Sp2-carbon-conjugated　covalent　organic　frameworks　(sp2c-COFs)　have　emerged　as　promising　platforms　for　phototo-chemical　energy　conversion　due　to　their　tailorable　optoelectronic　properties,　in-plane　π-conjugations,　and　robust　structures.　However,　the　development　of　sp2c-COFs　in　photocatalysis　is　still　highly　hindered　by　their　limited　linkage　chemistry.　Herein,　we　report　a　novel　thiadiazole-bridged　sp2c-COF　(sp2c-COF-ST)　synthesized　by　thiadiazole-mediated　aldol-type　polycondensation.　The　resultant　sp2c-COF-ST　demonstrates　high　chemical　stability　under　strong　acids　and　bases　(12　M　HCl　or　12　M　NaOH).　The　electro-deficient　thiadiazole　together　with　fully　conjugated　and　planar　skeleton　endows　sp2c-COF-ST　with　superior　photoelectrochemical　performance　and　charge-carrier　separation　and　migration　ability.　As　a　result,　when　employed　as　a　photocathode,　sp2c-COF-ST　exhibits　a　significant　photocurrent　up　to　∼14.5　μA　cm-2　at　0.3　V　vs　reversible　hydrogen　electrode　(RHE)　under　visible-light　irradiation　(＞420　nm),　which　is　much　higher　than　those　analogous　COFs　with　partial　imine　linkages　(mix-COF-SNT　∼　9.5　μA　cm-2)　and　full　imine　linkages　(imi-COF-SNNT　∼　4.9　μA　cm-2),　emphasizing　the　importance　of　the　structure-property　relationships.　Further　temperature-dependent　photoluminescence　spectra　and　density　functional　theory　calculations　demonstrate　that　the　sp2c-COF-ST　has　smaller　exciton　binding　energy　as　well　as　effective　mass　in　comparison　to　mix-COF-SNT　and　imi-COF-SNNT,　which　suggests　that　the　sp2c-conjugated　skeleton　enhances　the　exciton　dissociation　and　carrier　migration　under　light　irradiation.　This　work　highlights　the　design　and　preparation　of　thiadiazole-bridged　sp2c-COFs　with　promising　photocatalytic　performance.　©　2024　American　Chemical　Society.