Circularly polarized luminescence enhancement in rare-earth MOFs due to framework chirality and host–guest energy transfer

Owing to their tunable structures and strong emission, chiral metal–organic frameworks (CMOFs) incorporating rare-earth ions hold great promise for circularly polarized luminescence (CPL). Herein, enantiomeric rare-earth CMOFs are synthesized via the direct self-assembly of optically pure ligands (1,3-bis((S)- and (R)-1-carboxyethyl)-1H-imidazol-3-ium chlorides) with Tb³⁺ ions and shown to exhibit CPL with a dissymmetry factor (|g_lum|) of 0.016, which is attributed to efficient chirality transfer and the antenna effect. The introduction of a luminescent guest (MnCl₄²⁻) into the framework channels markedly enhances CPL and increases |g_lum| to 0.071. The results of control experiments and spectral analysis indicate that this enhancement arises from the synergy between host–guest energy transfer and chirality transfer. This work describes a modular strategy for constructing CPL-active rare-earth CMOFs and provides a general design principle for tuning their chiroptical properties through host–guest interactions.