N-Containing Compound-Assisted Morphological Engineering of Anisotropic Growth of MFI Crystals

The nanosheet MFI zeolite synthesized with a short b-axis length exhibits broad potential for industrial applications due to its ability to facilitate mass transfer through the large straight-through channel along the b-axis. The current focus of research lies in the regulation of the zeolite crystal anisotropic growth rate through the addition of specific additives to the precursor liquid. The range of available additives, however, is limited, and their effects as well as potential mechanisms are still poorly understood. The impact of incorporating ten mononitrogen compounds into the gel on crystal growth was investigated. The influence of the N-containing compounds (functional group, C/N ratio, electrostatic potential of N atoms, and compound concentration) and growth time on crystal size was analyzed. N,N-dimethylformamide (DMF) and N-methylformamide (NMF) were revealed as potential inducers of the nanosheet zeolite. Herein, the effect of DMF on the nonclassical growth of the nanosheet zeolite is unveiled within crystallization engineering. The effects of various synthetic parameters on the DMF-assisted synthesis of nanosheet zeolites were also investigated. It is revealed that DMF plays a role in accelerating crystal growth and in regulating anisotropic crystal growth. This strategy can be extended to the synthesis of different heteroatomic nanosheet zeolites (such as Al-MFI, Fe-MFI, and Ti-MFI), and it is suitable for different types of silicon and metal sources. This study presents a straightforward strategy for the systematic and precise design and synthesis of nanosheet MFI zeolites, which exhibits significant potential for industrial utilization.