MCM-41介孔分子筛合成与改性的研究进展

简要介绍了MCM-41介孔分子筛的特点,应用和改性原因.综述了MCM-41介孔分子筛的合成方法,主要包括水热合成法,室温合成法,微波合成法等,列出了每种合成方法的优缺点和合成过程中的影响因素,pH值、晶化时间、晶化温度、模板剂的种类及用量等都会对MCM-41介孔分子筛的结构和孔径产生很大影响.阐述了MCM-41介孔分子筛的改性方法,包括金属杂原子取代法,如主族金属、过渡金属、稀土金属等,有机修饰或功能化法,负载型改性法,如负载金属氧化物、无机酸、杂多酸、有机碱、金属的配合物等.最后就MCM-41介孔分子筛的应用前景做了展望.     

Synthesis of Rhodium Colloidal Nano‐Coating Grafted Mesoporous Silica Composite and its Application as Efficient Environmentally Benign Catalyst for Heck‐Type Reaction of Arylboronic Acids

The synthesis and characterization of rhodium colloidal layer grafted mesoporous SBA‐15 material, designated as SBA‐Rh, are presented. In the preparation of this new catalyst, SBA‐15 mesoporous material was used as support without any pretreatment. The Si H functional groups were introduced onto the surface which resulted in highly dispersed metal colloid layer both on the outer and inner surface of the supporting material. The material was investigated for Heck‐type coupling reactions of alkenes with ayboronic in organic/water solvent. The ultrahigh specific area, large pore opening, and highly dispersed catalyst species in SBA‐Rh material created one of the most active heterogeneous catalysts for such reactions. Rhodium element was not detected in the final mixture by ICP after reaction. The catalyst species showed very high stability against leaching from the matrix and can be recycled for repeated use.     

Synthesis of SBA-15 type mesoporous organosilicas with diethylenebenzene in the framework and post-synthetic framework modification

The SBA-15 type periodic mesoporous organosilicas (PMOs) containing different fraction of 1,4-diethylenebenzene groups in the framework were synthesized by co-condensation of 1,4-bis(trimethoxysilylethyl)benzene with tetramethoxysilane under acidic conditions using triblock copolymer Pluronic P123 as structural directing agent. The results of X-ray diffraction pattern (XRD), nitrogen sorption isotherm, and transmission electron microscopy (TEM) show that all materials have well-ordered mesoporous structure with uniform pore size distributions. The acidic sites were incorporated in the mesoporous framework by post-synthetic framework modification of 1,4-diethylenebenzene by sulfonation. The framework composition of the mesoporous organosilicas before and after modification was fully characterized by UV Raman spectroscopy, and ¹³C CP-MAS and ²⁹Si MAS NMR. From elemental analysis, it can be estimated that about 40% of the organic group within the mesoporous framework is available for further chemical reaction. The PMOs with aryl sulfonaic acid groups in the framework are efficient solid acids for the esterification of ethanol with aliphatic acid. With the alkyl chain of the aliphatic acid increasing, the activity of the material is enhanced by more amounts of 1,4-diethylenebenzene incorporated in the mesoporous framework. The post-synthetic modification is a facile approach for the generation of new functional groups in the mesoporous framewrok of PMOs.     

Highly efficient removal of bulky tannic acid by millimeter‐sized nitrogen‐doped mesoporous carbon beads

Millimeter‐sized nitrogen‐doped mesoporous carbon beads (NMCBs) with a controllable nitrogen content are synthesized for the first time via a suspension‐polymerization assisted hard templating method. In contrast to conventional activated carbons, NMCBs exhibit outstanding structural advantages, including macroscopic morphology, a developed mesoporous structure and enriched surface chemistry. When used as adsorbents for the removal of the bulky organic pollutant tannic acid, these NMCBs demonstrated fast adsorption kinetics and very high adsorption capacity. The adsorption capacity strongly depends on the nitrogen content doped into the carbon framework. At a nitrogen content of 4.1 wt %, the adsorption capacity reaches 318 mg g^?1. The molecular mechanics simulation and zeta potential measurements suggest that the enhanced adsorption by nitrogen doping may be due to the electrostatic attraction between the nitrogen functional groups and the phenol groups of tannic acid. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3016–3025, 2017     

