Nanoporous graphene carbon nitride/metal organic framework (g-C3N4/MOF) composites were prepared by solvothermal synthesis. The optical band gap of g-C3N4/MOFs is determined to be 2.69 eV by UV-Vis diffuse reflectance spectroscopy, which is significantly lower than the corresponding value of 3.86 eV for the MOF-5 material. The average diameter of the nanoporous g-C3N4/MOF-5 composites ranged from 10 to 15 mu m. The nanoporous g-C3N4/MOF-5 composites were stratiform in shape, and the pores ranged from 10 to 100 nm in diameter. Photocatalytic activity of the nanoporous g-C3N4/MOF-5 composites was evaluated by measuring the curing time of a UV-light-cured coating which had g-C3N4/MOF-5 added to it. The nanoporous g-C3N4/MOF-5 composites exhibited high photocatalytic curing activity for the UV photocurable coating, shortening the curing time to 13 min from 20 min.