Rational one-step synthesis of cobalt clusters embedded-graphitic carbon nitrides for the efficient photocatalytic CO2 reduction under ambient conditions.

• The rational synthesis of homogeneously surface embedded cobalt clusters: g-C 3 N 4 system. • The cobalt clusters are successfully stabilized via NH 2 -bpy moieties. • Resulted photocatalyst was effective for the CO 2 reduction under sunlight irradiation. • Achieved very high rate of conversion (CO 2 to CO) and apparent quantum yield (3.2% at 420 nm). • A new one-step strategy to prepare metal clusters embedded photocatalysts. Metal clusters catalyst embedded in semiconductors is the key factor for an efficient photocatalyst toward photocatalytic CO 2 reduction. However, developing a simple method to synthesize such photocatalyst with these features has remained challenging. Herein, a rational one-step synthesis of cobalt clusters embedded in g-C 3 N 4 layers is developed for an enhanced photocatalytic CO 2 reduction. The tiny cobalt clusters are embedded into the g-C 3 N 4 structure and stabilized through the interaction with NH 2 -bpy moieties. Besides, the ligands of cobalt complex can copolymerize with urea during the synthesis owing to the presence of amino groups, thus providing a direct electron transfer between carbon nitride and cobalt clusters, which act as the light harvester and active reduction site, respectively. Consequently, a volcano relationship between the CO generation rate and the cobalt clusters incorporated into the carbon nitride matrix was found. Under optimized conditions, representative C 3 N 4 -0.5CoO x exhibits the very high CO generation rate of 2.6 μmol.h−1. Its apparent quantum yield of 3.2% at 420 nm and 1.0% at 460 nm, which is one of the highest values reported so far. The finding offers new opportunities for designing metal clusters catalysts toward photocatalytic CO 2 reduction based on the judicious use of the metal complex. [ABSTRACT FROM AUTHOR]