Design of multifunctionalized mesoporous silicas for esterification of fatty acid

Organosulfonic acid mesoporous silicas further functionalized with hydrophobic organic groups were synthesized via postsynthesis grafting and one-step co-condensation methods. The resulting materials were tested in the esterification of fatty acid with methanol to produce methyl esters as a pretreatment step in the production of biodiesel. Incorporation of the hydrophobic group into the organic–inorganic hybrid acid catalyst was found to improve the performance of the resulting catalyst. However, the performance of the multifunctionalized mesoporous materials demonstrated a strong dependence on the incorporation method and on the size of the hydrophobic organic groups. Solution effects within the reaction mixture appeared to influence the catalytic activity of the catalysts. The results indicate the potential for intentional design of the catalytic environment at a molecular level with the use of organic–inorganic mesoporous materials.     

Mesoporous ordered silica structures modified by metal organic reagents and their application in catalytic Michael additions

Periodic mesoporous silica was modified with metal organic reagents via direct surface substitution reactions, thus introducing functional groups into the channels of the structure. Using materials functionalised with basic aromatic molecules as catalysts, the efficient Michael addition of diethyl malonate to trans-β-nitrostyrene was achieved. The catalysts anchored to the silica surface show high activity in the catalytic process even at low concentrations and low temperatures. The catalysts also prove to be stable during many recycling procedures. In combination with the remarkably reduced cost for the synthesis of these solid bases, the new hybrid systems are promising candidates for a new generation of catalysts.     

Carboxyl functionalization of carbon fibers through a grafting reaction that preserves fiber tensile strength

Composite materials can be enhanced by grafting a secondary material to a functional group on the surface of the reinforcing fibers to improve thermal, electrical or mechanical properties. Grafting secondary materials onto carbon fibers is often limited by the low reactivity of graphitic carbon and there is strong demand to create novel grafting methods with versatile functional groups. One desirable functional group is a carboxylic acid, which strongly interacts with many organic and inorganic materials. In this work, the surface of carbon fibers is functionalized by a reaction of naturally existing surface hydroxyl groups with isopropylidene malonate to graft terminal malonic esters, effectively creating a carboxyl functionalized surface. The reaction does not employ pre-oxidation to generate functional groups prior to grafting and is shown to preserve the tensile strength and morphology of the fiber. The surface functionalization is quantified by X-ray photoelectron spectroscopy, which shows that the relative surface coverage by carboxylic acid groups is increased from an initial 5.2% up to 9.2%. The effects of solvent, temperature, concentration and reaction time on the quantity of surface carboxylic acid groups are studied. This functionalization opens up new opportunities as a precursor reaction for further grafting reactions without sacrificing fiber strength.     

微波辅助合成金丝桃素四磺酸衍生物

利用微波辅助合成的方法,对金丝桃素四磺酸衍生物合成路线中的大黄素蒽酮缩合反应分别从微波加热温度、辐射时间和催化剂3个因素进行了优化,确定了最佳反应条件:温度150℃,反应时间1 h,不使用催化剂;该步反应的产率可达82.2%,整个合成路线经放大后的总产率为65.3%。与常规加热方法相比,微波辅助合成法提高了反应效率和产率,减少了副反应的发生,使合成工艺更加低碳环保。     

Immobilization of Co(III) using tethered cyclam ligand on SBA-15 mesoporous silica for aerial oxidation of ethylbenzene

Cyclam type macrocyclic ligand was tethered onto mesoporous silica surface through N-functionalization of the cyclam. The mesoporous silica was synthesized directly with in-built chloropropyl functional group by applying microwave synthesis approach and the cyclam ligand was tethered via the surface substitution reaction of the chloro group. The tethered cyclam ligand was proven to facilely accommodate Co(III) cation into its cavity. This Co(III)cyclam-functionalized mesoporous silica showed good catalytic activity in the aerial oxidation of ethylbenzene to give acetophenone as the major product, which exceeded 60%. The presence of pyridine ligand which bounded to the axial sites of the tethered Co(III)cyclam complex enhanced the activity of the catalyst with sustaining the selectivity.     

