Chiral Metal–Organic Cluster Induced High Circularly Polarized Luminescence of Metal–Organic Framework Thin Film

Guest-induced host–guest assembly in metal–organic frameworks (MOFs) has become a critical strategy to achieve circularly polarized luminescence (CPL). Herein, chiral metal–organic clusters (MOCs) induced CPL of achiral MOF are reported. Enantiopure titanium-oxo clusters (R/S-TOCs) are effectively loaded into the pores of a fluorescent, highly stable MOF NU-901 thin film by using a liquid-phase epitaxial layer-by-layer encapsulation method. The resulting chiral TOCs@NU-901 MOF thin films exhibit strong chirality, intense photoluminescence, and excellent CPL performance with the highest dissymmetry factor (±0.025) reported so far for the downshifted MOF-based materials. Further, the comparison experiments and density functional theory (DFT) calculations demonstrate that the excellent performance benefited from the strong chirality and charge transfer caused by the significant π–π interactions between the host (MOF) and guest (R/S-TOCs). This novel chiral MOCs induced approach provides a powerful toolbox for new host–guest CPL thin film materials.