A Cobalt-Based Metal-Organic Framework Nanosheet as the Electrode for High-Performance Asymmetric Supercapacitor

Inspired by the significant advantages of the bottom-up synthesis whose structures and functionalities can be customized by the selection of molecular components, a 2D metal-organic framework (MOF) nanosheet Co-BTB-LB has been synthesized by a liquid-liquid interface-assisted method. The as-prepared Co-BTB-LB is identified by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDX) and X-ray photoelectron spectroscopy (XPS), and the sheet-like structure is verified by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM). Co-BTB-LB electrode exhibits an excellent capacity of 4969.3 F g-1 at 1 A g-1 and good cycling stability with 75% capacity retention after 1000 cycles. The asymmetric supercapacitor device with Co-BTB-LB as the positive electrode shows a maximum energy density of 150.2 Wh kg-1 at a power density of 1619.2 W kg-1 and good cycling stability with a capacitance retention of 97.1% after 10000 cycles. This represents a state-of-the-art performance reported for asymmetric supercapacitor device using electroactive bottom-up metal-complex nanosheet, which will clearly lead to a significant expansion of the applicability of this type of 2D nanomaterials.

Shear Exfoliated Metal-Organic Framework Nanosheet-Enabled Flexible Sensor for Real-Time Monitoring of Superoxide Anion

Recently, two-dimensional metal-organic framework (2D MOF) nanosheets have drawn a lot of attention on account of their various advantages, like ultrathin thickness, ultralarge specific surface area, abundant accessible active sites, favorable solution dispersion properties, and ease of designability. However, until now, it is still difficult to produce 2D MOF nanosheets in large scale, which hinders the practical applications of 2D MOF nanosheets. Here, for the first time, we introduced a novel shear exfoliation method to prepare scalable 2D MOF nanosheets by using a commercial blender. As a proof of concept, we used two kinds of layer-structured MOFs (ELM-12, Cu(bpy)₂(OTf)₂, bpy = 4,4-bipyridine, OTf = trifluoromethanesulfonate and Zn₂(bim)₄, bim = benzimidazole) as samples to prepare MOF nanosheets. The thickness of the two kinds of MOF nanosheets obtained is 3-5 nm. Notably, the exfoliated MOF nanosheet (ELM-12) shows improved electrochemical catalytic activity compared with its bulk counterpart. Based on this, an ELM-12 nanosheet-based flexible sensor was developed for detecting superoxide anions (O₂^•-) released from cancer cells. The fabricated flexible sensor displays excellent sensitivity, selectivity, flexibility, stability, and reproducibility.