<p>As a vital industrial feedstock, carbon monoxide (CO) is widely employed in pharmaceutical, electronic and fine chemical synthesis, yet its efficient production in high purity remains challenging. Here we report a solar-driven route to high-purity CO from formic acid using a nonmetallic plasmonic photocatalyst based on aluminum-doped tungsten oxide (Al-W₁₈O₄₉). Plasmon-derived hot electrons drive the cleavage of C-H in adsorbed formic acid, while a concomitant photothermal effect markedly accelerates the overall kinetics. This synergistic mechanism lowers the apparent activation energy of HCOOH dehydration to 10.5 kJ mol⁻¹, substantially below its thermocatalytic barrier of 80.6 kJ mol⁻¹, and enables a CO production rate of 1.88 mol g⁻¹ h⁻¹ under 1 W cm⁻² irradiation. A continuous-flow reactor operated stably for 350 hours, delivering CO at a maximum rate of 2000 L m⁻² h⁻¹ under concentrated sunlight. This work develops a practical photocatalytic system for the sustainable production of high-purity CO.</p>