Extended Conjugation Tuning Carbon Nitride for Non‐sacrificial H₂O₂Photosynthesis and Hypoxic Tumor Therapy**

Abstract

Artificial photocatalysis offers a clean approach for producing H2O2. However, the poor selectivity and activity of H2O2 production hamper traditional industrial applications and emerging photodynamic therapy (PDT)/chemodynamic therapy (CDT). Here, we report a well-defined C5N2 photocatalyst with a conjugated C=N linkage for highly selective and efficient non-sacrificial H2O2 production both in normoxic and hypoxic systems. The strengthened delocalization of −electrons by linkers in C5N2 significantly downshifted the band position, which eliminated the side photoreduction reaction of H2 evolution in thermodynamics and promoted water oxidation ability in kinetics. As a result, C5N2 had a competitive overall H2O2 production with solar-tochemical conversion efficiency of 0.55% and more interestingly, exhibited the highest activity so far in hypoxic condition (698 M/h). C5N2 was further applied to hypoxic PDT/CDT, exhibiting outstanding performance in conspicuous cancer cell death and synchronous bioimaging. It shed light on unlocking linker functions in electronic structure engineering of carbon nitrides for highly efficient overall photosynthesis of H2O2 and expanded the scope of their prospective application in health care.

Nanotechnological strategies to increase the oxygen content of the tumor

“…Photocatalytic water splitting is a clean, simple and sustainable pathway for producing O 2 and hydrogen, which has led to great achievements in the fields of the environment, energy and biomedicine ( Liao et al, 2020 ; An et al, 2021 ; Teng et al, 2021 ). Carbon nitride (C 3 N 4 ) has been applied as a non-metallic photocatalyst for the photolysis of water in tumors to produce oxygen due to its visible light response and non-toxicity ( Liu et al, 2020b ; Ma et al, 2022 ). This endogenous oxygen production can enhance aerobic-based therapy.…”

Organocatalysis with carbon nitrides

“…Although C 3 N 5 , C 3 N 6 , and C 3 N 7 are prevalent stoichiometries of carbon nitrides of interest, various other forms have also been reported recently with promising results in catalytic applications. The C 5 N 2 with conjugated C=N linkage with a reduced band gap is suitable for H 2 O 2 production [ 73 ]. The C 3 N 2 containing a five-membered ring synthesized from the zeolitic imidazole framework possesses a narrow optical band gap of 0.81 eV and is efficient for photoelectrochemical biosensing [ 74 ].…”

Nanostructured Carbon Nitride for Continuous-Flow Trifluoromethylation of (Hetero)arenes

“…2.7 eV, excellent thermo- and photostability, and tunable surface area achievable through different synthetic methods that lead to the formation of allotropes. These allotropes include graphitic carbon nitride (gC 3 N 4 ), exfoliated nanosheets of graphitic carbon nitride (nC 3 N 4 ), and mesoporous graphitic carbon nitride (mpgC 3 N 4 ). ,− …”