钌掺杂MCM-48介孔分子筛的表征及催化氧化环己烷性能的研究

以在室温条件下快速制备的一系列Ru掺杂的MCM-48介孔分子筛为催化剂,进行了无溶剂条件下空气催化氧化环己烷制环己醇和环己酮的反应研究,并通过XRD、N2吸附脱附、FT-IR等多种表征手段对该催化剂进行系统研究.表征结果表明该催化剂具有典型的MCM-48介孔材料结构,合成过程中加入的Ru以不同形态同时存在于催化剂中.催化反应的结果显示该催化剂在较温和反应条件下具有良好催化活性,并且不同的Ru物种在反应中呈现不同的活性.     

In Situ Loading of Drugs into Mesoporous Silica SBA‐15

In a new strategy for loading drugs into mesoporous silica, a hydrophilic (heparin) or hydrophobic drug (ibuprofen) is encapsulated directly in a one‐pot synthesis by evaporation‐induced self‐assembly. In situ drug loading significantly cuts down the preparation time and dramatically increases the loaded amount and released fraction of the drug, and appropriate drug additives favor a mesoporous structure of the vessels. Drug loading was verified by FTIR spectroscopy and release tests, which revealed much longer release with a larger amount of heparin or ibuprofen compared to postloaded SBA‐15. Besides, the in vitro anticoagulation properties of the released heparin and the biocompatibility of the vessels were carefully assessed, including activated partial thromboplastin time, thrombin time, hemolysis, platelet adhesion experiments, and the morphologies of red blood cells. A concept of new drug‐release agents with soft core and hard shell is proposed and offers guidance for the design of novel drug‐delivery systems.     

Efficient Liquid‐Phase Oxidation of Diphenylmethane to Benzophenone over Vanadium‐Containing MCM‐41 Catalysts

The liquid‐phase oxidation of diphenylmethane with tert‐butylhydroperoxide has been studied using vanadium‐containing MCM‐41 materials, which were prepared by direct hydrothermal (V‐MCM‐41) and wet impregnation (V/MCM‐41) methods. These catalysts were characterized in detail by ICP‐AES, N₂‐sorption, XRD, FT‐IR, ²⁹Si and ⁵¹V NMR, TPD of ammonia, TPR of hydrogen, and chemisorption of oxygen. Both series of catalyst show good catalytic results, which are attributed to their highly ordered mesoporous structure, large BET surface area as well as the presence of easily accessible vanadium‐oxygen species as active centers in the catalyst. Further, V‐MCM‐41 exhibit superior catalytic activity (based on turnover number) than V/MCM‐41 mainly due to well‐dispersed tetrahedral vanadium‐oxygen species with higher oxidation ability. The effect of reaction parameters, i.e., temperature, time, solvent, etc. were investigated. Catalyst recycling test reveals good stability with only slight extent of leaching during the reaction.     

Efficient Selective Oxidation of Aromatic Alkanes by Double Cobalt Active Sites over Oxygen Vacancy-rich Mesoporous Co3O4

The development of efficient catalyst for selective oxidation of hydrocarbon to functional compounds remains a challenge. Herein, mesoporous Co₃O₄ (mCo₃O₄-350) showed excellent catalytic activity for selective oxidation of aromatic-alkanes, especially for oxidation of ethylbenzene with a conversion of 42 % and selectivity of 90 % for acetophenone at 120 °C. Notably, mCo₃O₄ presented a unique catalytic path of direct oxidation of aromatic-alkanes to aromatic ketones rather than the conventional stepwise oxidation to alcohols and then to ketones. Density functional theory calculations revealed that oxygen vacancies in mCo₃O₄ activate around Co atoms, causing electronic state change from Co³⁺_(Oh)→Co²⁺_(Oh). Co²⁺_(Oh) has great attraction to ethylbenzene, and weak interaction with O₂, which provide insufficient O₂ for gradual oxidation of phenylethanol to acetophenone. Combined with high energy barrier for forming phenylethanol, the direct oxidation path from ethylbenzene to acetophenone is kinetically favorable on mCo₃O₄, sharply contrasted to non-selective oxidation of ethylbenzene on commercial Co₃O₄.     

