A series of chiral metal–organic frameworks based on fluorene di- and tetra-carboxylates: syntheses, crystal structures and luminescence properties

Abstract

A series of optically pure carboxylate ligands based on a fluorene backbone were synthesized and used for the elaboration of four chiral metal–organic frameworks (6, 7, 8, and 9) containing Cu-based paddle-wheels. The positions and numbers of coordinating carboxylate functions on the ligand core govern the resulting MOF topologies, leading to a 1D framework (8), 2D grids with (7) or without interpenetration (6), and a 3D (9) framework and showing calculated porosities ranging from 8 to 47% of the unit-cell volumes. Ligands as well as corresponding MOFs possess luminescence properties with blue emission. The most porous MOF (9), made of a tetracarboxylate ligand, exhibits a BET apparent surface area of 467 m² g⁻¹ and methane and carbon dioxide storage capacities of 26.5 cm³ g⁻¹ and 129 cm³ g⁻¹, respectively, at 303 K and 30 bar.