Pristine MIL-101 Research Articles

Enhanced dye degradation using MIL-53(Fe)-Modified kraft lignin as a heterogeneous Fenton catalyst

MIL-53(Fe), a metal–organic framework (MOF), is capable of degrading harmful organic contaminants, but it has relatively low Fenton catalytic efficiency. To enhance the degradation performance of MIL-53(Fe), we synthesized MIL-53(Fe)-MKL by incorporating modified kraft lignin (MKL) into pristine MIL-53(Fe). The as-prepared composite demonstrated Fenton activity, degrading 97 % of methylene blue (MB) within 50 min. Compared to pristine MIL-53(Fe) (which achieved 62.4 % MB degradation), the MIL-53(Fe)-MKL composite showed a 34.6 % improvement in MB degradation under identical reaction conditions. The incorporated MKL promotes Fe2+ regeneration from Fe3+ in the Fenton process, activating H2O2 to produce OH radicals, which were identified through scavenging experiments and chemical dosimetry with ESR analysis. The MIL-53(Fe)-MKL composite was reused for at least five cycles without a significant decrease in catalytic efficiency. This reported catalyst takes advantage of both MKL and MIL-53(Fe) to enhance catalytic activity, providing a basis for developing innovative catalysts for organic pollutant degradation.

Exploring the Potential of Beta-Cyclodextrin-Based MIL-101(Cr) for Pharmaceutical Removal from Wastewater: A Combined Density Functional Theory and Molecular Simulations Study.

Pharmaceutical contaminants pose significant risks to ecosystems and human health, necessitating effective removal strategies. This research focuses on developing advanced adsorbents for removing pharmaceutical pollutants from the environment. Metal-organic frameworks (MOFs), specifically MIL-101(Cr) functionalized with biodegradable beta-cyclodextrin (β-CDex), were investigated as potential nanocomposite adsorbents for the removal of ketorolac (KTRK), naproxen (NPXN), and tramadol (TRML). The study employed molecular simulations and density functional theory (DFT) calculations to explore the interactions between the pollutants and adsorbents. Analyses of DFT results, including electrostatic potential, ionization energy, density of states, and molecular orbital analysis, provided insights into the reactivity of pollutants and adsorbents. Additionally, the structural properties of the adsorbents, such as fractional free volume, radius of gyration, and system energies, were thoroughly examined. Molecular dynamics (MD) and Monte Carlo (MC) simulations were used to evaluate the adsorption capacities of MIL-101(Cr) for the target pharmaceutical pollutants. The results demonstrated the superior adsorption performance of the nanocomposite adsorbent, particularly for KTRK, with an adsorption energy of -1934 kcal/mol, compared to the pristine MIL-101(Cr), which had an adsorption energy of -1916 kcal/mol. This enhanced adsorption is attributed to the optimal molecular fit, guest-host solid interactions, and the selective encapsulation capabilities of β-CDex. This research highlights the potential of MOF-based nanocomposites as effective and sustainable solutions for pharmaceutical pollution. By advancing the understanding of molecular interactions through simulations, this study contributes to developing innovative adsorbents for wastewater treatment and the protection of water resources.

Nanoarchitectonics of MIL-101(Fe)/g-C3N4 S-Scheme heterojunction for photocatalytic nitrogen fixation: Mechanisms and performance

