Abstracts

Chiral recognition of molecules holds significant importance in numerous fields including analytical chemistry, food chemistry, and biotechnology. Chiral fluorescence spectroscopy has the advantages of simple operation, low cost, and high analytical flux, but it requires highly sensitive chiral optical probes. Compared with small molecular probes, chiral covalent organic framework (COF) probes have large specific surface areas, easily regulated structures, and can be reused.Two C=C bond-linked chiral COFs were synthesized by Knoevenagel polycondensation of chiral tetrabenzaldehyde of dibinaphthyl-22-crown-6 with 1,4-phenylenediacetonitrile or 4,4’-biphenyldiacetonitrile. Reduction of olefin linkages of the as-prepared chiral COFs produces two C–C bond-linked frameworks, which retain high crystallinity and porosity as well as high chemical stability in both strong acids and bases. Compared to the C=C bond-linked chiral COFs, the C–C bond-linked COFs display blue-shifted emission with enhanced quantum yields and fluorescence lifetimes, while the parent C=C bond-linked COFs exhibit higher enantioselectivity than the reduced analogs when be used as fluorescent sensors to detect chiral amino alcohols via supramolecular interactions with the built-in crown ether moieties (J. Am. Chem. Soc. 2021, 143, 369).The chiral memory effect was investigated for the first time during the dynamic transformation from porous organic cages to COFs. A total of six 2D chiral COFs constructed by entirely achiral building blocks were successfully synthesized by the transformation of amine bond-linked chiral cages. The prepared chiral COFs exhibited high enantioselectivity as fluorescence sensors and can be utilized for the sensing of chiral amino alcohols and amino acids. To microscopically elucidate the host-guest interactions between chiral COFs and enantiomers and reveal the mechanism of chiral COF-based fluorescence sensing system, preliminary investigations were conducted into the host-guest interactions using energy-minimized density functional theory (DFT) calculation (J. Am. Chem. Soc. 2024, 146, 7594).Consequently, these studies underscore the significant potential of employing chiral COFs as luminescent sensors. Evidence suggests that COF-derived fluorescent probes display superior fluorescence properties, pronounced enantioselectivity, and excellent reusability. Moreover, the well-ordered crystalline framework of COFs allows for the investigation of chiral recognition processes at an atomic level, a feat that is not readily achievable with conventional probes.