The Synthesis of Hexaazatrinaphthylene‐Based 2D Conjugated Copper Metal‐Organic Framework for Highly Selective and Stable Electroreduction of CO₂ to Methane

Abstract

2D conjugated MOFs have attracted significant interests in recent years owing to their special structural features and promising physical and chemical properties. These intriguing attributes, to a large extent, stem from the nature of incorporated ligands. The available ligands for the construction of 2D conjugated MOFs are still limited, especially those that have heteroatoms included and exposed to the pores. In this work, we designed and synthesized a highly symmetric hexaazatrinaphthylene (HATNA)-based ligand with two different coordination sites. Through selective coordination, a highly crystalline and porous 2D conjugated copper metal-organic framework was constructed. Due to the synergic effects of HATNA and copper catecholate node, this HATNAbased 2D conjugated MOF can mediate the electrocatalytic reduction of CO 2 to methane with high selectivity of 78 % at high current density of 8.2 milliamperes per square centimetre (mA cm À2 ) for long durability over 12 hours.

Hydroxy‐Group‐Functionalized Single Crystal of Copper(II)‐Porphyrin Complex for Electroreduction CO2 to CH4

“…[31] The peaks at 941.5, 944.4, and 962.9 eV are associated with the satellite peaks of Cu 2 + . [32] Furthermore, a nearly symmetrical signal was observed at g = 2.06 in the solidstate electron paramagnetic resonance (EPR) spectrum, which also validates the existence of Cu II (Figure S8). [33] The porphyrins and metalloporphyrins have characteristic absorption bands in the visible range because of the strong π conjugated electron system.…”

“…Of note, the partial current density of CH 4 (j CH 4 ) is as high as 23.2 mA cm À 2 at À 1.5 V in Hcell. The j CH 4 of Cu-PorOH is higher than those of most reported aqueous-based CO 2 RR electrocatalysts in H-cell reactor such as HATNAÀ Cu-MOF (8.2 mA cm À 2 ), [32] CuPc/CNTs (13 mA cm À 2 ), [36] Cu 2 O@Cu-HHTP (10.8 mA cm À 2 ), [37] and Cu 2 O@HKUST-1 (8.4 mA cm À 2 ). [38] The detailed performance comparison is given in Table S3.…”

“…The two peaks at 934.7 and 954.5 eV in the Cu 2p spectrum are attributed to Cu 2p 3/2 and Cu 2p 1/2 spin‐orbit states, respectively, which indicates the Cu 2+ state in the Cu‐PorOH (Figure 2e) [31] . The peaks at 941.5, 944.4, and 962.9 eV are associated with the satellite peaks of Cu 2+ [32] . Furthermore, a nearly symmetrical signal was observed at g =2.06 in the solid‐state electron paramagnetic resonance (EPR) spectrum, which also validates the existence of Cu II (Figure S8) [33] .…”

Toward High‐Performance CO2‐to‐C2 Electroreduction via Linker Tuning on MOF‐Derived Catalysts

“…A mild reduction peak at about −0.6 V versus reversible hydrogen electrode (V vs. RHE) is observed on NH 2 ‐Cu‐BDC, indicating that NH 2 ‐Cu‐BDC is redox‐active. [ 7 ] The LSV curves clearly show that the linker‐appended MOFs have a higher current density than that with none linker appended. Furthermore, the linker‐appended MOFs have lower onset potential (2F‐Cu‐BDC ≈ F‐Cu‐BDC < OH‐Cu‐BDC < NH 2 ‐Cu‐BDC < Cu‐BDC), suggesting that organic linkers greatly improve the eCO 2 RR activity.…”

“…Electrochemical reduction of CO 2 (eCO 2 RR) to achieve valueadded chemicals, especially C 2 products ethylene (C 2 H 4 ) [1,2] and ethanol (C 2 H 5 OH) [3] has been identified as the most potential solution to mitigate the greenhouse effect and the energy crisis. [4] As a kind of porous material, metal-organic frameworks (MOFs) have been extensively explored in eCO 2 RR due to their ordered structure, [5,6] high porosity, [7,8] adjustable chemical functionality, [9][10][11] and flexibility in the structure design. [10,12] Additionally, the structures of MOF catalysts are easy to be in situ reconstructed under electrochemical conditions to be derive to new structures, [2,13] which are commonly referred to as MOF-derived catalyst.…”