Recently, there has been a growing interest in the fundamental understanding of the mechanism of how MIL-101(Fe)/g-C3N4 heterojunctions facilitate the occurrence of photocatalytic nitrogen fixation reactions, especially the electron transfer mechanism has attained increasing attention in photocatalysis. Herein, we implemented a "triple win scenario" strategy to fabricate the S-scheme MIL-101(Fe)/g-C3N4 heterojunction through a straightforward solvothermal process. The MC-6 heterojunction minimizes the recombination of photogenerated carriers, enhances light utilization efficiency, and activates the N≡N bond, thus boosting photocatalytic nitrogen fixation efficiency. The transition metal iron activates the N≡N bond, while S-scheme heterojunctions reduce the photogenerated carrier recombination. In addition, the decrease in band gap (Eg) leads to an increase in visible light utilization efficiency. ISIXPS proved the mechanism of interelectron transfer of MIL-101(Fe)/g-C3N4 heterojunction under illumination. Upon the creation of the heterojunction, electrons migrate from g-C3N4 to MIL-101(Fe), establishing an inherent electric field due to the disparate Fermi levels between the two materials. The electrons (e-) on the g-C3N4 CB with a more negative reduction potential and the holes (h+) on the MIL-101(Fe) VB are retained, which increased the redox capacity to a great extent required for the reduction of N2 to NH3. The ammonia production efficiency of MC-6 photocatalyst was 160 µmol gcat-1 h-1, representing an 8-fold and 2.8-fold improvement over pristine g-C3N4 (20 µmol gcat-1 h-1) and MIL-101(Fe) (57 µmol gcat-1 h-1), respectively.

Synergistic ionic liquid encapsulated MIL-101 (Cr) metal-organic frameworks for an innovative adsorption desalination system

The transformations of brackish water into freshwater employing porous materials such as metal-organic frameworks (MOFs) show a great potential for a green environment. But the adsorption-based desalination slows down due to slow water adsorption/desorption rates and inadequate water storage capacity in conventional adsorbents. Therefore, the restructuring of porous MOFs increases water storage and transfer rates. This paper presents a comprehensive investigation on the fabrication of ionic liquid encapsulated MIL-101 (Cr) MOFs (metal-organic frameworks), and its interactions with water for desalination applications. Firstly, the pristine MIL-101 (Cr) is encapsulated with various types/amounts of ionic liquids. Next, these MOFs are characterized via SEM (Scanning electron microscope), FTIR (Fourier transform infrared), XRD (X-ray diffraction), TGA (Thermal gravimetric analysis), N2 adsorption techniques. The water adsorption on these MOFs is performed experimentally for a wide temperature (30–80 °C) and pressure (0 < P/Ps < 0.95) ranges. The effects of the size (or type) as well as the encapsulation ratio of ionic liquids on water adsorption behaviors are conducted. Based on the experimentally proven water adsorption (isotherms and kinetics) data, an AD (adsorption desalination) system is modelled and simulated. Finally, the AD performances in terms of the specific daily water production (SDWP) and performance ratio (PR) are parametrically studied with respect to various regeneration temperature (50–80 °C) and cycle times (100 s–1000 s). It is found that by ionic liquid encapsulation, the water uptakes/offtake rates are expedited up to 48% (for adsorption)/55% (for desorption), respectively. In addition, the water transfer (Δq) improves up to 45% more than the parent MIL-101(Cr) MOFs. Furthermore, the SDWP increases from 38 to 56 m3 of water per tonne of MOFs per day at the regeneration temperature of 70 °C. The simulation results also show that the ionic-liquid-encapsulated MIL-101 (Cr) MOFs generates water (>25 m3 water per tonne of IL-MOFs) at the regeneration temperature of 50 °C and is potential for the next generation desalination applications.

A novel ionic liquid-entrapped MIL-101(Cr) framework with enhanced removal efficiency towards phosphate from aqueous solution.

