Interlayer Modification of a Layered Silicate RUB-18 with 4-Phosphonophenylsilane and Its Surface Acidic Functions

Abstract

The interlayer silylation of a layered silicate H-RUB-18 (Si4O7(OH)2) using a new aromatic silylating reagent containing a phosphonic acid group (4-phosphonophenylsilane: PPS) was demonstrated (H-PPS-RUB-18). The phosphonic acid groups were attached to the silicate layers through the reaction of H-RUB-18 with (4-diethoxyphosphorylphenyl)-triethoxysilane (p-PPS-E), and the ester moieties were subsequently hydrolyzed with hydrochloric acid. H-PPS-RUB-18 is a solid acid, as indicated by the intercalation of various alkylamines and the catalytic acetalization of ketones. A systematic increase in interlayer spacing leading to surface acidic properties was obtained through intercalation with a series of alkylamines. In addition, H-PPS-RUB-18 was exfoliated, resulting in single-layer nanosheets with ca. 2.0 nm thickness. The catalytic acetalization of ketones was related to the interlayer spacing of the modified RUB-18.

Synthesis and Crystal Structures of Two Crystalline Silicic Acids: Hydrated H-Apophyllite, H16Si16O40 • 8–10 H2O and H-Carletonite, H32Si64O144

“…Typically, chlorosilanes (e.g., (CH 3 ) 2 SiCl 2 ) or disilizanes, e.g., [(CH 3 ) 3 Si]NH, are used. A more recent example was presented by Nomi et al The authors used 4-phosphono-phenylsilane to modify the inter-layer region of H-RUB-18 via a grafting reaction [32].…”

Integrating Structural and Thermodynamic Mechanisms for Methanol Intercalated Kaolinite Nanoclay: Experiments and Density Functional Theory Simulation

“…Kaolinite layers are assembled and stacked together by hydrogen bonding (Figure ). The strong cohesion between consecutive layers limited the specific surface area and therefore the reactivity of kaolinite. − Through the intercalation and exfoliation with organic molecules, the nanoclays had enhanced properties, such as dispersity, stability, mechanical property, fire retardancy, and so on. − More importantly, extensive researches showed that kaolinite can be functionalized to meet particular requirements by intercalation with organic molecules. ,,,− But only a few small molecules (DMSO, urea, potassium acetate, N -methylformamide, hydrazine, etc.) can be directly intercalated to form “pre-intercalates”. − …”