Cellulose-based three-dimensional scaffolds with in-situ MOF growth for enzyme-immobilized modular reactors: A sustainable strategy for chemical pollutant degradation

Metal organic frameworks (MOFs) are porous crystal-structured materials with high specific surface area and chemical properties that offer unique advantages as enzyme immobilization carriers. However, MOFs suffer from nanoparticle aggregation and poor recyclability. This study proposes a strategy utilizing the multiscale pore architecture of wood to host MOFs as enzyme immobilization platforms. Initially, microporous HKUST-1 was grown in situ in the oriented macropores of delignified wood. Subsequently, a partial cation substitute reaction (Cu²⁺→Fe³⁺) coupled with hydrolysis-assisted conversion transformed HKUST-1 into HP-MIL-100(Fe), yielding MOF@Wood composite. The experimental data demonstrated the enzyme loading capacity of 68.92 mg/g for the porous carrier matrix. Notably, the immobilized enzyme showed greater environmental tolerance, retaining more than 80 % of its relative activity after incubation at 60°C for 2 h and more than 70 % of its activity in an alkaline environment (pH 9). Furthermore, a gravity-driven catalytic degradation reactor was designed, which demonstrated nice degradation efficiency (achieving a maximum phenol degradation rate of 97.21 % at 120 mg/L) and reusability (maintaining 85.29 % degradation efficiency after 8 cycles). By utilizing biomass-derived porous carriers, this study provides a green and sustainable solution for phenolic wastewater treatment. • The prepared MOF@Wood has a hierarchical porous structure, which improves the enzyme loading and catalytic efficiency. • HRP@MOF@Wood degrades 99 % of phenol at low concentrations (<40 mg/L). • A gravity-driven and adjustable device was developed to make it suitable for continuous wastewater treatment processes. • This work provides an eco-friendly, scalable approach for phenolic wastewater treatment.