Developing adsorbent materials with high adsorptive dephosphorization (ADP) is significant for treating phosphate from aqueous solutions and eutrophic water. Herein, the MIL-101(Cr) framework was entrapped ionic liquid (IL) of 1-butyl-3-methylimidazoliumbromide ionic liquid ([C4mem]+[Br]-) using a ship-in-a-bottle approach to obtain novel adsorbents [C4mem]+[Br]-@MIL-101(Cr) contained varied IL contents, namely C4mem@MIL-101. The characterization results revealed that the formed [C4mem]+[Br]- molecules interacted with the MIL-101(Cr) frameworks, enhanced their stability, and offered additional adsorption sites. The batch adsorptions of phosphate showed that the optimized C4mem@MIL-101 adsorbent loaded with ~ 7% IL-based N content had the highest phosphate absorbing capacity of ~ 200mg/g, outperforming the pristine MIL-101(Cr) and other adsorbents. The ADP efficiency was facilitated in the acidic media, where the phosphate ions of H2PO4- and HPO42- captured onto the C4mem@MIL-101 via several interactions, including electrostatic attraction, H-bonds, and chemical interactions. In the meantime, the coexisting anions diminished the phosphate adsorption because they competed with the pollutants at adsorption sites. Furthermore, phosphate treatment under the continuous fixed-bed conditions showed that 1g of the polyvinyl alcohol (PVA)-mixed C4mem@MIL-101 pellets purified 25l of water containing phosphate with a 1mg/l concentration. The results suggest that the novel [C4mem]+[Br]-@MIL-101(Cr) structure had a high potential for treating phosphate in aqueous solutions.

Molecular encapsulation of 5, 10, 15, 20-tetrakis (4-methylphenyl) porphyrinato iron (III) chloride (FeTPP) into MIL-101(Cr) for superior CO2/N2 separation performance

The greenhouse effect associated with excessive CO2 emission has led to a series of environmental issues, thus developing excellent adsorbents for CO2 capture from flue gas offers a sustainable approach. To combine the merit of multiple functional components, novel FeTPP@MIL-101(Cr) was prepared by incorporation of 5,10,15,20-tetrakis(4-methylphenyl)porphyrinato iron (III) chloride (FeTPP) into MIL-101(Cr) cages via in-situ packaging strategy. The cage-confined FeTPP can both regulate the pore structures of MIL-101(Cr) and provide additional binding sites for CO2 adsorption. Profiting from extra interactions for CO2 component and the “sieving effect” for N2 component induced by incorporation of FeTPP, the discrepancy of isosteric heat for CO2 and N2 was largely amplified. Notably, the CO2/N2 selectivity (15/85, v/v) calculated by ideal adsorbed solution theory (IAST) increased from 17.1 (MIL-101 (Cr)) to 41.8 (FeTPP@MIL-101 (Cr) with FeTPP loading of 4.98 wt%) at 273 K, 100 kPa, which is 2.44 times larger than that of pristine MIL-101 (Cr) and also exceeds most reported adsorbents.

Facile shaping of flexible MIL-53(Al) for effective separation of propylene over propane

A facile granulation approach using polyvinyl butyral (PVB) as a polymer binder was developed to control the textural properties of the flexible metal–organic framework MIL-53(Al). The large pore (LP) structure of MIL-53(Al) contracted after granulation due to a strong interaction between MOF and polymer binder. This contraction enhances propylene's selectivity over propane at saturation pressure (region II), as confirmed by single-component adsorption isotherms. The adsorption kinetics showed faster adsorption of C3H6 compared to C3H8 over time in the case of the granules, while no difference was observed for the powder sample. Breakthrough experiments successfully separated C3H6 over C3H8 using MIL-53(Al)-B10% granules, whereas the pristine MIL-53(Al) powder did not separate the C3H8-C3H6 gas mixture. The breakthrough finding reaffirms that the observed gate-opening effect in MIL-53(Al) within pressure region I is ineffective for separating a mixed gas system containing propane and propylene. The constrained pores of the shaped granules could facilitate strong π-π stacking interactions with C3H6 and decrease the diffusion rate for C3H8 molecules. These findings indicate that the simple granulation approach can modulate the textural properties of flexible MIL-53(Al) and improve its selectivity for C3H6/C3H8 separation resulting from increased MOF-propylene affinity and kinetic factors.

