Piperazine-functionalized ordered mesoporous polymer as highly active and reusable organocatalyst for water-medium organic synthesis

Abstract

A piperazine-functionalized mesoporous polymer (PP-MPs) was synthesized through a one-step surfactant-directed phenol–formaldehyde–piperazinecarbaldehyde oligomer self-assembly approach. This novel PP-MP catalyst exhibited highly catalytic reactivity and selectivity for water-medium Knoevenagel reaction, water-medium [3 + 3] cycloaddition reaction and intermolecular cross-conjugated addition reaction. The excellent performance could be attributed to its high dispersion of piperazine active sites and ordered mesoporous structure, which effectively diminished the steric hindrance and diffusion limitation. Moreover, its pure organic framework could enhance surface hydrophobicity, which promoted organic reactant molecule adsorption, especially in water. Meanwhile, piperazine functional groups embedded in the polymeric framework could inhibit the leaching of active species and thus resulted in the excellent durability without significant loss of activity for recovery and recycling at least four times.