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

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.