<p>The photocatalytic reduction of CO₂ to syngas (a mixture of CO and H₂) is a crucial approach to realizing industrial Fischer-Tropsch Synthesis (FTS) and carbon neutrality. However, achieving efficient syngas production remains a critical challenge due to the severe limitation by the rapid recombination of photogenerated charge carriers. Herein, we propose a solvent-induced defect engineering strategy to fabricate a nitrogen vacancy (N_v)-modified Fe₃O₄ catalyst (Fe₃O₄-N_v-12h). Under visible light irradiation (<i>γ</i> ⩾ 420 nm), Fe₃O₄-N_v-12h exhibits exceptional photocatalytic performance, achieving a total syngas production rate of 43.55 mmol g⁻¹ h⁻¹ with a nearly 1:1 CO/H₂ ratio. This productivity represents an 805.2-fold higher than the performance of pristine Fe₃O₄ and surpasses reported state-of-the-art photocatalytic CO₂-to-syngas systems operating at this ratio. Electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) characterizations confirm that N_v introduction modulates the electronic structure of Fe₃O₄ by acting as efficient electron traps to suppress recombination and promote transport of photogenerated charge carriers. <i>In situ</i> Fourier transform infrared (FTIR) spectroscopy identifies *COOH and *CO species as key intermediates for CO formation in syngas. This work establishes an effective nitrogen vacancy modification strategy for effective photocatalytic CO₂ conversion to syngas and offers novel strategies for the development of high-performance catalysts.</p>