Selective aerobic oxidative coupling of thiols that are catalyzed by La(III)-substituted 5-oxopyrrolidine-2-carboxylic acid (Glp) immobilized on SBA-15 (SBA-15@Glp–La; SBA = Santa Barbara amorphous) was studied. Using SBA-15@Glp–La, the complete conversion was achieved at room temperature in the presence of air without producing any over-oxidized yields. SBA-15@Glp–La was prepared by post-grafting technique. 5-Oxopyrrolidine-2-carboxylic acid (Glp) condensation followed by La(III) impregnation caused this La(III)-grafted 5-oxopyrrolidine-2-carboxylic acid (Glp) to immobilize on SBA-15. This SBA-15@Glp–La catalyst shows excellent catalytic activity in the selective aerobic oxidative coupling of thiols. Effects of amount of the catalyst, polarity of the solvent, effects of substrate, and catalyst reusability were investigated. It has been observed that seven repetitive reaction cycles did not cause any appreciable loss in the catalytic activity of this catalyst. The catalyst characterization by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, thermal gravimetric analysis, transmission electron microscopy, inductively coupled plasma, elemental mapping, and N2 adsorption–desorption is reported. The procedure developed is heterogeneous and environmentally benign. 相似文献
A new catalyst, Pd particles supported on the N-doped porous carbon(PC) derived from Zn-based metal–organic frameworks(zeolitic imidazolate framework: ZIF-8), was successfully prepared for the first time.The as-prepared catalyst was designated as N-doped PC-Pd, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscope, N_2 adsorption and inductively coupled plasma atomic emission spectroscopy. The N-doped PC-Pd composite exhibited high catalytic activity toward the Suzuki–Miyaura cross-coupling reactions. The yields of the products were in the range of 90%–99%. The catalyst could be readily recycled and reused at least 6 consecutive cycles without a significant loss of its catalytic activity. 相似文献
The reactions of norfloxacin (H-Norf) with Mn(ClO4)2·6H2O and Mn(OH)2 yield Mn(H-Norf)(ClO4)2·2H2O (1) and [Mn(Norf)2·4H2O]n (2) , respectively. 1 is monomeric while 2 has a novel 2D neutral square grid with an antibacterial drug as building block. Crystal data for 1: triclinic, space group P1 (No.2), a=9.0939(3), b=9.4395(3), c=12.7182(3)?, α=111.447(2), β=90.340(2), γ=112.357(1)°, V=926.34(5)?3, Z=1, ρcacl=1.664g·cm-3. MoKα radiation (λ=0.71073?), T=293(2)K, μ=0.595mm-1, R1=0.0692, wR2=0.1482 for 2320 observed reflections from 4390 independent reflections, GOF=0.940; Crystal data for 2: Monoclinic, P21/c, a=5.7530(12), b=21.865(4), c=13.343(3)?, β=98.25(3)°, V=1661.1(6)?3, Z=2, ρcacl=1.527g·cm-3, T=293(2)K, μ=0.477mm-1, R1=0.0531, wR2=0.1552 for 2070 observed reflections from 2870 independent reflections, GOF=1.384. CCDC: 140819; 151063. 相似文献
The preparation of bicontinuous nanoporous covalent frameworks, which are promising for caging active enzymes, is demonstrated. The frameworks have three‐ dimensionally continuous, hydrophilic pores with widths varying between 5 and 30 nm. Enzymes were infiltrated into the bicontinuous pore by applying a pressured enzyme solution. The new materials and methods allowed the amount of caged proteins to be controlled precisely. The resulting enzyme‐loaded framework films could be recycled many times with nearly no loss of catalytic activity. Entropic trapping of proteins by a bicontinuous pore with the right size distribution is an unprecedented strategy toward facile in vitro utilization of biocatalysts. 相似文献
