<p>The increasing release of nitrogen oxides (NOx) is a serious risk to human and environmental health, and thus, the stringent scrutiny and application of clean and highly efficient NOx remediation technologies are required. To support this, photocatalytic remediation has become a promising method, and oxygen vacancies (OVs) have become crucial in the activity of the immobilised bismuth catalysts. This review offers an extensive summary of the new advances achieved in the engineering of OVs into complex Bi-based photocatalysts to deliver highly efficient NOx reduction. The major approaches that are discussed in terms of their ability to create controlled OV populations are thermal treatment, chemical reduction, atomic-scale accuracy, and radiation. The relationships between structure and properties of OV incorporation, synergistic metal or elemental doping, light absorption promotion, charge separation enhancement, and surface redox acceleration and morphological changes, including heterojunction construction, plasmonic nanoparticle loading, and elemental doping, are explained. Spectroscopic and computational analyses explain the mechanisms through which NOx undergoes activation and transformation into nitrates by the mechanisms of adsorption, activation, and transformation of NOx. Lastly, the review determines key challenges, viable aspects, and future perspectives of translating these sophisticated photocatalysts to scalability, functionality, and real-world application of removing NOx in the world.</p>