Hydrofluoroalkylation　serves　as　an　effective　strategy　for　introducing　fluoroalkyl　groups　into　alkenes.　Current　methods,　however,　rely　on　expensive　hydrogen　donors　such　as　thiols　to　facilitate　the　hydrogenation　step.　Although　water　represents　an　environmentally　benign　and　abundant　potential　hydrogen　source　for　photocatalytic　reactions,　its　high　dissociation　energy　(5.2　eV)　poses　a　fundamental　challenge　for　efficient　utilization.　We　report　a　photocatalytic　system　using　a　K-modified-hydroxylated　carbon　nitride　(PCN-OH-K)　with　water　as　the　hydrogen　donor　without　requiring　additional　additives.　The　hydroxyl　groups　activate　water　by　reducing　its　bond　dissociation　energy,　while　potassium　ions　enhance　substrate　adsorption　via　K-I　interaction.　PCN-OH-K　thus　achieves　an　AQE　of　4.7　%,　surpassing　existing　hydrofluoroalkylation　catalysts　and　competes　with　leading　photocatalysts　in　other　water-based　organic　transformations.　This　work　advances　sustainable　organic　synthesis　and　provides　insights　for　future　photocatalyst　design　in　solar　energy　conversion,　with　significant　potential　for　applications　in　the　pharmaceutical　and　agrochemical　industries.　©　2025　Elsevier　B.V.