An Extra-Large Pore Zeolite Enabled by 1D-to-3D Topotactic Condensation

Zeolites are microporous silicates that find an ample variety of applications as catalysts, adsorbents, and cation exchangers. Natural and synthetic zeolites possess a fully connected three-dimensional network of corner-sharing SiO4 tetrahedra (i.e. they are tectosilicates or framework silicates, with Si occasionally substituted by other atoms). Stable silica-based zeolites with increased porosity are of interest to allow processing of large molecules, but challenge our synthetic ability. Here we report a novel zeolite, ZEO-3, with a multidimensional, interconnected system of extra-large pores open through windows made by 16 and 14 SiO4 tetrahedra, which, with a specific surface area of over 1000 m2/g and an extraordinary performance for Volatile Organic Compounds abatement, is the less dense polymorph of silica known so far. This zeolite, however, is not directly synthesized as a tectosilicate but is the first three-dimensional zeolite that is obtained by topotactic condensation from a one-dimensional chain silicate (inosilicate, ZEO-2), a process that bears a 17% contraction of the structure but that does not alter the topology of the chain silicate (hence the term “topotactic”). This discovery challenges concepts deeply-rooted into zeolite science, and opens up the possibility of chain silicates as precursors for the crystallization of zeolites.