介孔金属有机框架材料吸附水中重金属离子研究进展

介孔金属有机框架材料（介孔MOFs）相较于传统吸附剂具有孔径大、孔隙率可调、比表面积大、官能团丰富,便于功能化改性修饰等优点,可高效地吸附水体中重金属污染物。本文介绍介孔MOFs的特性、合成策略及四种合成介孔MOFs的方法,重点分析四种方法的介孔形成机理及其所面临的问题,并将四种合成方法的优劣进行了比较。详述介孔MOFs吸附去除水中重金属离子、类重金属阴离子以及放射性金属离子的研究进展;介绍了介孔MOFs在吸附去除重金属离子方面的可重复利用性;阐述介孔MOFs吸附去除水中重金属污染物的作用机理。对介孔MOFs成本高昂、合成条件苛刻、回收利用难等问题提出了优化方向,指出提高介孔MOFs的水稳定性、易回收利用、简便绿色合成技术以及痕量去除将是未来的研究方向。     

Effects of Surface Functional Groups and Porous Structures on Adsorption and Recovery of Perfluorinated Compounds by Inorganic Porous Silicas

The effects of porous structures and surface functional groups (silanol, 3-aminopropyltriethoxy, 3-mercaptopropyltrimethoxy, n-octyldichloroethoxy, and titanium substitution) on perfluorinated compounds (PFCs) adsorption and recovery were evaluated. The adsorption of PFCs on all adsorbents followed the pseudo-second-order model, and the adsorption rate was controlled by the pore diffusion, except for microporous zeolites and powder activated carbon (PAC). 3-aminopropyltriethoxy-grafted surface produced the highest PFCs adsorption capacities. Perfluorooctane sulfonic acid (PFOS) recovery from silica-based adsorbents (by ethanol extraction) efficiencies were higher than those of PAC and approached 100%. Hydrophobic organic functional groups can protect mesoporous structure from hydrolysis reactions in adsorption and solvent recovery processes.

Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the free supplemental file.     

Synthesis and characterization of mesoporous and amorphous silica modified with silica-organo-sulfogroups

Amorphous silica gel and mesoporous MCM-41 with sulfo organic layer were prepared by post synthesis two step modifications, i.e. silylation with benzylchloro-dimethyl-silane, followed by treatment with chlorosulfonic acid. Resulting composites have a porous structure similar to that of non-modified materials, as shown by nitrogen adsorption and X-ray diffraction measurements. The successful incorporation of the functional groups was indicated by IR spectroscopy and NMR analysis. The grafted functional groups are thermally stable up to 723 K, as found by thermo gravimetrical and IR measurements. The results obtained from catalytic conversion of methylbutinol indicate the presence of acidic centers.     

The examination of surface chemistry and porosity of carbon nanostructured adsorbents for 1-naphthol removal from petrochemical wastewater streams

Chemically modified mesoporous carbon (CMMC) and chemically modified activated carbon (CMAC) were prepared by an acid surface modification method from mesoporous carbon (MC) and commercial activated carbon (AC) by wet impregnation method. The structural order and textural properties of the nanoporous materials were studied by XRD and nitrogen adsorption. The presence of carboxylic functional groups on the carbon surface was confirmed by FTIR analyses. Adsorption of 1-naphthol over various porous adsorbents such as CMMC, CMAC, MC and AC was studied. The adsorption isotherms of 1-naphthol were in agreement with a Langmuir model; moreover, the uptake capacity of 1-naphthol followed the order: CMMC>MC>CMAC>AC.     

