Enhancement of structural stability of mesoporous silica via infiltration of SnCl4 vapor

Sn-infused MCM-41 was prepared using a pre-mixing method and two different vapor phase methods. The sample prepared by the pre-mixing method showed lower hydrothermal stability than pure silica MCM-41. MCM-41 prepared by vapor phase treatment with SnCl4 before calcination showed higher structural stability in water and hexane at 423 K than the sample treated with SnCl4 vapor after calcination. The pore size and pore volume of MCM-41 treated with SnCl4 vapor before calcination were larger than those of pure silica MCM-41. With SnCl4 vapor treatment after calcination, the SnCl4 vapor must have reacted with silanol groups around the pore entrance and partly plugged the pore mouth of MCM-41. On the other hand, SnCl4 also penetrated into the pore wall and uniformly dispersed into the silicate network. Thus, SnCl4 vapor treatment before calcination was more effective in enhancing the structural stability in water and hexane.