Dependence of C( sp 3 )–C( sp 2 ) cross-coupling reaction performance at different nickel loadings. Conditions: 4 mol% photocatalyst, X mol% NiCl 2 ·glyme (glycol ether), X × 1.5 mol% L2, 1.5 equiv. Cs 2 CO 3 base, DMF and blue-LED irradiation source.