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Photocatalytic CO2 reduction is one of the best solutions to solve the global energy crisis and to realize carbon neutralization. The tetradentate phosphine‐bipyridine (bpy)‐phosphine (PNNP)‐type Ir(III) photocatalyst, Mes‐IrPCY2, was reported with a high HCOOH selectivity but the photocatalytic mechanism remains elusive. Herein, we employ electronic structure methods in combination with radiative, nonradiative, and electron transfer rate calculations, to explore the entire photocatalytic cycle to either HCOOH or CO, based on which a new mechanistic scenario is proposed. The catalytic reduction reaction starts from the generation of the precursor metal‐to‐ligand charge transfer (3MLCT) state. Subsequently, the divergence happens from the 3MLCT state, the single electron transfer (SET) and deprotonation process lead to the formation of one‐electron‐reduced species and Ir(I) species, which initiate the reduction reaction to HCOOH and CO, respectively. Interestingly, the efficient occurrence of proton or electron transfer reduces barriers of critical steps. In addition, nonadiabatic transitions play a nonnegligible role in the cycle. We suggest a lower free‐energy barrier in the reaction‐limiting step and the very efficient SET in 3MLCT are cooperatively responsible for a high HCOOH selectivity. The gained mechanistic insights could help chemists to understand, regulate, and design photocatalytic CO2 reduction reaction of similar function‐integrated molecular photocatalyst. [ABSTRACT FROM AUTHOR]

Photocatalytic CO2 reduction is one of the best solutions to solve the global energy crisis and to realize carbon neutralization. The tetradentate phosphine‐bipyridine (bpy)‐phosphine (PNNP)‐type Ir(III) photocatalyst, Mes‐IrPCY2, was reported with a high HCOOH selectivity but the photocatalytic mechanism remains elusive. Herein, we employ electronic structure methods in combination with radiative, nonradiative, and electron transfer rate calculations, to explore the entire photocatalytic cycle to either HCOOH or CO, based on which a new mechanistic scenario is proposed. The catalytic reduction reaction starts from the generation of the precursor metal‐to‐ligand charge transfer (3MLCT) state. Subsequently, the divergence happens from the 3MLCT state, the single electron transfer (SET) and deprotonation process lead to the formation of one‐electron‐reduced species and Ir(I) species, which initiate the reduction reaction to HCOOH and CO, respectively. Interestingly, the efficient occurrence of proton or electron transfer reduces barriers of critical steps. In addition, nonadiabatic transitions play a nonnegligible role in the cycle. We suggest a lower free‐energy barrier in the reaction‐limiting step and the very efficient SET in 3MLCT are cooperatively responsible for a high HCOOH selectivity. The gained mechanistic insights could help chemists to understand, regulate, and design photocatalytic CO2 reduction reaction of similar function‐integrated molecular photocatalyst. [ABSTRACT FROM AUTHOR]

Photosensitization associated with electron/energy transfer represents the central science of natural photosynthesis. Herein, we proposed a protocol to dramatically improve the sensitizing ability of metal–organic frameworks (MOFs) by switching their excited state distribution from 3MLCT (metal‐to‐ligand charge transfer) to 3IL (intraligand). The hierarchical organization of 3IL MOFs and Co/Cu catalysts facilitates electron transfer for efficient photocatalytic H2 evolution with a yield of 26 844.6 μmol g−1 and CO2 photoreduction with a record HCOOH yield of 4807.6 μmol g−1 among all the MOF photocatalysts. Systematic investigations demonstrate that strong visible‐light‐absorption, long‐lived excited state and ingenious multi‐component synergy in the 3IL MOFs can facilitate both interface and intra‐framework electron transfer to boost photocatalysis. This work opens up an avenue to boost solar‐energy conversion by engineering sensitizing centers at a molecular level. [ABSTRACT FROM AUTHOR]