Dual positive charging sites for MIL-101 enhanced adsorption of toluene under high humidity conditions: Experimental and theoretical studies

Highly efficient capture of volatile organic compounds (VOCs) under humid conditions is a significant yet formidable task for metal–organic frameworks (MOFs). Based on the material simulation technique, we proposed implanting a significantly positive-density ligand (DABA) to modify MIL-101 and constructing dual positive-charging centers to improve MIL-101 competitive adsorption of benzene VOCs over H2O vapors both thermodynamically and kinetically. The introduction of DABA containing two –NH2 groups with electrostatically positive charges into MIL-101 resulted in the formation of an open tetrahedral cage with a dual positive charging center. This facilitated strong N-H…π interactions with toluene molecules, leading them to accumulate firmly in MOF pores, and thus dramatically enhanced its adsorption capacity from 17 to 31 toluene molecules per unit cell compared to pristine MIL-101. Moreover, the open tetrahedral cage in D-MIL-101 preferentially captured toluene and occupied the strongest adsorption sites first, thus effectively preventing H2O entry into MOF pores to contact with hydrophilic metal sites. This realized high water resistance and toluene adsorption uptake under high humidity conditions. Results showed that D-MIL-101 had a high specific surface area of 2558 m2/g and a new microporous structure of 9.5 Å size. It presented higher toluene uptake of 4.69 mmol/g at lower vapor pressure of P/P0 = 0.013 and 298 K temperature, as well as 3.3 folds higher working capacity of toluene compared to pristine MIL-101 under 80 % RH. This study presents a novel approach for constructing hydrophobic MOFs using new positive charging ligands and delves deeper into the competitive adsorption of VOCs/H2O in MOF composites for large-scale applications.

Enhanced photocatalytic CO2 reduction by integrating an iron based metal-organic framework and a photosensitizer

The conversion of CO2 into fuels via photoreduction is a promising method to reduce environmental pollution and alleviate the energy crisis. Herein, we report iron-based metal-organic frameworks (Fe-MOFs) that can host a photosensitizer Ru(dcbpy)3Cl2 (PS) to form a range of photocatalytic systems, PS-Fe-MOFs, that are capable of increasing the activity of CO2 conversion. Among the four Fe-MOFs and PS composites, PSMIL-101(Fe) showed the highest activity for photocatalytic CO2 reduction under simulated visible light irradiation (yielding CO and CH4 at 116.7 and 79.1 μmol·g−1 within 5 h, respectively), approximately 13 times higher than that of pristine MIL-101(Fe). In situ FTIR spectra and theoretical calculations further elucidated the coexistence of CO and CH4 as the products of CO2 reduction by PSMIL-101(Fe). Additionally, the optical and electrochemical experiments, alongside theoretical calculations, indicated that PS bound on the surface of the Fe-MOFs provided a greater charge transfer efficiency, thus leading to a high photocatalytic CO2 reduction activity.

The preparation and adsorption performance of Co-doped MIL-101(Cr) for low-concentration C3F8

Octafluoropropane (C3F8) is a kind of super greenhouse gas, and the low concentration of octafluoropropane makes it difficult to be adsorbed and removed. In this study, a series of Co-doped MOFs (CoxCr-MIL-101) have been successfully synthesized using a hydrothermal method without the addition of strong acids such as HF. The structural properties of the prepared CoxCr-MIL-101 are characterized using SEM, XRD, nitrogen adsorption desorption test, etc. The adsorption properties of C3F8 are measured by single-component isothermal adsorption experiments and fixed bed adsorption breakthrough experiments. The adsorption mechanism was investigated via the adsorption theory models. The results show that the introduction of cobalt ions can effectively improve the adsorption capacity of MIL-101, among which the Co0.2Cr-MIL-101 exhibits the best adsorption performance. The C3F8 equilibrium adsorption capacity reaches 0.077 mmol/g at 298 K and 180 Pa, which is 3.03 times that of the pristine MIL-101 and the dynamic adsorption capacity is 20.710 mmol/g (298 K, 1.2 L/min), which is 9.37 times that of the pristine MIL-101. Inspiringly, the IAST separation selectivity of C3F8/N2 at 100 kPa is up to 146.7, which is 14.3 times that of the pristine MIL-101. More importantly, the co-modified adsorbent showed better thermal stability and cyclic stability. In addition, Co0.2Cr-MIL-101 fits the Freundlich isothermal adsorption model, and the adsorption mechanism analysis shows that the high adsorption capacity of Co0.2Cr-MIL-101 benefits from the unique pore structure and abundant active sites of the modified MOFs.

