Surface-chemistry control of enzyme–substrate coupling in porous supports for benzotriazole transformation

The performance of enzyme-assisted systems for transforming persistent organic contaminants is often interpreted as an apparent adsorption–catalysis synergy; however, the interfacial factors governing enzyme–substrate coupling remain poorly understood. Here, we demonstrate that benzotriazole (BTA) transformation in immobilized laccase systems is governed by the support interface's physicochemical properties rather than by adsorption capacity alone. Laccase was immobilized on activated carbon (ACK) and MOF-199, enabling a direct comparison between a chemically heterogeneous carbon surface and a structurally ordered porous framework. Although MOF-199 exhibited higher initial BTA uptake at short contact times, the overall transformation efficiency after 120 min reached ∼92% for ACK–laccase, compared to ∼68% for MOF-199–laccase under identical conditions. This contrast is not explained by enzyme loading (82 mg g −1 for ACK vs. 65 mg g −1 for MOF-199) or by equilibrium adsorption, but by differences in the effective coupling between substrate confinement and catalytic accessibility. Kinetic analysis showed that the apparent rate constant for BTA transformation in the ACK-supported system was about 1.7-fold higher than in the MOF-based system, while diffusion modeling indicated reduced intraparticle transport limitations within the carbon matrix. Surface characterization further suggests that the disordered distribution of functional groups in ACK promotes a broader range of interaction energies, enhancing substrate mobility toward the enzyme's active site. In contrast, the confined and chemically uniform environment of MOF-199 imposes orientation and diffusion constraints that limit catalytic turnover. These findings demonstrate that removal efficiency in enzyme–solid systems is governed not by adsorption equilibria but by the nature of the interface that mediates substrate accessibility and reaction dynamics. This work establishes surface chemistry as a primary control parameter in interfacial reaction engineering and provides a mechanistic basis for the rational design of hybrid catalytic materials.