Rapid Formation of Active Mesoporous TiO2 Photocatalysts via Micelle in a Microwave Hydrothermal Process

Rapid formation of active, mesoporous, and crystalline TiO₂ photocatalysts via a novel microwave hydrothermal process is presented. Crystalline anatase mesoporous nanopowders 100–300 nm in size with worm hole-like pore sizes of 3–5 nm were prepared by a modified sol–gel of titanium tetra-isopropoxide, accelerated by a microwave hydrothermal process. The organic surfactant, tetradecylamine, which is used as a self-assembly micelle in the sol–gel and microwave hydrothermal process, enables to harvest crystallized mesoporous anatase nanoparticles with a high-surface area. Mesoporous worm hole-like and crystalline powders with surface areas of 243–622 m²/g are obtained. X-ray diffraction, N₂-adsorption isotherms (Barrett–Joyner–Halenda and Brunauer–Emmet–Teller method), scanning electron microscope, and transmission electron microscope are used to identify the characteristics and morphologies of the powders. It is shown that crystallization by calcination at 400°C/3 h inevitably reduced the surface area, while the microwave hydrothermal process demonstrated a rapid formation of crystalline mesoporous TiO₂ nanopowders with a high-surface area and excellent photocatalytic effects.     

Reactivity of mesoporous carbon against water – An in-situ XPS study

Functionalized mesoporous carbon catalysts can be used in the acid catalyzed dehydration of fructose to 5-hydroxymethyl furfural (HMF). However, strong deactivation can be observed after preconditioning of the material in the reaction solvent 2-butanol. Surface changes caused by the pretreatment have been studied by XPS. The comparison of the pristine sample and the pretreated carbon sample showed similar distribution of oxygen functional groups by ex-situ XPS, as well as similar behavior during heating in vacuum. However, the addition of water (0.1 mbar vapor pressure) and subsequent heating to 130 °C exhibited prominent differences in the evolution of the O1s, as well as for the C1s spectra of the two samples. Changes in the surface termination and hydrophobicity of the materials are discussed under the aspect of possible reactions of surface functional groups with the alcoholic solvent and water.     

One-Step Hydrogenation/Esterification Activity Enhancement Over Bifunctional Mesoporous Organic–Inorganic Hybrid Silicas

Bifunctional mesoporous organic–inorganic hybrid silica incorporating both platinum and organosulfonic acid groups were synthesized for use in simultaneously catalyzing the one-step hydrogenation/esterification (OHE) of acetic acid and acetaldehyde, which was considered as a model reaction for the upgrading of biomass-derived bio-oil. The work explored optimizing the synthesis procedure to generate a bifunctional catalyst with enhanced combined activity for the OHE reaction. The presence of Pt was found to enhance the acidic properties of the organosulfonic acid functionalized silica. The mechanism by which the Pt incorporation affected the acid sites was investigated by the using XPS, FT-IR, FT-Raman characterization. The XPS results indicated the presence of electron transfer between the Pt and –SO₃H groups. The FT-IR and FT-Raman results, which were in agreement with XPS, demonstrated an electron density increase for S and a S–O bond energy increase, which was proposed to be the reason for the acidity enhancement due to the presence of Pt. Additionally, arenesulfonic acid groups were substituted for propylsulfonic acid groups and the resulting material had higher catalytic activity due to the increased acid strength. An optimal synthesis procedure was demonstrated in which the Pt was first impregnated on the mesoporous silica using reductive deposition. Then Pt was activated and the material further modified by grafting on arenesulfonic acid groups. The resulting catalyst was about four times more active than the original base case bifunctional material.     

