Minerals as materials - Silicate sheets based on mixed rings as modules to build heteropolyhedral microporous frameworks

Abstract

In general, a material is classified as porous if its crystal structure is crossed by channels with a free aperture (effective channel width=ecw) at least 3.2Å wide, such that the nitrogen molecule, N2, can pass through. In oxysalts, the ecw is calculated by subtracting the ionic diameter of O2- (2.8Å) to the O⋯O distances across the channel (McCusker et al. 2003).