五乙烯六胺改性金属有机骨架材料MIL-101(Cr)对CO_2的吸附性能

采用溶剂热法合成金属有机骨架材料MIL-101(Cr),用回流法将五乙烯六胺(PEHA)负载到MIL-101(Cr)孔道中的不饱和金属位点上,使用扫描电镜、粉末X射线衍射、氮气物理吸附、元素分析和傅里叶变换红外光谱等表征手段考察材料的结构和形貌,测试氨基改性前后的MIL-101(Cr)在25℃、不同压力下对CO_2的吸附效果。结果表明,负载0.24 m L五乙烯六胺后的MIL-101(Cr)对CO_2的吸附效果最好,在25℃、常压下对CO_2的饱和吸附量可达58.944 mg/g,相比未负载五乙烯六胺的MIL-101(Cr)吸附量(CO_2饱和吸附量为44.208 mg/g)增加了33%。随着吸附压力的增加,MIL-101(Cr)和0.24PEHAM IL-101(Cr)对CO_2的饱和吸附量逐渐增加,当吸附压力为1.1 MPa时,两者的吸附量分别为1 147.59和1 256.74 mg/g,表明该类材料在高压下对CO_2有着良好的吸附效果。     

铬-对苯二甲酸MOF的框架异构：MIL-88B(Cr)和MIL-101(Cr)

可以通过简单地控制乙酸浓度的方法,在相似的水热合成条件下合成2种同一家族的金属有机框架材料(MOFs):MIL-88B(Cr)和MIL-101(Cr)。在相对较低的乙酸浓度下,可以得到平均粒径为100 nm的MIL-101(Cr),并拥有很高的BET比表面积(3543 m^2·g^-1)。而在相对较高的乙酸浓度下,则可得到另一种具有“呼吸”特性结构的MOF——MIL-88B(Cr)。利用粉末X射线衍射、扫描电镜、N2吸附-脱附分析、热重分析等对它们的结构、形貌、孔隙率等性质做了详细的分析。     

金属-有机骨架MIL-101(Cr)掺杂聚合物整体柱的制备及其用于酚类化合物的在线固相萃取

制备了金属-有机骨架（MOF）MIL-101（Cr）掺杂聚合物整体柱，建立了在线固相萃取-高效液相色谱检测水中4-硝基苯酚、2-硝基苯酚、3-甲基苯酚和2，4-二氯苯酚的方法。考察了样品溶液pH值、上样时间、上样流速和解吸时间对酚类化合物萃取效果的影响。在最优萃取条件下，采用制备的整体柱检测水中酚类化合物，其富集因子高，线性范围宽，精密度好，检出限低，适用于水中酚类化合物的检测。制备掺杂聚合物整体柱是促进和拓宽MOFs在线固相萃取应用的有效方法之一。     

A competitive microcystin-LR immunosensor based on Au NPs@metal-organic framework (MIL-101)

A porous metal organic frameworks (MOFs) material (MIL-101) based on trivalent chromium skeleton were synthesized by hydrothermal synthesis method, and loaded with Au nanoparticles (Au NPs) to prepare Au NPs@MIL-101 composite materials which were used as a marker to label anti microcystin-LR (Anti-MC-LR). The composite materials have strong catalytic properties to the oxidation of ascorbic acid. Anti-MC-LR was immobilized on glassy carbon electrode surface using electrodeposition graphene oxide (GO) as a fixed matrix to construct a competitive microcystin-LR immunosensor.     

