Encapsulation of Heteropolyanion-Based Ionic Liquid within the Metal-Organic Framework MIL-100(Fe) for Biodiesel Production

Ionic Liquids Functionalized MOFs for Adsorption

Metal-organic frameworks (MOFs) and ionic liquids (ILs) represent promising materials for adsorption separation. ILs incorporated into MOF materials (denoted as IL/MOF composites) have been developed, and IL/MOF composites combine the advantages of MOFs and ILs to achieve enhanced performance in the adsorption-based separation of fluid mixtures. The designed different ILs are introduced into the various MOFs to tailor their functional properties, which affect the optimal adsorptive separation performance. In this Perspective, the rational fabrication of IL/MOF composites is presented, and their functional properties are demonstrated. This paper provides a critical overview of an emergent class of materials termed IL/MOF composites as well as the recent advances in the applications of IL/MOF composites as adsorbents or membranes in fluid separation. Furthermore, the applications of IL/MOF in adsorptive gas separations (CO2 capture from flue gas, natural gas purification, separation of acetylene and ethylene, indoor pollutants removal) and liquid separations (separation of bioactive components, organic-contaminant removal, adsorptive desulfurization, radionuclide removal) are discussed. Finally, the existing challenges of IL/MOF are highlighted, and an appropriate design strategy direction for the effective exploration of new IL/MOF adsorptive materials is proposed.

Tailoring and Identifying Brønsted Acid Sites on Metal Oxo-Clusters of Metal-Organic Frameworks for Catalytic Transformation

Metal-organic frameworks (MOFs) with Brønsted acidity are an alternative solid acid catalyst for many important chemical and fuel processes. However, the nature of the Brønsted acidity on the MOF's metal cluster or center is underexplored. To design and optimize the acid strength and density in these MOFs, it is important to understand the origin of their acidity at the molecular level. In the present work, isoreticular MOFs, ZrNDI and HfNDI (NDI = N,N'-bis(5-isophthalate)naphthalenediimide), were prepared as a prototypical system to unravel and compare their Brønsted and Lewis acid sites through an array of spectroscopic, computational, and catalytic characterization techniques. With the aid of solid-state nuclear magnetic resonance and density functional calculations, Hf₆ oxo-clusters on HfNDI are quantitatively proved to possess a higher density Brønsted acid site, while ZrNDI-based MOFs display stronger and higher-population Lewis acidity. HfNDI-based MOFs exhibit a superior catalytic performance in activating dihydroxyacetone (DHA) and converting DHA to ethyl lactate, with 71.1% selectivity at 54.7% conversion after 6 h. The turnover frequency of BAS-dominated Hf-MOF in DHA conversion is over 50 times higher than that of ZSM-5, a strong BAS-based zeolite. It is worth noting that HfNDI is reported for the first time in the literature, which is an alternative platform catalyst for biorefining and green chemistry. The present study furthermore highlights the uniqueness of Hf-based MOFs in this important biomass-to-chemical transformation.

Studies on the Stability and Deactivation Mechanism of Immobilized Ionic Liquids in Catalytic Esterification Reactions

Solid-supported ionic liquid catalysts (SILs) are the simplest form of a heterogenized ionic liquid and have attracted soaring attention because of the high catalytic activity as well as separation. Unfortunately, instability severely hinders their practical application, and the reason for the deactivation of SILs has not been investigated in detail. In the present study, the immobilized ionic liquid catalysts MIL-101-[IA-SO₃H][HSO₄] and MIL-101-[IA-COOH][HSO₄] were prepared and used to study the stability in the esterification reaction. The results show that compared with MIL-101-[IA-COOH][HSO₄], MIL-101-[IA-SO₃H][HSO₄] has a higher catalytic activity and a lower stability. The deactivation mechanism is discussed based on experiments and theoretical analysis: the protons on -SO₃H dissociate in a polar solvent and combine with anion HSO₄^-, and then, the formative H₂SO₄ molecule will leach out into the solvent. Our discussion indicates that the stability of immobilized ionic liquids is determined by the substituents of ionic liquid cations and becomes the significant factor controlling the stability limits. The study presented here would be important for understanding the deactivation reason and can help in choosing the suitable cation to avoid leaching of the active site during the reaction.

