Controlled release of siliceous species for the fabrication of highly b-oriented MFI zeolite films†
The MFI zeolite film with specialized b-axis-orientation holds great potential for many technological applications in separation and catalysis. The elimination of parasitic twin crystals on oriented films has aroused widespread interest in recent years. Here we demonstrate for the first time that the generation of MFI nuclei can be substantially prohibited by introducing a chelating agent of 1,2-dihydroxybenzene (C6H6O2) into the synthesis system. Specifically, the silicate precursor nanoparticles (PNs) are complexed with C6H6O2 and their behavior of growing bigger or aggregation is therefore strictly confined. During secondary growth, siliceous species are gradually released from the complexed PNs at high temperature and only used to feed the growth of MFI seed crystals, resulting in the achievement of twin-free b-oriented MFI zeolite film. The controlled release approach enables the delicate micro-structure manipulation of many types of films/membranes.