A Toroidal Zr₇₀ Oxysulfate Cluster and Its Diverse Packing Structures

Abstract

Herein, we report the discovery of a toroidal inorganic cluster of zirconium(IV) oxysulfate of unprecedented size with the formula Zr₇₀ (SO₄ )₅₈ (O/OH)₁₄₆ ⋅x(H₂ O) (Zr₇₀ ), which displays different packing of ring units and thus several polymorphic crystal structures. The ring measures over 3 nm across, has an inner cavity of 1 nm and displays a pseudo-10-fold rotational symmetry of Zr₆ octahedra bridged by an additional Zr in the outer rim of the ring. Depending on the co-crystallizing species, the rings form various crystalline phases in which the torus units are connected in extended chain and network structures. One phase, in which the ring units are arranged in layers and form one-dimensional channels, displays high permanent porosity (BET surface area: 241 m² g^-1 ), and thus demonstrates a functional property for potential use in, for example, adsorption or heterogeneous catalysis.