Quasicrystal approximants in isoreticular metal-organic frameworks via Cairo pentagonal tiling

Crystalline solids with structural motifs of five-vertex semi-regular Archimedean tessellations are referred to as quasicrystal approximants (ACs). However, the synthesis of crystalline porous frameworks with AC patterns remains a challenge because of a limited number of planar 5-fold nodes. Geometrically, Cairo pentagonal tiling, the dual form of the snub square tiling, enriches the access of ACs. We serendipitously obtain a two-dimensional metal-organic framework (MOF) with Cairo pentagonal tiling by combining the square-planar and triangular nodes. Reticular chemistry further allows the synthesis of an isoreticular MOF with planar tessellation of pentagons. Such isoreticular design is rarely presented in reported AC structures. Our study not only enriches the structural database of ACs but also paves the way for AC-MOFs with programmable structures and functionalities.