Construct efficient substrate transport and catalytic sub-nanochannels in metal-organic framework-based nanozymes for boosting peroxidase-like catalytic activity

The mixed valence bimetallic Ni x Fe-MOF nanozymes with efficient and selective substrate transport and catalytic sub-nanochannels were successfully developed through metal node engineering for boosting peroxidase-like catalytic activity and bioassay performance. • Ni x Fe-MOF* nanozyme with transport and catalytic sub-nanochannels was fabricated. • The sub-nanochannels were decorated by introducing Ni II and Fe II /Fe III nodes. • Ni x Fe-MOF* nanozyme exhibited high affinity toward H 2 O 2 and large ν max . • Ni x Fe-MOF* nanozyme can detect H 2 O 2 and GSH with high sensitivity and selectivity. Transition metal-based metal-organic frameworks (MOFs) nanozymes, as an ideal artificial metalloenzymes, have recently attracted extensive attention due to their unique porous structure and promising applications in many fields. However, due to the lack of in-depth understanding of the catalytic mechanisms of MOF-based nanozymes, especially the influence of the inherent structure of MOFs on the enzyme-like catalytic process, it is still a very difficult task to reasonably construct high-performance MOF-based nanozymes to date. Inspired by biological ion channels with ultra-high ion conductivity and selectivity, a facile metal node engineering strategy was developed in this study to directly construct highly efficient 1D substrate transport and catalytic sub-nanochannels within Fe-based (MIL-53(Fe)) nanozymes. Through Ni-doping and H 2 -treatment at low temperature (200 °C), Ni II and mixed-valence Fe II /Fe III nodes were successfully generated in 1D iron oxide octahedral chains of MIL-53(Fe) to act as adsorption and reversible catalytic sites of H 2 O 2 , respectively. Benefiting from the confinement effect and optimized catalytic microenvironment of Ni II and Fe II decorated sub-nanochannels, the as-obtained Ni x Fe-MOF-based nanozymes exhibited lower values of K m (0.068 mM) toward H 2 O 2 and larger ν max (2.92 × 10 −7 M s −1 ) in comparison with previously reported studies. Furthermore, the well-designed nanozymes illustrated high sensitivity and selectivity toward the detection of H 2 O 2 and glutathione. This work not only deepens our understanding of enzyme-mimetic activity of MOF, but also the proposed strategy could be potential used for the design and synthesis of other highly efficient MOF-based catalysts.