Optimizing Organic Functionality in Mesostructured Silica:  Direct Assembly of Mercaptopropyl Groups in Wormhole Framework Structures

Abstract

A series of mercaptopropyl-functionalized wormhole mesostructures, denoted MP-HMS, have been prepared through the S0I0 assembly of alkylamine surfactants (S0) and mixtures of 3-mercaptopropyltrimethoxysilane and tetraethyl orthosilicate as framework precursors (I0). Unprecedented levels of organo functionalization, corresponding to at least 50% of the silicon sites, were achieved while retaining well-expressed mesostructures with pore sizes, pore volumes, and surface areas as high as 2.8 nm, 0.69 cm3/g, and 1225 m2/g, respectively. Also, up to ∼90% of the framework silicon sites could be fully cross-linked, lending exceptional hydrothermal stability to the mesostructures. The key to highly functionalized MP-HMS derivatives lies in the use of long-chain alkylamine surfactants as structure directors (e.g., octadecylamine) in combination with a relatively high assembly temperature (e.g., 65 °C) and a high-polarity water−ethanol solvent. Increasing the assembly temperature increased both the framework pore size and the degree of framework cross-linking, whereas increasing the MP content lowered the pore size while improving the framework cross-linking. The effects of assembly temperature and MP loading were attributable to changes in hydration at the H-bonded S0I0 interface and concomitant changes in the surfactant packing parameter. Highly functionalized MP-HMS derivatives are promising materials for use as heavy-metal ion-trapping agents and as precursors for sulfonic-acid-functionalized mesostructured catalysts.

Hydrogen-Bonding-Driven Self-Assembly of PEGylated Organosilica Nanoparticles with Poly(acrylic acid) in Aqueous Solutions and in Layer-by-Layer Deposition at Solid Surfaces

“…The Stöber method has often been used for synthesis of organosilica particles through condensation of tetraethoxysilane (TEOS) 6,7 or TEOS co-condensation with other functional silanes, such as 3-aminopropyltriethoxysilane (APTS) [8][9][10] and 3-mercaptopropyltrimethoxysilane (MPTS). [10][11][12] The typical size of organosilica particles synthesized using Stöber conditions is often greater than 500 nm. 6,7,9 The Stöber method was also used to generate mesoporous materials, where homo-or co-condensation of TEOS with other functional silanes was conducted in the presence of low molecular weight or polymeric surfactants as a template.…”

Characteristics of Au/HMS catalysts for selective oxidation of benzyl alcohol to benzaldehyde

“…A simple method for tailoring the framework pore size of HMS materials in the presence of a single amine surfactant could make them even more attractive for such applications. Consequently, the framework sites of HMS silicas are generally more accessible for metal ion trapping and chemical catalysis in comparison to their hexagonal SBA-15 and MCM-41 counterparts with the same framework pore size, but with highly monolithic particle morphologies [21]. Thus, HMS silicas prepared with dodecylamine as template were selected as catalyst support.…”

Phosphonate Modified Silica for Adsorption of Co(II), Ni(II), Cu(II), and Zn(II)

“…As an adsorbent, the resulting material has been analyzed its physical and chemical character, such as active sites and pores properties [29]. Fig.…”

“…The presence of silica gel is identified with the existence of due to Si-O stretching and bending vibration, respectively [32]. Silanol is indicated with the band at 972 cm -1 due to Si-O stretching vibration on silanol group [29]. Phosphonate is identified with band at 1257 cm -1 of P=O and band at 1028 cm -1 of P-O stretching vibration of organic phosphate [33].…”