Microwave-Assisted Rapid Preparation of Mesoporous Phenolic Resin Nanospheres toward Highly Efficient Solid Acid Catalysts

A novel microwave-assisted polymerization and self-assembly protocol was developed to prepare ordered mesoporous phenolic resin (MPRN) with nanospherical morphology for the first time. This unique strategy dramatically saved the synthesis time about 2 days with an energy-efficient way. Owing to its abundant phenyl groups in the framework, it was easily transformed to benzenesulfonic acid-functionalized MPRN (SO3H-MPRN) by simple sulfonation treatment. The obtained SO3H-MPRN sample still possessed a large surface area, two-dimensional hexagonal mesoporous structure, and uniform spherical shape. Importantly, because of its intrinsic organic framework, the pore surface of SO3H-MPRN was hydrophobic. Accordingly, it exhibited the excellent catalytic activity and selectivity in aqueous formaldehyde-participated Prins reaction and water-medium Fischer-indole reaction. On the basis of material characterizations and the control experiments, this remarkable catalytic performance could be ascribed to the synergetic effect derived from its short mesoporous channel and hydrophobic pore surface, which resulted in the decreased reactant diffusion limitation and the reduced water competitive adsorption. Also, it was stable in water because of the periodically arranged acid species in the resin framework and thus was easily recycled and used repetitively for at least five times.