Single-Atom Catalysts on Covalent Organic Frameworks for CO₂ Reduction

Abstract

The long-unresolved issue of CO2 release and the resulting atmospheric change can be solved through the application of effective catalysts. Thus, single-atom catalysts (SACs) have been rapidly developed for the CO2 reduction reaction (CO2RR), as they show improved catalytic metrics and enable the generation of C2+ products. Among numerous novel SACs, such as those based on graphene, metal–organic frameworks, and covalent organic frameworks (COFs), the COF-based SACs are the most promising owing to their high stability, porosity, and designability. Considering this, we describe two synthesis methods of COF-based SACs: ligand coordination and macrocycle backbone integration, and explore the pros and cons of each. We also propose routes for designing superior COF-based SACs and evaluate the factors influencing CO2RRs over COF-based SACs, such as metal loading and ligand types.

Perylenediimide-Incorporated Covalent Triazine Framework: A Highly Conductive Carbon Support for Copper Single-Atom Catalysts in Electrocatalytic CO2 Conversion

“…CTF-Cu-N-900 produced a current density (∼11 mA cm –2 ) in linear sweep voltammetry (LSV) higher than that of the other catalysts (Figure a). A significantly greater current density of CTF-Cu-N-900 under CO 2 -saturated electrolytic conditions (Figure b) than N 2 -saturated conditions (Figure b) suggests its superior catalytic performance in CO 2 RR . Also, the extra N-doping to the CTF-Cu-SACs demonstrated tremendous relevance in raising the current densities, a crucial aspect for the electrocatalytic CO 2 RR.…”

“…A significantly greater current density of CTF-Cu-N-900 under CO 2 -saturated electrolytic conditions (Figure 5b) than N 2 -saturated conditions (Figure 5b) suggests its superior catalytic performance in CO 2 RR. 24 Also, the extra N-doping to the CTF-Cu-SACs demonstrated tremendous relevance in raising the current densities, a crucial aspect for the electrocatalytic CO 2 RR. N-doping into the carbon matrix creates additional defects to anchor single metal sites and tune the electrical structure of the entire system.…”

“…Single-atom catalysts (SACs) − are a novel class of emerging catalytic materials. Various nanostructured materials, including graphene, , metal–organic frameworks (MOFs), − carbon nanotubes (CNTs), , and covalent organic frameworks (COFs) − have been exploited as the carbon support for synthesizing SACs. The carbon support provides a unique electronic structure along with high conductivity .…”

“…Despite the significant advancements in developing various photo- and electrocatalysts for CO 2 RR, − SACs based on COFs and CTFs are scarce in the literature. ,− Moreover, the production of methanol with high selectivity remains limited. , Copper-based single-atom catalysts (Cu-SACs), in particular, are promising for the electrocatalytic conversion of CO 2 into hydrocarbons and alcohols with high product selectivity in an aqueous solution. − Thus, herein, we report CTF-Cu-SACs using PDI-incorporated CTFs as the conductive carbon support for CO 2 RR. The CTF-Cu-SACs demonstrated high catalytic efficiency of converting CO 2 to methanol with an FE of 72.6% at 0.2 V vs RHE.…”

Highly Conductive Covalent–Organic Framework Films

“…Owing to their high crystallinity, permanent porosity, structural integrity, and design versatility, 2D covalent-organic frameworks (COFs) are widely used in various applications, including catalysis, energy storage, optoelectronics, sensing, adsorption, and water purification. [1][2][3] As COFs are polymeric in nature, various building blocks, such as macrocycles, can be introduced through relevant linkages. In macrocycle-conjugated COFs, the fully conjugated COF networks can promote electron transport along DOI: 10.1002/smll.202306634 inter-and intralayer directions.…”