Chiral mesoporous organosilica spheres: Synthesis and chiral separation capacity

New mesoporous organic–inorganic spheres with trans-(1R,2R)-bis-(ureido)-cyclohexane covalently bridged in the pore wall were prepared by co-condensation of N,N′-bis-[(triethoxysilyl)propyl]-trans-(1R,2R)-bis-(ureido)-cyclohexane and 1,2-bis(trimethoxysilyl)ethane through a hierarchical double templating method. The octadecyltrimethylammonium chloride (C18TMACl) and ethanol direct the formation of mono-dispersed hybrid spheres. N,N-dimethyldecylamine, acting as a pore expanding agent, can expand the pore diameter of the hybrid material from less than 1.7–10 nm during the post-synthetic treatment process. The hybrid material was employed as a novel kind of chiral stationary phase for high performance liquid chromatography (HPLC). The column packed with the hybrid material with particle size of 6–9 μm can efficiently separate the R/S-1,1′-bi-2-naphthol enantiomers even at high sample loading and high flow rate because of its high chiral ligand loading (0.93 mmol/g) and high surface area (597 m2/g).