Tailor-Made Nanoseeds for the Synthesis of Zeolites with Nanosized Dimensions

Abstract

While seeding is a long-established strategy for the synthesis of zeolites with the desired phase in a faster crystallization rate and it is believed that the added seeds are at least partially dissolved in the synthetic gel for zeolite nucleation and growth, the solubility of seed crystals is seldom explored as a potential modulating factor for the tuning of zeolite properties. Herein, NH4F etching was used as a “chemical scissors” for the cutting of existing zeolites into nanosized crystals with enhanced solubility for the subsequent synthesis pursuing for zeolites with nanosized dimensions. Exemplified by the synthesis of mordenite, the tailor-made seeds reduced the size of the synthetic products by 1.9 times and further by 8.5 times compared with the synthesis seeded by the uncut sample and without seeding, respectively. Further, the general applicability of the size tailoring strategy is illustrated by the synthesis of ZSM-5 nanosheets using the top-down prepared nanoseeds. Considering the tunability and convenience of NH4F etching in the postsynthesis engineering of zeolite particle size, it is envisaged that the successful utilization of this chemical cutting strategy will be instrumental in many systems aiming for nanosized zeolite synthesis.

Zeolite Crystal Engineering

“…Mass transport limitations in zeolites have motivated efforts to design materials with nanosized or hierarchical (e.g., mesoporous, pillared, etc.) architectures. − Soft templating techniques have been used as bottom-up approaches, whereas postsynthesis modification offers a top-down approach to enhance diffusion properties of zeolitic materials. Methods that combine heteroatom (e.g., Ti) incorporation in the design of hierarchical materials is also discussed in this virtual special issue. , …”