Then the solution was allowed to cool down to room temperature. The white precipitate was filtered, washed with distilled water and alcohol for 6 times to remove the ions possibly remaining in the final products, and finally dried in air at 60 ◦C for more than 10 h. The as-obtained precipitate was then calcined at 580 ◦C in a muffle furnace for 2 h in air to get porous
ZnSnO3 cubes.