Promoting photocatalytic degradation of tetracycline over in-situ grown single manganese atoms on polymeric carbon nitride

Introducing single-atom metals into polymeric carbon nitride (PCN) framework is a promising strategy to offer more active sites along with pollutant degradation kinetics. Herein, single manganese atoms decorated PCN (denoted as MCN) was fabricated via a straightforward in-situ thermopolymerization strategy using urea as PCN precursor and manganese acetylacetone as manganese (Mn) source. The as-synthesized optimal sample MCN-2 exhibits legible monatomic Mn sites on PCN framestructure and enhanced specific surface area (122.4 m2·g−1). The monatomic Mn introduced via the Mn-N/O coordination is demonstrated to be able to narrow the bandgap and facilitate separation and transfer of photo-excited carriers, which has a salutary effect on visible-light harvesting and MCN utilization. Consequently, the MCN-2 exerts a superior pseudo-first-order kinetic rate constant k of 0.041 min−1 in visible-light-driven TC photodegradation, with ca. 13-fold higher than that of the pristine PCN. Further, the intermediates and reactive oxygen species (1O2, h+ and •O2–) generating in the TC photodegradation process are experimentally manifested and a plausible mechanism for TC degradation over MCN is proposed. This work not only proves the efficacy of MCN in photodegradation of TC but expands Mn to other single-atom metals for pollutant removal.