Herein,　Pd　and　Pt-catalysts　loaded　on　non-oxide　support　(g-C3N4)　were　prepared　and　compared　for　CO　and　toluene　co-oxidation,　and　Pt/C3N4　presented　excellent　catalytic　performance.　A　series　of　characterizations　including　TEM,　H2-TPR,　O2-TPR　and　XPS　etc.,　indicated　that　Pt/C3N4　exhibited　the　smaller　Pt　NPs,　better　low　temperature　reduction　ability,　more　active　oxygen　species　and　positive　charged　Pt　species,　which　could　account　for　its　better　catalytic　performance.　Additionally,　DFT　calculations　further　confirmed　that　the　lower　activation　barrier　of　O2　and　the　higher　adsorption　for　CO　and　toluene　triggered　the　efficient　CO　and　toluene　degradation　over　Pt/C3N4.　Interestingly,　the　introduction　of　H2O　(10.0　vol%)　suppressed　the　catalytic　performance　of　Pd/　C3N4,　while　expedited　CO　and　toluene　oxidation　over　Pt/C3N4,　which　was　revealed　by　DFT　calculations.　Furthermore,　the　difference　in　degradation　intermediates,　corresponding　distributions　and　toxicity　generated　during　toluene　oxidation　under　different　conditions　over　Pd/C3N4　and　Pt/C3N4　were　exposed.　Compared　with　Pd/C3N4,　less　variety,　toxicity　and　content　of　intermediates　produced　over　Pt/C3N4.　This　work　would　inspire　many　rational　designs　of　supported　noble　metal　catalysts　for　environmentally　friendly　catalysis.