A novel mesoporous MCM-41 with remarkable wide channel diameters and thick walls was synthesized. The procedure involved the acid-catalyzed hydrolysis of tetraetheylorthosilicate (TEOS) in a water/ethanol/isopropoanol solvent mixture while employing 1-hexadecylamine as a templating agent and mesitylene as an auxiliary agent. After removal of the template by either extraction or calcination at 560 °C, the resulting mesoporous materials had surface areas of 1,289 and 1,210 m2/g. The channel diameters were found to be 46.8–51.2 Å, while the wall thicknesses were 20.9–21.1 Å. X-ray powder diffraction proved that the synthesized mesoporous structure belongs to MCM-41 family. Notably, they displayed higher thermal and hydrothermal stabilities, and have higher surface areas than conventionally prepared MCM-41 silica. The thickest channel walls (21.1 Å) can withstand calcination to nearly 850 °C with minimal structural damage. The calcined sample was more resistant to hydrothermal treatment in boiling water than was the solvent-extracted product but both materials showed minimal change after 35 h of hydrothermal treatment.