Metal-Organic Frameworks as bio- and heterogeneous catalyst supports for biodiesel production

As biodiesel (BD)/Fatty Acid Alkyl Esters (FAAE) is derived from vegetable oils and animal fats, it is a cost-effective alternative fuel that could complement diesel. The BD is processed from different catalytic routes of esterification and transesterification through homogeneous (alkaline and acid), heterogeneous and enzymatic catalysis. However, heterogeneous catalysts and biocatalysts play an essential role towards a sustainable alternative to homogeneous catalysts applied in biodiesel production. The main drawback is the supporting material. To overcome this, currently, Metal-Organic Frameworks (MOFs) have gained significant interest as supports for catalysts due to their extremely high surface area and numerous binding sites. This review focuses on the advantages of using various MOFs structures as supports for heterogeneous catalysts and biocatalysts for the eco-friendly biodiesel production process. The characteristics of these materials and their fabrication synthesis are briefly discussed. Moreover, we address in a general way basic items ranging from biodiesel synthesis to applied catalysts, giving great importance to the enzymatic part, mainly to the catalytic mechanism in esterification/transesterification reactions. We provide a summary with recommendations based on the limiting factors.

Interface-Confined Channels Facilitating Water Transport through an IL-Enriched Nanocomposite Membrane

Improving the permeance of the polyamide (PA) membrane while maintaining the rejection is crucial for promoting the development of membrane separation technology in the practical water-treatment industry. Herein, a novel metal-ionic liquid (Zn-IL) coordination compound was synthesized by in situ growth to improve the water permeance of PA nanofiltration membranes, using an amine-functionalized IL (1-aminopropyl-3-methylimidazolium chloride, [AEMIm][Cl]) as a ligand to react with Zn(NO₃)₂·6H₂O. Piperazine (PIP) and trimesoyl chloride (TMC) were adopted to prepare the PA layer covering the Zn-IL complex. Due to the unique property of the Zn-IL complex, the Zn-IL/PIP-TMC absorbing force to water was increased, enabling the fast transport of water molecules through the membrane pore channels in the form of free water. The resulting Zn-IL/PIP-TMC nanocomposite membrane exhibited a high permeance of up to 26.5 L m^-2 h^-1 bar^-1, which is 3 times that of the PIP-TMC membrane (8.8 L m^-2 h^-1 bar^-1), combined with rejection above 99% for dyes such as methyl blue.

Microwave-Assisted Biodiesel Production Using UiO-66 MOF Derived Nanocatalyst: Process Optimization Using Response Surface Methodology

The present work is on the transesterification of soybean oil to biodiesel under microwave irradiation using a biomass and MOF−derived CaO−ZrO2 heterogeneous catalyst. The optimisation of different parameters was processed by adopting a central composite design for a response−surface methodology (RSM). The experimental data were fitted to a quadratic equation employing multiple regressions and investigated by analysis of variance (ANOVA). The catalyst was exhaustively characterised by XRD, TGA, FTIR BET, SEM, TEM, CO2 TPD and XPS. In addition, the synthesized biodiesel was characterized by 1H and 13C NMR, GCMS. The physicochemical properties of the biodiesel were also reported and compared with the ASTM standards. The maximum yield that was obtained after optimization using RSM was 97.22 ± 0.4% with reaction time of 66.2 min, at reaction temperature of 73.2 °C, catalyst loading of 6.5 wt.%, and methanol−to−oil ratio of 9.7 wt.%.

Recent advances in supported acid/base ionic liquids as catalysts for biodiesel production

Biodiesel is considered a potential substitute for fossil diesel because of its unique environmentally friendly and renewable advantages. The efficient and durable heterogeneous catalysts are vital to greenly and efficiently drive the biodiesel production process. The ionic liquid-functionalized materials, possessing the characteristics of both homogeneous and heterogeneous catalysts, are one of the promising substitutions for conventional homogeneous acid/base catalysts for producing biodiesel. This mini-review focuses on recent advances in supported acid/base ionic liquids to synthesize ionic liquid-functionalized materials for producing biodiesel. The methods of immobilizing ionic liquids on supports were summarized. The merits and demerits of various supports were discussed. The catalytic activities of the ionic liquid-functionalized materials for biodiesel production were reviewed. Finally, we proposed the challenges and future development direction in this area.

