Metal-Free Z‑Scheme aza-CMP/C₂N Heterostructure to Facilitate Photocatalytic CO₂ Reduction: A Computational Study

Inspired by photosynthesis in nature, Z-scheme heterostructures have attracted increasing attention due to their narrow forbidden bandwidth and strong redox capability. Herein, by means of density functional theory (DFT) computations, a metal-free Z-scheme aza-CMP/C₂N heterostructure was proved to be an effective CO₂ reduction reaction (CO₂RR) photocatalyst. Compared with aza-CMP and C₂N, aza-CMP/C₂N has excellent photocatalytic activity due to its narrow band gap and strong light absorption capacity. By calculating the free energy change during the CO₂ reduction process, we found that aza-CMP/C₂N can catalyze CO₂ reduction to CH₄ and CH₃OH, among which CO₂ → COOH* is the rate-determining step with a ΔG of 0.58 eV. Therefore, the Z-scheme aza-CMP/C₂N heterostructure is expected to be an excellent metal-free catalyst for photocatalytic CO₂ reduction.