In-MOFs based on amide functionalised flexible linkers

Abstract

Two new amide functionalised metal–organic frameworks, In(OH)CSA and In(OH)PDG, were synthesized using two flexible linkers, N-(4-carboxyphenyl)succinamic acid (CSA) and N,N′-(1,4-phenylenedicarbonyl)diglycine (PDG), respectively. Both structures consist of corner-sharing {InO₄(OH)₂} octahedra in the form of trans indium hydroxide chains, which are interconnected by the dicarboxylate linkers to form stacked 2-dimensional layers. The different symmetries and configurations of the flexible and rigid features on the linkers results in different supramolecular interactions dominating between linkers, resulting in different shaped pores and functional group orientation. In(OH)CSA lacks hydrogen bonding between linkers, which results in close packing between the layers and very small solvent accessible pores running perpendicular to the plane of the layers. In(OH)PDG exhibits strong intra- and interlayer hydrogen bonding, which prevents the layers from close packing and results in larger cylindrical pores running parallel to the indium hydroxide chains, producing a total accessible volume of 25% of the unit cell volume.