Quasi-Cu-MOFs: highly improved water stability and electrocatalytic activity toward H2O2 reduction among pristine 3D MOFs

Metal-organic frameworks (MOFs) with multienzyme activity have been used as direct surrogates for conventional enzymes, while the catalytic activity of pristine MOFs is lacking, and further improvements are needed. We can accelerate electron transfer to enhance the catalytic activity by exposing catalytically active metal sites in MOFs with maintained porosity. In this work, the catalytic activity of five kinds of pristine 3D MOFs was investigated. Among these typical MOFs, HKUST-1 exhibits the best electrocatalytic activity toward H2O2 reduction and the highest peroxidase-mimicking activity. Then, quasi-HKUST-1 (QHKUST-1) products were obtained from the low-temperature calcination of HKUST-1 in an air atmosphere and controlled partial pyrolysis. Remarkably, the QHKUST-1 material (calcined at 250 degrees C for 1 h) maintains the perfect octahedral morphology of HKUST-1 while having more exposed active centers and exhibiting better electrical conductivity. The peroxidase-mimicking and electrocatalytic activities of QHKUST-1 for sensing are greatly improved. Moreover, QHKUST-1 exhibits superior moisture stability and catalytic properties compared to the originally water-sensitive HKUST-1. QHKUST-1 was further explored in the detection of H2O2 from living cells with an impressive detection limit of 0.3 mu M. This work opens a new way to design 3D quasi-MOFs for enhanced electrochemical sensing and catalysis.

Automated summary

This research explores how exposing catalytically active metal sites in metal-organic frameworks (MOFs) enhances their catalytic activity through accelerated electron transfer. HKUST-1 shows the best electrocatalytic and peroxidase-mimicking activities among the MOFs studied. By low-temperature calcination and controlled partial pyrolysis, quasi-HKUST-1 (QHKUST-1) with more active centers and better electrical conductivity is obtained. QHKUST-1 exhibits superior moisture stability and catalytic properties compared to HKUST-1.