Novel anatase TiO2 hierarchical microspheres with selectively etched high-energy {001} crystal facets were synthesized by a facile hydrothermal method, in which etched degrees of {001} facets could be facilely tuned by pH value. Gas sensing properties of the etched TiO2 microspheres were investigated for the first time. Interestingly, it was found that the etched TiO2 microspheres showed a much higher acetone response than that of TiO2 microspheres with intact {001} facets and slightly-etched {001} facets. The relevant gas sensing mechanism was. discussed in detail. Moreover, the etched TiO2 microspheres also, showed a potential application in photocatalytic degradation of methyl orange. We expect this work would make one step closer to fully understand crystal-facets-dependent gas-sensing effect of TiO2, and provide a new TiO2 material platform for gas sensing and photcatalysis application. (C) 2017 Elsevier Ltd. All rights reserved.