Adsorption behaviour of a Cd II -triazole MOF for butan-2-one in a single-crystal-to-single-crystal (SCSC) fashion: the role of hydrogen bonding and C-H...π interactions

The adsorption behaviour of the Cd -MOF {[Cd(L) (ClO ) ]·H O (1), where L is 4-amino-3,5-bis[3-(pyridin-4-yl)phenyl]-1,2,4-triazole, for butan-2-one was investigated in a single-crystal-to-single-crystal (SCSC) fashion. A new host-guest system that encapsulated butan-2-one molecules, namely poly[[bis{μ -4-amino-3,5-bis[3-(pyridin-4-yl)phenyl]-1,2,4-triazole}cadmium(II)] bis(perchlorate) butanone sesquisolvate], {[Cd(C H N ) ](ClO ) ·1.5C H O} , denoted C H O@Cd-MOF (2), was obtained via an SCSC transformation. MOF 2 crystallizes in the tetragonal space group P4 2 2. The specific binding sites for butan-2-one in the host were determined by single-crystal X-ray diffraction studies. N-H...O and C-H...O hydrogen-bonding interactions and C-H...π interactions between the framework, ClO anions and guest molecules co-operatively bind 1.5 butan-2-one molecules within the channels. The adsorption behaviour was further evidenced by H NMR, IR, TGA and powder X-ray diffraction experiments, which are consistent with the single-crystal X-ray analysis. A H NMR experiment demonstrates that the supramolecular interactions between the framework, ClO anions and guest molecules in MOF 2 lead to a high butan-2-one uptake in the channel.