Two-Dimensional Covalent Organic Framework with Synergistic Active Centers for Efficient Electrochemical Sodium Storage

Abstract

Benefiting from the adjustable molecule structures, abundant functional units, large specific surface areas, and ordered pores, covalent organic frameworks (COFs) are highly desirable for electrochemical energy storage. Herein, a two-dimensional COF (denoted as HHTP-TABQ) with a fully π-conjugated framework and C�N and C�O dual-active sites has been synthesized and applied as the anode in organic rechargeable sodium-ion batteries (SIBs). During the sodium-storage process, it delivered remarkable rate capability, satisfactory ultra-long cycle stability (84.5% capacity retention ratio after 1000 cycles at 5000 mA g −1 ), and facile charge exchange kinetics (2.49 × 10 −7 cm 2 s −1 ), which is superior among most reported COF-based electrodes. Furthermore, the sodiation mechanism was investigated by density functional theory calculations and ex situ characterizations, which confirms that the electrochemical reaction is dominated by the synergistic reaction of C�N and C�O groups. These results suggest that COFs with stable π-conjugated structures, insoluble characteristics, and abundant active sites would have great potential for practical applications in rechargeable SIBs.

Advancements in two-dimensional covalent organic framework nanosheets for electrocatalytic energy conversion: current and future prospects

“…Compared to their three-dimensional (3D) counterparts, 2D COFs offer superior capabilities in modulating molecular dimensions and crystallinity. This adaptability aids in finetuning intermolecular interactions, thus promoting specific reactions [26] . Additionally, the interactions between layers in 2D COFs enhance their electrochemical properties.…”

“…XRD reveals the crystal structure and phase composition, thereby offering valuable insights into the atomic arrangement within the material [28,29] . The BET analysis reveals the specific surface area and porosity of the samples, thus providing crucial information regarding their physical properties and potential practical applications [26,30] . Furthermore, we provide illustrative examples of the utilization of 2D COFs as catalysts for energy conversion processes, such as the electrochemical oxygen evolution reaction (OER), oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and CO 2 reduction reaction (CO 2 RR).…”

Highlights from 2023 and Chemistry of Materials’ 35th Year

“…Covalent organic frameworks (COFs) and metal organic frameworks (MOFs) continue to be of broad interest to our community, with seven papers of this topical area making our list of most cited and downloaded. These papers include one Review and two studies of COFs for separations, where the hierarchical form and functionalization of these porous materials were critical to this application. − Hollow, spherical COF particles also were found to be excellent drug delivery platforms, while COFs with redox-active units can be used as the anode in organic rechargeable sodium-ion batteries . In contrast, the highly engaged content based on MOFs addressed fundamental questions, as in Quantification of Linker Defects in UiO-Type Metal–Organic Frameworks , and reported an excellent community resource, as in ARC-MOF: A Diverse Database of Metal–Organic Frameworks with DFT-Derived Partial Atomic Charges and Descritors for Machine Learning …”