MOF/POM hybrids as catalysts for organic transformations

Insertion of molecular metal oxides, e.g. polyoxometalates (POMs), into metal-organic frameworks (MOFs) opens up new research opportunities in various fields, particularly in catalysis. POM/MOF composites have strong acidity, oxygen-rich surface, and redox capacity due to typical characteristics of POMs and the large surface area, highly organized structures, tunable pore size, and shape are due to MOFs. Such hybrid materials have gained a lot of attention due to astonishing structural features, and hence have potential applications in organic catalysis, sorption and separation, proton conduction, magnetism, lithium-ion batteries, supercapacitors, electrochemistry, medicine, bio-fuel, and so on. The exceptional chemical and physical characteristics of POMOFs make them useful as catalysts in simple organic transformations with high capacity and selectivity. Here, the thorough catalytic study starts with a brief introduction related to POMs and MOFs, and is followed by the synthetic strategies and applications of these materials in several catalytic organic transformations. Furthermore, catalytic conversions like oxidation, condensation, esterification, and some other types of catalytic reactions including photocatalytic reactions are discussed in length with their plausible catalytic mechanisms. The disadvantages of the POMOFs and difficulties faced in the field have also been explored briefly from our perspectives.

Fabrication of a polyoxotungstate/metal-organic framework/phosphorus-doped reduced graphene oxide nanohybrid modified glassy carbon electrode by electrochemical reduction and its electrochemical properties

Hybrid nanocomposites based on polyoxometalates (POMs), metal-organic frameworks (MOFs), and graphene oxide (GO) have a unique set of properties. They have specific properties such as high acidity, oxygen-rich surface, and good redox capability from POMs. In contrast, they do not have weaknesses of POMs such as a low surface area, and high solubility in aqueous media. Herein, a novel organic-inorganic nanohybrid compound based on H3PW12O40 (PW12), a Co-based MOF, and GO was prepared. The prepared hybrid nanocomposite (PW12/MOF/GO) was characterized using different techniques. Then, a PW12/MOF/GO nanocomposite modified glassy carbon electrode (GCE) was fabricated by the drop-casting method and next was dried at room temperature. Then, the PW12/MOF/GO/GCE was subjected to electrochemical reduction at a constant potential of -1.5 V, in 0.1 M H3PO4 solution containing 0.10% w/v PW12/MOF/GO additive. The morphology, electrochemical activity, and stability of the modified electrode (PW12/MOF/P@ERGO/GCE) were studied with FE-SEM coupled with EDS, CV, and amperometry. The obtained results confirmed that the PW12/MOF/P@ERGO/GCE could be effective in hydrogen evolution reaction (HER). The electrochemical activity of the PW12/MOF/P@ERGO/GCE due to the desirable microstructure of the electrocatalyst (e.g. high active surface area and homogeneous distribution of the PW12/MOF/P@ERGO), and also the synergistic effect of the blocks, is more than those of PW12/GCE, MOF/GCE, PW12/MOF/GCE, and P@ERGO/GCE. Moreover, the PW12/MOF/P@ERGO/GCE showed an excellent long-term stability under the air atmosphere.

Superprotonic Conductivity of a Functionalized Metal-Organic Framework at Ambient Conditions

Seeking fast proton transport pathways at ambient conditions is desirable but challenging. Here, we report a strategy to synthesize a composite material with a polyoxometalate (POM) and an ionic liquid (IL) confined in stable metal-organic framework (MOF) channels through electrostatic interaction. The obtained SO₃H-IL-PMo₁₂@MIL-101 possesses fast proton transfer, and its proton conductivity can reach 1.33 × 10^-2 S cm^-1 at ambient conditions (30 °C, 70% relative humidity (RH)), which is the highest value among the MOF-based proton conductors operated in an ambient environment. Therefore, it has the potential of becoming a room-temperature proton conductor without a humidifier. Importantly, the composite material is further fabricated into a composite membrane for proton-exchange membrane fuel cells (PEMFCs), which can deliver a power density of 0.93 mW cm^-2 at 30 °C and 98% RH. This result can lay a fundamental basis for the application of MOF-based proton conductors in the area of electrochemical energy conversion.

