Synthesis and Structure of ITQ‐3, the First Pure Silica Polymorph with a Two‐Dimensional System of Straight Eight‐Ring Channels

Hydrothermal syntheses in fluoride medium readily yield very open materials, as the example of ITQ-3 demonstrates. This new polymorph of silica with the formula [SiO2]64 has a framework characterized by a low density (16.3 SiO4 tetrahedra per 1000 Å3), a very large void volume (0.23 cm3 g−1), and a two-dimensional system of straight channels whose intersection defines a large cage (picture on the right).