Room-temperature ferromagnetism in graphene has attracted considerable attention due to its potential application as spintronics. Theoretically, magnetic moment of graphene can be generated by removing a single p z orbital from the π system, which introduces an unpaired electron into the graphene motif for magnetic coupling. In this work, p z orbital of graphene is experimentally removed by cleaving the π bond of graphene using H 3 BO 3 with the assistance of supercritical CO 2 (SC CO 2 ), which simultaneously introduces -B(OH) 2 groups and unpaired electrons. As a result, ferromagnetic coupling between unpaired electrons substantially enhances the magnetic properties of the 2D graphene motif, leading to room-temperature ferromagnetism. Overall, unpaired electrons were introduced into a 2D graphene motif through π bond cleavage, which provides a novel approach for magnetic manipulation of 2D materials with conjugated structures.