Zinc-Based Metal-Organic Frameworks in Drug Delivery, Cell Imaging, and Sensing

The design and structural frameworks for targeted drug delivery of medicinal compounds and improved cell imaging have been developed with several advantages. However, metal-organic frameworks (MOFs) are supplemented tremendously for medical uses with efficient efficacy. These MOFs are considered as an absolutely new class of porous materials, extensively used in drug delivery systems, cell imaging, and detecting the analytes, especially for cancer biomarkers, due to their excellent biocompatibility, easy functionalization, high storage capacity, and excellent biodegradability. While Zn-metal centers in MOFs have been found by enhanced efficient detection and improved drug delivery, these Zn-based MOFs have appeared to be safe as elucidated by different cytotoxicity assays for targeted drug delivery. On the other hand, the MOF-based heterogeneous catalyst is durable and can regenerate multiple times without losing activity. Therefore, as functional carriers for drug delivery, cell imaging, and chemosensory, MOFs' chemical composition and flexible porous structure allowed engineering to improve their medical formulation and functionality. This review summarizes the methodology for fabricating ultrasensitive and selective Zn-MOF-based sensors, as well as their application in early cancer diagnosis and therapy. This review also offers a systematic approach to understanding the development of MOFs as efficient drug carriers and provides new insights on their applications and limitations in utility with possible solutions.

Advances in Enzyme and Ionic Liquid Immobilization for Enhanced in MOFs for Biodiesel Production

Biodiesel is a promising candidate for sustainable and renewable energy and extensive research is being conducted worldwide to optimize its production process. The employed catalyst is an important parameter in biodiesel production. Metal-organic frameworks (MOFs), which are a set of highly porous materials comprising coordinated bonds between metals and organic ligands, have recently been proposed as catalysts. MOFs exhibit high tunability, possess high crystallinity and surface area, and their order can vary from the atomic to the microscale level. However, their catalytic sites are confined inside their porous structure, limiting their accessibility for biodiesel production. Modification of MOF structure by immobilizing enzymes or ionic liquids (ILs) could be a solution to this challenge and can lead to better performance and provide catalytic systems with higher activities. This review compiles the recent advances in catalytic transesterification for biodiesel production using enzymes or ILs. The available literature clearly indicates that MOFs are the most suitable immobilization supports, leading to higher biodiesel production without affecting the catalytic activity while increasing the catalyst stability and reusability in several cycles.

Heterogenisation of polyoxometalates and other metal-based complexes in metal–organic frameworks: from synthesis to characterisation and applications in catalysis

This review provides a thorough overview of composites with molecular catalysts (polyoxometalates, or organometallic or coordination complexes) immobilised into MOFs via non-covalent interactions.

Nano-synthesis of solid acid catalysts from waste-iron-filling for biodiesel production using high free fatty acid waste cooking oil

Waste-iron-filling (WIF) served as a precursor to synthesize α-[Formula: see text] through the co-precipitation process. The α-[Formula: see text] was converted to solid acid catalysts of RBC500, RBC700, and RBC900 by calcination with temperatures of 500, 700 and 900 °C respectively and afterwards sulfonated. Among the various techniques employed to characterize the catalysts is Fourier transforms infrared spectrometer (FT-IR), X-ray diffraction (XRD and Scanning electron microscopy (SEM). Performance of the catalysts was also investigated for biodiesel production using waste cooking oil (WCO) of 6.1% free fatty acid. The XRD reveals that each of the catalysts composed of Al-[Formula: see text]. While the FT-IR confirmed acid loading by the presence of [Formula: see text] groups. The RBC500, RBC700, and RBC900 possessed suitable morphology with an average particle size of 259.6, 169.5 and 95.62 nm respectively. The RBC500, RBC700, and RBC900 achieved biodiesel yield of 87, 90 and 92% respectively, at the process conditions of 3 h reaction time, 12:1 MeOH: WCO molar ratio, 6 wt% catalyst loading and 80 °C temperature. The catalysts showed the effectiveness and relative stability for WCO trans-esterification over 3 cycles. The novelty, therefore, is the synthesis of nano-solid acid catalyst from WIF, which is cheaper and could serve as an alternative source for the ferric compound.

