The　development　of　efficient　and　yet　economic　photocatalysts　that　can　utilize　solar　light　is　crucial　for　the　sustainable　future.　We　report　a　simple　approach　to　introduce　a　bidentate　type　of　metal　coordination　site　in　polymeric　carbon　nitride　(PCN)　by　an　in　situ　keto-enol　cyclization　route　of　acetylacetone　and　urea　to　incorporate　a　metal　chelating　pyrimidine　derivative　into　the　molecular　framework　of　PCN.　The　resulting　new　metal　coordination　sites　provide　both　N-　and　O-complexing　ligands　unlike　the　unmodified　PCN　that　has　N-ligands　only.　As　a　proof-of-concept　experiment,　we　introduced　Al3+　ions　into　these　coordination　sites,　which　induced　significant　enhancements　in　visible　light　photocatalytic　activities　for　organic　pollutant　degradation　and　H2　evolution　as　compared　to　those　of　bulk　PCN　and　the　conventional　＂nitrogen　pot＂　metal-coordinated　PCN.　The　optimized　Al　loading　was　as　low　as　0.32　wt　%.　The　photocatalytic　activities　sensitively　depended　on　the　Al　incorporation,　and　the　Al-incorporated　sample　demonstrated　an　excellent　stability　in　water　with　showing　little　sign　of　metal　leaching.　While　the　aluminum　ions　complexed　in　the　nitrogen　pot　little　influenced　the　photocatalytic　activity,　Al3+　ions　complexed　by　both　N　and　O　ligands　in　the　alternative　coordination　sites　significantly　enhanced　the　photocatalytic　activity　of　PCN.　This　study　demonstrates　a　facile　and　scalable　synthesis　of　PCN　with　alternative　metal　coordination　sites　for　efficient　solar　energy　conversion.　©　2018　American　Chemical　Society.