Design and synthesis of hydrophobic and stable mesoporous polymeric solid acid with ultra strong acid strength and excellent catalytic activities for biomass transformation

Novel and efficient mesoporous polydivinylbenzene (PDVB) based solid strong acid (PDVB-SO3H-SO2CF3) has been successfully prepared by grafting of strong electron withdrawing group of SO2CF3 onto the network of performed mesoporous solid acid of PDVB-SO3H, which could be synthesized from sulfonation of superhydrophobic mesoporous PDVB or copolymerization of DVB with sodium p-styrene sulfonate. Characterizations of N2 sorption isotherms, TG curves and contact angle tests show that PDVB-SO3H-SO2CF3 has large Brunauer–Emmett–Teller (BET) surface area, superior thermal stability, good hydrophobicity and oleophilicity. Solid 31P NMR spectra and NH3–TPD curves show that the Brønsted acidic site in PDVB-SO3H-SO2CF3 has been significantly enhanced and rather homogeneously distributed when compared with that of PDVB-SO3H. Catalytic tests show that PDVB-SO3H-SO2CF3 exhibits excellent catalytic activities and good recyclability in biomass transformation toward transesterification to biodiesel and depolymerization of crystalline cellulose to sugars when compared with those of PDVB-SO3H, solid strong acids of SO4/ZrO2 and Nafion NR50. The excellent catalytic activity and good recyclability of PDVB-SO3H-SO2CF3 result from its unique characters such as large surface area, ultra strong acid strength, adjustable hydrophobic–oleophilic and stable network.

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► Introduction of SO2CF3 group enhances acid strength of PDVB-SO3H.
► Abundant mesoporosity is favorable for the fast diffusion of reactants.
► Strong acid strength results in excellent catalytic activity for biomass transformation.
► Hydrophobic–oleophilic network results in high exposition degree of active sites.
► The stable network of mesoporous solid strong acid results in its good recyclability.