Synthesis of Olive‐Shaped Mesoporous Platinum Nanoparticles (MPNs) with a Hard‐Templating Method Using Mesoporous Silica (SBA‐15)

Well‐ordered mesoporous Pt nanoparticles (MPNs) with uniform olive shapes are synthesized by using two‐dimensional (2D) hexagonal mesoporous silica (SBA‐15) as a hard template. The average particle sizes are controllable in the range of 150 to 230 nm by changing the reduction time. Low‐angle XRD profiles for the obtained MPNs show three distinct peaks assignable to the (10), (11), and (20) planes of a highly ordered 2D hexagonal symmetry. From high‐magnification SEM images, periodically arranged Pt nanowires are observed clearly, which are a negative replica of the 2D hexagonally ordered mesoporous silica (SBA‐15). Furthermore, the single crystallinity of the Pt fcc structure coherently extends over the whole particles. As a result of such unique character as well as high surface area, the obtained MPNs show distinctly enhanced electrocatalytic properties for methanol oxidation reaction compared to other Pt samples, such as Pt black.     

Detailed Structural Characterizations of SBA‐15 and MCM‐41 Mesoporous Silicas on a High‐Resolution Transmission Electron Microscope

Using high‐resolution transmission electronic micrograph (HR‐TEM) observation, one can clearly see the pore geometry of the MCM‐41 and SBA‐15 mesoporous silicas to determine that their pore shapes are hexagonal and round, respectively. With the perpendicular orientations of the nanochannels to the electron beam, parallel line images of the (100) and (110) repeating spacings were observed. In the SBA‐15 mesoporous silicas, there are byproducts of the granular silica and disordered mesostructures, attributed to the weak hydrogen interactions between Pluronic 123 blockcopolymer and the silica species. There are also many different and significant +π disclination defects in SBA‐15 and MCM‐41 surfactant‐silica composites. The SBA‐15 with a thicker silica wall is more stable under irradiation by high‐energy electron beams compared to MCM‐41, which has thinner wall thickness. Some carbon nanostructure impurities were found in some carbon films on the metal grids.     

Graphene‐Supported Ultrafine Metal Nanoparticles Encapsulated by Mesoporous Silica: Robust Catalysts for Oxidation and Reduction Reactions

Graphene nanosheet‐supported ultrafine metal nanoparticles encapsulated by thin mesoporous SiO₂ layers were prepared and used as robust catalysts with high catalytic activity and excellent high‐temperature stability. The catalysts can be recycled and reused in many gas‐ and solution‐phase reactions, and their high catalytic activity can be fully recovered by high‐temperature regeneration, should they be deactivated by feedstock poisoning. In addition to the large surface area provided by the graphene support, the enhanced catalytic performance is also attributed to the mesoporous SiO₂ layers, which not only stabilize the ultrafine metal nanoparticles, but also prevent the aggregation of the graphene nanosheets. The synthetic strategy can be extended to other metals, such as Pd and Ru, for preparing robust catalysts for various reactions.     

Adsorption of Acid Dyes by Functionalized SBA‐15 Mesoporous Silica of Different Pore Lengths

SBA‐15 materials of different pore lengths and functionalized with various organic groups were synthesized by one‐pot co‐condensation and applied as adsorbents for the acid orange 12 (AO12) and acid red 73 (AR73) dyes. The materials were characterized by techniques such as X‐ray powder diffraction, nitrogen sorption isotherms, scanning electron microscopy, and infrared (FTIR) spectroscopy. The adsorption behaviors of the SBA‐15 materials toward AO12 and AR73 dyes were investigated by varying several factors including morphologies of adsorbents, pH of solution, functional groups on SBA‐15, and temperature. The equilibrium adsorption data agreed with Langmuir isotherms. The kinetic parameters were also calculated and the first‐order kinetic model fitted well for amino‐functionalized SBA‐15 material. The short channeling pores of the amino‐functionalized SBA‐15 platelets facilitated the diffusion of dye molecules inside the pores and prevented the aggregation of dye molecules from the blocking of the pores. To conclude, however, the adsorption capacity is dependent on the amount of amino‐loading and surface area of the SBA‐15 materials.     

