BiomaterialBiomaterial-based separations of rare earth elementsRare earth elements (REEs) have gained significant attention over the past decade due to their high selectivity and potential for developing environmentally friendly processes. However, challenges such as high energy input and material production costs persist, impeding the development of scalable and practical applications. To address this issue, we introduce an innovative approach utilizing a thermo-responsive virus for the REE separation. Specifically, we genetically engineered the pVIII coat proteins of the Fd bacteriophageBacteriophage (phage) to express two peptides on a single phage: elastin-like peptideElastin-like peptide (ELP) and lanthanide-binding peptideLanthanide-binding peptide (LBP). This thermo-responsive lanthanide-binding phage (TR-LBPh) features ELP on the major pVIII coat protein, enabling temperatureTemperature-dependent coacervation in an aqueous solution, and LBP on recombinant pVIII coat protein, facilitating selective lanthanide binding in a pH-dependent manner. Utilizing the bifunctional characteristics of TR-LBPh, we demonstrate a selective REE recovery system through pH and temperatureTemperature modulations. This novel virus-based method holds significant potential for advancing sustainable REE recovery, offering an energy- and cost-effective solution for a largeTemperature-dependent coacervation scale.