(a) (b) The Ishitani research group has proposed a novel and efficient photocatalytic CO 2 reduction method utilizing Cu + diamine complexes as photosensitizers and Fe 2+ diamine complexes as catalysts . A heteroleptic Cu(I) diamine complex with both diamine and phosphine ligands has been chosen as the photosensitizer due to its longer lifetime and stronger oxidation state at higher energy levels. Although halide perovskite quantum dots (QDs) are promising optoelectronic materials for LED and photovoltaic devices, their stability is compromised in polar solvents or in the presence of moisture, hindering their use in photocatalytic processes. However, organicinorganic halide perovskites exhibit a high extinction coefficient, wide absorption ranges, and low electron-hole diffusion lengths . CsPbBr3 QDs, as a stable halide perovskite material, along with CsPbBr3 QD/graphene oxide composites, have been investigated by the Kuang group as photocatalysts for CO 2 reduction to ethyl acetate. This research represents the first artificial photosynthesis approach based on halide perovskite QDs. QD/GO photocatalyst. Quantum dots are highly effective photocatalysts due to their high surface area and short charge transfer pathways. In the study conducted by the Kuang group, ethyl acetate was chos en as the solvent because of its mild polarity, which stabilizes the CsPbBr3 quantum dots, and its high solubility for CO 2 . The selectivity for CO 2 reduction was observed to be greater than 99%, highlighting the preference for halide perovskite materials over conventional metal oxide semiconductors. Ground state CO 2 reduction can be explained by the concept of frustrated Lewis pairs (FLPs) . Despite the high cost of In2O3, it is considered an effective photocatalyst due to its superior chemical stability under light . The photocatalytic activity of carbon -coated In2O3 Nanobelts was studied by the Goodenough group. In2O3 generates CO 2 -from CO 2 , which acts as a key species in the reduction process. Additionally, the reduction potential of In2O3 ( -0.62V) is sufficient for the conversion of CO 2 to CO (-0.53V) and CH 4 (-0.24V) . In2O3 exhibits a greater affinity for H 2 generation and lower activity for carbon-related products in the photocatalytic reduction of carbon dioxide with water. The coating of carbon on In2O3 nanobelts enhances its photocatalytic activity for CO 2 reduction to CO and CH 4 , using water as a reductant and Pt nanoparticles as a co-catalyst, as summarized by the Goodenough group in their article. The carbon coating induces a higher eagerness for absorbing visible light, separates photoinduced electron-hole pairs, and suppresses proton reduction to H 2 . These are the stepwise processes for CO 2 reduction to CO and CH 4 .