Calcination and deboronation of [B]-MFI single crystals

Calcination and deboronation of [B]-MFI and silanol nest reoccupation of deboronated MFI were studied by variable temperature FTi.r. spectroscopy, X-ray diffraction, and 1H, 11B, and 29Si MAS n.m.r. spectroscopy techniques. Boron loss from the framework upon calcining [B]-MFI was minimized by using an improved calcination procedure, during which boron is kept in a stable tetrahedral/saturated coordination and boron hydrolysis and extraction as well as T-atom reorganizations are avoided. Framework boron can be extracted from the calcined boron MFI material by refluxing in aqueous hydrochloric acid (pH <- 5), leaving thermally stable (up to 400°C, N2) homogeneously distributed silanol nests, which are useful reactive sites for postsynthesis reoccupation.