A rhenium catalyst with bifunctional pyrene groups boosts natural light-driven CO₂ reduction

Abstract

A rhenium–pyrene catalyst that dramatically promotes sunlight-induced CO2RR efficiency was developed by enhancing intermolecular electron transfer efficiency and visible light-harvesting ability.

Highly efficient CO2 reduction under visible-light on non-covalent Ru⋯Re assembled photocatalyst: Evidence on the electron transfer mechanism

“…4c). These results seem contradictory to what has been reported recently on the benefit effect of the pyrene-modified photosensitizer [28,29] where a higher efficiency of Ru•••ReCOPy systems (as well as for RuPy•••ReCO) is expected with respect to Ru•••ReCO.…”

“…In this context, Kubiak et al reported, recently, intramolecular ET by assembling Ru(dac)(bpy)2(PF6)2 and Re(dac)(CO)3Cl (dac = 4,4′-bis(methyl acetamidomethyl)-2,2′-bipyridine, bpy = 2,2′-bipyridine) via (-NH---O=C-) hydrogen bond interactions resulting in a substantial improvement of the CO2 conversion as compared to the combination of Re(dac)(CO)3Cl with the commercial Ru(bpy)3PF6. [26,27] Another system stabilized by π-π stacking interactions was reported, recently, by He et al, with Re[4,4′-di(pyren-1-yl)-2,2′-bipyridine](CO)3Cl (4.4'dipyrenyl-Re) as co-catalyst in the presence of Ru(bpy)3Cl2 enabling an efficient conversion of CO2 into CO. [28] This intermolecular π-π stacking was found to boost ET leading to a turnover number (TON) twice higher than that obtained using the commercial Re(bpy)CO3Cl. On the other hand, the 4.4'-dipyrenyl-Re was active for CO2 photoreduction without the photosensitizer under solar light.…”

“…It should be noted that no significant influence of the grafted pyrene group on the absorbance coefficient was observed in this work, in contrast to what has been observed when pyrene is directly linked to the bipyridine group of Re(bpy)(CO)3Cl. [28] In the last case, a significant increase in the coefficient molar absorption of the MLCT is observed in addition to the red-shift. This difference can be explained by a higher delocalization of the electron between the directly-linked pyrene and the 4,4'dipyrenyl-Regroup via a single bond.…”

Prolonging the Triplet State Lifetimes of Rhenium Complexes with Imidazole‐Pyridine Framework for Efficient CO2 Photoreduction

“…[13][14][15][16] Among metal complexes for photocatalytic CO 2 reduction reaction (CO 2 RR), the most investigated rhenium(I) tricarbonyl complexes (Re(CO) 3 ) with αdiimine ligands shows high selectivity towards carbon monoxide (CO) formation. [17][18][19][20][21][22] One of advantages with [Re-(CO) 3 (diimine)Cl] complexes is the well-defined structure able to design intentionally, which offers the possibility to enhance the visible light absorption ability and excited (triplet) state lifetime through ligand designing and optimization. [23][24][25][26][27][28] In general, with long excited triplet (T1) lifetime, photocatalysts could have enough time to realize electron transfer between different components so as to dramatically improve the activity.…”

“…Although most of the photocatalytic CO 2 RRs employing Re(CO) 3 unit focus on regulating various bipyridine ligands, [17][18][19][20][21][22] Re(CO) 3 with imidazole-pyridine framework (hereafter referred as Re(CO) 3 ImÀ Py) for photocatalytic CO 2 reduction has not been reported to date. [31] Firstly, the photophysical properties of the Re(CO) 3 ImÀ Py complexes are different from that with the bipyridine ligand, mainly due to the fact that imidazole is more electron-rich than pyridine and the bipolar properties of 1,3imidazole based on two nitrogen atoms with different bonding patterns.…”