金属有机骨架材料MIL-53(Al)负载钴催化剂的CO催化氧化反应性能

采用溶剂法合成了热稳定性高的金属有机骨架材料MIL-53(Al)(MIL:Materials of Institut Lavoisier),用此材料为载体负载钴催化剂用于CO的催化氧化反应,并与Al2O3负载的钴催化剂进行了对比.采用热重-差热扫描量热(TG-DSC)、傅里叶变换红外(FTIR)光谱、X射线衍射(XRD)、N2物理吸附-脱附、透射电子显微镜(TEM)、氢气程序升温还原(H2-TPR)等方法对催化剂的结构性质进行了表征.TG和N2物理吸附-脱附结果表明,载体MIL-53(Al)有好的稳定性和高的比表面积;XRD以及TEM结果表明Co/MIL-53(Al)上负载的Co3O4颗粒粒径(平均约为5.03 nm)明显小于Al2O3上Co3O4颗粒粒径(平均约为7.83 nm).MIL-53(Al)的三维多孔结构中分布均匀的位点能很好地分散固定Co3O4颗粒,高度分散的Co3O4颗粒有利于CO的催化氧化反应.H2-TPR实验发现Co/MIL(Al)催化剂的还原温度低于Co/Al2O3催化剂的还原温度,低的还原温度表现为高的催化氧化活性.CO催化氧化结果表明,MIL-53(Al)负载钴催化剂的催化活性明显高于Al2O3负载钴催化剂,MIL-53(Al)负载钴催化剂在160°C时使CO氧化的转化率达到98%,到180°C时CO则完全转化,催化剂的结构在催化反应过程中保持稳定.     

Highly efficient oxidative cleavage of alkenes and cyanosilylation of aldehydes catalysed by magnetically recoverable MIL‐101

The catalytic activity of magnetically recoverable MIL‐101 was investigated in the oxidation of alkenes to carboxylic acids and cyanosilylation of aldehydes. MIL‐101 was treated with Fe₃O₄ and the prepared catalyst was characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, N₂ adsorption measurements, field emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and inductively coupled plasma analysis. The catalytic active sites in this heterogeneous catalyst are Cr³⁺ nodes of the MIL‐101 framework. This heterogeneous catalyst has the advantages of excellent yields, short reaction times and reusability several times without significant decrease in its initial activity and stability in both oxidation and cyanosilylation reactions. Its magnetic property allows its easy separation using an external magnetic field.     

Pd/MIL-101的制备及非均相催化吲哚C-H活化

水热合成MIL-101,过量浸渍法吸附Pd(OAc)_2,原位还原Pd~(2+)制得Pd/MIL-101催化剂.采用XRD、XPS、SEM、ICP、HRTEM和N_2吸/脱附实验对其结构进行表征,催化剂Pd纳米粒子尺寸在1.5~2.5 nm之间,含量为1.5%.催化实验表明,Pd/MIL-101能高效催化吲哚C_2位芳基化,对于活性较差的溴代芳烃,也能得到中等以上的收率,催化剂循环5次后仍能保持较高的反应活性,发展了吲哚C_2位衍生物的简单、高效的合成方法.     

Pt/MIL-101(Cr)在肉桂醛选择性加氢反应中的催化性能

采用简单易行的浸渍法将Pt纳米粒子负载到MIL-101(Cr)上, 制备了Pt/MIL-101(Cr)催化剂, 并对其在肉桂醛选择性加氢反应的催化性能进行了研究。XRD、N₂吸附、TEM和催化性能的研究结果表明, Pt的负载量对负载于MIL-101(Cr)上Pt纳米粒子的尺寸及所制备催化剂对肉桂醇的选择性有很大影响。低Pt负载量(1.0wt%)的Pt/MIL-101(Cr)较其他MOFs和无机材料在肉桂醛选择性加氢反应中表现出了高的催化性能, 在优化的反应条件下肉桂醛转化率和对肉桂醇的选择性可分别达96.5%和86.2%。Pt/MIL-101(Cr)催化剂具有良好的稳定性。Pt/MIL-101(Cr)所表现出的优良的催化性能同MIL-101(Cr)载体的孔道结构及其表面性质密切相关。     

