in this report, upstanding and nanoporous hexagonal tio2 nanosheet arrays were achieved via using kassite [cati2o4(oh)(2)] as an intermediate. the process developed involved a tio2 nanorod-derived synthesis of upstanding hexagonal kassite nanosheet arrays and a transformation of the kassite to tio2. to the best of our knowledge, this is the first successful attempt to grow ordered hexagonal kassite nanosheet arrays. the as-obtained kassite nanosheets showed a single-crystalline nature with their c-axis parallel to the substrate. a stepwise study of the growth of the interesting hexagonal kassite nanosheet arrays was demonstrated. upon hydrothermal treatment with diluted hno3 aqueous solution, the single-crystalline hexagonal kassite got converted to nanoporous ruble tio2, with shape preservation. the approach described in this study provides a novel method for the synthesis of kassite and tio2 nanosheet arrays and are ready for a variety of applications such as in catalytic or optoelectronic fields.