Exploring the Chiroptical Properties of Chiral Covalent Organic Framework Enantioselectively Synthesized with Circularly Polarized Light

Abstract

Precise control of chirality in the solid state remains a significant challenge in materials science. This difficulty arises from the rarity of spontaneous symmetry breaking and the limited understanding of chirality amplification mechanisms, often requiring complex procedures or the use of stereochemically defined reagents. Despite these challenges, chiral covalent organic frameworks (CCOFs) have emerged as promising candidates in chiral chemistry, owing to their highly ordered pore structures, tunable design, and favorable electronic properties such as high conductivity. With growing demand for chiral materials in fields such as enantioselective sensing, asymmetric catalysis, and chiroptical devices, there is an increasing need for novel synthetic strategies that can induce and spatially control chirality without relying on chiral reagents. In this study, I propose a novel strategy to synthesize CCOFs without the use of chiral reagents by utilizing circularly polarized light as an asymmetric external stimulus. The TAPB-OMePDA CCOF was synthesized in both powder and film forms to meet different characterization and application demands. Circular dichroism (CD) spectroscopy confirmed that the chirality of the synthesized CCOFs was effectively governed by the handedness and duration of circularly polarized light exposure. Circularly polarized luminescence (CPL) measurements further revealed that the resulting COFs reflected the handedness of the incident light, achieving a maximum g lum value of ± 0.12. Additionally, spatially resolved enantiomeric domains were fabricated, with the resulting films exhibiting localized CPL emissions, demonstrating the feasibility of precise chiral patterning in solid-state systems. The CCOFs also showed enantioselective fluorescence quenching in response to D-alanine and D-glucose, with notable quenching ratios of 3.25 and 15.51, respectively. These results demonstrate that the TAPB-OMePDA CCOF possesses both strong chiroptical properties and enantioselective sensing capabilities. Its ability to simultaneously exhibit selective interactions with specific enantiomers and CPL behavior underscores its potential in chiroptical devices and enantioselective chemical sensing.