• • The NSC-Mo-0.5-30% catalyst achieves 81.3% methanol conversion at 220 °C, with 58.7% overall DMMx selectivity and 11.3% DMM2–6 selectivity, demonstrating a viable one-step route for producing diesel additives from methanol.
• • Molybdenum doping increases weak Lewis acid site density, while sulfuric acid impregnation introduces gradient-distributed Brønsted acid sites and raises Mo5+/Mo6+ redox pair content, enabling synergistic oxidation and C–O chain growth.
• • The catalyst design balances oxidation depth and chain growth, addressing the bottleneck of over-oxidation to COx or under-chain-growth to DMM1, as evidenced by the significant DMM2–6 fraction.
• • The study provides a new approach for constructing multifunctional active sites in NASICON materials, offering a foundation for industrial scale-up of direct methanol-to-DMMx processes.