Mixed-Ligand Architected Unique Topological Heterometallic Sodium/Cobalt-Based Metal–Organic Framework for High-Performance Supercapacitors

Abstract

A new Na/Co-based heterometallic metal–organic framework, [Na2Co­(SDCA)­(μ 2-OH)2(μ 2-H2O)2(Azopy)] n (where Azopy = 4,4′-Azopyridine and SDCA = 2,5′-thiophenedicarboxylic acid) (1) with nanorod-shaped morphology was synthesized using mixed-ligand approach via slow-diffusion technique under ambient conditions. The crystal structure study demonstrates the proportion of Co­(II) and Na­(I) metal node to be 1:2 and the acquired coordination network reveals as a 3D architecture. Topologically, the 4-c Na­(I) ion directs in situ assembly of 4-c SDCA linker and 6-c Co­(II) ion, resulting in the formation of 4,4,6-c net with a topology named as smm3. Additionally, 1 was incorporated as a binder-free material for a glassy carbon electrode (1-GCE) to explore its supercapacitor performance, which reveals a high specific capacitance of 321.8 F g–1 at 4 A g–1 and notable rate performance (∼78.9% of initial capacitance up to 16 A g–1) as well as excellent cycling stability (retains 97.4% after 5000 cycles). The demonstrated strategy of employing different heterometallic clusters with mixed ligands markedly increases MOF’s complexity and induces synergistic properties, which is highly favorable for electrochemical applications. Hence, the present approach can be extended to build a wide range of MOFs and synergistically enhanced electrochemical performance can be achieved.

Supercapacitor electrodes based on metal‐organic compounds from the first transition metal series

“…In the last decade, heterometallic organic compounds (especially bimetallic MOFs) and their composites ( 211 ‐ 264 ), also have aroused an increasing attraction due to their unique SC performances 26,37,66,76,203‐222 . Owing to the tunable structures resulting from the mole ratios of different metal centers, the properties of bimetallic organic compounds could be adjusted and thus novel and special applications can be obtained on the basis of the monometallic organic compounds 57 .…”

“…Bimetallic‐organic compounds with SC properties are mainly the bimetallic MOFs with either polycarboxylate ligands ( 221 ‐ 245 , 260 ‐ 264 ) 26,37,66,203‐216,222 or 3‐methylimidazole ( 246 ‐ 256 ) 217‐220 ligands. As shown in Tables 13 and 14, cobalt, nickel and zinc are the most popular metal elements used to fabricate SC electrodes based on bimetallic‐organic compounds.…”

“…So far, bimetallic‐organic compounds have attracted numerous research interest due to their good SC performances. Rajak and coworkers synthesized a new heterometallic Na/Co‐based MOF ( 221 ) by a facile mixed ligand strategy with slow‐diffusion technique at room temperature 203 . For 221 , the high cycling stability (with less than 3% capacitance loss after 5000 charge‐discharge cycles) was observed at a quite high current density of 18 A g −1 .…”

Sonochemical synthesis of a trinuclear Cu(ii) complex with open coordination sites for the differentiable optical detection of volatile amines

“…42,43 The peaks at approximately 1600-1400 cm À1 are ascribed to the asymmetric and symmetric stretching vibrations of the carboxylate group for the pzdc ligand. 44,45 The UV-vis diffuse reectance spectrum of 1 (Fig. S3 †) was performed.…”

Synthesis, Crystal Structure and Characterization of Two Cobalt (II) Complexes Based on Pyridine Carboxylic Acid Ligands

“…Pyridine carboxylic acid ligands combine the functions of N‐containing heterocyclic ligands and O‐containing carboxylic acid ligands, on the one hand, nitrogen atoms and carboxyl oxygen atoms easily coordinate with transition metal ions to form stable coordination bonds, which increases the structural diversity and stability; on the other hand, partially or completely deprotonated carboxylic acids act as both proton donors and acceptors in hydrogen bonds, structures made with different dimensions are easy to implement [16] . Considering metals as nodes, the metal and ligand are self‐assembled to form a variety of topological structures or condensed structures through hydrogen bonding or π‐π interactions [17] . MOFs based on transition metal and carboxylate ligands have great application value and have received extensive attention in the chemical community.…”