Helical Chiral Covalent Organic Frameworks Enable Enantioselective Surface Wetting

Enantioselective surface wetting is a promising approach for chiral recognition but is limited by weak interactions and small contact angle shifts in conventional, disordered materials. Here, we address this challenge using crystalline chiral covalent organic frameworks (CCOFs), whose rigid, ordered frameworks enable confined stereoselective interactions, resulting in significantly enhanced wettability differences. Two helical 3D CCOFs (35-2F and 35-4F) are synthesized via the condensation of enantiopure di- and tetrafluorobenzaldehydes of 2,2'-dihydroxy-1,1'-binaphthyl with a tetramine. These fluorinated CCOFs adopt distinct helical rod-like morphologies─right-handed for (S)-CCOF and left-handed for (R)-CCOF─stabilized by an 11-fold interpenetrating diamond network, unlike their nonfluorinated analogs, which lack helicity. The periodic arrangement of chiral dihydroxy groups and electron-withdrawing fluorine substituents on the pore surfaces creates highly defined recognition environments that promote strong stereospecific interactions. Consequently, when fabricated into solid surfaces, these helical CCOFs exhibited remarkable enantioselective wetting behavior, achieving contact angle differences of up to 26.9° for sugars, amino acids and their methyl esters, far surpassing the nonhelical counterparts and previous amorphous systems. This enhanced discrimination arises from the helical chiral architectures, which promote stronger and more selective chiral interactions through its periodic, confined pore geometry. This study pioneers the use of crystalline porous materials in enantioselective wetting, establishing a robust platform for chiral sensing and interface engineering.