Self-Sustained Hydrogen Relay Enables Thermodynamically Coupled Cyclohexane-CO2 Conversion to Aromatics over Tandem Catalysts.

Naphthenes constitute major components of naphtha, yet their conversion to aromatics via dehydrogenation remains thermodynamically constrained and energy-intensive. Here we report a thermodynamically coupled strategy that integrates endothermic cyclohexane dehydrogenation with exothermic CO2 hydrogenation, enabling thermodynamically compensated aromatization under mild conditions. Using a tandem Pd@S-1 and ZnZrOx/ZSM-5 catalyst, cyclohexane dehydrogenation, CO2 activation, and methanol-mediated alkylation are synergistically coupled within a hydrogen-shuttling network. Under continuous-flow conditions (370 °C, 3 MPa), the system achieves 99% cyclohexane conversion and 99% aromatics selectivity with 38% CO2 conversion. Operando X-ray absorption spectroscopy (XAS) reveals dynamic Pd0/PdO interconversion, while Zn-O-Zr sites remain structurally stable to facilitate CO2 activation. 13CO2 isotopic tracing confirms direct incorporation of CO2-derived carbon into aromatic products. This work establishes a hydrogen shuttle-enabled thermochemical paradigm for coupling endothermic and exothermic reactions, offering an energy-efficient route for naphthene upgrading and CO2 valorization.