A facile microexplosion approach has been successfully developed to produce an interwoven mesopore network in zeolite crystals via the rushing-out of gases generated by decomposition of H 2 O 2 under microwave irradiation. This "gas imprint" method creates the mesopores from the interior crystal toward the exterior, in line with the direction of the pristine microporous channels, and is different from the previous methods in which the reagent starts an attack from the crystal surface and perforates inward. The created mesopores extend throughout the whole crystal and highly blend into the intrinsic micropores around. The acidity of zeolite is also well preserved due to this unique mechanism of pore creation. The continuous high quality hierarchical architecture with intact acidity leads to a notable increase both in the conversion of 2-methoxynaphthalene acylation and in the selectivity to the target molecule of 2-acetyl-6-methoxynapthalene. This microexplosion approach offers an efficient synthesis protocol of zeolitic hierarchy integrating intersected mesoporosity and zeolitic microporosity and opens the way to the rational organization of meso-and microporosity for maximal advantage in applications.
electrical, [3] catalytic, [4] and magnetic [5] properties. To overcome the poor stability and severe aggregation in catalytic processes that remain major problems for UMNPs, MNPs have been immobilized onto/into various supports through postsynthetic and one-pot synthesis methods. [6] With either method, it is critical to control the interaction between the metal ions and supports and interactions between metal ions. Various functional groups have been selected and used to improve metal precursor impregnation rates and metal-support interactions to avoid metal leaching into the liquid phase and to control particle aggregation and growth; for example, P and N ligands constituted with bisphosphinoamino moieties, diphenylphosphinopyridine moieties, dendrimers, small organic molecules (amines, thiols, citrate, etc.), surfactants (hexadecyltrimethylammonium bromide), and silanization reagents (SH, NH 2 , and COOH) have been used. [7] However, these methods are not universally applicable to a large number of metals because of the limit of the coordination selectivity of ligands.DNA is one of the most attractive "building blocks" because of its double-stranded helical structure with well-defined minor and major grooves, well-regulated micrometer length, and a uniform diameter of ≈2 nm. More importantly, the unique chemical composition of DNA provides a variety of binding Supported ultrasmall metal/metal oxide nanoparticles (UMNPs) with sizes in the range of 1-5 nm exhibit unique properties in sensing, catalysis, biomedicine, etc. However, the metal-support and metal-metal precursor interactions were not as well controlled to stabilize the metal nanoparticles on/in the supports. Herein, DNA is chosen as a template and a ligand for the silica-supported UMNPs, taking full use of its binding ability to metal ions via either electrostatic or coordination interactions. UMNPs thus are highly dispersed in silica via self-assembly of DNA and DNA-metal ion interactions with the assistance of a co-structural directing agent (CSDA). A large number of metal ions are easily retained in the mesostructured DNA-silica materials, and their growth is controlled by the channels after calcination. Based on this directing concept, a material library, consisting of 50 mono-and 54 bicomponent UMNPs confined within silica and with narrow size distribution, is created. Theoretical calculation proves the indispensability of DNA with combination of several organics in the synthesis of ultrasmall metal nanoparticles. The Pt-silica and Pt/Ni-silica chosen from the library exhibit good catalytic performance for toluene combustion. This generalizable and straightforward synthesis strategy is expected to widen the corresponding applications of supported UMNPs.
Tremendous efforts have been made in recent years to synthesize ordered mesoporous zeolite materials due to the accelerating demands of industrial bulky molecule conversion. Here, we develop a novel gradient acidic assembly growth strategy to prepare ordered highly-zeolitized mesoporous aluminosilicate (SBA-16) materials in a mixed template system. This gradient acidic assembly growth strategy can achieve the high zeolitization of mesoporous aluminosilicate walls without any ordering loss of the mesostructure. The resultant highly-zeolitized mesoporous materials, composed of the intergrown zeolite sub-crystal particles (2-3 nm), exhibit high surface area (∼834 m 2 g -1 ) and pore volume (∼0.64 cm 3 g -1 ), typical channel of MFI framework (0.52 nm) and uniform mesopore (∼5.75 nm), respectively. Moreover, these highly-ordered crystallized mesostructures endow them with high exposed active sites and excellent hydrothermal stability, which consequently make their catalytic activities in bulky molecule transformations at least 10 times higher than conventional zeolites or amorphous mesoporous materials. Without the use of any special surfactants, this general synthetic process provides a brand new view for the synthesis and application of highly-crystalline ordered mesoporous materials.
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