The
construction of circularly polarized luminescence (CPL) materials
with high porosity and high rigidity is still challenging. Herein,
we propose a chiral reticular chemistry strategy to prepare the homochiral
porous metal–organic frameworks (MOFs) as CPL-active materials.
Two pairs of enantiomeric MOFs are synthesized through the self-assembly
of chiral D/L-cam (DL-camphorates) and achiral fluorescent ligand
TPB (1,2,4,5-tetra(pyridin-4-yl)benzene). The g
lum values of Cd-CMOF-D and Cd-CMOF-L were up to 0.010 and
0.009; the high g
lum values could be compared
to those of the partially pure multicomponent self-assembly systems
obtained by the complicated process. We further trace the generation
and transfer of the hierarchical chirality from chiral molecule to
3D framework, demonstrating that the CPL was dominated by the original
molecular chirality rather than the global chirality of the hierarchical
structure. Moreover, the single-phase white-light materials with nearly
ideal CIE coordinates (0.33, 0.33) were constructed through the introduction
of dye emitters into Zn-CMOF (Zn-based chiral MOF). This work provided
not only an insightful view of the chirality transfer and disappearance
mechanism but also an efficient method for the preparation of the
highly porous CPL materials.
Exploiting the chirality transfer and amplification in the hierarchical chiral systems by the visible and accurate structures is still a challenge. Herein, a pair of homochiral metal-organic frameworks (MOFs) DCF-12 and LCF-12 with high rigidity and high porosity are synthesized via reticular chemistry. Interestingly, these two enantiomers can act as nano-containers, in which four chromophores, covering acridine, pyrene, 9,10-Bis(phenylvinyl) anthracene (BPEA), and coronene can be introduced by in situ encapsulation. Importantly, the precise single crystal structures of all guest-loaded MOFs by X-ray diffraction technique can be obtained smoothly. It not only clearly reveals the chirality transfer from chiral host framework to achiral guest emitters through space chirality transfer, but also circularly polarized luminescence can be achieved and modulated through the synergistic effect. Extraordinarily, both pyrene@DCF-12 and pyrene@ LCF-12 exhibit fascinating multi-color tunable room temperature phosphorescence (RTP) and dynamic circularly polarized luminescence. Besides, the RTP quantum yields of pyrene@DCF-12 and pyrene@LCD-12 are high up to 75.39% and 73.43%, which exceeds most of that of RTP materials. These results demonstrate that chiral MOFs can serve as an accurate platform to investigate the mechanism of chirality transfer and amplification and to prompt the development of CPL-active materials.
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