Pt/MIL-101(Cr)在肉桂醛选择性加氢反应中的催化性能

采用简单易行的浸渍法将Pt纳米粒子负载到MIL-101(Cr)上,制备了Pt/MIL-101(Cr)催化剂,并对其在肉桂醛选择性加氢反应的催化性能进行了研究。XRD、N₂吸附、TEM和催化性能的研究结果表明,Pt的负载量对负载于MIL-101(Cr)上Pt纳米粒子的尺寸及所制备催化剂对肉桂醇的选择性有很大影响。低Pt负载量(1.0%)的Pt/MIL-101(Cr)较其他MOFs和无机材料在肉桂醛选择性加氢反应中表现出了高的催化性能,在优化的反应条件下肉桂醛转化率和对肉桂醇的选择性可分别达96.5%和86.2%。Pt/MIL-101(Cr)催化剂具有良好的稳定性。Pt/MIL-101(Cr)所表现出的优良的催化性能同MIL-101(Cr)载体的孔道结构及其表面性质密切相关。     

Copper-doped sulfonic acid-functionalized MIL-101(Cr) metal–organic framework for efficient aerobic oxidation reactions

A series of Cr-based metal–organic framework MIL-101-SO₃H bearing sulfonic acid functional groups were utilized for the immobilization of catalytically active copper species via a post-synthetic metalation method. The novel materials were fully characterized by scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), the Brunauer–Emmett–Teller method, and thermogravimetric analysis. XPS and the EDX element map both suggested that Cu²⁺ is coordinately bonded to the MIL-101-SO₃H, which forms the MIL-101-SO₃@Cu structure. The obtained copper-doped MIL-101-SO₃@Cu-1, MIL-101-SO₃@Cu-2, and MIL-101-SO₃@Cu-3 catalysts were utilized in the selective oxidation of alcohols and epoxidation of olefins using molecular oxygen as an oxidant. Catalytic aerobic oxidation optimization showed that MIL-101-SO₃@Cu-1 is the optimal catalyst and it can be reused ten times without compromising the yield and selectivity.     

Encapsulation of Microperoxidase-8 into MIL-101(Cr/Fe) Nanoparticles: A New Biocatalyst for the Epoxidation of Styrene

A new biocatalyst MP8@MIL-101(Cr/Fe) was prepared by immobilization of a heme octapeptide, Microperoxidase 8 (MP8) within a mixed metal MOF, MIL-101(Cr/Fe). Both MIL-101(Cr/Fe) and MP8@MIL-101(Cr/Fe) were characterized by PXRD, FTIR spectroscopy and TGA. The catalytic activity of MP8@MIL-101(Cr/Fe) for the oxidation of styrene by H₂O₂ and tBuOOH was then examined under various reaction conditions (nature of the co-solvent and of the oxidant, concentration of the oxidant and of the substrate, time, pH) and compared to that of MP8 alone. Under the best conditions used, MP8@MIL-101(Cr/Fe) was then shown to catalyze the oxidation of styrene about 3 times more efficiently than MP8 alone with approximately 50 % selectivity for styrene oxide.     

A new Brønsted acid MIL-101(Cr) catalyst by tandem post-functionalization; synthesis and its catalytic application

A new heterogeneous Brønsted solid acid catalyst was prepared by tandem post-functionalization of MIL-101(Cr) and utilized for acetic acid esterification and alcoholysis of epoxides under solvent-free conditions. First, MIL-101(Cr) was functionalized with pyrazine to achieve MIL-101(Cr)-Pyz. Afterwards, the nucleophilic reaction of MIL-101(Cr)-Pyz with 1,3-propane sultone and next acidification with diluted sulfuric acid gave MIL-101(Cr)-Pyz-RSO₃H Brønsted solid acid catalyst. Various characterization methods such as Fourier transformation infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), elemental analysis (CHNS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersiveX-ray(EDX) spectroscopy, thermal analysis (TGA/DTA), acid–base titration, and N₂ adsorption/desorption analysis were employed to fully characterize the prepared catalyst. The catalyst showed high activity compared to unmodified MIL-101(Cr) in both catalytic acetic acid esterification and alcoholysis of epoxides. It can also be readily isolated from the reaction mixture and reused three times without major decrease in its activity.     

