Re‐Determination of the Crystal Structure of MIL‐91(Al)

The structure of one of the first permanently porous metal phosphonates, MIL‐91(Al) was re‐determined using high resolution synchrotron powder X‐ray diffraction data. The new model is in a lower symmetry space group, with no disordered ligands in the structure, whilst remaining otherwise consistent with the reported compound. New milder synthetic conditions were also developed.     

Lithium‐Doped Silica‐Rich MIL‐101(Cr) for Enhanced Hydrogen Uptake

Metal‐organic frameworks (MOFs) show promising characteristics for hydrogen storage application. In this direction, modification of under‐utilized large pore cavities of MOFs has been extensively explored as a promising strategy to further enhance the hydrogen storage properties of MOFs. Here, we described a simple methodology to enhance the hydrogen uptake properties of RHA incorporated MIL‐101 (RHA‐MIL‐101, where RHA is rice husk ash—a waste material) by controlled doping of Li⁺ ions. The hydrogen gas uptake of Li‐doped RHA‐MIL‐101 is significantly higher (up to 72 %) compared to the undoped RHA‐MIL‐101, where the content of Li⁺ ions doping greatly influenced the hydrogen uptake properties. We attributed the observed enhancement in the hydrogen gas uptake of Li‐doped RHA‐MIL‐101 to the favorable Li⁺ ion‐to‐H₂ interactions and the cooperative effect of silanol bonds of silica‐rich rice‐husk ash incorporated in MIL‐101.     

Improving the Hydrogen‐Adsorption Properties of a Hydroxy‐Modified MIL‐53(Al) Structural Analogue by Lithium Doping

Lithium makes the difference : A simple strategy for the synthesis of lithium‐doped porous metal–organic frameworks (MOFs) is developed (see structure; C black, O red, AlO₆ blue octahedra), thus paving the way for the facile preparation of lithium‐doped MOFs. Moreover, the significant increase in hydrogen adsorption predicted by theoretical calculations is observed.

     

High‐performance liquid chromatography separation of phthalate acid esters with a MIL‐53(Al)‐packed column

In this study, a MIL‐53(Al)‐packed column was successfully prepared and firstly applied to separate phthalate acid esters (butyl benzyl phthalate, di‐n‐butyl phthalate, diethyl phthalate, bis(2‐ethylhexyl) phthalate, and dimethyl phthalate). Their baseline separation could be achieved within 12 min with a mobile phase of methanol/H₂O ratio at 92:8, and the temperature and flow rate was 40°C and 0.6 mL/min, respectively. The stacking effect and electrostatic force were the key factors in the separation. Moreover, there was a substantial linear relation between the peak height, peak area, and the analyte mass, and the relative standard deviations of retention time, peak height, peak area, and half peak width for five replicate separations of the analytes were within the ranges 0.31–0.88%, 0.72–1.52%, 1.33–1.53%, and 0.46–0.95%, respectively. The results of the calculation of the thermodynamics parameters showed that the separation of phthalate acid esters was controlled by both enthalpy change (ΔH) and entropy change (ΔS).     

Synthesis and Catalytic Performance of Hierarchically Porous MIL‐100(Fe)@polyHIPE Hybrid Membranes

Metal‐organic frameworks (MOFs) nanoparticles in combination with a nonionic surfactant (Pluronic L‐121) are used to stabilize dicyclopentadiene (DCPD)‐in‐water high internal phase emulsions (HIPEs). The resulting HIPEs containing the MIL‐100(Fe) nanoparticles (MIL: Materials of Institut Lavoisier) at the interface between the oil‐ and the water‐phases are then cured, and 100 μm thick, fully open, hierarchically porous hybrid membranes are obtained. The properties of the MIL‐100(Fe)@pDCPD polyHIPE membranes are characterized and it is found that up to 14 wt% of the MIL‐100(Fe) nanoparticles are incorporated in the hybrid material resulting in an increase of the microporosity up to 130 m² g⁻¹. Hybrid membranes show an appealing catalytic activity in Friedel–Crafts alkylation in a batch mode as well as in a flow‐through mode, thereby demonstrating the preserved accessibility of Lewis acidic sites in the MOF nanostructures.