Photosensitization associated with electron/energy transfer represents the central science of natural photosynthesis. Herein, we proposed a protocol to dramatically improve the sensitizing ability of metal–organic frameworks (MOFs) by switching their excited state distribution from 3MLCT (metal‐to‐ligand charge transfer) to 3IL (intraligand). The hierarchical organization of 3IL MOFs and Co/Cu catalysts facilitates electron transfer for efficient photocatalytic H2 evolution with a yield of 26 844.6 μmol g−1 and CO2 photoreduction with a record HCOOH yield of 4807.6 μmol g−1 among all the MOF photocatalysts. Systematic investigations demonstrate that strong visible‐light‐absorption, long‐lived excited state and ingenious multi‐component synergy in the 3IL MOFs can facilitate both interface and intra‐framework electron transfer to boost photocatalysis. This work opens up an avenue to boost solar‐energy conversion by engineering sensitizing centers at a molecular level. [ABSTRACT FROM AUTHOR]

In recent years, much attention has been paid to γ-graphynes due to their high potential in practical applications. The unique combination of sp2–sp carbon atoms, an extended π-conjugated structure and evenly distributed dehydrobenzo[n]annulene pores provide excellent performance of γ-graphynes in gas separation, water purification, sensors, and catalysis. In this work, we report the ground and excited state properties of γ-graphyne, γ-graphdiyne, and γ-graphtriyne and their non-covalent complexes with fullerenes. Our results demonstrate that the non-covalent complexes are stable and exhibit low mobility of C 60 across the graphtriyne sheet. The electron-withdrawing ability of these materials is enhanced by passing from γ-graphyne to γ-graphtriyne, which assists in photoinduced electron transfer from endohedral fullerenes to graphyne. The process is found to occur on a sub-nanosecond time scale in the complexes of γ-graphdiyne and γ-graphtriyne with Sc 3 N@C 80. These theoretical results provide useful insights for the development of carbon materials for photovoltaic applications. [Display omitted] • Electron-withdrawing character of γ-graphyne materials is enhanced when moving from γ-graphyne to γ-graphtriyne. • Extended acetylene linkages between phenyl rings reduce the movement of fullerene over γ-graphyne surface. • Photoinduced electron transfer in the complexes of γ−graphyne with fullerene is facilitated by replacing C 60 with Sc 3 N@C 80. • Lowest charge transfer states correspond to the electron transfer from endohedral fullerene to γ-graphyne. [ABSTRACT FROM AUTHOR]

[Display omitted] • electronic properties of γ-graphyne cluster models converge rapidly. • electronic properties of γ-graphyne clusters have a low dependence on vacancy defects. • γ-graphyne is an efficient electron acceptor (low LUMO and ability to delocalize excess charge). • photoinduced electron transfer from electron donors to γ-graphyne is efficient and fast. The search for new materials is constantly ongoing. Recently, a two-dimensional carbon allotrope , γ-graphyne , has been synthesized with a unified crystalline structure. Because of its low LUMO and excellent electron mobility, it appears to be a promising electron acceptor for photovoltaic applications. Here we report an analysis of the electronic properties of model van der Waals complexes of γ-graphyne with several partners of different electronic nature. We show that photoinduced electron transfer from electron-donating partners to γ-graphyne is favorable and occurs on nano to picosecond time scale. In contrast, electron transfer from γ-graphyne to strong electron acceptors is unlikely. Our results open perspectives for the future application of γ-graphyne in photovoltaic devices. [ABSTRACT FROM AUTHOR]

Photoenzymes use light to initiate biochemical reactions. Although rarely found in nature, their study has advanced understanding of how light energy can be harnessed to facilitate enzyme catalysis, which is also of importance to the design and engineering of man-made photocatalysts. Natural photoenzymes can be assigned to one of two families, based broadly on the nature of the light-sensing chromophores used, those being chlorophyll-like tetrapyrroles or flavins. In all cases, light absorption leads to excited state electron transfer, which in turn initiates photocatalysis. Reviewed here are recent findings relating to the structures and mechanisms of known photoenzymes. We highlight recent advances that have deepened understanding of mechanisms in biological photocatalysis. [ABSTRACT FROM AUTHOR]