Rapid microwave-hydrothermal conversion of lignin model compounds to value-added products via catalytic oxidation using metal organic frameworks

Microwave irradiation is an effective method for faster heating to shorten reaction time of oxidative valorization of lignin. However, studies using microwave irradiation for lignin oxidation all employ homogeneous catalysis. Thus, this study aims to investigate heterogeneous catalytic oxidation of lignin under microwave irradiation. Especially, metal organic frameworks (MOFs) are adopted as transition metal-containing heterogeneous catalysts for lignin oxidation. In particularly, MOFs (MIL-101 (Cr), MIL-101 (Fe), UiO-66, HKUST-1, and MOF-801) are also prepared using microwave irradiation and used as for oxidative conversion of a model lignin compound, vanillyl alcohol (VAL), to the valuable products, vanillin (VN) and vanillic acid (VAC), using H₂O₂ as an oxidant. While the tested MOFs all exhibit catalytic activities for VAL conversion to VN/VAC, MIL-101 and MOF-801 appear to be relatively effective. Through investigating the effect of temperature, VAL conversion to VN/VAC is less favorable at higher temperature possibly due to degradation of H₂O₂ at high temperatures. While a higher dosage of H₂O₂ increases VAL conversion, the additionally added H₂O₂ seems to further oxidize VN to VAC instead of converting more VAL to VN. Through the EPR analyses, the mechanism of VAL conversion to VN/VAC may be attributed to both the OH-based and non-OH^? routes. The most effective MOF, MOF-801, also exhibited very similar catalytic activities over several cycles. The results indicate that MOFs can convert VAL to valuable products of VN and VAC within a very short time (10 min) under microwave irradiation. MOF-801 was also validated as a promising MOF for VAL conversion.     

An Effective Hybrid Heterogeneous Catalyst to Desulfurize Diesel: Peroxotungstate@Metal–Organic Framework

A peroxotungstate composite comprising the chromium terephthalate metal–organic framework MIL-101(Cr) and the Venturello peroxotungstate [PO₄{WO(O₂)₂}₄]³⁻ (PW₄) has been prepared by the impregnation method. The PW₄@MIL-101(Cr) composite presents high catalytic efficiency for oxidative desulfurization of a multicomponent model diesel containing the most refractory sulfur compounds present in real fuels (2000 ppm of total S). The catalytic performance of this heterogeneous catalyst is similar to the corresponding homogeneous PW₄ active center. Desulfurization efficiency of 99.7% was achieved after only 40 min at 70 °C using H₂O₂ as an oxidant and an ionic liquid as an extraction solvent ([BMIM]PF₆, 2:1 model diesel/[BMIM]PF₆). High recycling and reusing capacity was also found for PW₄@MIL-101(Cr), maintaining its activity for consecutive oxidative desulfurization cycles. A comparison of the catalytic performance of this peroxotungstate composite with others previously reported tungstate@MIL-101(Cr) catalysts indicates that the presence of active oxygen atoms from the peroxo groups promotes a higher oxidative catalytic efficiency in a shorter reaction time.     

Matrices based on meso antibacterial framework

In this paper, the synthesis of three types of porous materials (PMs) (porous Fe₃O₄, MIL-101 metal-organic framework (MOF), and MCM-41 mesoporous silica) by hydrothermal method was performed. The incorporation of Ag nanoparticles (Ag NPs) was carried out after the synthesis reaction of supports in MCM-41 and MIL-101 MOF. Ag core@ porous Fe₃O₄ core–shell system was prepared via a one-pot hydrothermal method. Ag-MIL-101 was obtained using Urtica dioica leaf extract as the green solvent and reducing agent. The antibacterial activity of Ag-PM nanocomposites (NCs) was investigated on both Gram-negative and Gram-positive bacteria. The size of the silver NPs was determined to be 12 and 30 nm in MCM-41 and MIL-101 MOF, respectively. The diameter of Ag core in Ag@Fe₃O₄ shell was ~135 nm. The antibacterial activity of Ag-PMs was in the order Ag-MCM-41 > Ag-MIL-101 > Ag core@Fe₃O₄ shell. The loading percent of Ag NPs in MCM-41 (84%) was more than that in MIL-101 (53%) and Fe₃O₄ (31%). The release of Ag⁺ ions from Ag-MCM-41, Ag-MIL-101, and Ag@Fe₃O₄ NCs was 46, 2, and 1 ppm, respectively. The release of the Ag⁺ ions and, consequently, the antibacterial activity of NCs depend on the uniform distribution, particles size, and the absence of aggregation of Ag NPs in PMs.     

