Ultrafast crystallization of mesoporous Sn-MFI single crystals achieved by addition of the cationic polyelectrolyte in starting gels

Heteroatoms substituted zeolites (HSZ) are important absorbents/catalysts for many industrial processes. However, precisely locating the heteroatoms in the desired zeolite frameworks is still challenged by the low crystallization rate. Herein, we report that poly dimethyl diallyl ammonium chloride (PDDA) can greatly accelerate the HSZ crystallization with the simultaneous creation of mesopores. Significantly, highly crystallized Sn-MFI single crystals are obtained within 6 h, which is over one hundred times faster than that of the available methods (∼720 h). The addition of PDDA is revealed to speed up the in-situ depolymerization and re-condensation of nanosized silica precursors, leading to the rapid crystallization of MFI framework with the concomitantly homogeneous incorporation of tetra-coordinated Sn atoms. The obtained Sn-MFI mesoporous zeolites exhibit excellent catalytic performance for the hydration of epichlorohydrin to 1, 2-diol. More importantly, the realization of Sn-MEL, ZSM-11, Ga-MFI and ZSM-5 zeolites with prominently short time and the diversity of the cationic polyelectrolyte make the thus developed strategy a highly efficient and general method for synthesizing HSZ.