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 makes 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 the assembly of multinuclear metal-centered clusters. In this work, non-toxic bismuth(III) oxide (Bi₂O₃) was incorporated into a series of two-dimensional (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 is found that ZrL2/Bi₂O₃ (‒F functionalized on triazine core) exhibits the best eCO₂RR performance with the highest Faradaic efficiency (FE) of 96.73% at −1.07 V vs. RHE, the largest electroactive surface (C_dl = 4.23 mF cm⁻²) and the 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.