Synthesis and design of Nickel-Enzyme Ligand Framework for adsorption and catalytic degradation of environmental pollutants

Abstract

Metal-organic frameworks (MOFs) are a versatile family of porous materials whose modular architecture enables tunable structural diversity and functional versatility. Here we performed the in-situ construction of MOF elements through the direct involvement of enzymes as ligand during framework formation (ELF). The synthesis has been performed in aqueous media and room temperature. In the absence of enzymes, Ni-MOF exhibited a typical compact, closed morphology, whereas enzyme-assisted synthesis produced well-defined snowflake-like microstructures. Notably, the enzyme structure played a key role in determining the final architecture. The use of larger enzymes resulted in the formation of a sandwich-like layered structure. Structural characterization confirmed the formation of a porous material with an average pore diameter size ranging from 3 to 6 nm and pore volumes between 0.17 and 0.22 cm³/g. The Ni-ELF hybrids exhibited surface areas ranging from 82 m²/g up to 139 m²/g (for Ni-ELF 1). Fluorescent labeling of the protein enabled the localization of the enzyme within the flake-like structures, showing a preferential distribution at the periphery while maintaining accessibility of the central region. This arrangement results in a novel hierarchical hybrid porous material with enhanced functional organization. These materials were evaluated for the adsorption of aquatic micropollutants, including rhodamine B (RhB), phenol, p-aminophenol (pAP), and p-benzoquinone (p-BQ). Ni-ELF 1 exhibited the highest adsorption efficiency, up to 300 ppm/h. Additionally, as a proof of concept, Ni-ELF 1 showed notable activity in the degradation by hydrolysis of direct PET bottle fragments into microstructured products (135 nmol of degradation products•mL⁻¹•day⁻¹).