A　series　of　modified　carbon　nitride　with　a　controlled　amount　of　carbon　vacancies　is　prepared　successfully　by　simple　acid　treatment,　and　the　performances　of　the　corresponding　Pd/CN-X　catalysts　in　phenol-selective　hydrogenation　are　investigated.　It　is　found　that　the　Pd/CN-30　catalyst　exhibits　the　highest　activity,　while　Pd/CN-60　shows　a　very　low　activity.　The　characterization　of　powder　X-ray　diffraction,　transmission　electron　microscopy,　X-ray　photoelectron　spectra,　temperature-programmed　desorption　of　phenol　and　cyclohexanone,　phenol　adsorption　experiments,　and　isotope　experiment　show　that　the　high　catalytic　activities　and　selectivity　of　Pd/CN-30　are　related　to　its　relatively　high　Pd　dispersity,　high　phenol　adsorption　capacity,　and　proper　hydrophilicity.　However,　the　much　lower　activity　of　Pd/CN-60　can　be　attributed　to　the　existence　of　competitive　adsorption　of　phenol　and　water　molecules　on　the　catalyst　surface　and　its　low　hydrogen　activation　ability　due　to　the　support　over　modification　that　results　in　the　much　stronger　hydrophilicity　and　the　near　atomic　Pd　dispersion.　In　addition,　the　stability　of　Pd/CN-X　is　positively　correlated　with　the　carbon　vacancy　contents　due　to　the　strong　interaction　between　the　Pd　species　and　the　support.　©　2024　American　Chemical　Society.