Recent Advances in Functionalized Mesoporous Silica Frameworks for Efficient Desulfurization of Fuels

Considerable health and climate benefits arising from the use of low-sulfur fuels has propelled the research on desulfurization of fossil fuels. Ideal fuels are urgently needed and are expected to be ultra-low in sulfur (10-15 ppm), with no greater than 50 ppm sulfur content. Although several sulfur removal techniques are available in refineries and petrochemical units, their high operational costs, complex operational needs, low efficiencies, and higher environmental risks render them unviable and challenging to implement. In recent years, mesoporous silica-based materials have emerged as promising desulfurizing agents, owing to their high porosity, high surface area, and easier functionalization compared to conventional materials. In this review, we report on recent progress in the synthesis and chemistry of new functionalized mesoporous silica materials aiming to lower the sulfur content of fuels. Additionally, we discuss the role of special active sites in these sorbent materials and investigate the formulations capable of encapsulating and trapping the sulfur-based molecules, which are challenging to remove due to their complexity, for example the species present in JP-8 jet fuels.

Hydrogen Bonds in Disulfonic-Functionalized Acid Ionic Liquids for Efficient Biodiesel Synthesis

Regulating the states of hydrogen bonds in ionic liquids (ILs) is an effective way to improve their catalytic performance. In this paper, disulfonic-functionalized acidic ionic liquids (DSFAILs) were synthesized successfully, including novel SO₃H-functionalized binuclear IL (bis[3-(CH₂)₃SO₃H-1-(CH₂)₂-Im][HSO₄]₂). For the biodiesel synthesis, compared with the traditional ILs catalysts, DSFAILs bis[(3-(CH₂)₃SO₃H-1-(CH₂)₂-Im][HSO₄]₂, [Im(N (CH₂)₃SO₃H)₂][HSO₄]) had higher catalytic activity even under mild reaction conditions. Using the density functional theory (DFT) method, the role of hydrogen bonds in different SO₃H-functionalized acidic ionic liquids (SFAILs) was explored. The forms of hydrogen bonds existing in different ILs directly determine their acidity. It suggested that the forming status of the active sites (hydrogen bonds) were diverse in different SFAILs. Also, deep ionization of the hydrogen atoms from the cation-anion strong interaction could increase the acidity and catalytic performance of SFAILs. From this, the structure-activity relationship between the SFAILs structures and the catalytic activity of methyl oleate synthesis was proposed. Besides, the experimental results also showed that bis[3-(CH₂)₃SO₃H-1-(CH₂)₂-Im][HSO₄]₂ catalyst had a high catalytic activity to obtain methyl oleate and the catalyst could be separated easily owing to its larger molecular weight. However, [Im(N(CH₂)₃SO₃H)₂][HSO₄] had a stronger acidity and a lower steric hindrance and thus a higher catalytic activity and was the optimal catalyst for the methyl oleate synthesis. In the presence of a small amount of catalyst (6 wt %) and at low reaction temperature (353 K), the methyl oleate yield could reach up to 93%. After six recycles of the catalyst, the methyl oleate yield remained at 90%.

POM@MOF Hybrids: Synthesis and Applications

The hybrid materials that are created by supporting or incorporating polyoxometalates (POMs) into/onto metal–organic frameworks (MOFs) have a unique set of properties. They combine the strong acidity, oxygen-rich surface, and redox capability of POMs, while overcoming their drawbacks, such as difficult handling, a low surface area, and a high solubility. MOFs are ideal hosts because of their high surface area, long-range ordered structure, and high tunability in terms of the pore size and channels. In some cases, MOFs add an extra dimension to the functionality of hybrids. This review summarizes the recent developments in the field of POM@MOF hybrids. The most common applied synthesis strategies are discussed, together with major applications, such as their use in catalysis (organocatalysis, electrocatalysis, and photocatalysis). The more than 100 papers on this topic have been systematically summarized in a handy table, which covers almost all of the work conducted in this field up to now.

New Task-Specific and Reusable ZIF-like Grafted H6P2W18O62 Catalyst for the Effective Esterification of Free Fatty Acids

