Complex Phase Behaviour and Structural Transformations of Metal-Organic Frameworks with Mixed Rigid and Flexible Bridging Ligands.

Two new heteroleptic metal-organic framework materials show strong adsorption of H and ethanol. [Co (L1)(bdc) ], where L1=N ,N -bis(4-pyridinylmethyl)-2,5-dimethylbenzene-1,4-diamine and bdc is benzene-1,4-dicarboxylate, has a twofold interpenetrating pillared layer structure with pcu topology. It has a stepped, hysteretic EtOH adsorption that can be related to complicated phase and structural transformation behaviour that occurs on de-solvation and re-solvation, including major conformational changes to the geometry of the flexible L1 ligand. [Co (L1)(bpdc) ], where bpdc=biphenyl-4,4'-dicarboxylate, has a unique six-connected self-catenating framework structure. Solvation changes occur without significant structural change and a partially-hydrolysed material binds its own decomposition products as guests.