Ruthenium(II)-Bipyridine/NanoC3 N4 Hybrids: Tunable Photochemical Properties by Using Exchangeable Alkali Metal Cations.

A series of nanoporous carbon nitrides that contained a range of alkali metal cations (M@nanoC3 N4 : M=Li+ , Na+ , K+ , Rb+ , and Cs+ ) have been successfully synthesized from as-synthesized g-C3 N4 by delamination with concentrated sulfuric acid, followed by neutralization with aqueous solutions of the corresponding alkali metal hydroxides. Tris(2,2'-bipyridine)ruthenium(II) complexes, [Ru(bpy)3 ]2+ , were grafted onto the carbon nitrides in an effort to explore the physicochemical properties of the deposited [Ru(bpy)3 ]2+ , as well as its photocatalytic activity in the aerobic photooxidation of phenylboronic acid and H2 production from aqueous media in the presence of a Pt co-catalyst under visible-light irradiation. Highly porous nanoC3 N4 could significantly enhance photocatalytic activity, because of its high surface area, owing to its unique porous structure. More interestingly, the photoluminescence intensities of [Ru(bpy)3 ]2+ complexes that were associated with M@nanoC3 N4 increased in the presence of lighter alkali metal cations, which correlated with increased photocatalytic activities for both reactions. This study demonstrates that M@nanoC3 N4 are fascinating supports, in which the local environment of an immobilized metal complex can be precisely controlled by varying the alkali metal cation from Li+ to Cs+ .