2D zirconium-based metal-organic framework/bismuth(III) oxide nanorods composite for electrocatalytic CO2-to-formate reduction

Electrocatalytic carbon dioxide reduction reaction (eCO2RR) represents one of the most promising technologies for sustainable conversion of CO2 to value-added products. Although metal-organic frameworks (MOFs) can be vastly functionalized to create active sites for CO2RR, low intrinsic electrical conductivity always make MOFs unfavorable candidates for eCO2RR. Besides, studies on how to regulate eCO2RR activity of MOFs from linkers' functionalities viewpoint lag far behind when compared with assembly of multinuclear metal-centered clusters. In this work, non-toxic bismuth(III) oxide (Bi2O3) was incorporated into a series of 2D MOFs (ZrLX) established from Zr-oxo clusters and triazine-centered 3-c linkers with different functionalities (LX = 1∼5) to give composites ZrLX/Bi2O3. To investigate how functionalities on linkers distantly tune the eCO2RR performance of MOFs, electron-donating/withdrawing groups were installed at triazine core or benzoate terminals. It was found that ZrL2/Bi2O3 (‒F functionalized on triazine core) exhibits the best eCO2RR performance with highest Faradaic efficiency of 96.73% at ‒1.07 V vs. RHE, largest electroactive surface (Cdl = 4.23 mF cm−2) and highest electrical conductivity (5.54 × 10−7 S cm−1), highlighting tuning linker functionalities and hence electronic structure as an alternative way to regulate eCO2RR.