A novel carbon nitride based self-cleaning hydrogel photocatalyst (KI-PCN gel, potassium and iodine co-doped carbon nitride confined in alginate) has been successfully constructed by a facile method. Fabricated photocatalyst showed enhanced synergistic adsorption-photocatalytic degradation property on a high concentration of methylene blue (HMB) because of enhanced carrier separation efficiency and improved light adsorption capacity of KI-PCN. As expected, the KI-PCN gel showed the highest apparent rate constant value ₍$K_{\mathit{app}}$ =0.0310 min⁻¹), which was about 38.8 and 5.8 times as that of blank hydrogel ($K_{\mathit{app}}$=0.0008 min⁻¹) and PCN gel ($K_{\mathit{app}}$=0.0053 min⁻¹), respectively. Meanwhile, KI-PCN gel can continuously adsorb low concentration of MB (LMB), and the MB-adsorbed KI-PCN gel can self-clean under light irradiation. The bench-scale experiments simulating real river showed that KI-PCN gel can effectively and continuously remove LMB (0.1–20 ppm), indicating the possibility for the removal of contaminants in natural rivers. Furthermore, the possible degradation pathways were proposed by combining the density functional calculations (DFT) and intermediates identified by liquid chromatography-mass spectrometry (LC-MS). This work proposed a new perspective to acquire a novel self-cleaning and easily recyclable photocatalyst for treatment of wide concentration range organic wastewater as well as remediation of natural waterbody.

一种新型的基于氮化碳的自清洁水凝胶光催化剂（KI-PCN 凝胶，钾和碘共掺杂的氮化碳限制在海藻酸盐中）已通过简便的方法成功构建。由于提高了载流子分离效率和提高了 KI-PCN 的光吸附能力，因此制备的光催化剂在高浓度亚甲蓝 (HMB) 上显示出增强的协同吸附-光催化降解性能。正如预期的那样，KI-PCN 凝胶显示出最高的表观速率常数值_（${钾}_{\mathit{应用程序}}$=0.0310 min ^-1 ),分别是空白水凝胶的38.8倍和5.8倍(${钾}_{\mathit{应用程序}}$=0.0008 min ^-1 ) 和 PCN 凝胶 (${钾}_{\mathit{应用程序}}$=0.0053 分钟^-1），分别。同时，KI-PCN凝胶可以持续吸附低浓度的MB（LMB），吸附MB的KI-PCN凝胶可以在光照射下自清洁。模拟真实河流的小型实验表明，KI-PCN凝胶可以有效且持续地去除LMB（0.1-20 ppm），表明去除天然河流中污染物的可能性。此外，通过结合密度泛函计算 (DFT) 和液相色谱-质谱 (LC-MS) 鉴定的中间体，提出了可能的降解途径。这项工作提出了一种新的视角来获得一种新型的自清洁且易于回收的光催化剂，用于处理宽浓度范围的有机废水以及修复天然水体。