Planar Chiral [2.2]Paracyclophane-Based Zr(IV) Metal-Organic Frameworks

Self-assembly has been widely explored to improve the circularly polarized luminescence (CPL) activities of molecular chromophores, but it is hard to amplify CPL while maintaining strong emissions. Optically pure, planar-chiral [2.2]paracyclophane (pCp) is one of the most important sources of chirality for electronic and optoelectronic materials, but the photoluminescence of its derivatives is significantly quenched after forming aggregates. Here we demonstrate that reticulation of pCp chromophores into highly stable Zr(IV) metal-organic frameworks (MOFs) can simultaneously boost the dissymmetry factor (|g(lum)|) and luminescence efficiency (Phi(PL)). Functionalization of pCp enables the synthesis of two tetracarboxylate linkers with different side arms, which are assembled into two highly stable Zr-MOFs with different topological structures. Geometrical constraints and segregated arrangements of the pCp chromophores imposed by the framework inhibit the aggregation-caused quenching effect and boost their CPL behaviors. Both Zr-MOFs display strong CPL emissions, affording |glum| and OPL values of up to 8.3 x 10(-3 )and 87%, respectively, which are amplified by similar to 18-and 52-fold compared to the corresponding free ligands. This work highlights the potential of optimizing CPL performances of chiral chromophores by using MOFs as support structures.