Boosting the adsorptive and photocatalytic performance of MIL-101(Fe) against methylene blue dye through a thermal post-synthesis modification

Photocatalytic degradation under ultra-low powered light is a viable advanced oxidation process technique against extensive emerging contaminants. As a new and remarkable class of nanoporous materials, metal-organic frameworks (MOFs), attract interest for the supreme adsorptive and photocatalytic functionalities. An outstanding MOF, MIL-101(Fe) chosen as a photocatalyst template for the synthesis of α-Fe2O3 by a simple thermal modification to improve the structural properties toward methylene blue (MB) eradication. Octahedron-like α-Fe2O3 photocatalyst (Modified MIL-101(Fe), M-MIL-101(Fe)) was superior in dispersion and separation properties in aqueous medium. Moreover, the adsorptive and catalytic performance was increased for modified form by ~ 7.3% and ~ 17.1% compared to pristine MIL-101(Fe), respectively. Synergistic improvement of MB removal achieved by simultaneous adsorption/degradation under 5-W LED irradiation. Parametric study indicated an 18.1% and 44.5% improvement in MB removal was observed by increasing pH from 4 to 10, and M-MIL-101(Fe) dose from 0.2 to 1 g L−1, respectively. MB removal followed the pseudo-second-order kinetics model and the process efficiency dropped by 38% as MB concentration increased from 5 to 20 mg L−1. Radical trapping tests revealed the significant role of {mathrm{OH}}^{.} and electron radicals as the major participants in dye degradation. A significant loss in the efficiency of M-MIL-101(Fe) was observed in the reusability tests that is good to study further. In conclusion, a simple thermal post-synthesis modification on MIL-101(Fe) improved its structural, catalytic, and adsorptive properties against MB.

A computational investigation on the roles of binding affinity and pore size on CO2/N2 overall adsorption process performance of MOFs through modifying MIL-101 structure

To develop an appropriate metal-organic framework to capture CO2 from dry flue gas, understanding the roles of structural modifications, location of primary adsorption sites and underlying adsorption mechanisms is crucial. Herein, effects of type, position and concentration of nitrogen-containing functional groups and C/N-substituted ligands are investigated on overall CO2/N2 adsorption process performance and mechanism of pristine and metal-substituted MIL-101 MOFs. In this investigation, density functional theory computations, grand-canonical Monte-Carlo, and molecular dynamics simulations are applied. Taguchi-based overall evaluation criteria objective function is also used to assess the overall adsorption performances of these MIL-101 MOFs in terms of CO2 uptake capacity, CO2/N2 selectivity, isosteric heat of adsorption and mass transfer resistance. The PBE/DZVP computations resulted in the CO2-framework binding energies ranging from −3.85 to −21.01 kJ/mol implying an acid-base type of physisorption. A correlation is introduced to estimate the CO2 uptake capacity from binding affinity and pore diameter of these MIL-101 MOFs. Mechanistic investigations show that to enhance CO2 uptake capacity and CO2/N2 selectivity, functionalization of the linker ligands is more successful than functionalization of the open metal sites having strong interactions with CO2 molecules. Results also showed that the best possible scenario to improve the overall adsorption process performance of MIL-101 is to substitute the C atom(s) of the BDC ligands with the N atom(s), regardless of the central metal atom type. The comprehensive molecular design approach introduced in this work can be used as a methodology by scientists for the development of new MOFs for practical CO2 capture applications.

