Metal-Mediated Self-Assembly of a Twisted Biphenyl-Tetraacid Linker with Semi-rigid Core and Peripheral Flexibility: Concomitant Formation of Compositionally Distinct MOFs

Abstract

A semi-rigid organic linker, namely, 3,3′,5,5′-tetrakis(4-(α-carboxy)methoxyphenyl)-2,2′,6,6′-tetramethoxy-1,1′-biphenyl (H4L), was designed and synthesized to access metal–organic frameworks (MOFs). While the ortho-methoxy substituents in the biphenyl core of H4L were surmised to twist the aromatic planes and impart porosity to the resultant MOFs, the (α-carboxy)methoxyphenyl moieties at the periphery were envisaged to enable requisite flexibility for metal–ligand coordination polymerization. The reactions of H4L with Cd, Mn, and Zn salts indeed yielded MOFs, i.e., Cd-L, Mn-L, Zn-Lsqc, and Zn-Ldia, with interesting structural features and unusual inorganic SBUs. In particular, the reaction of H4L with ZnI2 in DMF at 90 °C over 2 days led to concomitant formation of a pair of compositionally distinct Zn-MOFs, i.e., Zn-Ldia and Zn-Lsqc, each of which could be accessed exclusively by controlling the reaction conditions. The diversity observed in the structures of MOFs formed with the linker H4L with a limit...