Formation of mesoporous silica particles with hierarchical morphology

• Published in: Microporous and mesoporous materials 2020-08, Vol.303, p.110240, Article 110240
• Main Authors: Ijaz, Aatif, Yagci, M. Baris, Ow-Yang, Cleva W., Demirel, A. Levent, Mikó, Annamaria
• Format: Article
• Language: English
• Subjects: Acid catalyst; Hierarchical morphology; Mesoporous silica; Non-ionic surfactant template; Room temperature synthesis
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2020.110240

The transformation of mesoporous silica morphology from monoliths to spherical particles was investigated at room temperature in Pluronic F127/TEOS system as a function of HCl acid catalyst concentration to understand and control the mechanism. It is shown that the specific surface area and the size of mesoporous spherical silica particles can simply be adjusted by the catalyst concentration without using any additives or post-treatment. Above 3 M acid concentration, novel monodisperse micron sized spherical silica with hierarchical order of two levels was obtained. These silica spheres were formed of densely packed distorted hexagonal platelets of 20–30 nm in diameter. Within these platelets mesoporous channels were oriented along a single direction, however the platelets were randomly oriented in the spherical particles. Controlling the agglomeration of mesoporous silica primary particles by the concentration of the acid catalyst to obtain micron-sized spherical particles is novel. This approach allows the synthesis of particles whose sizes can be controlled in the range of ~1–4 μm and specific surface area in the range of ~200–500 m2/g. The morphology of the particles transforms from spherical shape to mesoporous monoliths at acid concentrations below 1 M due to slow hydrolysis and condensation. These results are important in understanding the role of catalyst concentration on the formation mechanism of different morphologies of mesoporous silica. [Display omitted] •Morphology of mesoporous silica was controlled in Pluronic/TEOS system by HCl catalyst.•Spherical mesoporous silica particles with hierarchical morphology are synthesized.•Distorted hexagonal platelet primary particles contained oriented mesopores.•Mesoporous primary particles agglomerated to monodisperse spherical particles.•Spherical particle size and specific surface area were controlled by HCl catalyst.