Induced CO₂ Electroreduction to Formic Acid on Metal−Organic Frameworks via Node Doping

Abstract

Metal−organic frameworks (MOFs), combining the advantages of heterogeneous and homogeneous components, have been explored as catalytic materials for the CO2 electroreduction reaction (CO2ERR). However, the unmatched metal nodes result in MOFs having lower faradaic efficiencies (FEs) and limited current densities in CO2ERR. Herein, we report a general strategy to promote activities of MOFs via node doping in CO2ERR. With ion exchange, an active tin node was doped into zeolitic imidazolate framework‐8 (ZIF‐8) to facilitate the reduction kinetics of CO2. The divalent Sn2+ node accelerates the formation of formic acid (HCOOH), resulting in the highest HCOOH FE of 74 % and total current density (Jtotal) of 27 mA/cm2 at −1.1 V (vs. reversible hydrogen electrode, RHE) over 0.6 wt% Sn‐doped ZIF‐8 with stable catalytic performance after seven reuse cycles, which is clearly better compared to the catalytic properties of pristine ZIF‐8 (FEHCOOH=0 %, Jtotal=13 mA/cm2). This work opens an avenue for promoting the CO2ERR performance of MOFs by node doping.

Synthetic strategies for MOF-based single-atom catalysts for photo- and electro-catalytic CO2 reduction

“…Geng and collaborators utilize node metal ion exchange strategy to prepare an Sn-doped ZIF-8 (Geng et al, 2020). The doping method is also a good method for introducing two metals at the same time.…”

Gas-phase CO2 electroreduction over Sn–Cu hollow fibers

“…3, although the Cu HF electrode itself shows some electrochemical active for gas-phase CO 2 reduction to multicarbon products, the current density and their faradaic efficiencies are much lower compared to the Sn-modified electrodes. Introducing Sn species into aqueous CO 2 electroreduction usually promote the formation of HCOOH [24][25][26][27][28] , while during gas-phase CO 2 electroreduction, SnO 2 nanoparticles on Cu surface play more important roles. The HCOOH species facilitated by virtue of SnO 2 are further converted into *CHO intermediate at the SnO 2 /Cu interfacial, which subsequently dimerize into C2 intermediate glyoxal (CHO) 2 .…”

“…27 Geng et al found the Sn 2+ node in ZIF-8 can accelerate the HCOOH formation with a FE of 74 % and a total current density of 27 mA cm -2 . 28 These findings witnessed the great promotion of HCOOH formation by introducing of Sn species in aqueous CO 2 electroreduction. However, during gas-phase CO 2 electroreduction, SnO 2 nanoparticles on HF surface would play more important roles beyond facilitating to produce HCOOH species.…”

“…The porous Cu HF electrode is applied as a selfsupported gas-diffusion electrode, while its surface is modified by Sn component via wet chemistry reduction with sodium citrate as stabilizing agent and sodium borohydride (NaBH 4 ) as reductive agent (see the supplementary information for details). The Sn-based catalysts always help the formation of formate [24][25][26][27][28] , while Cu-based catalysts are famous for the potential to promote C-C coupling and C 2 products formation, such as ethylene and ethanol 8,[29][30][31] . The loadings of Sn element in Sn-Cu HFs are controlled by varying the molar ratio between SnCl 2 precursor and Cu HF.…”

Fixing carbon dioxide in situ during ethanol production by formate dehydrogenase

“…52 In a previous report, ZIF-8 was employed in the CO 2 electroreduction reaction by FDH and played an important role in increasing the CO 2 dissolvability. 53 There is also information on the application of ZIF-8 in living cells. The addition of ZIF-8 promoted CO 2 reduction by 72.9% compared to the condition without ZIF-8 by Arthrospira platensis cells.…”