Controlling Particle Morphology and Pore Size in the Synthesis of Ordered Mesoporous Materials.

Yaregal Awoke,Isabel Díaz,Yonas Chebude

doi:10.3390/molecules25214909

Yaregal Awoke, Isabel Díaz + Show 1 more

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https://doi.org/10.3390/molecules25214909

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Abstract

Ordered mesoporous materials have attracted considerable attention due to their potential applications in catalysis, adsorption, and separation technologies, as well as biomedical applications. In the present manuscript, we aim at a rational design to obtain the desired surface functionality (Ti and/or hydrophobic groups) while obtaining short channels (short diffusion paths) and large pore size (>10 nm). Santa Barbara Amorphous material SBA-15 and periodic mesoporous organosilica PMO materials are synthesized using Pluronic PE 10400 (P104) surfactant under mild acidic conditions to obtain hexagonal platelet-like particles with very short mesochannels (300–450 nm). The use of expanders, such as 1, 3, 5-trimethylbenzene (TMB) and 1, 3, 5-triisopropylbenzene (TIPB) were tested in order to increase the pore size. TMB yielded in the formation of vesicles in all the syntheses attempted, whereas P104 combined with TIPB resulted both in expanded (E) E-SBA-15 and E-PMO with 12.3 nm pore size short channel particles in both cases. Furthermore, the synthesis method was expanded to the incorporation of small amount of Ti via co-condensation method using titanocene as titanium source. As a result, Ti-E-SBA-15 was obtained with 15.5 nm pore size and isolated Ti-sites maintaining platelet hexagonal morphology. Ti-PMO was obtained with 7.8 nm and short channels, although the pore size under the tried synthesis conditions could not be expanded further without losing the structural ordering.

Highlights

The synthesis, characterization, and application of novel porous materials have been strongly encouraged due to their wide range of applications in adsorption, separation, catalysis, and biomedical field
Periodic mesoporous organosilicas (PMO) with highly ordered pore structures and uniformly distributed organic groups inside of siliceous framework provided with a new range of surface chemistry in ordered mesoporous materials [5]
We introduce the morphology control using Pluronic PE 10400 (P104) to the synthesis of PMO, and develop a method to obtain large pore, or expanded, E-SBA-15 and E-PMO in the synthesis conditions that produce hexagonal platelet-like morphology

Summary

Introduction

The synthesis, characterization, and application of novel porous materials have been strongly encouraged due to their wide range of applications in adsorption, separation, catalysis, and biomedical field. Due to the limited pore size of M41S materials, a new class of well-ordered mesoporous silica materials was synthesized at the University of California, being denoted as Santa Barbara Amorphous materials (SBA-15) in 1998 [2], which have relatively larger pore sizes and pore wall thicknesses as compared with the M41S family. Silicate mesoporous materials with high surface areas, combined with large and uniform pore sizes, have acquired great scientific interest in the use as hosts to support catalytic active sites [3] or to confine guest molecules, such as enzymes [4]. Periodic mesoporous organosilicas (PMO) with highly ordered pore structures and uniformly distributed organic groups inside of siliceous framework provided with a new range of surface chemistry in ordered mesoporous materials [5].

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