Delamination of Layered Zeolite Precursors Under Mild Conditions

Delaminated zeolite precursor materials expand the range of reactions that zeolites catalyze, by providing access for larger reactant molecules, as demonstrated by Corma and his coworkers with the discovery of materials such as ITQ-2, ITQ-6, and ITQ-18.  Syntheses of these materials requires a high pH medium during precursor material swelling, typically in the pH range of 13.5–13.8, which is known to lead to partial amorphization of the zeolite layers during delamination.  Here, we report a new class of delaminated zeolite catalysts consisting of materials that are synthesized by delaminating layered zeolite precursors at near-neutral pH conditions, using fluoride/chloride anions. We demonstrate that the new method efficiently delaminates layered zeolite precursors such as MCM-22 (P) with retention of high structural order of the zeolite framework in the delaminated layers.  We provide evidence of delamination by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and nitrogen gas adsorption characterization of the synthesized material, and compare with conventional delaminated materials.  The new materials demonstrate high structural integrity of the exfoliated layers using ²⁹Si MAS NMR and FT-IR characterization.  Furthermore, results from pyridine chemisorption on the new delaminated materials show features that suggest these materials to be active for acid catalysis applications.