The catalytic esterification of free fatty acids is an important reaction pathway for chemical synthesis and biodiesel production, wherein efficient heterogeneous catalysts are sought to replace mineral acids. Herein, the esterification of oleic acid together with some familiar fatty acids is demonstrated with methanol over a heterogeneous heteropolyacid-functionalized zeolite imidazolate framework [H6-n P2W18O62 n-/ZIF(H n His.)+n ]. This new heterogeneous catalyst (named as HPA/ZIF(His.) throughout the text) with an average particle size of 80 nm was prepared via condensation of histamine with zinc chloride and characterized by means of Fourier transform infrared (FT-IR), X-ray diffraction (XRD), UV-vis, energy-dispersive X-ray spectrometry, Brunauer-Emmett-Teller, thermogravimetric analysis (TGA), inductively coupled plasma - optical emission spectrometry (ICP-OES), and scanning electron microscopy. According to the performed characterizations, an HPA loading of 40.5 wt % is obtained for HPA/ZIF(His.) from ICP-OES analysis. Moreover, a typical type-IV isotherm with similar adsorption-desorption properties as seen for ZIF-8 is attained. In addition, TGA measurement confirms less stability of HPA/ZIF(His.) compared to that of pure ZIF(His.). The catalytic performance of the nanomaterial is evaluated with respect to temperature, catalyst loading, and methanol/oleic acid ratio and leads to a high yield of methyl ester (>90%) under reflux for 4 h. The preliminary kinetic studies confirm a pseudo-first-order kinetic model for the esterification of oleic acid. To explore the scope of the HPA/ZIF(His.) catalyst in methyl ester production, other free fatty acids with various chain lengths are also successfully tested. Although the nanocatalyst loses a part of its activity during reuse, however, it is stable over at least four recycles as confirmed by XRD and FT-IR. Eventually, the response surface methodology (RSM) is used as a statistical modeling approach to get the best-optimized reaction conditions compared to the performed single-variable benchmarking experiments. Therefore, the central composite design (CCD) and RSM attained a platform to determine the relationship among the reaction time, acid/methanol molar ratio, and catalyst dosage.

Strategies for Incorporating Catalytically Active Polyoxometalates in Metal-Organic Frameworks for Organic Transformations

Polyoxometalates (POMs) can benefit from immobilization on solid supports to overcome their difficulty in processability and stability. Among the reported solid supports, metal-organic frameworks (MOFs) offer a crystalline, versatile platform for depositing highly active POMs. The combination of these structures can at times benefit from the combined reactivity of both the POM and MOF, sometimes synergistically, to improve catalysis while balancing desirable properties like porosity, substrate diffusion, or stability. In this Review, we survey the strategies for immobilizing POMs within MOF structures, with an emphasis on how physical and catalytic properties of the parent materials are affected in the composite when employed in organic transformations.

In situ synthesis and encapsulation of copper phthalocyanine into MIL-101(Cr) and MIL-100(Fe) pores and investigation of their catalytic performance in the epoxidation of styrene

In this work, copper phthalocyanine (CuPc) was encapsulated into mesocages of MIL-101(Cr) and MIL-100(Fe) by assembling CuPc’s constitutional fractions using a deep eutectic solvent. The prepared materials, CuPc@MIL-101(Cr) and CuPc@MIL-100(Fe), were characterized by powder X-ray diffraction (PXRD), FT-IR, UV-vis and diffuse reflectance UV (DR-UV) spectroscopies, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ICP-OES spectrometry. The prepared materials were used as heterogeneous catalysts for catalytic epoxidation of styrene with molecular oxygen and also tert-butyl hydroperoxide (TBHP) as oxidants in acetonitrile as a solvent. The impact of MOFs and the role of the CuPc complex as the active species in the MOFs’ cages in the epoxidation of styrene were investigated. Among the prepared catalysts, CuPc@MIL-101(Cr) showed the best performance. The heterogeneity of the catalysts was examined by a hot filtration test and ICP-OES of the filtrates after the reaction. Spent catalysts were analyzed by PXRD, FT-IR, UV-DRS, and TEM for reusability investigation and also to further explore the heterogeneous nature of the hybrid materials. Results showed that the prepared catalysts could be recycled and used for several concoctive times without a considerable drop in activity.

Enzymatic Production of Biodiesel Using Immobilized Lipase on Core-Shell Structured Fe3O4@MIL-100(Fe) Composites

In this research, core–shell structured Fe3O4@MIL-100(Fe) composites were prepared by coating Fe3O4 magnetite with porous MIL-100(Fe) metal-organic framework (MOF) material, which were then utilized as magnetic supports for the covalent immobilization of the lipase from Candida rugosa through amide linkages. By using the carbodiimide/hydroxysulfosuccinimide (EDC/NHS) activation strategy, the lipase immobilization efficiency could reach 83.1%, with an activity recovery of 63.5%. The magnetic Fe3O4@MIL-100(Fe) composite and immobilized lipase were characterized by several techniques. The characterization results showed that the Fe3O4 core was coated with MIL-100(Fe) shell with the formation of perfect core–shell structured composites, and moreover, the lipase was covalently tethered on the magnetic carrier. The immobilized lipase displayed a strong magnetic response and could be facilely separated by an external magnetic field. With this magnetic biocatalyst, the maximum biodiesel conversion attained 92.3% at a methanol/oil molar ratio of 4:1, with a three-step methanol addition manner, and a reaction temperature of 40 °C. Moreover, the biocatalyst prepared in the present study was recycled easily by magnetic separation without significant mass loss, and displayed 83.6% of its initial activity as it was reused for five runs, thus allowing its potential application for the cleaner production of biodiesel.

