Chiral Mesoporous Organosilica Hierarchical Hollow Nanostructures for Enantioselective Adsorption

The synthesis of a new class of chiral mesoporous organosilica hollow nanostructures with tunable architectures is reported using a controlled stepwise sol–gel approach. By modulating the sequence of precursor addition, both yolk-shell and multishelled hollow nanospheres are obtained, enabling precise spatial control over the distribution of chiral and achiral domains. The chiral framework is constructed from enantiopure bridged organosilane monomers, synthesized by reacting 3-isocyanatopropyltriethoxysilane with either (R,R)- or (S,S)-diphenylethane-1,2-diamine (DPEN) or cyclohexane-1,2-diamine (DAC). The achiral component is formed from a mixture of tetraethyl orthosilicate (TEOS) and 1,2-bis(triethoxysilyl)ethane (BTSE), providing structural stability and mesoporosity. By controlling the sequence of precursor addition during the sol–gel process, the chiral framework is selectively introduced at different stages of formation, allowing precise spatial positioning within the hollow architecture. The resulting materials exhibit well-defined morphology, high organic content, and accessible mesoporosity. Enantioselective adsorption studies using tryptophan (Trp) reveal that the spatial location of the chiral framework is a decisive factor in chiral recognition. The highest enantioselectivity is observed when the chiral domains are confined within the interior of the structure, where the nanoconfined environment enhances host–guest interactions, yielding selectivity factors up to 7.0.