Bifunctional Cage‐Type Cubic Mesoporous Silica SBA‐1 Nanoparticles for Selective Adsorption of Dyes

Bifunctional SBA‐1 mesoporous silica nanoparticles (MSNs) with carboxylic acid and amino groups (denoted as CNS‐10‐10) have been successfully synthesized, characterized, and employed as adsorbents for dye removal. Adsorbent CNS‐10‐10 shows high affinity towards cationic and anionic dyes in a wide pH range, and exhibits selective dye removal of a two‐dye mixture system of cationic methylene blue and anionic eosin Y. By changing the pH of the medium, the selectivity of the adsorption behavior can be easily modulated. For comparison purposes, the counterparts, that is, pure silica SBA‐1 MSNs (CS‐0) and those with either carboxylic acid or amino functional groups (denoted as CS‐10 and NS‐10, respectively) were also prepared to evaluate their dye‐adsorption behaviors. As revealed by the zeta‐potential measurements, the electrostatic interaction between the adsorbent surface and the dye molecule plays an important role in the adsorption mechanism. Adsorbent CNS‐10‐10 can be easily regenerated and reused, and maintains its adsorption efficiency up to 80 % after four cycles.     

Maximizing the Number of Interfacial Sites in Single‐Atom Catalysts for the Highly Selective,Solvent‐Free Oxidation of Primary Alcohols

The solvent‐free selective oxidation of alcohols to aldehydes with molecular oxygen is highly attractive yet challenging. Interfacial sites between a metal and an oxide support are crucial in determining the activity and selectivity of such heterogeneous catalysts. Herein, we demonstrate that the use of supported single‐atom catalysts (SACs) leads to high activity and selectivity in this reaction. The significantly increased number of interfacial sites, resulting from the presence of individually dispersed metal atoms on the support, renders SACs one or two orders of magnitude more active than the corresponding nanoparticle (NP) catalysts. Lattice oxygen atoms activated at interfacial sites were found to be more selective than O₂ activated on metal NPs in oxidizing the alcohol substrate. This work demonstrates for the first time that the number of interfacial sites is maximized in SACs, providing a new avenue for improving catalytic performance by developing appropriate SACs for alcohol oxidation and other reactions occurring at metal–support interfacial sites.     

Three‐Component Reaction of Isocyanides and 2‐Formylbenzoic Acid with Dibenzylamine Catalyzed by Silica Nanoparticles under Solvent‐Free Conditions

Reaction of an isocyanide with an iminium ion intermediate, formed by reaction between 2‐formylbenzoic acid and dibenzylamine in the presence of silica nanoparticles (silica NP, ca. 42 nm) proceeds smoothly at room temperature to afford isocoumarin (=1H‐2‐benzopyran‐1‐one) derivatives in high yields (Scheme 1 and Table 1).     

Solvent‐Free One‐Pot Synthesis of Amidoalkyl Naphthols Catalyzed by Silica Sulfuric Acid

An efficient, inexpensive, and mild method for the synthesis of amidoalkyl naphthols, catalyzed by ‘silica sulfuric acid’ (SSA), was elaborated under solvent‐free conditions at room temperature. Various amidoalkyl naphthols were synthesized in high yields from aromatic or aliphatic aldehydes, α‐ or β‐naphthols, and amides or urea or thiourea.     

Mesoporous SBA‐15 Silica Phenylsulfonic Acid (SBA‐15‐Ph‐SO3H) as Efficient Nanocatalyst for One‐pot Three‐component Synthesis of 3‐Methyl‐4‐aryl‐2,4,5,7‐tetrahydropyrazolo[3,4‐b]pyridine‐6‐ones

A simple, economical, and efficient approach to the one‐pot synthesis of 3‐methyl‐4‐aryl‐2,4,5,7‐tetrahydropyrazolo[3,4‐b]pyridine‐6‐ones by multicomponent assembling of 5‐methylpyrazol‐3‐amine, aldehydes, and Meldrum's acid using mesoporous silica phenylsulfonic acid (SBA‐15‐Ph‐SO₃H) as recyclable and heterogonous solid acid nanocatalyst has been described. This protocol has the advantages of high yields, wide application scope, and an environmental benign procedure.     

Kinetics of Heterogeneous Solvent‐free Liquid Phase Oxidation of Alcohol Using ZrO2 Catalyst with Molecular Oxygen

Clean liquid phase solvent‐free oxidation of alcohol to aldehyde/ketone using ZrO₂ catalyst with molecular oxygen has been studied. Monoclinic phase ZrO₂ has been synthesized and characterized by XRD, SEM, EDX and surface and pore size analyses. Oxidation of alcohol was carried out in a typical batch reactor at different speed of agitation (150–1200 r/min), temperature (373–413 K), catalyst loading (50–300 mg) and partial pressure of oxygen (12–101 kPa). These parameters influence alcohol conversion as well as selectivity. A handy touch of kinetics was given to the experimental data and apparent activation energy was calculated.