Wet-oxidization and exfoliation of non-swollen MCM-22P to dispersible two-dimensional MWW zeolite nanosheets

Two-dimensional (2D) zeolite nanosheets open exciting opportunities for the application in catalysis and separations. Exfoliation of layered zeolite shows a promising way for the preparation of 2D zeolite nanosheets. Herein, non-swollen MCM-22P with ordered layer spacing was successfully exfoliated to dispersible MWW nanosheets. Firstly, a wet-oxidization method, i.e., heating in a mixture of H2SO4 and H2O2 (called piranha solution) was adopted to remove the template of pyridine (PI) from as-synthesized MCM-22P zeolite. IR, TG, XRD, N2 adsorption confirmed that the wet-oxidization could efficiently remove PI from MCM-22P zeolite while preserving the MWW crystal structure. Exfoliation of the detemplated MCM-22P zeolite was successfully achieved by an ultrasonic treatment in water. After purification by sedimentation, 2D MWW zeolite nanosheets dispersed in aqueous solution were obtained. The monolayer MWW nanosheets with high purity are confirmed by SEM and TEM observations. The wet oxidation followed by the sonication method provides an alternative way for the exfoliation of layered zeolite to dispersed nanosheets.