Stretchable Tb-Tb Distance Regulates the Piezofluorochromic Behavior of Chiral Tb(III)-MOF upon Compression.

ABSTRACT

Luminescent chiral Tb-MOF microcrystals with the Tb2(COO)4 subunit indicated strong green mechano-luminescence under compression. Furthermore, piezofluorochromic behavior in the diamond anvil cell was observed, with the intensity tendency of decreasing-increasing-decreasing and a shortened lifetime upon compression, due to the reversible stretchable Tb-Tb interactions. The Tb-Tb distance upon compression was refined through in situ high-pressure X-ray absorption spectra, which was consistent with the tendency of the piezofluorochromic intensity. In situ high-pressure UV-vis absorption spectra, Fourier transform infrared spectra, and powder X-ray diffraction demonstrated the full recovery of Tb-MOF after over 10 GPa compressions due to the semiflexible ligand. This work not only provided an ultrastable Tb-MOF but also illustrated the relationship of the piezofluorochromic behavior with the detailed structural transformation for the first time.