A　noble-metal-free　system　for　photochemical　reduction　of　CO2　has　been　developed　by　integrating　graphitic　carbon　nitride　(g-C3N　4)　with　a　cobalt-containing　zeolitic　imidazolate　framework　(Co-ZIF-9).　g-C3N4　acts　as　a　semiconductor　photocatalyst,　whereas　Co-ZIF-9　is　a　cocatalyst　that　facilitates　the　capture/concentration　of　CO2　and　promotes　light-induced　charge　separation.　The　two　materials　cooperate　efficiently　to　catalyze　CO2-to-CO　conversion　upon　visible　light　illumination　under　mild　reaction　conditions.　A　13C-labelled　isotropic　experiment　proved　that　CO2　is　the　carbon　source　of　the　produced　CO.　Even　without　noble　metals,　the　system　still　achieved　an　apparent　quantum　yield　of　0.9　percent.　The　system　displayed　high　photocatalytic　stability,　without　noticeable　alterations　in　the　chemical　and　crystal　structures　of　g-C3N4　and　Co-ZIF-9　after　the　reaction.　©　the　Partner　Organisations　2014.