Methylation of formaldehyde with various aromatics under functionalionicliquids catalysis has been developed. Among the ionicliquids investigated, triphenyl-(4-sulfobutyl)-phosphonium triflate ([TTPBs][CF3SO3]) showed high activity and afforded excellent yields of diarylmethane derivatives. A mechanism for the catalytic performance of [TTPBs][CF3SO3] is proposed. Besides, the catalyst can simply