A new heteropolyanion-based acidic ionic liquid-functionalized mesoporous copolymer P(VB-VMS)PW was prepared by anion-exchange of 1,3-propanesulfonate poly(N-vinylimidazole-co-divinylbenzene) with Keggin 12-phosphotungstic acid. The obtained hybrid material was characterized by fourier transform infrared spectroscopy, thermogravimetry, nuclear magnetic resonance, scanning electron microscope, X-ray diffractometer, nitrogen sorption isotherm, elemental analysis and Hammett indicator. Its catalytic performance was assessed and compared with analogues in the Friedel-Crafts benzylation reaction between single-ring aromatic compounds with benzyl alcohol under solvent-free condition. Owning to the suitable mesoporous copolymeric structure, P(VB-VMS)PW showed a relatively high yield of benzylating products (96.7%), and it could be facilely recovered and reused. Besides, functionalization of the mesoporous ionic copolymer with heteropolyanion was able to enhance the structural stability and the acidity of the sulfonic group, favoring superior acid catalysis performance in benzylation reaction.