A hydroxyl-tagged porous aromatic framework PAF-NBU2-OH was task-specifically designed and successfully synthesized targeted toward immobilizing chiral catalysts. Using proline-type compound as model chiral organocatalyst, PAF-NBU2-OH was used as a platform to covalently link proline-type group. The obtained PAF-immobilized organocatalyst PAF-NBU2-OPro featured high chemical stability in different solvents even under very harsh conditions. PAF-NBU2-OPro showed excellent catalytic activity, diastereoselectivity and enantioselectivity with complete and easy recyclability when catalyzing the aldol reaction between p-nitrobenzaldehyde and cyclohexanone, which could undergo at least 30 cycles without any activity, diastereoselectivity or enantioselectivity loss for catalyzing the current reaction.
Keywords: Aldol reaction; Enantioselective organocatalysis; Heterogeneous catalyst; Porous aromatic frameworks; Proline-type catalyst.
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