Transition Metal-Based Perovskite Derivatives for Selective CO₂ Photoreduction: Role of Orbital Occupancy

Transition metals are renowned for their effective catalytic properties. Incorporating transition metals into halide perovskite derivatives is a key strategy for tuning the properties of perovskites to enhance their photocatalytic performance. Understanding the d-orbital occupancy and spin activity of these transition metals in the CO₂ photoreduction process is essential for fully realizing the photocatalytic potential of these materials. In this study, layered perovskite derivatives are synthesized using cobalt (Co) and copper (Cu) as transition metal components. We observed that Cu and Co exhibit complementary absorption properties attributed to their d-orbital configuration. Additionally, (DMAP)₂CuCl₄ (DMAP = 4-Dimethylaminopyridine) exhibited the highest performance in CO₂ photoreduction with remarkable selectivity for CH₄ formation (≈97%). Pressure-dependent experiments showed that higher pressures enhance catalytic activity by improving CO₂ saturation and adsorption, accelerating the reaction rate and boosting product yield. The ferromagnetism, hysteresis, and strong spin species detection of (DMAP)₂CuCl₄ enhance carrier separation and charge availability, boosting CO₂ conversion efficiency. Further, the first-principles-based atomistic computations reveal that a more delocalized conduction band edge makes mobile electrons available for CO₂ reduction in (DMAP)₂CuX₄. These findings guide the design of selective CO₂ reduction photocatalysts and highlight layered perovskite derivatives for sustainable energy solutions.