Preparation of mesoporous silica materials with non-surfactant hydroxy-carboxylic acid compounds as templates via sol–gel process

Mesoporous silica materials with pore sizes of 2–6 nm have been prepared through the sol–gel reactions of tetraethyl orthosilicate (TEOS) in the presence of hydroxy-carboxylic acid compounds, including citric acid (CA), malic acid (MA), tartaric acid (TA) and lactic acid (LA), as templates or pore-forming agents, followed by extraction with ethanol to remove the template molecules. The materials are characterized by infrared spectroscopy, nitrogen adsorption–desorption tests, powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results indicate that the materials prepared at template concentrations of 40–60 wt% have large surface areas (ca. 900 m2/g) and pore volumes (ca. 1.0 cm3/g). The mesoporosity arises from interconnecting channels and pores with, however, disordered channel arrangements. The pore diameters and pore volumes increase as the template concentration is increased. The mesoporous materials retain high surface areas and pore volumes with a little change in pore diameters upon calcination at 773 K for 6 h.