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 Zn-2(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 (O-2(center dot-)) released from cancer cells. The fabricated flexible sensor displays excellent sensitivity, selectivity, flexibility, stability, and reproducibility.