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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.
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