Nb-MCM-Type Mesoporous Material Synthesis Using Ionic Solid as Structure-Directing Agent for In Situ Lipase...

Area of Science:

• Materials Science
• Nanotechnology
• Biocatalysis

Background:

• Mesoporous silica materials like MCM-41 and MCM-48 are widely used supports for enzyme immobilization due to their high surface area and tunable pore structures.
• Niobium incorporation into silica frameworks can enhance material properties, potentially improving enzyme stability and catalytic performance.
• Efficient immobilization of enzymes like Candida antarctica lipase B (CALB) is crucial for developing robust and reusable biocatalysts for industrial applications.

Purpose of the Study:

• To synthesize niobium-containing MCM-41 and MCM-48 (Nb-MCM) using 1-tetradecyl-3-methylimidazolium chloride ([C14MI]Cl) as a structure-directing agent.
• To immobilize Candida antarctica lipase B (CALB) enzyme in situ within the synthesized Nb-MCM supports.
• To evaluate the physicochemical properties, stability, and catalytic performance of the CALB-immobilized Nb-MCM materials for esterification reactions.

Main Methods:

• Synthesis of Nb-MCM-41 and Nb-MCM-48 using [C14MI]Cl and a Si/Nb molar ratio of 20.
• In situ immobilization of CALB enzyme within the Nb-MCM supports.
• Characterization using Scanning Electron Microscopy (SEM) to analyze morphology.
• Determination of surface area, pore volume, and pore size using BET analysis.
• Evaluation of enzyme reusability and stability through repeated esterification reactions and storage tests.
• Assessment of catalytic activity at different temperatures (40, 60, and 80 °C).

Main Results:

• Successfully synthesized Nb-MCM-41 and Nb-MCM-48 with regular spherical agglomerates (0.25–0.75 μm diameter).
• Nb-MCM-41 exhibited a surface area of 954 m²/g and pore volume of 0.321 cm³/g; Nb-MCM-48 showed 704 m²/g and 0.286 cm³/g, both with a pore size of 2.261 nm.
• CALB immobilized in Nb-MCM-41 achieved 26 recycles with 49.62% residual activity; in Nb-MCM-48, it achieved 16 recycles with 53.01% residual activity.
• Enzyme activity remained stable for 5 months under storage conditions.
• The immobilized enzyme catalyzed esterification effectively at temperatures up to 80 °C.

Conclusions:

• Niobium incorporation and [C14MI]Cl templating provide a viable method for creating highly active and selective enzyme catalysts.
• The synthesized Nb-MCM supports offer enhanced stability and reusability for immobilized enzymes, increasing catalyst service life.
• These novel enzyme catalysts demonstrate significant potential for industrial applications, particularly in high-temperature esterification reactions.