Confinement-triggered conformational relaxation and electron transfer synergy in cytochrome c-encapsulated metal organic framework for robust removal of phenolic and dye pollutants.

Traditional wastewater remediation often relies on resource-intensive processes. Although enzymatic treatment offers a green and efficient alternative, the practical deployment of enzymes in sustainable industrial operations is hindered by the inherent instability of free enzymes and the compromised activity upon immobilization. Addressing this challenge, we report a facile strategy for the in situ encapsulation of cytochrome c (Cyt c) within a Cu-squarate metal-organic framework (Cyt c@Cu-MOF). Unlike conventional carriers, the Cu-MOF matrix induces a dual-modulation mechanism involving confinement-triggered conformational relaxation of Cyt c and electron transfer synergy with Cu nodes. This dual modulation enhances the catalytic efficiency (kcat/Km) by 3-fold compared to free Cyt c, achieving 1.6- to 14-fold and 3- to 16-fold improvements in removing diverse phenols and dyes, respectively. Mechanistic studies confirm that the confined microenvironment optimizes substrate accessibility to the enzyme active site and accelerates radical generation via the reversible Cu2+/Cu+ redox cycle. Notably, the Cyt c@Cu-MOF demonstrates exceptional stability under extreme environments, including high temperatures and organic solvents. In a continuous-flow reactor, it also demonstrates exceptional operational stability, maintaining over 95% degradation efficiency for 112 h of continuous operation and exhibiting a 2.5-fold higher treatment capacity than batch mode. This work not only provides a practical approach for high-efficiency enzyme immobilization but also elucidates the critical role of host-guest engineering in boosting enzymatic activity, providing a promising paradigm for the development of robust biocatalysts in sustainable industrial applications.