Influence of the alkyl chain length of HSO3-R-MCM-41 on the esterification of glycerol with fatty acids

Ordered mesoporous materials functionalized with alkyl sulfonic acid groups have been proved to be efficient catalysts for esterification. In this paper we report on the synthesis and characterization of new materials containing simultaneously alkyl groups (vinyl, chloromethyl), that have been sulfonated in a post-synthesis step, and methyl groups. Different techniques have been used to characterize the obtained materials: XRD, TEM, elemental analysis, nitrogen adsorption, TGA, ²⁹Si and ¹³C MAS NMR. Finally, the influence of the different synthesis parameters and functional groups on the behavior of the catalysts in the reaction of esterification of glycerol with lauric and oleic acids has been studied. The catalytic performance of the resulting HSO₃-ethyl-MCM-41, HSO₃-ethyl/methyl-MCM-41 and HSO₃-methyl-MCM-41 new materials is also compared to those of HSO₃-phenyl/methyl-MCM-41 and HSO₃-propyl/methyl-MCM-41 synthesized previously. It has been demonstrated that an optimum balance among parameters such as nature of the organic group which support the sulfonic acid, distance between the sulfonic group and the silica surface, average pore size of the material, etc., allows to obtain catalysts with improved activity and selectivity for these reactions.     

Synthesis chemistry and application development of periodic mesoporous organosilicas

This paper provides a comprehensive and critical overview of recent advances in synthesis chemistry and application development of periodic mesoporous organosilicas (PMOs). A number of organic bridge-bonded functional and multifunctional PMOs with inorganic–organic hybridized framework have been synthesized from varieties of precursors. The syntheses of a series of PMOs have been accomplished typically by resorting to the co-condensation of the mixed precursors of tetraalkoxysilane and bridged organosiloxane, bridged organosiloxane with terminal organosiloxane, or the co-condensation of multiple bridged organosiloxane. The choice of precursors depends on the desired location of organic groups which can be either on the surface or within the pore wall in resulting PMOs. Besides precursors, synthesis conditions evidently play an important role in the formation, morphologies and pore structure of PMOs. Recent advances show that the morphologies and mesopores of PMOs can be adjusted by changing the synthetic parameters such as template, additives, pH value, and temperature. The PMOs with tunable composition, morphology and even-distributed hydrophobic organic groups in the framework endow such periodic mesoporous hybrids with great potentials in the fields of catalysis, environmental remediation, biology, pharmacy, analytical chemistry and microelectronics. The synthesis chemistry of PMOs and application development would particularly and continuously appeal to the researchers in chemistry and materials science in future.     

Remarkable effect of ordered mesoporous carbon support in tantalum oxide-catalyzed selective epoxidation of cyclooctene

The olefin epoxidation is one of the most important reactions in chemical industry. Metal oxide supports often cause drawbacks in catalytic activity and selectivity, which has been overcome by introducing hydrophobic organic groups onto the oxide supports. The present study utilizes ordered mesoporous carbon (CMK-3 and CMK-1) as structurally defined hydrophobic catalyst support. Well-dispersed tantalum oxides supported on the ordered mesoporous carbon were prepared. Their application in catalytic epoxidation of cyclooctene demonstrates that the tantalum oxide catalysts on the ordered mesoporous carbon supports show higher performances than those of the catalysts supported on activated carbon and ordered mesoporous silica SBA-15.     

Hybrid MCM-41 grafted by a general microwave-assisted procedure: a characterization study

Hybrid materials obtained through a Microwave-assisted grafting of organic functional groups on mesoporous silica (MCM-41 type) have been characterized by X-ray powder diffraction, TG-DSC, N₂ adsorption, solid state ¹³C- and ²⁹Si-NMR, TEM and SEM. The studied grafting procedure is effective in the preparation of hybrid organosilicas under solvent-free conditions. Microwaves allows an ultra-fast and clean functionalization of the mesoporous materials and the method has been applied to produce a wide series of functional materials. The hybrid materials maintain the original mesoporous structure when the loading of linked organic groups does not exceed 10 %. In this cases, the slight pore volume reduction is linearly correlated to the organic amount in the product. If functional groups able to interact among them through hydrogen bond are used, hybrid materials exhibit high Organic/SiO₂ ratios and low pore volumes due to the formation of a network occluding the pores, where functional groups of free organosilane molecules interacts with the functional groups of molecules linked to the matrix. NMR data confirm that the network is composed by organosilane molecules linked or not to the framework. Acid washing is able to labilize hydrogen bond and open the network. In the case of bulky but chemically inert functionalising agents the network is not produced.