聚甲基苯基乙烯基硅氧烷固相微萃取探头的特性

用溶胶－凝胶及自由基引发交联方法，成功地制备了聚甲基苯基乙烯基聚硅氧烷和羟基硅油复合涂层的固相微萃取探头，与进口商用探头比较，研制的探头对芳香化合物具有高的萃取能力和热稳定性（350℃）以及长的使用寿命。     

Preparation of novel solid-phase microextraction fibers by sol-gel technology for headspace solid-phase microextraction-gas chromatographic analysis of aroma compounds in beer

3-(Trimethoxysilyl)propyl methacrylate (TMSPMA) was first used as precursor as well as selective stationary phase to prepare the sol-gel-derived TMSPMA-hydroxyl-terminated silicone oil (TMSPMA-OH-TSO) solid-phase mircroextraction (SPME) fibers for the analysis of aroma compounds in beer. TMSPMA-OH-TSO was a medium polarity coating, and was found to be very effective in carrying out simultaneous extraction of both polar alcohols and fatty acids and nonpolar esters in beer. The extraction temperature, extraction time, and ionic strength of the sample matrix were modified to allow for maximium sorption of the analytes onto the fiber. Desorption temperature and time were optimized to avoid the carryover effects. To check the matrix effects, several different matrices, including distilled water, 4% ethanol/water (v/v) solution, a concentrated synthetic beer, a "volatile-free" beer and a real beer were investigated. Matrix effects were compensated for by using 4-methyl-2-pentanol as internal standard and selecting the "volatile-free" beer as working standard. The method proposed in this study showed satisfactory linearity, precision and detection limits and accuracy. The established headspace SPME-gas chromatography (GC) method was then used for determination of volatile compounds in four beer varieties. The recoveries obtained ranged from 92.8 to 105.8%. The relative standard deviations (RSD, n = 5) for all analytes were below 10%. The major aroma contributing substances of each variety were identified via aroma indexes.     

Are metal-organic frameworks able to provide a new generation of solid-phase microextraction coatings? – A review

Solid-phase microextraction (SPME) is a powerful technique commonly used in sample preparation for extraction/preconcentration of analytes from a wide variety of samples. Among the trends in improving SPME applications, current investigations are focused on the development of novel coatings able to improve the extraction efficiency, sensitivity, and thermal and mechanical stability, within other properties, of current commercial SPME fibers. Metal-organic frameworks (MOFs) merit to be highlighted as promising sorbent materials in SPME schemes. MOFs are porous hybrid materials composed by metal ions and organic linkers, presenting the highest surface areas known, with ease synthesis and high tuneability, together with adequate chemical and thermal stability. For MOF based-SPME fibers, it results important to pretreat adequately the SPME supports to ensure the correct formation of the MOF onto the fiber or the attachment MOF-support. This, in turn, will increase the final stability of the fiber while generating uniform coatings. This review provides a critical overview of the current state of the use of MOFs as SPME coatings, not only highlighting the advantages of these materials versus commercial SPME coatings in terms of stability, selectivity, and sensitivity; but also insightfully describing the current methods to obtain reproducible MOF-based SPME coatings.     

Study of the effect of different fiber coatings and extraction conditions on dry cured ham volatile compounds extracted by solid-phase microextraction (SPME)

Extraction of dry cured ham volatile compounds by solid-phase microextraction (SPME) was optimized. Different fiber coatings (carboxen/polydimethylsiloxane (CAR/PDMS), divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS), polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB)), times of extraction (15, 30, 60 min) and sample preparation (ground samples and homogenates with NaCl saturated solution) were assayed. CAR/PDMS and DVB/CAR/PDMS fiber coatings extracted more than 100 volatile compounds and showed the highest area counts for most volatile compounds. CAR/PDMS coating extracted better those compounds whose Kovats index (KI) was lower than 980 (on average) and DVB/CAR/PDMS those with higher KI. Fifteen minutes of extraction provided a volatile compound profile with lower area counts for most compounds and qualitatively different to that obtained with 30 and 60 min of extraction. Homogenates gave a different profile compared to ground samples, with lower total counts for most compounds but higher proportion of aldehydes, and presence of several compounds not found in ground samples.     

