Assembly of Mesoporous Lamellar Silicas with Hierarchical Particle Architectures

Abstract

A family of silica molecular sieves with lamellar frameworks and hierarchical structure (denoted MSU-V) was assembled from homogeneous solutions of neutral H2N(CH2) n NH2 bolaamphiphiles (n = 12−22) as the structure directors and tetraethylorthosilicate as the inorganic precursor. Optimal lamellar order was observed for four as-synthesized and calcined (550 °C) mesostructures when they were assembled at the following reaction temperatures (T, °C) and surfactant/silica ratios (R) of T = 25 °C, R = 0.26 (C12); T = 45 °C, R = 0.20 (C16); T = 55 °C, R = 0.15 (C18); T = 55 °C, R = 0.11 (C22). MSU-V silica assembled from the short C12 alkyl chain bolaamphiphile exhibited gallery-confined micropores (1.3 nm), but the derivatives prepared from the longer C16−C22 diamines showed gallery-confined mesopores. As the alkyl chain length of the bolaamphiphile surfactant increased from C16 to C22, the size of the gallery-confined mesopores increased from 2.0 to 2.7 nm. The described synthetic strategy afforded hierarchical MSU-V structures with biomimetic multilamellar vesicular particle architectures. Distorted vesicular, plate, and spiral-ribbon shaped particles also were observed, particularly for the lamellar silica assembled from the C16 bolaamphiphile. The variation in morphologies was attributed to agitation effects during synthesis. MSU-V silica assembled from the C22 diamine was the least stable member of the series and partially decomposed upon calcination. Remarkably, surfactant removal by calcination did not affect the biomembrane-like, hollow disk morphology of the original as-synthesized C22 product. This bolaamphiphile assembly approach provides new opportunities for the preparation of lamellar mesoporous molecular sieves with hierarchical structures specifically tailored to applications as diverse as sorbents, catalysts, sensors, bone implants, and nanoscale devices.

Synthesis, characterization and photocatalytic applications of Zn-doped TiO2 nanoparticles by sol–gel method

“…Surfactantassisted sol-gel method was widely used to synthesize mesoporous materials (Jentys et al 1996;Beck et al 1992;Wang et al 1999;Tanev et al 1997).With successfully synthesized MCM-like mesoporous material (Liu et al 2004;Yang et al 2015), it is believed that nanoparticles of zinc-doped titania could be possible to synthesize using similar surfactant-assisted sol-gel method.…”

Control of morphology in synthesizing mesoporous silica

“…The MCM-41 nanochannels form the wall of these micrometersized hierarchical structures. Thus, the preparation of mesoporous aluminosilicate materials was elevated to an exciting new level by having at least two length scales-micrometers and nanometers [13]. The ability to control structures in both length scales will have crucial impacts on catalysis, biomineralization, and design of the nanomaterials.…”

Biochemical evolution. I. Polymerization on internal, organophilic silica surfaces of dealuminated zeolites and feldspars

“…Y mutinaite, as above, Y tschernichite, the Al-bearing analog of the Mobil high silica zeolite Beta (59-67), which has a remarkable polytypic domain structure with a 10-ring, three-dimensional channel system, Y boggsite, with a 10-to 12-ring, three-dimensional channel system, which occurs with tschernichite in Columbia basalt (68), Y faujasite, the natural analog of Linde Type Y, the main industrial catalyst with a 12-ring, three-dimensional channel system; can be de-aluminated by various processes (not referenced in detail); known only as a very rare mineral until discovery in sedimentary beds of diagenetic tuffs in Jordan (69), Y mordenite, an easily de-aluminated, common, high silica natural zeolite, with industrial analogs, whose one-dimensional channel can be blocked by either faulting or an Al-complex , Y mesoporous silicas with nanometer channels and mainly hydrophilic surfaces but some organophilic behavior (91)(92)(93)(94)(95)(96)(97)(98)(99)(100)(101)(102)(103), Y all-silica analog (Chevron SSZ-24) of Union Carbide aluminophosphate AlPO-5, for which one might envisage unipolar segments of aluminophosphate interleaved with nonpolar silica down the 12-ring cylindrical channel (104)(105), and Y theoretical chiral frameworks in the database of the Consortium for Theoretical Frameworks, University of Chicago, being prepared for publication.…”