     

Evidence of Photoinduced Charge Separation in the Metal–Organic Framework MIL‐125(Ti)‐NH2

Herein, we describe the photochemical behavior of the porous metal–organic framework MIL‐125(Ti)‐NH₂, built up from cyclic Ti₈O₈(OH)₄ oxoclusters and 2‐aminoterephthalate ligands. While MIL‐125(Ti)‐NH₂ does not emit upon excitation at 420 nm, laser flash photolyses of dry samples (diffuse reflectance) or aqueous suspensions (transmission) of the solid have allowed detecting a transient characterized by a continuous absorption from 390 to 820 nm decaying in the sub‐millisecond timescale, which is quenched by oxygen. This transient has been attributed to the charge‐separation state. Firm evidence for this assignment was obtained by lamp irradiation of aqueous suspensions of MIL‐125(Ti)‐NH₂ in the presence of electron‐donor (N,N,N′N′‐tetramethyl‐p‐phenylenediamine) or electron‐acceptor (methylviologen) probe molecules, which has allowed the visual detection of the corresponding radical ions, in agreement with the occurrence of photoinduced charge separation in MIL‐125(Ti)‐NH₂.     

Coordination Polymer Nanobamboos of {FexIn1−x}‐MIL‐88B: Induced Formation of a Virtual In‐MIL‐88B

A precise fabrication of nanobamboo structures made from hybrid coordination polymers of the type {Fe_xIn_1?x}‐MIL‐88B is demonstrated. The compositions of the hybrid coordination polymer nanobamboos of {Fe_xIn_1?x}‐MIL‐88B (x=0.06, 0.19, or 0.75) are regulated by altering the amount of metal ions used in the reactions. Interestingly, the formation of a virtual In‐MIL‐88B (precise structure, {Fe_0.06In_0.94}‐MIL‐88B), which cannot be created in a typical reaction, is induced by the assistance of a Fe‐MIL‐88B structure. The a and c cell parameters of {Fe_0.06In_0.94}‐MIL‐88B are calculated at 10.95 and 19.86 Å, respectively. These values of {Fe_0.06In_0.94}‐MIL‐88B are larger than those of pure Fe‐MIL‐88B owing to the large ionic size of In³⁺ within the framework.     

Adsorptive Separation of Acetylene from Light Hydrocarbons by Mesoporous Iron Trimesate MIL‐100(Fe)

A reducible metal–organic framework (MOF), iron(III) trimesate, denoted as MIL‐100(Fe), was investigated for the separation and purification of methane/ethane/ethylene/acetylene and an acetylene/CO₂ mixtures by using sorption isotherms, breakthrough experiments, ideal adsorbed solution theory (IAST) calculations, and IR spectroscopic analysis. The MIL‐100(Fe) showed high adsorption selectivity not only for acetylene and ethylene over methane and ethane, but also for acetylene over CO₂. The separation and purification of acetylene over ethylene was also possible for MIL‐100(Fe) activated at 423 K. According to the data obtained from operando IR spectroscopy, the unsaturated Fe^III sites and surface OH groups are mainly responsible for the successful separation of the acetylene/ethylene mixture, whereas the unsaturated Fe^II sites have a detrimental effect on both separation and purification. The potential of MIL‐100(Fe) for the separation of a mixture of C₂H₂/CO₂ was also examined by using the IAST calculations and transient breakthrough simulations. Comparing the IAST selectivity calculations of C₂H₂/CO₂ for four MOFs selected from the literature, the selectivity with MIL‐100(Fe) was higher than those of CuBTC, ZJU‐60a, and PCP‐33, but lower than that of HOF‐3.     

Effective removal of 2,4,6‐trinitrophenol over hexagonal metal–organic framework NH2‐MIL‐88B(Fe)

A nanostructured organic–inorganic framework, hexagonal NH₂‐MIL‐88B, has been prepared through a facile one‐pot reflux reaction and then it was characterized using various techniques. The as‐prepared sample with high specific surface area (414 m² g^?1) showed excellent adsorption for 2,4,6‐trinitrophenol (TNP) in the liquid phase. Detailed studies of the adsorption kinetics, adsorption mechanism, adsorption isotherm, activation energy and various thermodynamic parameters were conducted. The adsorption mechanism of NH₂‐MIL‐88B for TNP may be ascribed to hydrogen bond interaction, and the complexation between ─OH in TNP and unsaturated Fe(III) on the surface of NH₂‐MIL‐88B. The maximum adsorption capacity of NH₂‐MIL‐88B for TNP based on the Langmuir isotherm was 163.66 mg g^?1. The as‐prepared NH₂‐MIL‐88B adsorbent seems to be a promising material in practice for TNP removal from aqueous solution.     

Incorporation of N‐Methyl‐d‐glucamine Functionalized Oligomer into MIL‐101(Cr) for Highly Efficient Removal of Boric Acid from Water

Polymeric resins are practically important adsorbents in a wide variety of applications, but they generally suffer from low surface areas and limited functionalized adsorption sites owing to their closely compacted and tangled polymeric chains. A metal–organic framework (MOF)–polymer composite with enhanced adsorption capacity against the compacted polymeric resins was reported. The strategy to incorporate functionalized oligomer within the cavities of the MOF was demonstrated by the preparation of MIL‐101(Cr) incorporated with N‐methyl‐d ‐glucamine‐based organosiloxane polymer. The resulting MOF composite shows high efficiency for the removal of boric acid from water because of exceptionally high loading of functional groups responsible for the boron adsorption. This material offers promising perspectives for boron removal applications in seawater desalination.     

