From Solution to Surface: How the Catalytic Environment Modulates Peptide Bond Cleavage by Metal-Oxo Cluster...

Nanozymes that selectively cleave proteins offer a promising alternative to natural proteases due to their superior stability, tunability, and scalability. However, they are either water-soluble, preventing efficient recovery and limiting their practical application, or structurally ill-defined and insoluble, hindering mechanistic understanding and rational catalyst design. To address this, we developed a structurally well-defined dodecanuclear hafnium-based metal-oxo cluster with a tunable solubility that enables direct comparison of homogeneous and heterogeneous catalytic behavior in peptide bond hydrolysis. The soluble cluster, Hf₁₂(sol), and its insoluble counterpart, Hf₁₂(precip), share identical core structures according to pair distribution function analysis and possess highly similar ligand environments as indicated by solution- and solid-state NMR as well as FT-IR spectroscopy. We demonstrate that both forms efficiently cleave peptide bonds in the dipeptide glycylglycine and the more complex protein myoglobin. Solution-based spectroscopic studies with Hf₁₂(sol) show direct coordination of the peptide bond to Hf(IV) centers, with substrate stabilization via cooperative binding to the cluster, whereas Hf₁₂(precip) shows reusability over multiple reaction cycles without loss of structural integrity. This highlights the potential of group IV metal-oxo clusters as synthetic proteases and offers a rare platform to correlate molecular reactivity with macroscopic catalytic behavior across phases, thereby deepening our understanding of how proteolytic reactions can be modulated by catalyst structure and solubility.