Investigation of CO and formaldehyde oxidation over mesoporous Ag/Co3O4 catalysts

CO and formaldehyde (HCHO) oxidation reactions were investigated over mesoporous Ag/Co₃O₄ catalysts prepared by one-pot (OP) and impregnation (IM) methods. It was found that the one-pot method was superior to the impregnation method for synthesizing Ag/Co₃O₄ catalysts with high activity for both reactions. It was also found that the catalytic behavior of mesoporous Co₃O₄ and Ag/Co₃O₄ catalysts for the both reactions was different. And the addition of silver on mesoporous Co₃O₄ did not always enhance the catalytic activity of final catalyst for CO oxidation at room temperature (20 °C), but could significantly improve the catalytic activity of final catalyst for HCHO oxidation at low temperature (90 °C). The high surface area, uniform pore structure and the pretty good dispersion degree of the silver particle should be responsible for the excellent low-temperature CO oxidation activity. However, for HCHO oxidation, the addition of silver played an important role in the activity enhancement. And the silver particle size and the reducibility of Co₃O₄ should be indispensable for the high activity of HCHO oxidation at low temperature.     

A 3D MIL-101@rGO composite as catalyst for efficient conversion of straw cellulose into valuable organic acid

Efficient conversion of straw cellulose to chemicals or fuels is an attracting topic today for the utilization of biomass to substitute for fossil resources. The development of catalysts is of vital importance.In this work, a composite catalyst metal-organic frameworks(MOFs) immobilized on three-dimensional reduced graphene oxide(3D-r GO) were synthesized by in situ growth of the MIL-101(Cr) within the 3Dr GO matrix. The supporting of 3D-r GO guaranteed the dispersion and acid site density of MI...     

Ru(III) complex anchored onto amino-functionalized MIL-101(Cr) framework via post-synthetic modification: an efficient heterogeneous catalyst for ring opening of epoxides

In this work, the metallo Schiff base-functionalized metal–organic framework was prepared by post-synthetic method and used as an electron-deficient catalyst for the alcoholysis of epoxides. In this manner, the aminated MIL-101 was modified with 2-pyridine carboxaldehyde and then the prepared Schiff base reacted with RuCl₃. This new catalyst, MIL-101–NH₂–PC–Ru, was characterized by Fourier transform infrared, UV–Vis spectroscopic techniques, X-ray diffraction, BET, inductively coupled plasma atomic emission spectroscopy and field-emission scanning electron microscopy. In the presence of this heterogeneous catalyst, ring opening of epoxides was performed under mild condition to show the significant ability and successful applications of Lewis acid containing catalysts in corporation with metal–organic frameworks. The reusability of the catalyst was also investigated. No noticeable decrease in the catalytic activity was found after four consecutive times.     

Novel Synthesis of Cu-Schiff Base Complex@Metal-Organic Framework MIL-101 via a Mild Method: A Comparative Study for Rapid Catalytic Effects

The use of metal complex immobilized/decorated porous materials as catalysts has found various applications. As such, finding a new and mild method for synthesis of metal complex immobilized over porous material is of great interest. Immobilized porous materials for styrene oxidation were reported in this work. Immobilized porous material of Cu-Schiff base complex @MIL-101 were described, in which immobilized Cu-Schiff base complex within super cage of a metal-organic framework (MOF)-based porous material, chromium (III) terephthalate MIL-101. They were systematically characterized by using elemental analysis, powder X-ray diffraction, fourier transform infrared spectroscopy, N₂ absorption-desorption, and so on, also used as catalyst for the selective oxidation of styrene to benzaldehyde. Comparatively, the immobilized heterogeneous catalyst of Cu-Schiff base complex@MIL-101 acted as an efficient heterostructure catalyst in the oxidation of styrene to benzaldehyde up to six cycles, and showed superior activity for styrene oxidation over MIL-101.     

