Promoting Active Sites in MOFs-Derived Homobimetallic Hollow Nanocages as High Performance Multifunctional Nanozyme Catalyst for Biosensing and Organic Pollutant Degradation.

Nanozymes are one of ideal alternatives to natural enzymes for various applications. The rational design of nanozymes with improved catalytic activity stimulates increasing attentions to address the low activity of current nanozymes. Here, we reported a general strategy to fabricate the Co-based homobimetallic hollow nanocages (C-CoM-HNC, M = Ni, Mn, Cu, Zn) by ion-assistant solvothermal reaction and subsequent low-temperature calcination from metal-organic frameworks. The C-CoM-HNCs are featured with hollow nanocages composed of interlaced nanosheets with homogeneous bimetallic oxides dispersion. The hierarchical structure and secondary metallic doping endow the C-CoM-HNCs highly active sites. In particular, the Cu doped C-CoCu-HNCs nanostructures exhibit superior performances over the other C-CoM-HNC as both oxidase mimicking and peroxymonosulfate (PMS) activator. A sensitive bioassay for acetylcholinesterase (AChE) was established based on the excellent oxidase-like activity of C-CoCu-HNC, offering a linear detection range from 0.0001 to 1 mU/mL with an ultra low detection limit of 0.1 mU/L. As PMS activator, the C-CoCu-HNC was applied for targeted organic pollutants (rhodamine B, RhB) degradation. A highly efficient RhB degradation was realized, along with good adaptability in a wide pH range and good reusability during eight-cycle run. The results suggest that C-CoCu-HNC holds a practical potential for clinical diagnostics and pollution removal. Further density functional theory (DFT) calculation reveals that Cu doping leads to a tighter connection and more negative adsorption energy for O2/PMS, as well as an up-shifted d-band center in the C-CoCu-HNCs nanostructures. These changes facilitated the adsorption of O2/PMS on C-CoCu-HNC surface for dissociation. This work not only offers a promising multifunctional nanozyme catalyst for clinical diagnostics and pollution removal, but also gives some clues for the further development of novel nanozymes with highly catalytic activities.