Solar-Driven Hydrogen Production Using a BODIPY Covalent Organic Framework Hybrid Photocatalyst

The search for photoactive materials that are able to efficiently produce solar fuels is a growing research field in the current energy crisis. Here, we report the synthesis and characterization of an enamine-linked covalent organic framework (COF) based on BODIPY (IEC-1). This COF is used as a platform to prepare TiO2-based hybrid photocatalysts for solar-driven hydrogen evolution reactions. Remarkably, this hybrid system has been scaled up and evaluated in a solar reactor at semipilot plant scale. The optimized hybrid IEC-1@T-10 photocatalyst, containing 10 wt % COF loading, achieved 2.9 times higher photonic efficiency than that of bare TiO2, and even surpassed by 6.5 times the lab-scale performance, in the absence of any noble metal cocatalyst. This system also shows high stability without deactivation during three sunny days. The secret of the hybrid's success lies on its high photostability. This interesting behavior is mainly due to the synergy between inorganic and organic semiconductors that leads to a 3-fold increase in the electron-hole (e(-)/h(+)) pair lifetime compared to that of bare TiO2, in good agreement with a type II charge transfer mechanism.