Copper Complexes Stabilized by Chitosans: Peculiarities of the Structure,Redox, and Catalytic Properties

Peculiarities of the structure and physicochemical properties of copper–chitosan complexes prepared by different methods were studied by IR, UV-visible, ESR spectroscopy, and electron microscopy. The catalytic activity of redox copper centers stabilized by the chitosan matrix in the reactions of oxidation of o- and p-dihydroxybenzenes in an aqueous medium was determined. Quantitative ESR measurements provide evidence for the localization of virtually all copper ions introduced in the initial heterogeneous chitosan samples with copper contents below 1.5 wt % in the form of isolated Cu²⁺ ions in square planar coordination. The chitosan matrix was shown to strongly bind copper ions under conditions of redox transformations in the catalytic tests or upon prolonged heating in boiling water. Reoxidation of the samples with H₂O₂ results in quantitative restoration of the initial ESR signal of Cu(II). Heterogenized copper–chitosan samples exhibited high activity and stability in the catalytic oxidation of dihydroxybenzenes into quinones, whereas the homogeneous system was characterized by irreversible poisoning due to formation of copper–hydroquinone complexes. Preparation of the binary composite system with a thin heterogeneous copper–chitosan film supported on a macroporous silica allows one to dramatically enhance the specific catalytic activity and the efficiency of the active component. Such an approach may turn out to be useful in the synthesis of supported chitosan catalyst with a low noble metal content.     

The Significance of Metal Coordination in Imidazole-Functionalized Metal–Organic Frameworks for Carbon Dioxide Utilization

The grafting of imidazole species onto coordinatively unsaturated sites within metal–organic framework MIL-101(Cr) enables enhanced CO₂ capture in close proximity to catalytic sites. The subsequent combination of CO₂ and epoxide binding sites, as shown through theoretical findings, significantly improves the rate of cyclic carbonate formation, producing a highly active CO₂ utilization catalyst. An array of spectroscopic investigations, in combination with theoretical calculations reveal the nature of the active sites and associated catalytic mechanism which validates the careful design of the hybrid MIL-101(Cr).     

超声改性的CuO/Al2O3-MgO催化剂结构 及其超低浓度甲烷催化燃烧性能

采用普通浸渍和超声改性的方法分别制备了CuO/Al₂O₃-MgO催化剂,用于超低浓度甲烷的催化燃烧,并利用SEM、XRD、XPS、H₂-TPR等技术对催化剂进行表征,研究了超声改性作用对催化剂的结构和性能的影响.结果表明,与普通浸渍法制备的催化剂相比,在超声改性的CuO/Al₂O₃-MgO催化剂上,甲烷的转化率得到提高,燃烧特征温度降低.随着超声时间的延长和超声功率的增加,催化剂的催化活性均呈现先增大后减小的趋势;催化剂制备的最佳超声工况为功率150 W、时间20 min.超声改性可使催化剂的比表面积和孔容积增大,表面催化活性较高的Cu⁺浓度增加,活性组分CuO由晶相向非晶相转变、分散度增大,晶粒粒径变小、分布更均匀;这使得甲烷催化燃烧的表观活化能下降、催化剂活性得到增强.     

Excess of nio loading - key for catalyst activity decline prevention

Summary The activity of co-precipitated NiO-Al₂O₃ catalyst for partial oxidation of methane in a steel flow reactor was investigated. The catalyst samples loaded with 5, 10 and 20 wt.% nickel before use were thermally treated at 400, 700 and 1100^oC. The feed gas for catalytic oxidation was prepared by dilution of natural gas with air, and had approximately the following volume composition: CH₄: O₂: N₂ = 5: 2: 8. The reaction was carried out over 100 mg unreduced NiO-Al₂O₃ catalyst at gas flow rate of 50 cm³/min at 650^oC and atmospheric pressure. The catalyst activity with 5 and 10 wt.% of nickel was very similar, decreasing with enhance of previous heat treatment. Further nickel loading did not increase significantly the catalyst activity compared to low level nickel samples. However, high nickel content has a levelling effect on catalyst activity, suppressing the undesired effect of previous heat treatment at high temperature