Bi-functionalized ionic liquid/metal-organic framework composite for low-concentration CO2 cycloaddition reaction under atmospheric pressure

Functionalized ionic liquid-based composites possess good CO2 affinity and heterogeneous catalytic performance, which are promising materials for CO2 separation and conversion to alleviate greenhouse effect and promote carbon source utilization. Herein, a new bi-functionalized ionic liquid 1-(2-hydroxyl-ethyl)− 3-methoxyethyl-imidazolium bromide ([HeMOEim][Br])/ aluminum terephthalate [MIL-53(Al), MIL: Materials of Institute Lavoisier] composite was synthesized via vacuum impregnation strategy under the solvent-free condition. The crystal structure of the composite transformed into narrow pore phase and the morphology of MIL-53(Al) remained unchanged after incorporating [HeMOEim][Br]. The ideal CO2/N2 selectivity of the composite was 15.9 at 25 oC and 0.1 MPa and was superior to that of the pristine MIL-53(Al) (2.3). The catalytic activity of the composite for low-concentration CO2 cycloaddition was investigated without solvent and co-catalyst under atmospheric pressure. The yield of cyclopropyl carbonate reached up to 95.7 % at 130 oC with 4 wt% composite for 12 h, indicating that the material has the potential for the direct conversion of CO2 from flue gas to high-value products.

Composite of MIL-101(Cr) with a Pyrrolidinium-Based Ionic Liquid Providing High CO2 Selectivity.

Capturing CO2 selectively from flue gas and natural gas addresses the criteria of a sustainable society. In this work, we incorporated an ionic liquid (IL) (1-methyl-1-propyl pyrrolidinium dicyanamide, [MPPyr][DCA]) into a metal organic framework (MOF), MIL-101(Cr), by wet impregnation and characterized the resulting [MPPyr][DCA]/MIL-101(Cr) composite in deep detail to identify the interactions between [MPPyr][DCA] molecules and MIL-101(Cr). Consequences of these interactions on the CO2/N2, CO2/CH4, and CH4/N2 separation performance of the composite were examined by volumetric gas adsorption measurements complemented by the density functional theory (DFT) calculations. Results showed that the composite offers remarkably high CO2/N2 and CH4/N2 selectivities of 19,180 and 1915 at 0.1 bar and 15 °C corresponding to 1144- and 510-times improvements, respectively, as compared to the corresponding selectivities of pristine MIL-101(Cr). At low pressures, these selectivities reached practically infinity, making the composite completely CO2-selective over CH4 and N2. The CO2/CH4 selectivity was improved from 4.6 to 11.7 at 15 °C and 0.001 bar, yielding a 2.5-times improvement, attributed to the high affinity of [MPPyr][DCA] toward CO2, validated by the DFT calculations. These results offer broad opportunities for the design of composites where ILs are incorporated into the pores of MOFs for high performance gas separation applications to address the environmental challenges.

Mechanism, interfacial interactions and thermodynamics of the monolayer adsorption of trace geogenic pollutants from water using mil metal-organic frameworks: Fluorides and arsenates

This paper analyzes the thermodynamics and interfacial interactions of the adsorption of fluorides and arsenates on pristine MIL-100(Fe) and MIL-101(Fe) structures. Experimental equilibrium studies showed that the fluoride adsorption was exothermic on both MOFs at 20–40 °C and pH 7, while the arsenate adsorption was endothermic at the same operating conditions. Density functional theory calculations indicated that the arsenate adsorption was governed by an ion exchange mechanism where Fe centers from MOFs were involved, while electrostatic interactions affected the ion exchange during the fluoride adsorption on these metal-organic structures. The adsorption properties of MIL-101(Fe) were better than those of MIL-100(Fe) for both fluoride and arsenate. Particularly, MIL-101(Fe) showed an outstanding performance for the arsenate removal with adsorption capacities up to 4.57 mmol/g (i.e., 342 mg/g) and it can be regenerated using NaOH. This MOF outperformed several adsorbents reported in the literature for the arsenate removal including other MOFs with higher surface areas. This crystalline material is attractive and promising to be applied in the intensification of treatment technologies to depollute aquifers contaminated by geogenic pollutants. These results contribute to the understanding of the adsorption properties of MIL-family MOFs, with the aim of consolidating their utilization in water purification.

