Direct synthesis of hydrothermally stable micro–mesoporous silicas templated by unsaturated α-linolenic acid self-assemblies under high temperature hydrothermal conditions

Herein, we report the direct synthesis of micro–mesoporous silicas using unsaturated anionic surfactant α-linolenic acid as mesophase template. The self-assembly of α-linolenic acid, which could transform to a rigid mesophase template via inner-micellar polymerization when heated, was successfully leveraged to fabricate hydrothermally stable mesoporous silicas at high temperature, which retained a BET surface area of 678 m2 g−1 after hydrothermal treatment in boiling water for 5 days. Different analysis methods, e.g. X-ray diffraction, nitrogen physisorption, the non-local density functional theory (NLDFT) analysis and transmission electron microscopy, were employed to investigate the mesostructure of as-synthesized samples, which revealed a micro- and mesopores hybrid in one phase. 1H NMR was applied to characterize the α-linolenic acid micellar structure and confirmed that CC bonds have been opened up and polymerization occurred within micelles. The 29Si MAS NMR spectra indicated Q4 silicon is the dominating species, which explains well the high hydrothermal stability of the materials.

The self-assembly of α-linolenic acid, which could transform to a rigid mesophase template via inner-micellar polymerization when heated, was successfully leveraged to fabricate hydrothermally stable mesoporous silicas at high temperature, which retained a BET surface area of 678 m2 g−1 after hydrothermal treatment in boiling water for 5 days. The 29Si MAS NMR spectra indicated Q4 silicon is the dominating species, which explains well the high hydrothermal stability of the materials.Figure optionsDownload as PowerPoint slideResearch highlights
► Direct synthesis of micro–mesoporous silicas under temperature higher than 180 °C using α-linolenic acid as template.
► Rigid template was formed via inner-micellar polymerization.
► High hydrothermal stability of the materials and the dominating Q4 silicon.