Rapid synthesis of high-quality ETS-10 crystals

Heating a gel consisting of briefly hydrolyzed tetraethyl orthosilicate (TEOS), 2–5-nm sized anatase, H2SO4, NaOH, KF, and H2O in the mole ratio of 5.5:1:2.2:8.4:1.43:350 at 200 °C for 7 h leads to production of ETS-10 crystals in fairly uniform size (∼500 nm) and shape having well-developed smooth facets in the truncated tetragonal bipyramidal structure. Characterization of the crystals revealed that the titanate (TiO32-) quantum wires are well-preserved within the produced crystals. The required reaction period under our reaction condition (7 h) is much shorter than under the previously reported conditions which use Degussa P25 (a mixture of ∼25 nm sized anatase and rutile) as the Ti source (>42 h at 200 °C). The marked increase in crystallization rate and uniformity of size and shape is attributed to the use of very small anatase nanoparticles and briefly hydrolyzed tetraethyl orthosilicate (TEOS) as the Ti and Si sources, respectively. This report also demonstrates for the first time that TEOS can be used as the Si source.