Defective materials for CO₂ photoreduction: From C₁ to C₂₊ products

Photocatalytic CO₂ conversion to carbon-based products has been proven as a versatile method to manage carbon balance. Engineering defects into photocatalysts is an effective strategy to maneuver their performance for CO₂ reduction. This critical review summarizes the advantages, state-of-the-art progress, remaining challenges, and perspectives regarding defective materials for CO₂ photoreduction, especially based on two-dimensional materials. Different types of defects are employed to tailor the electronic structure, atomic coordination configuration, carrier concentration or electrical conductivity for CO₂ photoreduction, namely anion vacancies, cation vacancies, vacancy pairs, planar defects and volume defects. The strategies for defect construction, defect identification are summarized. The key roles of various defects for CO₂ photoreduction from various aspects are presented, such as light absorption and electronic structure, charge separation and transfer, reactant adsorption and activation, reaction energy barriers, reaction pathways. Especially, the C[sbnd]C coupling via defect engineering is highlighted, certainly shows greater potentiality for future CO₂ photoreduction. Finally, major challenges and opportunities regarding the future exploration of defective materials for CO₂ photoreduction are presented.