Hydrophilic calix[4]arene dye-sensitized Co/g-C3N4 composites with Co single atoms for enhanced visible-light-driven photocatalysis

Single-atom hybrid photocatalysts (Co/g-C3N4/C4EOP) composed of hydrophilic calixarene dyes (C4EOP) and graphite-phase carbon nitrite with monodispersed Co atoms (Co/g-C3N4) are prepared by a facile solution impregnation method, and their photocatalytic performances are evaluated in visible light-driven H-2 evolution from water and CO2 conversion. The optimized Co/g-C3N4/C4EOP (1.0 wt%) catalyst exhibits moderate H-2 production activity (511 mu mol g(-1) h(-1)) and good durability within 60 h (TONC4EOP value of 2255) under visible light. In contrast, the Co/g-C3N4/C4BTP (1.0 wt%) and Co/g-C3N4/M-EOP (1.0 wt%) show much lower activities than Co/g-C3N4/C4EOP (1.0 wt%) under the same conditions. This could be attributed to the higher molar extinction coefficient and better hydrophilicity of C4EOP compared to C4BTP with hydrophobic alkane groups and M-EOP with single D-pi-A chain. In addition, Co/g-C3N4/C4EOP (1.0 wt%) catalyst displays highly selective photocatalytic activity for CO2 reduction to CO. This work provides a promising example for the development of efficient dye-sensitized photocatalytic system based on g-C3N4 with non-noble metal for the chemical utilization of solar energy.