Seed-mediated synthesis of a modified micro-mesoporous MIL-101(Cr) for improved benzene and toluene adsorption at room conditions

The modification of metal-organic frameworks (MOFs) for enhanced volatile organic compounds (VOCs) removal is a huge challenge. Therefore, it is of great importance to find a proper strategy to tune the porosity of MOFs and their VOCs removal performance. In this study, we report a novel seed-mediated synthesis strategy using a low-cost and heteroatom-rich carbon structure (MIC-COOH) to prepare hierarchical micro-mesoporous MIL-101(Cr). Different amounts of MIC-COOH were applied to investigate the efficiency of seed concentration on the fundamental specification of the created hierarchical MIL-101(Cr) and its benzene and toluene uptake. The results showed that the increase of MIC-COOH significantly enhanced the mesoporous volume in the MOF structure, resulting in the creation of large surface area (up to 2971.5 m2/g) and high pore volume (up to 2.21 cm3/g). MIL@MIC-4% nanostructure exhibited 235.3 ± 0.05 and 291.6 ± 0.04 wt% adsorption efficiency for benzene and toluene, respectively, which are ⁓3.0 and 4.1 times greater than those of pristine MIL-101(Cr). It also exhibited higher cyclic adsorption efficiency than that of the pristine MIL-101(Cr) after five consecutive adsorption-desorption cycles. The uptake behavior of benzene and toluene on the modified MIL@MIC structure was also perused by applying density functional theory (DFT) calculations. According to the findings, it was revealed that the cooperative charge transfers between MIL-101(Cr) and MIC-COOH through the structure can play an efficient role in the enhanced uptake of benzene and toluene molecules.

Modelling toluene sorption in ionic liquid/metal organic framework composite materials

Toluene is a prevalent pollutant in indoor environments and its removal is essential to maintain a healthy environment. Adsorption is one of the best alternatives for organic vapours removal, specially at low indoor concentrations. Metal Organic Frameworks (MOFs) and Ionic Liquids (ILs) are potential materials for this mean. In this work, the synthesis and application of IL/MOF composite materials for toluene removal is reported. Loading [BMIM][CH3COO] ionic liquid into MIL101 porous structure improves parent materials affinity towards toluene capture by two orders of magnitude (as Henry's constants, attesting to their synergy). MIL101(Cr) and absorption in [BMIM][CH3COO] IL is best described by Henry's Law, while the Langmuir adsorption model predicts toluene adsorption on [BMIM][CH3COO]/MIL101(Cr) better than Freundlich and Toth equations. Diffusional and kinetics models revealed that toluene diffusion is the rate limiting step for pristine MIL101. Kinetic and diffusion rates were systematically improved upon the incorporation of the ionic liquid due to shorter toluene hops with the adsorbed IL and the increased hydrophobicity in the composites making the sorption more favourable. This study provides a systematic analysis and modelling of the toluene capture process in IL/MOF composites aiding a better understanding of the sorption process in these novel materials.

