The Catalyst Review April 2024 - 15

A Bismuth-Based Zeolitic Organic Framework with Coordination-Linked Metal Cages for Efficient
Electrocatalytic CO2
Reduction to HCOOH
Electrochemical reduction of CO2
(CO2RR) to produce high value-added chemicals provides a promising approach for reducing CO2
Among reported electro-catalysts, Bi-based electrodes are promising materials for reduction CO2
to formic acid (HCOOH) with Faradaic efficiency as high as 91%.
reduction potential, low toxicity and rich materials availability. Efforts to enhance productivity have focused on the use of zeolitic metal-organic
frameworks (ZMOFs) catalysts although many of these materials suffer from either decreased stability during catalysis processes or low activity due
to inadequate active sites. Herein, the authors report the use of a novel bismuth-based zeolite-like metal−organic framework (Bi-ZMOF) capable
of reducing CO2
Figure 1. Schematic illustration of metal-organic cube, linkage, and ACO topology from
inorganic zeolites to ZMOFs , and BiZMOFs reported in this work.
The preparation of ZMOFs involves
the use of a tetra-coordinate metal
center and organic linker. The
tetrahedral metal (M) centers are
coordinated by nitrogen atoms in
the 1,3-positions of the imidazolate
(Im) bridging ligand, giving rise
to many three-dimensional open
frameworks with structures akin to
aluminosilicate zeolites. By using
pyrazole-3,5-dicarboxylic acid as
the ligand, these workers were able
to prepare a Bi-ZMOF (denoted
PZH-1) which exhibits a novel
3D crystalline open framework
featuring an ACO topological
crystal structure with strong
coordination bonding between the
Bi-based cages (Figure 1).
The electrocatalytic CO2
reduction
reaction (CO2RR) to produce formic
acid was then carried out using asprepared
PZH-1 employing cyclic
voltammetry (CV) and linear sweep
voltammetry (LSV) to measure
current densities. Compared with
tests conducted in an argon (Ar)
atmosphere, PZH-1 delivered much
higher current densities under a
CO2
2a) and CV thus exhibiting obvious
CO2
atmosphere by LSV (Figure
RR activities.
To further analyze the reduction
products, controlled potential
electrolysis of CO2
and
Figure 1. Schematic illustration of metal-organic cube, linkage, and ACO topology from
inorganic zeolites to ZMOFs , and BiZMOFs reported in this work.
emissions.
to HCOOH because of their high standard
Figure 2. (a) Linear sweep voltammetry curves in a 0.1 M KHCO3
under CO2
aqueous solution for PZH-1
or Ar atmosphere, where current density is total current density normalized by the
geometric area of electrode. (b) Applied potential dependance of Faradaic efficiencies for H2
,
CO, HCOOH products on PZH-1. (c) Partial current density of HCOOH. (d) Stability of PZH-1
at -1.1 V vs. RHE for 12 hours. (e) Faradaic efficiencies of CO product over PZH-1 and PZH-2.
Coordination environment of Bi centers in (f) PZH-1 and (g) PZH-2.
was collected
in a typical three-electrode H-type
cell. The amounts of generated
gas products, including H2
CO, were detected by online
gas chromatography (GC). Liquid
reduction products were collected
and analyzed by hydrogen nuclear
magnetic resonance spectroscopy.
The results indicate that HCOOH was the only reduction liquid product, and that only trace amounts of CO and H2
Further analysis of PZH-1 revealed that its porous structure contributes to exposing active sites to absorb CO2
were detected.
while suppressing CO
formation due to hydrogen bond interactions between carboxylate groups and *OCHO intermediates. A combination of in situ surfaceenhanced
infrared absorption spectroscopy and density functional theory calculations revealed that the Bi−N coordination contributes
to facilitating charge transfer from N to Bi atoms, which stabilizes the intermediate while boosting the reduction efficiency of CO2
to
HCOOH. Zhiqiang J, Minyi Z, Xingliang C, et al. (2023). Angew. Chem. Int. Ed., 62, e202311223
(doi.org/10.1002/anie.202311223)
The Catalyst Review
April 2024
15

The Catalyst Review April 2024

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