Formation of a robust, double-walled LiMOF from an L-shaped di-substituted N-heterocyclic adamantane-based ligand

The properties of adamantane render it an attractive building block towards the synthesis of robust frameworks. This work describes the synthesis of the L-shaped 1,3-bis(3′-carboxypyridine)adamantane ( L1 ) ligand and the corresponding Li( i ), Zn( ii ) and Cu( ii ) frameworks. Three topologically analogous Li( i ) frameworks LiMOF12 , LiMOF30 and LiMOF50 are reported, with calculated solvent accessible void volumes of 46, 43 and 36%, respectively. The reaction between the carboxylate groups of L1 and the Li( i ) cations resulted in the formation of Li-carboxylate rods. The Li-carboxylate rods contributed to the formation of a double-walled MOF with large, open one dimensional channels. The synergistic effect of the double wall, lithium-carboxylate rods and the adamantane core itself, resulted in the formation of a robust network stable up to temperatures of 300-350 °C and a minimum of three months stability in air. Furthermore, complexation of L1 with Cu(BF 4 ) 2 ·H 2 O and Zn(CF 3 SO 3 ) 2 provided a 2D → 3D interpenetrated network containing a classic dimeric copper paddle-wheel SBU, and an infinite 1D chain which extended into a 3D structure facilitated by hydrogen-bonding interactions, respectively. Reaction of a new adamantane-based ligand L1 with LiOH provides a rare example of a Li MOF which is porous, double walled and both thermally and hydrolytically stable.