Effective enhancement of capacitive performance by the facile exfoliation of bulk metal-organic frameworks into 2D-functionalized nanosheets

Efficient improvement in the electrochemical performance of petal-like lamellar NiMn-LDHs with affluent oxygen vacancies derived from Mn MOF-74

Supercapacitors (SCs) as a kind of novel energy storage devices have emerged to meet the urgent requirement of environmentally friendly clean energy storage equipment. However, unsatisfactory energy density and low operating voltage tremendously restrict their practical application. Herein, petal-like lamellar NiMn-layered double hydroxide (NiMn-LDH) was successfully fabricated through a simple Ni(NO3)2 etching method with Mn MOF-74 as a sacrificial template. This NiMn-LDH 3/NF electrode exhibited an improved specific capacitance of 1410.2 F g-1 at a current density of 1 A g-1 (Mn MOF-74/NF: 172.2) owing to its high redox activity, compositional flexibility and intercalating capability. Importantly, NiMn-LDH was further optimized via a facile hydroperoxide treatment to harvest NiMn-LDH (O-LDH) with abundant oxygen vacancies, exhibiting remarkable improvement in specific capacitance (990%) compared to original MOF-74 before modification. The preparation of O-LDH enriches the electrode material engineering strategy and achieves improved electrochemical performance for application in new-generation SCs.

The Realization of Uniform Growth of Conductive MOFs on LDHs and Their High Performance in Supercapacitors

Metal-organic frameworks (MOFs) have been widely investigated as functional materials with excellent properties. However, most MOFs are of poor electrical conductivity, which hinders their further application in electrochemical fields. Fortunately, the emergence of intrinsically conductive MOFs (c-MOFs) alleviates this problem. Layered double hydroxides (LDHs) possess Faraday redox reactivity, which is favorable to capacitors. In this paper, we combined c-MOFs with LDHs and prepared a series of NiCo-LDH@M-HHTP(-EtOH) (M=Ni or Co; HHTP=2,3,6,7,10,11-hexahydroxytriphenylene) multilayer nanoarrays, and the effects of solvent on the morphology and energy storage properties of the materials were investigated. When NiCo-LDH@Co-HHTP-EtOH is applied as an electrode material in supercapacitors, it exhibits a capacitance of 830 F g-1 at 1 A g-1 . Furthermore, it exhibits high energy density and excellent rate performance when assembled in aqueous asymmetric supercapacitors.

Rare Earth-Based Nanomaterials for Supercapacitors: Preparation, Structure Engineering and Application

Supercapacitors (SCs) can effectively alleviate problems such as energy shortage and serious greenhouse effect. The properties of electrode materials directly affect the performance of SCs. Rare earth (RE) is known as "modern industrial vitamins", and their functional materials have been listed as key strategic materials. In the past few years, the number of scientific reports on RE-based nanomaterials for SCs has increased rapidly, confirming that adding RE elements or compounds to the host electrode materials with various nanostructured morphologies can greatly enhance their electrochemical performance. Although RE-based nanomaterials have made rapid progress in SCs, there are very few works providing a comprehensive survey of this field. In view of this, a comprehensive overview of RE-based nanomaterials for SCs is provided here, including the preparation methods, nanostructure engineering, compounds, and composites, along with their capacitance performances. The structure-activity relationships are discussed and highlighted. Meanwhile, the future challenges and perspectives are also pointed out. This Review can not only provide guidance for the further development of SCs but also arouse great interest in RE-based nanomaterials in other research fields such as electrocatalysis, photovoltaic cells, and lithium batteries.

Interaction of Nucleic Acids with Metal-Organic Framework Nanosheets by Fluorescence Spectroscopy and Molecular Dynamics Simulations

The integration of nanomaterials and nucleic acids has attracted great attention in various research fields, especially biomedical applications. Designing two-dimensional nanomaterials and studying the mechanism of their interaction with nucleic acids are still attractive tasks. Herein, we designed and prepared a class of ultrathin two-dimensional metal-organic framework (MOF) nanosheets, named Zr-BTB MOF nanosheets, composed of Zr-O clusters and 1,3,5-benzenetribenzoate by a bottom-up synthesis strategy. The Zr-BTB MOF nanosheets possessed inherent excellent performance such as a high specific surface area, porosity, and biocompatibility. In addition, we clarified the interaction difference between the Zr-BTB MOF nanosheets and fluorophore-labeled double-stranded DNA and single-stranded DNA via molecular dynamics simulations and fluorescence measurement. Through molecular dynamics simulations, specific interactions between DNA and nanosheets such as forces, binding energies, and binding modes were deeply analyzed and clearly presented. Based on the affinity difference, the system showed the biosensing potential for target DNA detection with considerable specificity, sensitivity, and linearity. Our research results presented the Zr-BTB MOF nanosheet as a platform for nucleic acid detection, showing the potential for hybridization-based biosensing and related biological applications.