Adsorptive removal of carbazole from model esterified bio-oil composed of methyl laurate by using metal–organic frameworks functionalized with sulfonic acid both on metal and linker sites

Microalgae-derived esterified bio-oil can be an alternative energy source against the depletion of fossil fuel although the content of organonitrogen compounds (ONCs) can be high. Here, a metal–organic framework (MOF, MIL-101-NH2, with or without grafting ethylenediamine, ED) was modified to derive sulfonic acid-functionalized MIL-101 s. The obtained MOFs (including pristine MIL-101 and MIL-101-NH2), together with activated carbon (AC) as a reference, were utilized in adsorptive denitrogenation (ADN), especially the removal of carbazole (CBZ), one of the most difficult ONCs via hydrogenation or oxidation, from model fuel composed of methyl laurate. Although there was a study on ADN from model fuel composed of very light esters like methylacetate, there is no report using esters that are quite similar to fatty acid methyl esters of oils. Remarkably, MIL-101-NH-ED-SO3H, the first MOF having sulfonic acids on both the metal and linker sites, had noticeable maximum adsorption capacities (Qo) for the stubborn CBZ removal although the porosity is the lowest among the studied adsorbents. For example, Qo of the modified MOF was 205 mg/g which was higher than any studied adsorbents and was ca. 3 and 2 times that of AC and pristine MOF, respectively. The remarkable performance could be explained with H-bond (with a minor contribution of π-π interaction), based on calculations, FTIR, and functional groups of both the adsorbate and adsorbent. Furthermore, the recyclability of MIL-101-NH-ED-SO3H in CBZ adsorption was confirmed. Therefore, MOFs when adequately functionalized can be useful in ADN of fuel composed of esters.

In-situ one-step synthesis of activated Carbon@MIL-101 (Cr) composites for hydrogen storage

Metal-organic frameworks (MOFs) unlocked new prospects of developing novel adsorbing materials for H2 storage. However, MOF porosity is not yet fully utilized. To compensate for that disadvantage, we synthesized MIL-101(Cr) MOF-based activated carbon AC@MIL-101 (Cr) composites using in situ hydrothermal method. Different amounts of activated carbon (AC) derived from fir bark were added to adjust the pore structure of the resulting MOF-based composites. The pore number and their sizes increased and decreased, respectively, after pristine MIL-101(Cr) was combined with AC. The surface area and pore volume of pristine MIL-101(Cr) were equal to 2299 m2/g and 1.06 cm3/g, respectively. These values became equal to 3367 m2/g and 1.64 cm3/g after AC was combined with MIL-101(Cr) to form AC@MIL-101(Cr) composite. The highest H2 uptake by AC@MIL-101(Cr) was equal to 6.93 wt % at 77 K and 40 bar. Such excellent hydrogen storage performance (a 32.3% increase than what was observed for unmodified MIL-101(Cr) material) was attributed to a synergy between AC and MIL-101(Cr).

Spindle-like MIL101(Fe) decorated with Bi2O3 nanoparticles for enhanced degradation of chlortetracycline under visible-light irradiation.

Improving the photocatalytic performance of metal–organic frameworks (MOFs) is an important way to expand its potential applications. In this work, zero-dimensional (0D) Bi2O3 nanoparticles were anchored to the surface of tridimensional (3D) MIL101(Fe) by a facile solvothermal method to obtain a novel 0D/3D heterojunction Bi2O3/MIL101(Fe) (BOM). The morphology and optical properties of the as-prepared Bi2O3/MIL101(Fe) composite were characterized. The photocatalytic activity of the synthesized samples was evaluated by degrading chlortetracycline (CTC) under visible-light irradiation. The obtained BOM-20 composite (20 wt % Bi2O3/MIL101(Fe)) exhibits the highest photocatalytic activity with CTC degradation efficiency of 88.2% within 120 min. The degradation rate constant of BOM-20 toward CTC is 0.01348 min−1, which is 5.9 and 4.3 times higher than that of pristine Bi2O3 and MIL101(Fe), respectively. The enhanced photocatalytic activity is attributed to the formation of a Z-scheme heterojunction between Bi2O3 and MIL101(Fe), which is conducive to the rapid separation of photogenerated carriers and the enhancement of photogenerated electron and hole redox capacity. The intermediate products were analyzed by liquid chromatography–mass spectrometry (LC–MS), and a possible photocatalytic degradation path of CTC was proposed. This work provides a new perspective for the preparation of efficient MOF-based photocatalysts.