A bi-functional S-scheme cobalt-porphyrin conjugated polymer/C3N4 heterojunction for cooperative CO2 reduction and tetracycline degradation†

Abstract

The design of bifunctional photocatalysts for the removal of contaminants and the reduction of CO₂ is of significant practical importance in addressing pollution and energy challenges. However, the photocatalytic efficiency is limited by the inadequate redox ability, high carrier recombination rate, and insufficient reactive sites of existing photocatalysts. Herein, a 2D/2D S-scheme heterojunction composed of cobalt-porphyrin conjugated polymer nanoflakes and C₃N₄ nanosheets (CoPor-DBE/CN) was rationally synthesized, exhibiting matched redox ability and favorable CO₂ adsorption properties. The layered structure and functional groups of CoPor-DBE/CN provide numerous active sites, thereby enhancing the separation and transfer of charge carriers as well as the adsorption of reactants. Under visible light illumination, the optimized 50CoPor-DBE/CN hybrid achieved a CO production rate of 16.7 μmol g⁻¹ h⁻¹ and a tetracycline removal rate of 93.8%, which are significantly higher than those of the individual CN material. By employing X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and photo-irradiated Kelvin probe force microscopy (KPFM), we demonstrate that the transfer of charge carriers within the CoPor-DBE/CN system follows the S-scheme heterojunction mechanism. This work offers a promising blueprint for the design of multifunctional S-scheme photocatalysts aimed at the simultaneous efficient reduction of CO₂ and degradation of organic pollutants.