Synergistic Rh1-Cu1 Dual-Atom-Site Enhancing Performance of Ethane Low-Temperature Oxidation via Auto-Selective Oxygen Source From O2/H2O.

The low-temperature direct conversion of ethane is more appealing for the utilization of shale gas. Dual-atom catalysts have attracted considerable attention due to their unique cooperative effects. Herein, we report a porous organic polymer-supported Rh1-Cu1 dual-site catalyst (Rh1-Cu1@POPs-PPh3) for the selective oxidation of ethane to ethanol, acetaldehyde, and acetic acid with auto-selective oxygen mechanism. The optimized Rh1-Cu1 centers deliver a productivity of ca. 250 mol molRh -1 h-1 based on Rh with 65% acetaldehyde selectivity at 423 K, representing a four-fold improvement over the single-Rh-site catalyst. Through isotopic labeling and in situ characterizations, we uncover an auto-selective oxygen source mechanism in which dehydrogenated species of ethane with different grades possess self-selectivity for the combined oxygen source. Oxygen species derived from O2 activate ethane and subsequently couple with the ethyl fragment to produce ethanol. While OH radicals from H2O dissociation react with ethyl intermediates from ethane dehydrogenation to yield acetaldehyde. Concurrently, oxygen species recombine with reactive hydrogen species to regenerate new H2O, completing the catalytic oxidation cycle. The density functional theory (DFT) calculations reveal that the Rh-Cl-Cu configuration lowers the lowest unoccupied molecular orbital (LUMO) energy of Rh1, thereby strengthening adsorbate-metal interactions, weakening the C─H bond, and facilitating its activation.