Hierarchical covalent organic framework-foam for multi-enzyme tandem catalysis

Area of Science:

• Materials Science
• Biocatalysis
• Nanotechnology

Background:

• Covalent organic frameworks (COFs) offer high porosity for biomolecule immobilization but are limited by micropores, hindering large enzyme loading and substrate diffusion.
• Hierarchical porous structures with micro-, meso-, and macropores are advantageous for enzyme catalysis, improving immobilization efficiency and reaction kinetics.

Purpose of the Study:

• To develop a hierarchical COF-foam matrix with enhanced porosity for efficient enzyme immobilization and biocatalysis.
• To investigate the performance of immobilized cellulolytic enzymes (β-glucosidase, cellobiohydrolase, endoglucanase) within the novel COF-foam structure.

Main Methods:

• Synthesized hierarchical TpAzo COF-foam using an in situ CO₂ gas effervescence technique to create macropores within the ordered 2D COF nanostructure.
• Immobilized multiple cellulolytic enzymes (BGL, CBH, EG) onto the TpAzo foam matrix.
• Evaluated enzyme activity, stability in organic solvents, and kinetic parameters (K_m, V_max) for substrate hydrolysis.

Main Results:

• The hierarchical TpAzo COF-foam exhibited 1.5 to 4-fold higher enzyme immobilization efficiency compared to conventional COFs.
• Immobilized enzymes retained high activity, with BGL showing stability in organic solvents and at room temperature.
• The multi-enzyme immobilized TpAzo foam successfully catalyzed the one-pot tandem conversion of carboxymethylcellulose to glucose over 10 cycles.

Conclusions:

• Hierarchical COF-foam structures effectively overcome the limitations of microporous COFs for enzyme immobilization and catalysis.
• The developed TpAzo COF-foam is a promising platform for efficient, recyclable multi-enzyme systems in tandem biocatalysis.
• This approach opens new avenues for designing advanced enzyme-immobilized materials for industrial biocatalytic applications.