Herein, porous MIL-101 and SO3H-MIL-101 were systematically studied for their adsorption performances toward two common antibacterial drugs, gemifioxacin mesylate (GEM) and moxifloxacin hydrochloride (MOX). It was found that SO3H-MIL-101 can exhibit high adsorption capacities of 528 mg g−1 and 447 mg g−1 for GEM and MOX at natural pH respectively, superior to those of MIL-101 and other common MOFs-based adsorbents. The adsorption kinetics study indicates that the adsorption onto SO3H-MIL-101 follows pseudo-second-order model. Furthermore, it was found that the adsorption capacity of SO3H-MIL-101 increased at pH range of 2.0–7.0 and decreased at pH range of 7.0–10.0. Further study indicates that the two MOFs can be easily regenerated even after four cycles. Mechanism analysis demonstrates that surface potentials of the MOFs play critical effects on the adsorption processes for the amphipathic drugs and the introduction of –SO3H groups can effectively regulate the adsorption performance of the MOF. This work may provide an effective approach to modify the adsorption behaviour of the MOFs.

General Immobilization of Ultrafine Alloyed Nanoparticles within Metal-Organic Frameworks with High Loadings for Advanced Synergetic Catalysis.

The development of a general synthesis approach for creating fine alloyed nanoparticles (NPs) in the pores of metal–organic frameworks (MOFs) shows great promise for advanced synergetic catalysis but has not been realized so far. Herein, for the first time we proposed a facile and general strategy to immobilize ultrafine alloyed NPs within the pores of an MOF by the galvanic replacement of transition-metal NPs (e.g., Cu, Co, and Ni) with noble-metal ions (e.g., Pd, Ru, and Pt) under high-intensity ultrasound irradiation. Nine types of bimetallic alloyed NPs of base and noble metals were successfully prepared and immobilized in the pores of MIL-101 as a model host, which showed highly dispersed and well-alloyed properties with average particle sizes ranging from 1.1 to 2.2 nm and high loadings of up to 10.4 wt %. Benefiting from the ultrafine particle size and high dispersity of Cu–Pd NPs and especially the positive synergy between Cu and Pd metals, the optimized Cu–Pd@MIL-101 exhibited an extremely high activity for the homocoupling reaction of phenylacetylene under unprecedented base- and additive-free conditions and room temperature, affording at least 19 times higher yield (98%) of 1,4-diphenylbuta-1,3-diyne than its monometallic counterparts. This general strategy for preparing various MOF-immobilized alloyed NPs potentially paves the way for the development of highly active metal catalysts for a variety of reactions.

Chromium-Based Metal-Organic Framework MIL101(Cr)–CdSe Quantum Dot Composites: Synthesis, Morphology, Gas Adsorption and Photoluminescent Properties

Chromium-based metal-organic framework MIL101(Cr)–CdSe quantum dot (QD) composites were synthesized by two different approaches: (a) loading the pre-synthesized CdSe QDs onto the surface of the MIL101(Cr) particles [denoted as CdSe/MIL101(Cr)] and (b) in situ synthesis of CdSe QDs into the pores of MIL101(Cr) (denoted as CdSe@Cr-MIL-101). The effect of synthesis technique on morphology, gas adsorption and photoluminescent properties of the as-prepared MOF-QD composites has been investigated. It was found that the porosity of composite materials strongly depends on the loading amount of CdSe QDs. Interestingly, the incorporation of CdSe QDs into/onto to MIL101(Cr) has enhanced optical absorption of the composites in the visible region (redshift) and therefore has potential applications in photocatalysis or solar cells.

Palladium Nanoparticles Encapsulated in the MIL-101-Catalyzed One-Pot Reaction of Alcohol Oxidation and Aldimine Condensation.

