Controlled Synthesis of Perforated Oxide Nanosheets with High Density Nanopores Showing Superior Water Purification...

A method for creating genuine nanopores in high area density on monolayer two-dimensional (2D) metallic oxides has been developed. By use of the strong reduction capability of hydroiodic acid, active metal ions, such as Fe^III and Co^III, in 2D oxide nanosheets can be reduced to a divalent charge state (2+). The selective removal of FeO₂ and CoO₂ metal oxide units from the framework can be tuned to produce pores in a range of 1-4 nm. By monitoring of the redox reaction kinetics, the pore area density can be also tuned from ∼0.9 × 10⁴ to ∼3.3 × 10⁵ μm^-2. The universality of this method to produce much smaller pores and higher area density than the previously reported ones has been proven in different oxide nanosheets. To demonstrate their potential applications, ultrasmall metal organic framework particles were grown inside the pores of perforated titania oxide nanosheets. The optimized hybrid film showed ∼100% rejection of methylene blue (MB) from the water. Its water permeance reached 4260 L m^-2 h^-1 bar^-1, which is 1-3 orders of that for reported 2D membranes with good MB rejections.