Cu 12 -cluster-based metal-organic framework as a metastable intermediate in the formation of a layered copper phosphonate.

The solvothermal reaction of CuSO 4 ·5H 2 O and a chiral R -pempH 2 ligand (molar ratio 6 : 1) first forms the metastable intermediate [Cu 24 (OH) 20 ( R -pempH) 8 (SO 4 ) 10 (H 2 O) 10.5 ]·35H 2 O (1), followed by the formation of the stable phase [Cu 2 (OH)( R -pempH)(SO 4 )(H 2 O)]·H 2 O (2). Compound 1 displays a novel 3D open-framework structure containing Cu 12 cluster nodes and sulfate links, which can be converted to the layered compound 2. We also investigated the photothermal effects of both compounds.