Preparation of BiVO4/MIL‐125(Ti) composite with enhanced visible‐light photocatalytic activity for dye degradation

Because of their desired features, including very specific surface areas and designable framework architecture together with their possibility to be functionalized, Metal Framework (MOF) is a promising platform for supporting varied materials in respect of catalytic applications in water treatment. In this work, a novel visible‐light‐responsive photocatalyst that comprised BiVO₄ together with MIL‐125(Ti), was synthesized by a two‐step hydrothermal approach. The characterization of as‐obtained samples as performed by X‐ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscope, X‐ray photoelectron spectroscopy and ultraviolet‐visible diffuse reflection spectra. Rhodamine B was selected being a target for the evaluation of the photocatalytic function of as‐developed photocatalyst. The photocatalytic reaction parameters, for example, the content of BiVO₄ as well as initial concentration of Rhodamine B was researched. The composite photocatalyst possessing Bi:Ti molar ratio of 3:2 brought to light the fact that the greatest photocatalytic activity had the ability to degrade 92% of Rhodamine B in 180 min. In addition to that, the BiVO₄/MIL‐125(Ti) composite could keep its photocatalytic activity during the recycling test. The phenomenon of disintegration of the photo‐generated charges in the BiVO₄/MIL‐125(Ti) composite was brought to discussion as well.     

Photocatalyzed Hydrogen Evolution from Water by a Composite Catalyst of NH2‐MIL‐125(Ti) and Surface Nickel(II) Species

A composite of the metal–organic framework (MOF) NH₂‐MIL‐125(Ti) and molecular and ionic nickel(II) species, catalyzed hydrogen evolution from water under UV light. In 95 v/v % aqueous conditions the composite produced hydrogen in quantities two orders of magnitude higher than that of the virgin framework and an order of magnitude greater than that of the molecular catalyst. In a 2 v/v % water and acetonitrile mixture, the composite demonstrated a TOF of 28 mol H₂ g(Ni)^?1 h^?1 and remained active for up to 50 h, sustaining catalysis for three times longer and yielding 20‐fold the amount of hydrogen. Appraisal of physical mixtures of the MOF and each of the nickel species under identical photocatalytic conditions suggest that similar surface localized light sensitization and proton reduction processes operate in the composite catalyst. Both nickel species contribute to catalytic conversion, although different activation behaviors are observed.     

Guest‐Assisted Proton Conduction in the Sulfonic Mesoporous MIL‐101 MOF

Post‐synthesis modification of MIL‐101(Cr)‐NO₂ was explored in order to decorate the organic backbone by propyl‐sulfonic groups, with the aim to incorporate mobile and acidic protons for solid‐state proton electrolyte applications. The resulting solid switched from insulating towards proton superconductive behavior under humidity, while the conductivity recorded at 363 K and 95 % relative humidity reached 4.8×10^?3 S cm^?1. Propitiously, the impregnation of the material by strong acidic molecules (H₂SO₄) further boosted the proton conductivity performances up to the remarkable σ value of 1.3×10^?1 S cm^?1 at 363 K/95 % RH, which reaches the performances of the best proton conductive MOF reported so far.     

Preparation of disk‐like Pt/CeO2‐p‐TiO2 catalyst derived from MIL‐125(Ti) for excellent catalytic performance

A feasible strategy is reported for the synthesis of a disk‐like Pt/CeO₂‐p‐TiO₂ catalyst derived from the titanium‐based metal–organic framework (MOF) MIL‐125(Ti) through a few valid steps. To verify the successful synthesis and structural features of the Pt/CeO₂‐p‐TiO₂ catalyst, as‐prepared samples were characterized using several techniques. The characterizations demonstrated that MOF‐derived porous TiO₂ was appropriate for application as a support owing to its moderate surface area (101 m² g^?1) and suitable pore size (6 nm). Moreover, to study the effect of calcination temperature on the catalytic performance, the obtained catalyst was calcined at various temperatures. It was found that Pt/CeO₂‐p‐TiO₂ calcined at 550 °C exhibited the highest catalytic performance, evaluated by means of the reduction of 4‐nitrophenol monitored by UV–visible spectra. Furthermore, this catalyst showed good reusability with a conversion of 94% even after six cycles. Finally, a possible reaction mechanism was proposed to explain the reduction of 4‐nitrophenol to 4‐aminophenol over the Pt/CeO₂‐p‐TiO₂ catalyst.