Integration of Strong Electron Transporter Tetrathiafulvalene into Metalloporphyrin-Based Covalent Organic Framework for Highly Efficient Electroreduction of CO₂

Abstract

Electroreduction of CO 2 (CO 2 RR) into value-added fuels is of significant importance but remains a big challenge because of poor selectivity, low current density, and large overpotential. Crystalline porous covalent organic frameworks (COFs) are promising alternative electrode materials for CO 2 RR owing to their tunable and accessible single active sites. However, the poor electron-transfer capability of COFs limits their application. Herein, a tetrathiafulvalene (TTF) strut was integrated into a two-dimensional cobalt porphyrin-based COF (TTF-Por(Co)-COF) to enhance its electron-transfer capability from the TTF to the porphyrin ring. Compared with COF-366-Co without TTF, TTF-Por(Co)-COF showed enhanced CO 2 RR performance in water with 95% Faradaic efficiency of the CO 2 -to-CO conversion at −0.7 V vs RHE and a partial current density of 6.88 mA cm −2 at −0.9 V vs RHE. This work provides a new insight for the rational design of porous organic framework materials for improving the activity of CO 2 RR.

A Stable and Conductive Metallophthalocyanine Framework for Electrocatalytic Carbon Dioxide Reduction in Water

“…Compared to CoPc‐CN/CNT and COF‐367‐Co, CoPc‐PDQ‐COF achieves a much lower overpotential and a much higher current density. In comparison with other COFs, including TTF‐Por(Co)‐COF, COF‐Re_Fe, COF‐366‐F‐Co, COF‐2,2′‐bpy‐Re, and COF‐300‐AR, CoPc‐PDQ‐COF features the best overall performance. As shown in the Supporting Information, Table S6, CoPc‐PDQ‐COF surpasses the state‐of‐the‐art organic and inorganic molecular catalysts including perfluorinated CoPc, nanoporous Ag, Au nanowires, and Pd nanoparticles .…”

Conductive Phthalocyanine‐Based Covalent Organic Framework for Highly Efficient Electroreduction of Carbon Dioxide

“…As shown the Faradaic efficiency (FE) for CO and H 2 in Figure 5b, the NiPc-COF nanosheets display superior selectivity for the CO formation with FE CO over 93% in the wide applied potential range of −0.6 to −1.1 V and the highest FE CO reaches nearly 100% (99.1%) at −0.9 V. Obviously, such outstanding selectivity of NiPc-COF nanosheets for the CO 2 -to-CO conversion compares favorably with the similar conductive COF electrocatalyst CoPc-PDQ-COF [68] and exceeds most of the traditional COFs and metal-organic frameworks (MOFs) (Figure 5c; Table S4, Supporting Information). [33,[42][43][44][45][51][52][53] As shown in Figure S9 of the Supporting Information, the NiPc-COF nanosheets exhibited a distinctly decreased FE CO of 73.6% at −1.2 V and the hydrogen evolution reaction (HER) became the dominant process at a more negative potential of −1.3 V. The CO partial current density (j CO ) for CO 2 reduction at various applied potentials is presented in Figure S10 of the Supporting Information. The j CO increased significantly with an decrease in the applied potential from −0.6 to −1.1 V, and NiPc-COF nanosheets achieved a largest j CO of 35 mA cm −2 at −1.1 V, which is much higher than conventional COF and MOF electrocatalysts evaluated in H-type electrochemical cell (Figure 5c; Table S4, Supporting Information).…”

Transition metal-based catalysts for the electrochemical CO2reduction: from atoms and molecules to nanostructured materials

“…33 In this regard, the incorporation of electron carriers as building blocks of the framework has revealed to be an effective strategy to improve electron migration in COFs. For instance, crystalline COFs obtained through the assembly of Co porphyrin catalytic units and tetrathiafulvalene struts, serving as an electron donors, resulted in enhanced durability, activity and selectivity to CO. 79,169 Moreover, the exfoliation of bulk COFs into 2D ultrathin nanosheets (ca. 5 nm thickness) led to further improved CO 2 RR performances compared to the unexfoliated COF material, resulting in excellent CO selectivity in a wide potential range.…”