Two-dimensional metal–organic framework (MOF) nanosheets are utilized as effective enzyme inhibitors, providing an inspiring means to enhance the control of cellular processes as well as improve our understanding of the surface chemistry between MOFs and enzymes. In this paper, we demonstrated that the activity of α-chymotrypsin (ChT) can be effectively inhibited with 96.9% inhibition by 2-D Cu(bpy)2(OTf)2 nanosheets, while Zn2(bim)4 nanosheets show no significant inhibition effect toward ChT. Kinetic studies revealed that the material acts as a competitive inhibitor toward ChT. Furthermore, fluorescence and circular dichroism spectroscopy reveal that the 2-D MOF nanosheets do not change the secondary structure of the enzyme. The Cu(II) center of the 2-D nanosheets binds the 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) molecules in the buffer, leading to an electrostatic interaction between the nanosheets and the enzyme. In addition, the irreversible coordination interactions between Cu(II) center and His-57 played an important role during the inhibition process, as supported by ionic strength experiments and UV absorbance changes of Cu(II) d–d transitions. As a result, the substrate is prevented from reaching the active sites of the enzyme causing enzyme inhibition. The modulation of enzyme activity by 2-D MOF nanosheets opens up a new direction for the exploration of the MOF–bio interface in physiological and catalytic systems.

Stable 2-D metal–organic framework nanosheets were utilized as a superior clean-background matrix for MALDI-TOF MS analysis of small biomolecules and pollutants in both positive and negative ion modes. The matrix could unusually afford up to 1000 mM of the salt concentrations in the monitoring of the enzymatic hydrolysis of neurotransmitter acetylcholine.