Dodecatungstocobaltate heteropolyanion encapsulation into MIL‐101(Cr) metal–organic framework scaffold provides a highly efficient heterogeneous catalyst for methanolysis of epoxides

A heterogeneous catalyst was synthesized by encapsulation of a Keggin‐type heteropolytungstate, potassium dodecatungstocobaltate trihydrate, K₅[CoW₁₂O₄₀]·(Co‐POM), into chromium(III) terephthalate (MIL‐101). Encapsulation was achieved via a ‘build bottle around ship’ strategy in aqueous media, following a hydrothermal method. The structure of the resulting crystalline solid was characterized using X‐ray diffraction, correlated with Fourier transform infrared and UV–visible spectroscopy. The metal content was analysed using optical emission spectroscopy. Transmission electron microscopy was used to measure particle size and N₂ adsorption in a Brunauer–Emmett–Teller instrument to characterize the specific surface area. The catalytic activity was investigated using methanolysis of epoxides under mild conditions as a test reaction. The turnover frequency of the heterogeneous Co‐POM@MIL‐101 catalyst was more than 20 times higher than that of the homogeneous Co‐POM catalyst. The Co‐POM@MIL‐101 catalyst was reused several times with negligible leaching of Co‐POM and with no considerable loss of its initial efficiency. The simplicity of preparation, extraordinary stability and high reactivity make Co‐POM@MIL‐101 an exceptional catalytic matrix that is easily separable from reaction media.     

Preparation and evaluation of graphene-coated solid-phase microextraction fiber

In this paper, a novel graphene (G) based solid-phase microextraction (SPME) fiber was firstly prepared by immobilizing the synthesized G on stainless steel wire as coating. The new fiber possessed a homogeneous, porous and wrinkled surface and showed excellent thermal (over 330 °C), chemical and mechanical stability, and long lifespan (over 250 extractions). The SPME performance of the G-coated fiber was evaluated in detail through extraction of six pyrethroid pesticides. Although the thickness of G-coated fiber was only 6-8 μm, its extraction efficiencies were higher than those of two commercial fibers (PDMS, 100 μm; PDMS/DVB, 65 μm). This high extraction efficiency may be mainly attributed to huge delocalized π-electron system of G, which shows strong π-stacking interaction with pyrethroid pesticide. The G-coated fiber was applied in the gas chromatographic determination of six pyrethroids, and their limits of detection were found to be ranged from 3.69 to 69.4 ng L⁻¹. The reproducibility for each single fiber was evaluated and the relative standard deviations (RSDs) were calculated to be in the range from 1.9% to 6.5%. The repeatability of fiber-to-fiber and batch-to-batch was 4.3-9.2% and 4.1-9.9%. The method developed was successfully applied to three pond water samples, and the recoveries were 83-110% at a spiking of 1 μg L⁻¹.     

Preparation of ionic liquid based solid-phase microextraction fiber and its application to forensic determination of methamphetamine and amphetamine in human urine

A new solid-phase microextraction (SPME) procedure using an ionic liquid (IL) has been developed. Reusable IL-based SPME fiber was prepared for the first time by fixing IL through cross-linkage of IL impregnated silicone elastomer on the surface of a fused silica fiber. 1-Ethoxyethyl-3-methylimidazloium bis(trifluoromethane) sulfonylimide ([EeMim][NTf₂]) ionic liquid was employed as a demonstration and the prepared fiber was applied to the forensic headspace determination of methamphetamine (MAP) and amphetamine (AP) in human urine samples. Important extraction parameters including the concentration of salt and base in sample matrix, extraction temperature and extraction time were investigated and optimized. Combined with gas chromatography/mass spectrometry (GC/MS) working in selected ion monitoring (SIM) mode, the new method showed good linearity in the range of 20–1500 μg L⁻¹, good repeatability (RSD < 7.5% for MAP, and <11.5% for AP, n = 6), and low detection limits (0.1 μg L⁻¹ for MAP and 0.5 μg L⁻¹ for AP). Feasibility of the method was evaluated by analyzing human urine samples. Although IL-based SPME is still at the beginning of its development stage, the results obtained by this work showed that it is a promising simple, fast and sensitive sample preparation method.     

