Fabrication of b‐Oriented MFI Zeolite Films under Neutral Conditions without the Use of Hydrogen Fluoride

The fabrication of MFI zeolite films with particular b-axis orientation is especially fascinating. Unlike the conventional alkaline or hydrofluoric acid (HF) assisted neutral synthesis route, here we develop a novel neutral synthesis solution system of TPABr/fumed silica/H2O without the use of HF and successfully synthesize highly b-oriented MFI zeolite films on glass-plate substrates by secondary growth. The localized weak alkaline environment created by the dissolved Na2O species from the substrate is identified as the key factor for the depolymerization of fumed silica and subsequently the in-plane growth of zeolite seed layers. Continuous b-oriented MFI films can also be synthesized on other substrates in the presence of a glass plate or a trace amount of NaOH, which making our neutral synthesis route promising for the direct synthesis of MFI zeolite films and membranes on various substrates.