Synthesis of bimodal mesoporous molecular sieves under mild conditions with salts as mineralization agents

Using Na2EDTA and Al(NO3)3 as mineralization agents, bimodal mesoporous molecular sieves were synthesized in one-step at room temperature and mildly acidic pH. The XRD, N2 adsorption, SEM, and TEM techniques were used to investigate the topological and morphological properties of the synthesized mesoporous materials. The molar ratio of Na2EDTA to Al(NO3)3 significantly affects the pore structure of the as-synthesized mesoporous materials. The bimodal mesoporous molecular sieves with both worm-like and hexagonal mesostructures can be synthesized at molar ratios of Al(NO3)3 to Na2EDTA less than 0.1:0.3. On the other hand, if molar ratios of Al(NO3)3 to Na2EDTA are larger than 0.1:0.3 or only Al(NO3)3 is used, mesoporous materials with regular hexagonal array can be obtained. The present study provides an innovative method to use two different anions instead of two or more surfactants for fabricating bimodal mesoporous materials. Additionally, a mechanism is proposed to elucidate the formation of bimodal mesoporous materials.