Circularly Polarized Luminescence of Tetradentate-Ligand-Based Chiral MOFs: Structural Evidence of Chirality Inversion

Abstract

Chirality inversion modulation is of great importance in the preparation of chiroptical materials. The rational use of the stoichiometry of mixed ligands in chiral metal–organic frameworks (MOFs) to induce chiral inversion of the enantiomeric space groups is a crucial topic in structural chemistry. However, no remarkable results have been reported yet. In this work, we synthesized chiral MOFs through the assembly of chiral camphoric acid (d/l-cam) and achiral tetradentate ligands. Interestingly, the visible single-crystal structures confirmed that chirality inversion of the enantiomeric space groups can be achieved via stoichiometric modulation of mixed ligands. Significantly, the switches of circularly polarized luminescence (CPL) along with the inversion of enantiomeric space groups can be observed clearly. Moreover, the encapsulated guest emitters exhibit the inverted CPL, revealing the helical-channel-dependent chirality transfer. The obtained results constitute a milestone in the field of chiral crystal engineering of MOFs.