Photocatalytic　CO2　reduction　into　carbonaceous　feedstock　chemicals　is　a　promising　renewable　energy　technology　to　convert　solar　energy　and　greenhouse　gases　into　chemical　fuels.　Here,　a　covalent　triazine-based　framework　(CTF)　is　demonstrated　as　an　efficient　cocatalyst　to　reduce　CO2　under　visible-light　irradiation.　The　nitrogen-rich　triazine　moieties　in　CTF　contribute　to　CO2　adsorption,　while　the　periodical　pore　structure　of　CTF　favors　the　accommodation　of　CO2　and　electron　mediator.　Immobilization　of　cobalt　species　onto　CTF　promotes　the　photocatalytic　activity　with　a　44-fold　enhancement　over　pristine　CTF　and　the　optimal　CO　production　rate　of　the　obtained　Co/CTFs　was　up　to　50　μmol　g−1　h−1.　The　results　of　solid-state　UV-vis　diffuse　reflectance　spectra　(UV-vis　DRS),　CO2　adsorption　and　electrochemical　impedance　spectroscopy　(EIS)　illustrated　that　the　increased　activity　was　ascribed　to　the　enhanced　CO2　capture　capacity,　improved　absorption　of　visible-light　and　facilitated　the　transfer　of　charge　from　CTF　to　CO2　molecules.　The　CTF　not　only　serves　as　a　substrate　for　active　Co　species,　but　also　bridges　the　photosensitizer　with　cobalt　catalytic　sites　for　the　efficient　transfer　of　photoexcited　electrons.　This　work　highlights　the　capability　and　ease　of　fabricating　covalent　organic　framework-based　photocatalytic　systems　that　are　potentially　useful　for　energy-conversion　applications.　©　2019　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim