The synergistic combination of a heterogeneous organic semiconductor mesoporous graphitic carbon nitride (mpg-CN) and a homogeneous nickel catalyst with visible-light irradiation at room temperature affords the C(sp(2))-C(sp(3)) cross-coupling of aryl halides and potassium alkyl trifluoroborates by single electron transmetallation. Like the homogeneously catalyzed protocol, the reaction is compatible with a variety of functional groups including electron-donating and electron-withdrawing aryl and heteroaryl moieties. Moreover, this protocol allows the installation of allyl groups onto (hetero)arenes, enlarging the scope of the method. The heterogeneous mpg-CN photocatalyst is easily recovered from the reaction mixture and reused several times, paving the way for larger-scale industrial applications of this type of photocatalytic bond-forming reactions.