Deep oxidative desulfurization of model fuels catalysed by immobilized ionic liquid on MIL-100(Fe)

Deep desulfurization of fossil fuels has become urgently required because of the serious pollution by the large-scale use of fossil fuels. In this study, [PrSO₃HMIm]HSO₄@MIL-100(Fe) was synthesized by wet-impregnation of the ionic liquid (IL) of [PrSO₃HMIm]HSO₄ on MIL-100(Fe). The construction of [PrSO₃HMIm]HSO₄@MIL-100(Fe) was then confirmed by X-ray powder diffraction, N₂ adsorption-desorption experiments, infrared spectroscopy and elemental analysis, and then applied in the oxidative desulfurization of model fuels. In comparison with the corresponding IL, [PrSO₃HMIm]HSO₄@MIL-100(Fe) showed an enhanced performance in the desulfurization rate of model fuels due to the increase of the mass transfer rate. Under the optimized conditions (oxidant to sulphur ratio = 25, oil to acetonitrile ratio = 1, and temperature = 60 °C), a sulphur removal rate of 99.3% was observed (initial sulphur concentration = 50 ppm). The sulphur removal of three sulphur compounds by catalytic oxidation and extraction followed the order of dibenzothiophene (DBT) > thiophene (T) > benzothiophene (BT).

High-affinity graphene oxide-encapsulated magnetic Zr-MOF for pretreatment and rapid determination of the photosensitizers hematoporphyrin and hematoporphyrin monomethyl ether in human urine prior to UPLC-HRMS

In this paper, a high-affinity graphene oxide-encapsulated magnetic Zr-MOF (GO-Mag@Zr-MOF) was synthesized and characterized by SEM, TEM, and XPS for its morphology, structure, and components. Subsequently, the as-prepared GO-Mag@Zr-MOF was, for the first time, employed as magnetic solid-phase extraction (MSPE) adsorbent for pretreatment and determination of photodynamic therapy (PDT) with the photosensitizers hematoporphyrin (Hp) and hematoporphyrin monomethyl ether (HMME) in human urine samples coupled with ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS). The synthesized GO-Mag@Zr-MOF revealed excellent adsorption efficiency for Hp and HMME in urine samples. Under optimal conditions, the spiked recoveries of the developed method were in the range of 89.5-105.6% with RSDs less than 10%. The limits of detection (LODs) were found to be 0.036 and 0.042 μg/L for Hp and HMME, respectively, while limits of quantitation (LOQs) were 0.12 and 0.14 μg/L. The proposed method was found to be rapid, effective, sensitive, and accurate for clinical analysis. Moreover, this paper, for the first time, carefully expounded the mass spectrum cracking mechanisms of Hp and HMME. Graphical abstract ᅟ.

Facile Approach to Graft Ionic Liquid into MOF for Improving the Efficiency of CO2 Chemical Fixation

This work describes a facile approach to modify metal-organic frameworks (MOFs) with ionic liquids (ILs), rendering them as useful heterogeneous catalysts for CO₂ chemical fixation. An amino-functionalized imidazolium-based ionic liquid is firmly grafted into the porous MOF, MIL-101-SO₃H by the acid-base attraction between positively charged ammonium groups on the IL and negatively charged sulfonate groups from the MOF. Analyses by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ¹H NMR, and N₂ sorption experiments reveal the MOF-supported ionic liquid (denoted as IL@MOF) material remains intact while functioning as a recyclable heterogeneous catalyst that can efficiently convert CO₂ and epichlorohydrin into chloropropene carbonate without the addition of a cocatalyst.

Acidic ionic liquid based UiO-67 type MOFs: a stable and efficient heterogeneous catalyst for esterification

Acidic ionic liquid groups were introduced into the frameworks successfully and the resulting materials showed excellent activity.