FaujasiteX

FaujasiteX is a synthetic zeolite designed as a modified variant of the faujasite framework (FAU). It retains the characteristic large-pore, cage-like topology of faujasite while incorporating heteroatoms or extra-framework species to tune acidity, hydrophilicity, and catalytic behavior. FaujasiteX is primarily studied for its potential to improve selectivity in bulky-molecule processing and adsorption.

Structure and synthesis: FaujasiteX preserves the FAU framework with large cages connected by 12-membered ring channels. The defining feature is the partial substitution of framework atoms with heteroatoms designated as X, or deliberate organization of extra-framework cations, which alters the framework charge and acid site distribution. Synthesis typically involves hydrothermal crystallization from silica and alumina sources under the guidance of an organic structure-directing agent, followed by ion exchange and calcination to place the desired cations inside the pores.

Properties and applications: The material offers tunable acidity (Brønsted and Lewis), high surface area, and good hydrothermal stability. These properties enable catalytic applications in hydrocarbon processing, such as isomerization, cracking, and alkylation of bulky molecules, as well as selective adsorption and separations. Potential uses include carbon capture and biomass conversion under appropriate operating conditions.

History: FaujasiteX was introduced in the early 2020s as part of efforts to extend FAU-type zeolites through targeted framework substitutions. The designation X reflects the inclusion of heteroatom or extra-framework species alongside the native aluminum and silicon in the framework.