Atomic Cu-O-Zr sites for highly selective production of p-xylene from tandem upcycling of PET and CO2.

Exploring an efficient catalytic system for tandem upcycling of CO2 and polyethylene terephthalate (PET) is highly desirable for achieving efficient resource utilization of wastes. However, the high activation energy for C=O bonds (in both PET and CO2) and the difficulty in regulating the reaction pathways restricted PET recovery efficiency. Here, we demonstrated the rational design of a single-atom Cu catalyst for precisely catalyzing the hydrogenation of CO2 to methanol and tandem PET upcycling to ethylene glycol (EG) and p-xylene (PX). In the Cu/UiO-66-NH2-A catalyst, Cu atoms are selectively anchored to the Zr-oxo nodes of UiO-66-NH2 to form Cu-O-Zr sites. The Cu-O-Zr sites can effectively activate both CO2 and H2 by reducing the activation energy and accelerate the transformation of PET to dimethyl terephthalate (DMT), which is further hydro-deoxygenated to yield PX. As a result, 20.4% CO2 conversion was obtained within 36 h, with 89.5% and 92.1% yields of PX and EG, respectively. Rapid and precise hydrogen spillover from Cu atoms to adsorbed reactants/intermediates at the Cu-O-Zr sites also drives the reaction process.