Overcoming Diffusion Limitation of Faradaic Processes: Property‐Performance Relationships of 2D Conductive Metal‐Organic Framework Cu₃(HHTP)₂ for Reversible Lithium‐Ion Storage

Abstract

Faradaic reactions including charge transfer are often accompanied with diffusion limitation inside the bulk. Conductive two-dimensional frameworks (2D MOFs) with a fast ion transport can combine bothcharge transfer and fast diffusion inside their porous structure. To study remaining diffusion limitations caused by particle morphology, different synthesis routes of Cu-2,3,6,7,10,11-hexahydroxytriphenylene (Cu 3 (HHTP) 2 ), a copper-based 2D MOF, are used to obtain flake-and rod-like MOF particles. Both morphologies are systematically characterized and evaluated for redox-active Li + ion storage. The redox mechanism is investigated by means of X-ray absorption spectroscopy, FTIR spectroscopy and in situ XRD. Both types are compared regarding kinetic properties for Li + ion storage via cyclic voltammetry and impedance spectroscopy. A significant influence of particle morphology for 2D MOFs on kinetic aspects of electrochemical Li + ion storage can be observed. This study opens the path for optimization of redox active porous structures to overcome diffusion limitations of Faradaic processes.

Mo-X4 (X = O, NH and S)-mediated triphenylene-based two-dimensional carbon-rich conjugate frameworks for an efficient nitrogen reduction reaction

“…As shown in Table S1,† the optimized lattice constants of the Mo 3 (HOTP) 2 , Mo 3 (HITP) 2 and Mo 3 (THT) 2 monolayers are a = b = 22.39, 22.74 and 24.02 Å, respectively, consistent with earlier experimental reports. 57–62 The Mo–X bond lengths of the three structures are 1.96, 2.03 and 2.35 Å, respectively. The different bond strengths may cause significant differences in catalytic properties.…”

Toward Enhancing Performance of Electromagnetic Wave Absorption for Conductive Metal–Organic Frameworks: Nanostructure Engineering or Crystal Morphology Controlling

“…It is widely believed that Cu-HHTP crystal growth is preferred along the crystallographic c -direction possibly due to the π–π interaction of the hydrophobic HHTP links . Hoppe et al successfully redirected the Cu-HHTP crystal growth in a lateral direction by using ammonia as an inducer in the solution.…”

“…Hence, the Cu-HHTPs with highly symmetric conjugated structures were synthesized through simple hydrothermal methods, and by adding different structure inducers (such as concentrated ammonia, water, and pyridine), the nanostructure or crystal morphologies of Cu-HHTPs can be adjusted, as illustrated in Scheme . Ligands and inducers containing N element compete with Cu 2+ cations for coordination, slowing down crystal nucleation and growth, thereby reducing stacking between layers and inhibiting crystal growth in the c -axis direction. , …”

Conductive MOFs: Synthesis and Applications in Supercapacitors and Batteries

“…In addition to the redox activity of electrode materials affecting energy storage performance, recent work has pointed out that the particle morphology of 2D c‐MOFs significantly impacts the electrochemical lithium‐ion storage kinetics. Rod‐like and flake‐like Cu 3 (HHTP) 2 c‐MOFs were obtained by adjusting the proportions of reactants and the types of additives [101] . Due to the larger external surface area and shorter ion diffusion paths, plate‐shaped particles demonstrated higher kinetics and negligible diffusion limitation compared to rod‐like particles.…”