A bifunctional catalyst, Pd nanoparticles (NPs) encapsulated in MIL-101, has been synthesized by capillary impregnation. The as-prepared Pd@MIL-101 was characterized by powder X-ray diffraction, N2 physisorption, X-ray photoelectron spectroscopy, transmission electron microscopy, and high-angle annular dark field scanning transmission electron microscopy, indicating that Pd NPs were highly dispersed in the pores of MIL-101 without deposition of the nanoparticles on the external surface or aggregation. The bifunctional catalyst of Pd@MIL-101 exhibited highly catalytic activity for alcohol oxidation and aldimine condensation one-pot reactions, where Pd NPs affords good oxidation activity and MIL-101 offers Lewis acidity. In particular, Pd@MIL-101 yielded an effective catalytic performance with toluene as the solvent, K2CO3 as the co-catalyst, and 353 K as the optimum reaction temperature for the one-pot reaction. After five cycles of reuse, Pd@MIL-101 still shows high catalytic performance. Above all, it is found that the enhanced catalytic performance was achieved via the synergistic cooperation of MIL-101 and Pd NPs.

Effective Removal of Naphthalenesulfonic Acid from Water Using Functionalized Metal–Organic Frameworks

Effective removal of toxic 1,5-naphthalenedisulfonic acid (NDS) and 2-naphthalenesulfonic acid (NSA) from contaminated water still faces a challenge to date. Herein, porous MIL-101, MIL-101-NH2, and MIL-101-SO3H were systematically studied for their adsorption performances toward these toxic molecules. Upon the introduction of −NH2 groups, H-bond interaction and electrostatic interaction were enhanced, and accordingly MIL-101-NH2 can exhibit more excellent adsorption capacity (NDS, 188.1 mg g–1; NSA, 285.0 mg g–1) compared to MIL-101-SO3H, MIL-101, and some other common adsorbents. Further study indicates that MIL-101-NH2 can be easily regenerated even after three adsorption processes. This work demonstrates that MIL-101-NH2 may have large potential in naphthalenesulfonic acids removal and rational selection of organic functional groups may be critical in construction of adsorbents.

Hierarchical porous PANI/MIL-101 nanocomposites based solid-state flexible supercapacitor

Metal-Organic Frameworks (MOFs) have attracted increasing attention in the field of energy storage owing to their high porosity, high specific surface area, high charge storage. However, the poor conductivity in most MOFs largely hinders their electrical properties. In this work, we developed an effective strategy to grow the conductive polyaniline (PANI) inside the pores of MIL-101 (labeled as PANI/MIL-101) to form a fixed interpenetrating network structure. The electron-rich imine group in PANI is chelated with the coordinatively unsaturated metal sites (CUS) in MIL-101 to form a relatively strong bonded complex and through other synergistic effects to enhance the conductivity and electrochemical properties. The resultant PANI/MIL-101 exhibited a superior high capacitance of 1197 F g−1 (i.e., 957.6C g−1) at 1 A g−1 in constant current charge and discharge test. The assembled flexible solid-state supercapacitor showed a favorable specific capacitance, power density and good cycling stability (a 81% capacitance retention rate over 10,000 cycles). It also demonstrates a good flexibility, as evidenced by a small capacitance loss of 10% after being subject to 1000 bending cycles at 180°. The PANI/MIL-101 nanocomposite showed great potential in energy storage device.

High removal of thiophene from model gasoline by porous MIL-101(Cr)/SA hybrid membrane.

Membrane separation technologies have great promising potential for applications in several industries. Metal–organic frameworks (MOFs), for their large surface areas, low framework densities, transition-metal ions in the skeleton and high pore volumes relative to other porous matrices, have great potential for the removal of sulfur from gasoline with high efficiency. In the present study, a novel porous membrane adsorbent MIL-101(Cr)/SA was prepared by immobilizing MIL-101(Cr) onto sodium alginate (SA) matrix, which can combine the size/shape selectivity of MIL-101(Cr) with the processability and mechanical stability of SA polymer. The physico-chemical properties of MIL-101(Cr)/SA were investigated by FT-IR, SEM, BET, XRD and EDX methods. To investigate the effects of some important factors on the adsorption behavior for thiophene, a batch of experiments were performed by changing the concentration of porogen polyethylene glycol in the MIL-101(Cr)/SA, solution temperature, initial thiophene concentration and contact time. Meanwhile, benzothiophene, thiophene and 3-methyl thiophene were used to test the selectivity of MIL-101(Cr)/SA. The MIL-101(Cr)/SA showed an excellent uptake capacity of 671 mg g−1 under the optimal adsorption conditions. Selectivity testing indicated that the uptake capacity of MIL-101(Cr)/SA follows the order of benzothiophene > thiophene > 3-methyl thiophene. Kinetics experiments indicated the pseudo-second-order model displayed good correlation with adsorption kinetics data. The Crank model showed that the intraparticle solute diffusion is the rate-controlling adsorption step. Regeneration experiment result shows that the prepared MIL-101(Cr)/SA has excellent adsorption and desorption efficiencies.

