Solvent-Induced Single Crystal To Single Crystal Transformation and Complete Metal Exchange of a Pyrene-Based Metal-Organic Framework

The structure transformation of a metal-organic framework (MOF) constructed by a pyrene-based ligand 1,3,6,8-tetrakis(3,5-isophthalic acid)pyrene (H(8)TIAPy), [Zn-4(TIAPy)center dot(DMSO)(2)center dot(H2O)(4)]center dot(Guest) (JUC-118), was investigated when soaked in different solvents. Single crystal X-ray diffraction revealed that JUC-118 could convert into JUC-118-1, whose lattice parameters were obviously different in ethylene glycol monomethylether (EGME). It was found that the torsion angles between the pyrene and the benenze rings of the ligand changed from 41.2 deg to 61.3 deg. Thus, the channel structure in the direction [101] had an obvious difference from a compressed rhombic shape to an expanded one. In addition, EGME could also induce complete metal exchange of Cu(II) for Zn(II) when soaking either JUC-118 or JUC-118-1 in EGME. However, no similar phenomena were found while soaking them in DMF. As the lattice parameters changed, the fluorescence had a blue shift, from 485 to 460 nm. These observations might guide us to design and synthesize materials with a fluorescence response for guest recognition.