Water-Soluble Polymeric Carbon Nitride Colloidal Nanoparticles for Highly Selective Quasi-Homogeneous Photocatalysis

Abstract

Heptazine‐based polymeric carbon nitrides (PCN) are promising photocatalysts for light‐driven redox transformations. However, their activity is hampered by low surface area resulting in low concentration of accessible active sites. Herein, we report a bottom‐up preparation of PCN nanoparticles with a narrow size distribution (ca. 10±3 nm), which are fully soluble in water showing no gelation or precipitation over several months. They allow photocatalysis to be carried out under quasi‐homogeneous conditions. The superior performance of water‐soluble PCN, compared to conventional solid PCN, is shown in photocatalytic H2O2 production via reduction of oxygen accompanied by highly selective photooxidation of 4‐methoxybenzyl alcohol and benzyl alcohol or lignocellulose‐derived feedstock (ethanol, glycerol, glucose). The dissolved photocatalyst can be easily recovered and re‐dissolved by simple modulation of the ionic strength of the medium, without any loss of activity and selectivity.This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Projektnummer 364549901—TRR 234 [Projects B6, B7, C3 and Z2] and BE 5102/3‐1. We acknowledge also support by Spanish MINECO (MAT2016‐78155‐C2‐1‐R) and Gobierno del Principado de Asturias (GRUPIN‐ID2018‐170), and the project CICECO‐Aveiro Institute of Materials, FCT Ref. UID/CTM/50011/2019, financed by national funds through the FCT/MCTES. L.M., M.S., and M.I. also acknowledge the National NMR Network (PTNMR), partially supported by Infrastructure Project N° 022161, and FCT/MCTES for funding (Project PTDC/QEQ‐QAN/6373/2014). B.K. acknowledges the University of Iceland Research Fund for support through a PhD fellowship. Computational resources were provided by the state of Baden‐Württemberg through bwHPC and the German Science Foundation (DFG) under Grant No. INST 40/467‐1 FUGG. C.N. and A.T. acknowledge financial support of the DFG through the project TU 149/8‐2 “Towards photo‐active membranes for artificial photosynthesis” as well as the DFG through a research infrastructure grant INST 275/257‐1 FUGG. I.K. acknowledges the support of the Alexander von Humboldt Foundation through the Humboldt Research Fellowship.Peer reviewe