Adsorption of antimony using amino-functionalized magnetic MIL-101(Cr): Optimization by response surface methodology

Amino-functionalized magnetic MIL-101(Cr) was prepared via a one-step solvothermal method, characterized, and applied in adsorptive Sb(III) removal. The effects of solution pH, adsorbent dosage, and coexisting substances on the adsorption of Sb(III) by MIL-101(Cr)–NH₂/MnFe₂O₄ were studied. The adsorption kinetics were analyzed using pseudo-first order, pseudo-second order, intraparticle diffusion, and Elovich models, while Freundlich and Langmuir isotherm models were used to fit the experimental data. The pseudo-second-order kinetic model provided the best fit for the kinetic data. The maximum adsorption capacity of MIL-101(Cr)–NH₂/MnFe₂O₄ for Sb(III) was 91.07 ​mg/g, as calculated using the Langmuir adsorption isotherm model. Thermodynamic analysis revealed that the adsorption of antimony onto MIL-101(Cr)–NH₂/MnFe₂O₄ is spontaneous and endothermic, while response surface optimization revealed that the optimal conditions for Sb(III) adsorption by MIL-101(Cr)–NH₂/MnFe₂O₄ are an adsorbent loading of 222.55 ​mg/L, a pH of 4.5, and a temperature of 294.59 ​K. The predicted adsorption capacity of MIL-101(Cr)–NH₂/MnFe₂O₄ for Sb(III) is only a 1.8% deviation from the actual value. Furthermore, MIL-101(Cr)–NH₂/MnFe₂O₄ exhibits strong magnetism, allowing it to be separated from wastewater using a magnet. Finally, a preliminary economic analysis showed that the cost of treating a ton wastewater containing 25 ​mg/L antimony using this composite would be 26.24 USD. Thus, MIL-101(Cr)–NH₂/MnFe₂O₄ is promising for treatment of Sb(III)-containing wastewater.     

Ag-Y/MIL-101吸附剂的制备及其吸附脱硫性能

通过银、钇双金属改性制备了Ag-Y/MIL-101吸附剂,并对Ag-Y/MIL-101进行了X射线衍射(XRD)、电镜(SEMEDS)、比表面积(BET)和热重(TG-DTG)表征。考察了Ag-Y/M IL-101金属负载顺序、金属负载浓度、金属溶液用量、负载时间对脱硫性能的影响,优化了吸附脱硫条件。结果表明,金属改性得到的Ag-Y/MIL-101保持了MIL-101的晶格结构。与M IL-101相比,Ag-Y/MIL-101的比表面积和孔容均有所下降。适宜Ag-Y/MIL-101的制备条件为:先负载银后负载钇,银离子和钇离子的负载浓度均为30 mmol/L,金属溶液用量均为1 mL,负载时间为8 h。适宜Ag-Y/MIL-101的吸附脱硫条件为:吸附剂用量0.05 g,模拟油为10 mL,吸附温度为60℃,吸附时间为8 h。在此条件下,Ag-Y/MIL-101对噻吩的吸附量达到21.7 mg/g。Ag能显著提高MIL-101的吸附硫容,Y能显著提高MIL-101的吸附选择性,因此,Ag-Y/MIL-101吸附剂中Ag和Y的协同作用使其拥有比MIL-101更高的硫容和噻吩脱硫选择性。     

Cold fiber solid-phase microextraction device based on thermoelectric cooling of metal fiber

A new cold fiber solid-phase microextraction device was designed and constructed based on thermoelectric cooling. A three-stage thermoelectric cooler (TEC) was used for cooling a copper rod coated with a poly(dimethylsiloxane) (PDMS) hollow fiber, which served as the solid-phase microextraction (SPME) fiber. The copper rod was mounted on a commercial SPME plunger and exposed to the cold surface of the TEC, which was enclosed in a small aluminum box. A heat sink and a fan were used to dissipate the generated heat at the hot side of the TEC. By applying an appropriate dc voltage to the TEC, the upper part of the copper rod, which was in contact to the cold side of the TEC, was cooled and the hollow fiber reached a lower temperature through heat transfer. A thermocouple was embedded in the cold side of the TEC for indirect measurement of the fiber temperature. The device was applied in quantitative analysis of off-flavors in a rice sample. Hexanal, nonanal, and undecanal were chosen as three off-flavors in rice. They were identified according to their retention times and analyzed by GC-flame ionization detection instrument. Headspace extraction conditions (i.e., temperature and time) were optimized. Standard addition calibration graphs were obtained at the optimized conditions and the concentrations of the three analytes were calculated. The concentration of hexanal was also measured using a conventional solvent extraction method (697+/-143ng/g) which was comparable to that obtained from the cold fiber SPME method (644+/-8). Moreover, the cold fiber SPME resulted in better reproducibility and shorter analysis time. Cold fiber SPME with TEC device can also be used as a portable device for field sampling.     

