Ultra‐Nanostructured Phenazine Conjugated Porous Polymers as Efficient Photocatalyst for Solar‐Driven Hydrogen Production

Abstract Herein, the synthesis of a phenazine‐based ultrananostructured conjugated porous polymer (UN_IEP‐27) is described, using high‐performance microfluidic techniques (HPMT). This approach enables the obtention of small particle sizes, high homogeneity, good dispersibility, large surface areas, and therefore improved processability. The phenazine moiety provides redox‐active sites to the polymer. These features allow the fabrication of high‐quality thin films for photoelectrochemical characterization and, more importantly, significantly enhance the photocatalytic performance of its TiO 2 hybrid. The hybrid material, UN_IEP‐27@T10 (10 wt.% polymer), reaches hydrogen evolution rates of 4.1 mmol g − ¹ h − ¹ (ƺ = 1.52%) under laboratory conditions, and 0.11 mmol g − ¹ h − ¹ (ƺ = 0.58%) at solar‐pilot scale representing 51‐fold and 5.5‐fold improvements over bare TiO 2 , respectively. Moreover, after repeating the experiments under inert atmosphere for consecutive days, the activity increases, reaching up to 4.8 mmol g − ¹ h − ¹ (ƺ = 1.76%) and 0.34 mmol g − ¹ h − ¹ (ƺ = 1.81%) at lab and pilot scale, respectively. This behavior is attributed to the redox cycling of the phenazine unit, which undergoes reversible transitions between phenazine and its more photoactive form, dihydrophenazine. These results stand among the best reported for conjugated porous polymer (CPP)‐based hybrids for hydrogen photocatalysis.