Sandwich type polyoxometalates encapsulated into the mesoporous material: synthesis, characterization and catalytic application in the selective oxidation of sulfides.

The A-type sandwich polyoxometalates of [(HOSnIVOH)3(PW9O34)2]12− (P2W18Sn3) and [(OCeIVO)3(PW9O34)2]12− (P2W18Ce3) were immobilized for the first time into the porous metal–organic framework MIL-101(Cr). FT-IR, powder X-ray diffraction, SEM-EDX, ICP analysis, N2 adsorption and thermogravimetric analysis collectively confirmed immobilization and good distribution of polyoxometalates into cages of MIL-101(Cr). The catalytic activities of the homogeneous P2W18Sn3 and P2W18Ce3 and the corresponding heterogeneous catalysts were examined in the oxidation of sulfides to sulfones with H2O2 as the oxidant at room temperature. The effects of different dosages of polyoxometalates, type of solvent, reaction time, amount of catalyst and oxidant in this catalytic system were investigated. The new P2W18Sn3@MIL-101 and P2W18Ce3@MIL-101 nanocomposites exhibited good recyclability and reusability in at least five consecutive reaction cycles without significant loss of activity or selectivity.

N2 Capture Performances of the Hybrid Porous MIL-101(Cr): From Prediction toward Experimental Testing

The purification of nitrogen-containing gas mixtures, natural/shale gas, and dry air calls for economically viable adsorptive separation processes involving an adsorbent with a higher affinity for N2 over hydrocarbons and oxygen. This led to the discovery of a new class of unprecedented N2-selective metal–organic frameworks (MOFs) with coordinatively unsaturated chromium(III) sites, e.g., MIL-100(Cr) (MIL: Materials of Institut Lavoisier). Following this preliminary study, here grand canonical Monte Carlo simulations identified MIL-101(Cr), an analogue of MIL-100(Cr), as another N2-selective adsorbent from mixtures of both CH4–N2 (natural gas purification) and O2–N2 (air purification). This prediction was further compared to single gas adsorption and breakthrough separation experiments. It was evidenced that only the more energetic coordinatively unsaturated chromium sites released using an activation temperature of 523 K are responsible for the N2-selective behavior of MIL-101(Cr). The separation mechani...

Adsorption of organic arsenic acids from water over functionalized metal-organic frameworks

Organic arsenic acids (OAAs) are regarded as water pollutants because of their toxicity and considerable solubility in water. Adsorption of OAAs such as phenylarsonic acid (PAA) and p-arsanilic acid (ASA) from water was investigated over functionalized (with OH groups) metal-organic framework (MOF, MIL-101), as well as over pristine MIL-101 and commercial activated carbon. The highly porous MIL-101 bearing three hydroxyl groups (MIL-101(OH)3) exhibited remarkable PAA and ASA adsorption capacities. Based on the effects of pH on PAA and ASA adsorption, hydrogen bonding was suggested as a plausible mechanism of OAA adsorption. Importantly, OAAs and MIL-101(OH)3 can be viewed as hydrogen-bond acceptors and donors, respectively. Moreover, MIL-101(OH)3 could be regenerated by acidic ethanol treatment, being a promising adsorbent for the removal of PAA and ASA from water.