The 3-D 12-connected metal-organic framework [Cu12Br2(CN)(6/2)(SCH3)(6)][Cu(SCH3)(2)], containing dodecanuclear copper clusters, has been solvothermally synthesized and exhibits efficient yellow luminescence. The emission mechanism was studied in detail to elucidate the relationship of the luminescent properties and crystal structures, which is helpful for the design and synthesis of more efficient luminescent materials.