Cocrystallization Enabled Spatial Self‐Confinement Approach to Synthesize Crystalline Porous Metal Oxide Nanosheets for Gas Sensing

Crystalline metal oxide nanosheets show exceptional catalytic performance owing to the large surface‐to‐volume ratio and quantum confinement effect. However, it is still a challenge to develop a facile and general method to synthesize metal oxide nanosheets. Herein, we report a cocrystallization induced spatial self‐confinement approach to synthesize metal oxide nanosheets. Taking the synthesis of SnO2 as an example, the solvent evaporation from KCl and SnCl2 solution induces the cocrystallization of KCl and K2SnCl6, and the obtained composite with encapsulated K2SnCl6 can be in situ converted into SnO2 nanosheets confined in KCl matrix, after water washing to remove KCl, porous SnO2 nanosheets can be obtained. Notably, a series of metal oxide nanosheets can be obtained through this general and efficient green route. In particular, porous CeO2/SnO2 nanosheets with improved surface O− species and abundant oxygen vacancies exhibit superior gas sensing performance to 3‐hydroxy‐2‐butanone. A general cocrystallization induced spatial self‐confinement approach has been developed to synthesize crystalline porous two‐dimensional metal oxide nanosheets. The mechanism is proposed and various crystalline porous metal oxides nanosheets can be obtained. The resulting crystalline porous CeO2/SnO2 nanosheets show exceptional sensing performance towards 3‐hydroxy‐2‐butanone.