Metal–Organic Frameworks Mediate Cu Coordination for Selective CO₂ Electroreduction

Abstract

The electrochemical carbon dioxide reduction reaction (CORR) produces diverse chemical species. Cu clusters with a judiciously controlled surface coordination number (CN) provide active sites that simultaneously optimize selectivity, activity, and efficiency for CORR. Here we report a strategy involving metal-organic framework (MOF)-regulated Cu cluster formation that shifts CO electroreduction toward multiple-carbon product generation. Specifically, we promoted undercoordinated sites during the formation of Cu clusters by controlling the structure of the Cu dimer, the precursor for Cu clusters. We distorted the symmetric paddle-wheel Cu dimer secondary building block of HKUST-1 to an asymmetric motif by separating adjacent benzene tricarboxylate moieties using thermal treatment. By varying materials processing conditions, we modulated the asymmetric local atomic structure, oxidation state and bonding strain of Cu dimers. Using electron paramagnetic resonance (EPR) and in situ X-ray absorption spectroscopy (XAS) experiments, we observed the formation of Cu clusters with low CN from distorted Cu dimers in HKUST-1 during CO electroreduction. These exhibited 45% CH faradaic efficiency (FE), a record for MOF-derived Cu cluster catalysts. A structure-activity relationship was established wherein the tuning of the Cu-Cu CN in Cu clusters determines the CORR selectivity.

Ionic‐Liquid‐Functionalized UiO‐66 Framework: An Experimental and Theoretical Study on the Cycloaddition of CO2 and Epoxides

“…[47][48][49][50][51][52][53][54][55][56] Properties such as tunable particles ize, pore volume,t opology, versatile functionality,a nd high surface area make MOFs promising candidates in the field of catalysis. [47][48][49][50][51][52][53][54][55][56] Properties such as tunable particles ize, pore volume,t opology, versatile functionality,a nd high surface area make MOFs promising candidates in the field of catalysis.…”

“…MOFs have gained tremendous attention in the last few decades, and al arge number of MOFs have been prepared for variousb iological, energy,a nd environmental applications. [47][48][49][50][51][52][53][54][55][56] Properties such as tunable particles ize, pore volume,t opology, versatile functionality,a nd high surface area make MOFs promising candidates in the field of catalysis. Moreover,M OFs have exceptional porosity,a bility for guest encapsulation, and bal-Af acile approach for modifyingt he UiO-66-NH 2 metal-organic framework by incorporating imidazolium-based ionic liquids (ILs) to form bifunctional heterogeneouscatalysts for the cycloaddition of epoxides to CO 2 is reported.M ethylimidazoliumand methylbenzimidazolium-based IL units (ILA and ILB, respectively) were introduced into the pore walls of the UiO-66-NH 2 framework through ac ondensation reaction to generate ILA@U6N andI LB@U6N catalysts, respectively.T he resultant heterogeneous catalysts, especially ILA@U6N, exhibited excellent CO 2 adsorption capability,w hich makest hem effective for cycloaddition reactions producing cyclic carbonates under mild reactionc onditions in the absence of any cocatalyst or solvent.…”

Engineering Metal–Organic Frameworks for the Electrochemical Reduction of CO2: A Minireview

“…j–l) HAADF‐STEM images of Fe‐N‐C . m–r) Structural investigation of as‐fabricated HKUST‐1 by using SEM (m), bright‐field TEM (n), HAADF TEM (o), and energy‐dispersive X‐ray spectroscopy TEM (EDS TEM; p–r) …”

“…Nam et al. reported a strategy that involved the formation of MOF‐regulated copper clusters, which shifted the electroreduction of CO 2 towards multiple‐carbon‐atom‐containing products . The symmetrical “paddle‐wheel” copper dimer, the secondary building block of HKUST‐1, was distorted into an asymmetric motif by separating adjacent benzene tricarboxylate moieties under thermal treatment.…”

Recent Approaches to Design Electrocatalysts Based on Metal–Organic Frameworks and Their Derivatives

“…In addition, other hydrocarbons and alcohols such as ethylene, methanol, and ethanol can be produced via *CO dimerization approaches. Sargent and co‐workers synthesized Cu clusters with low coordination numbers based on the thermal distortion of HKUST‐1 Cu dimer and showed a faradaic efficiency of 45 % for C 2 H 4 , which is the highest reported value among Cu‐based MOFs catalysts . Pérez‐Yáñez and co‐workers introduced Ru III , Zn II and Pd II to the HKUST‐1, which show a faradaic efficiency of 47.2 % to methanol and ethanol …”