The rapid development of nanomaterials, particularly advanced hybrid nanoparticles, has made new opportunities for the design and fabrication of high‐performance metal‐based catalysts. However, generating metal nanoparticles of desired size without aggregation is an important challenge for enhancing the catalytic activity of metal nanoparticles supported in the host matrix. In this work, a hybrid nanoporous material, namely Pd nanoparticles@N‐heterocyclic carbene@ZIF‐8, with a high internal surface area was successfully prepared using a dispersed anionic sulfonated N‐heterocyclic carbene–Pd(II) precursor inside the cavities of zeolitic imidazolate framework (ZIF‐8) using an impregnation approach followed by reduction with NaBH4. The anionic sulfonated N‐heterocyclic carbene was found to be a superb ligand for the stabilization of Pd nanoparticles in the pores of ZIF‐8. The resulting system was applied to the Mizoroki–Heck cross‐coupling reaction, in which the catalyst showed high catalytic activity under mild reaction conditions. 相似文献
Visible light emission emanating from nanostructured porous silicon is sensitive to adsorption of a number of small molecules, suggesting its utility as a chemical sensor. In this work we investigate the mechanistic origin of the diminution of the luminescence by n-propyl amine adsorption and restoration by trifluoroacetic acid, most sensitively by an examination of the changes in observed lifetime of the porous Si luminescence. This is quantified in terms of a stretched exponential model that is consistent with a distribution of luminescent centers in this nanophase material. 相似文献
Summary: An ordered nanoporous monolith was prepared from a poly(isoprene‐b‐dimethylsiloxane) (PI‐PDMS) hexagonally packed cylinder precursor. The PDMS cylinders were macroscopically aligned, the PI was crosslinked with dicumyl peroxide, and the PDMS was removed using tetrabutylammonium fluoride. The stability of the pores depended on the modulus of the matrix. At high crosslink density the pores were stable, but they collapsed at a low crosslink density. The nanoporous materials could be swollen in toluene.
A scanning electron micrograph of the end‐on view of crosslinked degraded poly(isoprene‐b‐dimethylsiloxane). 相似文献
Characteristics of solid-state ionistors developed on the basis of nanoporous carbon synthesized by chlorination of metal carbides are presented. It is shown that the energy storage density in this type of devices reaches 150 J/g when they are operated in the hybrid mode. 相似文献
An efficient method was developed for the protection of alcohols as trityl ethers using triphenylmethanol in the presence of nanoporous MCM-41-SO3H as a heterogeneous catalyst under solvent-free ball-milling at room temperature. Low catalyst loading, high efficiency, reusability are among the advantages of this new solvent-free and environmentally friendly method. The deprotection of the produced trityl ethers was also efficiently achieved using the same catalyst in wet acetonitrile. 相似文献
Vanadium doped nanoporous Ti0.9Sn0.1O2 thin film has been prepared on an alumina substrate by sol‐gel method with Pluronic P123 as the organic template, and humidity sensing properties of it has been investigated. It is found that V‐doped nanoporous Ti0.9Sn0.1O2 thin film shows good humidity sensing properties, and impendence of it decreases more than four orders of magnitude in the relative humidity (RH) range of 11%–95% at 25°C. The response and recovery time of this sensor are about 13 and 17 s, respectively. High sensitivity, narrow hysteresis loop, rapid response and recovery, prominent stability and good repeatability are obtained. A possible mechanism is suggested to explain the humidity sensitive properties. 相似文献
Microporous and mesoporous molecular sieves like zeolite faujasites, AlPO4-5 and Si-MCM-41 are obtained by polycondensation of oxygen containing tetrahedra of the metal aluminium, the semimetal silicon and the non-metal phosphorus by conventional or microwave-assisted hydrothermal synthesis. The encapsulation of dyes after different methods is described. Monomolecular distribution of dyes in the framework of the hosts is obtained. The encapsulated dyes show high absorption and fluorescence intensities which is interesting for photochromic switches, optical sensors and lasing. The location of a dye is identified after single molecule spectroscopy. 相似文献