Tunable chiroptical application by encapsulating achiral lanthanide complexes into chiral MOF thin films

Chiral metal–organic frameworks (chirMOFs) have been widely considered on enantioselective adsorption/separation, asymmetric catalysis, biological and nonlinear optical applications. However, chirMOFs are facing a great challenge in development of chiroptical thin films with circularly polarized luminescence (CPL) property. Here, we first report CPL thin films by encapsulating achiral lanthanide complexes Ln(acac)₃ (Ln = Eu_aTb_bGd_c) into the pores of surface-coordinated chirMOF thin films (SURchirMOF) [Zn₂(cam)₂dabco]_n with layer by layer (lbl) encapsulation strategy. Due to the unique combination of chiral porous MOF and adjustable luminescent complexes in the host–guest thin films, the obtained Ln(acac)₃@SURchirMOF possess strong and tunable CPL property with high dissymmetry factors. The compared CPL and fluorescent lifetime results show that the advantage of this preparation strategy can effectively achieve energy transfer from Ln(acac)₃ to SURchirMOF, resulting in an excellent CPL performance. This study not only provides a novel strategy to develop new types of chiral thin films but also offers an efficient approach for tunable chiroptical applications.