Atomically Precise Titanium-Oxo Nanotube with Selective Water Adsorption and Semiconductive Behaviors

We report the first example of carbon nanotube (CNT)-like assembly of the titanium (Ti) framework, Ti oxo inorganic cluster (Ti6O6) hexagonal rings into a titanium oxide (Ti-O) nanotube, prepared by ionothermal synthesis. As determined by single-crystal X-ray diffraction analysis, the Ti-O nanotube arrays, stabilized by sulfate ligands, assumed proper parallel alignment with each other and were separated by supramolecular interactions with surrounding EMIm (1-Ethyl-3-methylimidazolium) counter cations. Our stability studies indicated that the Ti-O nanotube obtained is indeed stable in air and various solvents. Also, it could maintain its structure upon heating to similar to 300 degrees C. Moreover, inside the pores of the Ti-O nanotubes, a rare water molecules nanoconfinement behavior was observed at room temperature. Further, our current developed Ti-O nanotube arrays exhibited selective water adsorption over methanol and ethanol, showing potential applications for miscible solvents separations. Finally, these Ti-O nanotubes demonstrated typical semiconductive characteristics, with the electrical conductivity increasing four orders of magnitude, ranging from 3.15 x 10(-10)-1.03 x 10(-6) S/cm, as the temperature increased from 35 to 135 degrees C. This work represents a milestone in constructing inorganic Ti-O nanotube arrays with atomically precise structural information for applications as visible-lightinduced photocatalysts, semiconductors, sensors, and optoelectronics.