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

ABSTRACT 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, Hf ₁₂ (sol), and its insoluble counterpart, Hf ₁₂ (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 Hf ₁₂ (sol) show direct coordination of the peptide bond to Hf(IV) centers, with substrate stabilization via cooperative binding to the cluster, whereas Hf ₁₂ (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.