UiO-66-NH2 and Magnetic Fe3O4@Cellu@UiO-66-NH2 Composite as Efficient Supports for Cellulase Immobilization: Synthesis, Characterization, Performance Evaluation, and Reusability

Abstract

This study investigated the synthesis, characterization, and performance of UiO-66-NH₂ and magnetic Fe₃O₄@Cellu@UiO-66-NH₂ composites as efficient supports for cellulase immobilization and reusability. UiO-66-NH₂ was synthesized using an amine-functionalized ligand (H₂BDC-NH₂) to enhance its enzyme adsorption capacity, whereas Fe₃O₄ nanoparticles were surface-modified with cellulose to facilitate the growth of UiO-66-NH₂ crystals, forming a magnetic composite. The materials were systematically characterized using XRD, FTIR, nitrogen adsorption–desorption isotherms with BET analysis, SEM–EDX, and TEM to evaluate their crystallinity, functional groups, surface area and porosity, morphology, and elemental composition. The high surface area and microporous structure of UiO-66-NH₂ (900.67 m²/g) made it suitable for enzyme immobilization, whereas the Fe₃O₄@Cellu@UiO-66-NH₂ composite offered additional advantages such as magnetic recoverability and improved pore accessibility. Both materials were employed for cellulase immobilization via physical adsorption, yielding enzyme loading capacities of 290.63 mg/g for UiO-66-NH₂ and 295.47 mg/g for the composite. Reusability tests showed that more than 68% of enzymatic activity was retained after 10 cycles, whereas storage stability tests indicated over 52% activity retention after 30 days at 4°C. These findings underscore the superior stability, reusability, and immobilization efficiency of UiO-66-NH₂-based composites, particularly Fe₃O₄@Cellu@UiO-66-NH₂, making them promising candidates for industrial biocatalysis and enzyme reuse applications.