Photocatalytic CO2 reduction with H2O to chemicals without H2 generation is interesting, but challenging. Herein, we report temporally separated (in time) CO2 photoreduction and H2O photooxidation, which is achieved over redox-active o-hydroxyazobased conjugated organic polymer films (HAzo-COPFs), affording CO as the sole reduction product in high efficiency. HAzo-COPFs are prepared via interfacial diazo-coupling reactions of aromatic diamines and diphenols, and HAzo-COPF-1 from 4,4'-biphenol and benzidine shows the best performance with a CO generation rate of 53.6 μmol g−1 h−1 under visible-light irradiation (>420 nm). Interestingly, it is discovered that diphenol (DP-OH) moieties in HAzo-COPFs, serving as electron and proton donors to participate in CO2 photoreduction, are oxidized into quinone (DP=O) moieties, which are subsequently photoreduced to regenerate DP-OH in H2O photooxidation. Consequently, CO2 photoreduction and H2O photooxidation are temporally separated and perfectly coupled via redox transformation between DP-OH and in situ formed DP=O, affording enhanced charge carrier separation and inhibiting hydrogen evolution reaction. This work provides new insights for the design of COPs photocatalysts and artificial photosynthesis.