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。     

Aminated metal-organic framework (NH2-MIL-101(Cr)) incorporated polyvinylidene (PVDF) hybrid membranes: Synthesis and application in efficient removal of Congo red from aqueous solution

The efficient treatment of wastewater containing organic dyes generated in diverse industrial processes has become more crucial owing to increasing environmental concerns. In this paper, we incorporated the aminated functional NH₂-MIL-101(Cr) into the porous polyvinylidene fluoride (PVDF) to fabricate the MOFs/polymer hybrid membranes, which combined the surface activity of MOFs and the membrane's filtration plus the adsorption process, and can be used in the high-efficient removal of congo red (CR) from aqueous solution. Two synthesis strategies were employed, and both of which are useful in fabricating the NH₂-MIL-101(Cr)@PVDF hybrid membranes. The NH₂-MIL-101(Cr) particles are mainly incorporated into the pores of PVDF, and thus enhance the hydrophilicity, water flux as well as porosity of the hybrid membranes. In the adsorption experiments, the influences of various conditions including the solution pH, adsorption time, adsorption isotherms, reusability, and the filtration performances were investigated systematically, and all the hybrid membranes show evidently improved adsorption performances compared to original PVDF films. The adsorption thermal and dynamics analyses indicate that the adsorption process is mainly featured in Langmuir monolayer adsorption and chemical adsorption. The hydrogen bonding at the interface of CR/NH₂-MIL-101(Cr) is responsible for the selective adsorption of CR. The excellent reusability and the dynamic adsorption performances determine the potential applications of MOF-based hybrid membranes in the membrane separation of CR from practical waste water.     

金属有机框架MIL-101(Fe)对水中微囊藻毒素-LR的吸附

通过溶剂热法制备了性质稳定的金属有机框架材料MIL-101(Fe),并用于吸附去除水中的微囊藻毒素-LR。采用电子显微镜、傅立叶变换红外光谱(FT-IR)、Zeta电位和N_2吸附-脱附等方法对制备的纳米材料进行了表征。MIL-101(Fe)具有多孔结构和较高的比表面积(375.2 m~2/g),尺寸约为500 nm。考察了pH值、离子强度、温度、吸附时间、浓度等参数对吸附剂吸附能力的影响。结果表明,静电作用和配位作用是主要的作用机理。MIL-101(Fe)对微囊藻毒素-LR的吸附速度很快(20 min内达到吸附平衡),吸附过程符合准二级动力学模型;MIL-101(Fe)对微囊藻毒素-LR表现出良好的吸附性能,其最大吸附量为256.4 mg/g。溶液中存在的腐植酸对MIL-101(Fe)的吸附性能产生一定的影响。受腐殖酸、盐类的影响,相同条件下MIL-101(Fe)对江水中微囊藻毒素-LR的吸附性能有所下降,但仍可达到68.1 mg/g。因此,该方法简便、高效,适用于快速除去污染水体中的微囊藻毒素-LR。     

Tandem oxidative isocyanide-based cycloaddition reactions in the presence of MIL-101(Cr) as a reusable solid catalyst

The tandem oxidative three-component synthesis of two types of the heterocycles such as furans and imidazopyridines, via isocyanides [1+4] cycloaddition reactions in the presence of MIL-101(Cr) under aerobic conditions are reported. When the 4-toluenesulfonylmethyl isocyanide was used, an unexpected [3+2] cycloaddition reaction of isocyanides with aldehydes accomplished and dihydrophenyloxazoles and phenyloxazoles produced. These syntheses were successfully carried out using a wide scope of the substrates.