Simultaneous iron reinsertion and defect healing in zeolite beta via post-synthetic hydrothermal treatment

Abstract

A post-synthetic treatment strategy for modification of zeolites, microporous ceramics, is attractive for regulating the local environments of heteroatoms in zeolite frameworks. Herein, we report the post-synthetic treatment of Fe-containing zeolite beta for changing the introduced Fe environment. The Fe-containing zeolite beta is synthesized by a hydrothermal treatment of Si, Al, and Fe sources in the presence of tetraethylammonium hydroxide (TEAOH), followed by calcination, which causes detachment of framework Fe and formation of defect sites. Post-synthetic hydrothermal treatment of the Fe-containing zeolite beta in the presence of TEAOH and ammonium fluoride (NH₄F) enables reinsertion of Fe species into the framework while simultaneously healing defect sites. Fe incorporation can also be achieved by applying this treatment to commercially available zeolite beta after impregnation with Fe species. This approach provides a strategy for controlling heteroatom environments in zeolite frameworks, offering a versatile platform for zeolite framework engineering and materials design.