Synthesis of sulfonated porous polymers with improved hydrophobicity and stability is of extreme importance in both academic research and industrial applications. However, there is often a trade-off between acidity and surface hydrophobicity of sulfonated polymers. In this study, we report a strategy for the synthesis of sulfonated porous organic polymers (S-PT) with improved hydrophobicity via free radical polymerization method by using a rigid and large multidentate monomer, 1,3,5-tri(4-vinylphenyl)-benzene, having a hydrophobic core. The results of vapor adsorption measurement show that S-PT has more hydrophobic properties than sulfonated poly(divinylbenzene) (S-PD), attributed to the hydrophobic core of its multidentate monomer. Furthermore, the optimization of sulfonation time established a balance between surface acidity and hydrophobicity. Under optimized conditions, S-PT afforded up to 113 mmol g-1 h-1 TOF in the esterification of oleic acid with methanol, more active than commercial Amberlyst-15 with TOF of 15 mmol g-1 h-1 and Nafion NR50 with TOF of 7 mmol g-1 h-1 . We believe that the findings of this study will provide useful insights to advance the design and synthesis of solid acid catalysts for organic transformations.
Keywords: esterification; hydrophobic core; porous organic polymer; solid acid catalyst; sulfonated polymer.
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