Single-atom Ru coupled with AlCl3 to promote asymmetric C-C coupling between CH4 and CO2.

Direct synthesis of acetic acid from CH4 and CO2 offers a sustainable strategy to utilize these byproducts co-existed in many anthropogenic scenarios with 100% atom efficiency and mitigate greenhouse effect. But this reaction remains a grand challenge due to chemical inertness of two reactants and sluggish kinetics of C-C coupling. Herein, we propose a bifunctional catalyst design, consisted of metal and Lewis acid, to activate CH4 and CO2 via nucleophilic and electrophilic attacks, respectively, which generating two intermediates with opposite electron properties and promote asymmetric C-C coupling. To achieve this, a rational design with "six-step" screening predicts an efficient catalyst, i.e., Keggin-type phosphotungstic acid supporting equimolar single-atom ruthenium and aluminum chloride. Then we synthesize and demonstrate this catalyst with the activity with TOF of 19.3 h-1 and acetic acid selectivity of 95.7%. In situ infrared spectroscopy and theoretical studies reveal a Langmuir-Hinshelwood mechanism for C-C coupling with a low barrier of 14.03 kcal mol-1. Specifically, CO2 activation by AlCl3 via SE2 process yields a positively charged state, which readily interacts with the negatively charged *CH3 from CH4 activation.