Magnetic montmorillonite (MMT) nanomaterials are developing into highly promising adsorbents because they possess a large surface area, and excellent magnetism. However, the lack of a green synthesis and the absence of appropriate functional groups for selective adsorption limit their application on a wider scale. In this work, magnetic MMT nanocomposites (Fe₃O₄-Cu²⁺/MMT) were prepared in a facile manner without employing any hazardous organic solvents. A qualitative comparison of several factors showed these reported materials are synthesized via a procedure that is more green than is traditionally reported for these types of adsorbents. These Fe₃O₄-Cu²⁺/MMT nanomaterials function as a novel, selective adsorbent for the bovine hemoglobin (BHb). The MMT and Fe₃O₄-COOH nanoparticles respectively act as the carrier and magnetic component, while the copper ions play the role of a co-functional monomer for selectively removing BHb. In addition to imparting magnetic properties onto the material, the Fe₃O₄-COOH nanoparticles also facilitate the attachment of copper ions through chelation during the synthesis. The chemical, physical, and adsorptive properties of Fe₃O₄-Cu²⁺/MMT nanomaterials were comprehensively investigated via adsorption experiments and various characterization methods. The results demonstrated that the hybrid nanomaterials exhibited multiple outstanding features such as their excellent magnetism, adsorption capacity (638.6 mg g⁻¹), and selectivity (S > 3.69) towards BHb. Moreover, the nanocomposites have been effectively utilized for selectively separating and enriching BHb molecules from bovine blood samples, confirming its practicality for analysis of real biological samples.