A direct synthesis of polysubstituted olefins via construction of C-C bonds, which involves the direct dehydrative coupling of alcohols or alkenes with alcohols, was realized using a series of alkanesulfonic acid group-functionalized ionic liquids (SO₃H-functionlization ILs) without additives. The metal-free and recyclable catalyst system avoided the disposal and neutralization of acidic catalysts after reaction and tolerated a broad range of substrates, including benzylic, allyl, propargylic, aliphatic and aromatic or aliphatic olefins. Additionally, the catalytic system was suitable for a gram-scale preparation. Preliminary mechanistic studies indicated that the C-H bond cleavage in this reaction might be involved in the rate-determining step.