Ultrafast charge transfer dynamics in 2D covalent organic frameworks/Re-complex hybrid photocatalyst

Abstract

Rhenium(I)-carbonyl-diimine complexes have emerged as promising photocatalysts for carbon dioxide reduction with covalent organic frameworks recognized as perfect sensitizers and scaffold support. Such Re complexes/covalent organic frameworks hybrid catalysts have demonstrated high carbon dioxide reduction activities but with strong excitation energy-dependence. In this paper, we rationalize this behavior by the excitation energy-dependent pathways of internal photo-induced charge transfer studied via transient optical spectroscopies and time-dependent density-functional theory calculation. Under band-edge excitation, the excited electrons are quickly injected from covalent organic frameworks moiety into catalytic RheniumI center within picosecond but followed by fast backward geminate recombination. While under excitation with high-energy photon, the injected electrons are located at high-energy levels in RheniumI centers with longer lifetime. Besides those injected electrons to RheniumI center, there still remain some long-lived electrons in covalent organic frameworks moiety which is transferred back from RheniumI. This facilitates the two-electron reaction of carbon dioxide conversion to carbon monoxide.

PtS quantum dots/Nb2O5 nanosheets with accelerated charge transfer for boosting photocatalytic H2 production

“…4f, PtS/Nb 2 O 5 (6073.75 ps) shows a shorter average lifetime of photogenerated carriers compared to Nb 2 O 5 nanosheets (6634.05 ps), further illustrating that the quantum-dot-structured PtS cocatalyst can efficiently accelerate the disjunction and transfer of charges. 55–58 This is supported by the results of time-resolved fluorescence decay spectra (Table S5 and Fig. S6 in the ESI†).…”

Regulating Excitonic Effects in Covalent Organic Frameworks to Promote Free Charge Carrier Generation

“…However, the TA spectra of Tz-COF-3 clearly showed a fast decay (within 1 ps) of the PIA feature and the emergence of a long-lived and negative signal, which decayed in >1 ns. One possible explanation was the excited-state transformation from a normal exciton state to a polaron state and then forming long-lived free charge carriers. − Moreover, the dynamic behaviors of free charge carriers were simulated by NAMD with an electron distribution in CBM transferring to VBM in Tz-COFs. The lifetime of photogenerated free electrons in Tz-COF-3 was found to be distinctly prolonged compared to those of Tz-COF-1 and Tz-COF-2 (Figure S28).…”

Metalated covalent organic frameworks: from synthetic strategies to diverse applications

“…Briefly, post-synthetic metalation is a general and versatile method for 2,2′-bipyridine-COF metalation that has been widely used for the synthesis of metalated 2,2′-bipyridine-COFs, as summarized in Table 2. 136,141,146,229–254…”

“…Examples of metalated COF-based photocatalytic CO 2 RR to CO are summarized in Table 7 to provide a direct and clear understanding of the structure–function relationship of metalated COF-based photocatalysts. 141,186,187,212,240,241,251,575,601–605,607–613…”