In this work, iron doping was proposed to improve the photo(electro)catalytic activity of PhC₂Cu, an air stable metal–organic coordination polymeric photocatalyst. After displacement of partial Cu atoms by Fe, the energy band structure of PhC₂Cu was successively modulated, featuring a narrowed band gap and down-shift in the valence band towards a more positive potential. More interestingly, the luminescence chromism upon iron doping is indicative of inhibited ligand-to-metal charge transfer (LMCT) that is relevant to the recombination of photocarriers. When the mole ratio of Fe/Cu reached 2%, the photocurrent density achieved its maximum, which was 4 times higher than that of the PhC₂Cu photocathode, consistent with an enhanced separation of electron–hole pairs. Furthermore, the extremely negative conduction band potential of PhC₂Cu enabled efficient O₂ activation, generating a series of reactive oxygen species (ROS) for the degradation of organic pollutants. The rate of methyl orange (MO) and 2,4-dichlorophenol (2,4-DCP) degradation over 2% Fe–PhC₂Cu increased by 2 and 1.6 times. This study provides a promising strategy for improving the activity of metal–organic photocatalysts.