Synthesis of coesite nanocrystals from ethane bridged periodic mesoporous organosilica at low temperature and extreme pressure

摘要

Coesite nanocrystals have been synthesized from periodic mesoporous organosilica (PMO) with (CH_2)_2 bridges heated at 300 C for 150 min and 12 GPa. The crystals are not sintered, single crystalline, and have diameters of ca. 100-300 nm. Below 300 ℃, an amorphous non-porous organosilica glass was obtained. Heating above 300 ℃ at 12 GPa results in the rapid crystal growth and micron size coesite crystals were formed. Since their inception in 1999 periodic mesoporous organosilicas (PMOs) have become a very active field of study. The unique feature of PMOs is the presence of bridging organic groups inside of a siliceous periodic mesoporous framework. In PMOs synthesized from silsesquioxanes of the type (EtO)_3Si-R-Si(OEt)_3 formally one-third of O atoms of SiO_2 are replaced by organic bridging groups, R.