Phenanthroimidazole-Based Covalent Organic Frameworks with Enhanced Activity for the Photocatalytic Hydrogen Evolution Reaction

Abstract

The rational design of organic semiconductors based on crystalline covalent organic frameworks (COFs) as efficient photocatalysts is highly desirable. In this study, the first example of phenanthroimidazole-based COFs is reported: PIm-COF1 with an imine linkage and PIm-COF2 with a β-ketoenamine-linkage. Both COF materials showed substantial optical properties. The average hydrogen evolution rate was 7417.5 μmolg −1 h −1 for PIm-COF2, which was 14 times higher than that of PIm-COF1 (528.5 μmolg −1 h −1 ). This can be attributed to the strong donor− acceptor effect of PIm-COF2 and the continuous separation and transfer of the photoexcited electron−hole pair from the phenanthro[9,10-d] imidazole moiety which are verified by timedependent density functional theory and excitation state analysis.

Photocatalytic Hydrogen Peroxide Production through Functionalized Semiconductive Metal–Organic Frameworks

“…We further assessed the dissociation efficiency of the electron–hole pairs using electrochemical impedance spectroscopy (EIS). Nyquist plots showed reduced charge transport resistance after light irradiation for all samples, likely due to the increased charge density by photoexcitation (Figure b) . More importantly, the decrease in transport resistance for EFB-MOF was most pronounced among the samples, indicating a very rapid photoinduced charge transport capability by efficient exciton separation.…”

“…Nyquist plots showed reduced charge transport resistance after light irradiation for all samples, likely due to the increased charge density by photoexcitation (Figure 5b). 58 More importantly, the decrease in transport resistance for EFB-MOF was most pronounced among the samples, indicating a very rapid photoinduced charge transport capability by efficient exciton separation. These results align with the calculated exciton binding energy, emphasizing the pivotal role of fluorine in enhancing the photocatalytic efficiency, which was enabled by our material platform.…”

Recent advances on covalent organic frameworks (COFs) as photocatalysts: different strategies for enhancing hydrogen generation

“…Adopting this strategy, a variety of COFs have been prepared. [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] For example, Yang et al designed PETZ-COF via the solvothermal reaction of electron-donating 4PE-4NH 2 and electron-deficient TZTZ-2BA for photocatalytic H 2 generation. As a comparison, a COF (PEBP-COF) without D-A moieties was also constructed using 4PE-4NH 2 to react with BP-2BA (Fig.…”

Low-temperature synthesis of porous organic polymers with donor–acceptor structure and β-ketoenamine for photocatalytic oxidative coupling of amines

“…Enhancing photocatalytic performance involves constructing a Donor (D)-Acceptor (A) structure within the photocatalyst, facilitating the spontaneous transfer of charges from D to A. 27,28 Previous research has demonstrated that D-A structures effectively reduce the band gap, enhance charge transfer rates, and prolong carrier lifetimes. [29][30][31] Additionally, incorporating π units can impact the electron acceptor domain, expediting charge transfer and the migration of photoexcited electrons.…”