Comparative Studies in the Hydrogenolysis Cleavage of C–O and C–C Bonds in Aromatic Plastics over a Metal-free Nb ₂ O ₅ Catalyst

Upcycling and recycling waste plastics into valuable chemical products and fuels have emerged as a potentially viable strategy to address the depletion of fossil energy resources and escalating energy demand. C–O and C–C bonds are fundamental linkages in aromatic plastics, and the precise activation and cleavage of C–O and C–C bonds are highly desired. Herein, we study the hydrogenolysis cleavage of C–O and C–C bonds in aromatic plastics by using a metal-free Nb 2 O 5 catalyst. Hydrogenolysis cleavage of the C sp2 –C sp3 bond in oxygen-free plastics like polystyrene (PS) is feasible, while hydrogenolysis cleavage of the C–O bond in polyethylene terephthalate (PET) and poly(phenylene oxide) (PPO) is not. Electron paramagnetic resonance (EPR), X-ray absorption near-edge structure (XANES), temperature-programmed desorption (TPD), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reveal that the excessive adsorption of the C–O bond on the Nb 2 O 5 catalyst surface leads to the coverage of active sites for hydrogen dissociation, thereby preventing the hydrogenolysis cleavage of C–O bonds. Furthermore, future directions for the hydrogenolysis cleavage of the C–O bond on metal-free Nb 2 O 5 catalysts are provided. This study facilitates the development of economical and high-performance metal-free catalysts.