Simple fabrication of bimetallic metal-organic framework derived magnetic flower-like composites for selective adsorption of hemoglobin: isotherm, kinetic, and thermodynamic studies

Abstract An abnormal level of well-known his-rich protein, hemoglobin is related to various diseases. Efficient isolation of hemoglobin is of great significance in early disease diagnosis and biomedical analyses. Developing high-performance adsorption materials has become a research hotspot at present. This study proposes a facile pyrolysis-based strategy to prepare novel magnetic flower-like composites for selective hemoglobin separation. Methoxy-polyethylene glycol-carboxyl (PEG) can impart adhesion resistance to improve adsorption selectivity due to its unique ethylene oxide groups and the repulsive elastic forces from compression of the brush-like chains. Two types of magnetic composites were constructed from bimetallic metal–organic frameworks utilizing Co 2+ and Ni 2+ ions as magnetic sources and metal nodes, as well as modification with or without PEG. The properties of the two composites were demonstrated via FTIR, SEM, TEM, DLS, XPS, TGA, BET, and VSM analyses, including flower-like morphology, uniform size (∼2 μm), good dispersibility, porous structure, large surface area, and good magnetic responsiveness. The protein adsorption capacity was further investigated from material factor including the composites modified with/without PEG and environmental factors including incubation time, protein concentration and incubation temperature. Moreover, the adsorption behaviors were explored by kinetics and thermodynamic analysis. Both the PEG-modified and non-PEG-modified composites were effective magnetic adsorbents for selective hemoglobin separation, besides exhibited different adsorption mechanism due to introduction of PEG which induced non-spontaneous selective adsorption rather than spontaneous pure physical adsorption. The magnetic bimetallic MOF system shows promise for isolating His-rich proteins from complex biological systems.