Enhanced Electron Transport through Hydrogen Bonds and Ag Nanoparticles in the PCN-222/Ag/COF Core–Shell Photocatalyst for Efficient Oxytetracycline Degradation

Abstract

Enhancing the electron transport capability of photocatalysts is crucial for improving their photocatalytic performance. Therefore, a series of PCN-222/Ag/COF core–shell photocatalysts were synthesized using in situ growth and photoreduction methods. The alternating energy levels between PCN-222 and COF form a Z-scheme heterojunction facilitated by hydrogen bonds. The binding energy of these hydrogen bonds, calculated using density functional theory (DFT), is −71.53 kcal/mol. Moreover, the introduction of Ag nanoparticles creates a more favorable electron transfer bridge between PCN-222 and COF. Among the synthesized photocatalysts, the optimally developed PCN-222/Ag_3.0/COF₂ composite exhibited the highest photodegradation efficiency for oxytetracycline (OTC) (92.35%, k = 0.02703 min⁻¹) under simulated sunlight irradiation. This efficiency was 5.31 and 3.46 times higher than those of PCN-222 and COF, respectively. Electron paramagnetic resonance technology and free-radical capture experiments confirmed that ·O₂⁻ and h⁺ are the main active species in the degradation process. Furthermore, DFT calculations and ultra–high performance liquid chromatography–mass spectrometry were used to explore the photodegradation pathways and mechanisms. The Toxicity Estimation Software Tool was used to assess the toxicity of OTC and its degradation products.