The smallest characteristic unit in the SSZ-23 backbone structure is a small cage composed of three 4-membered rings and four 5-membered rings. The cages are linked by 4-membered and 6-membered rings to form a slightly twisted mesh layer parallel to the (010) plane. These network layers are further connected by 4-membered rings to form a three-dimensional backbone structure.
In the known structure of aluminosilicate molecular sieves, even-numbered rings, such as 4-membered, 6-membered, 10-membered, and 12-membered rings are ubiquitous, while in addition to the common 5-membered rings, odd-membered rings are Rare. In a few cases, there are 3-membered, 7-membered or 9-membered rings, and their presence is associated with ZN2+ or BE2+ on the tetrahedral building block. The LOV structure, VSV structure and RSN structure type are molecular sieves containing 3-membered ring and 9-membered ring, and there are tetrahedral ZN2+ or BE2+ in the structure. ZSM-18 is a molecular sieve with a 7-membered ring, and SSZ-23 is the first molecular sieve with a 9-membered ring and a 7-membered ring.
