Abstract: To achieve efficient recovery of lanthanum ions (La³⁺), hydroxyl-functionalized biphenyldicarboxaldehyde was used as the building block in this study. It was condensed with two types of tritopic amino benzene moieties via Schiff-base reaction to yield two covalent organic frameworks (COFs), namely DHDPDA-TAPB and DHDPDA-TAPA. Subsequently, post-synthetic modification was performed to introduce phosphoric acid groups, yielding two functionalized materials namely DHDPDA-TAPB-P and DHDPDA-TAPA-P. Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and nitrogen adsorption-desorption measurement were employed to characterize their chemical structures, crystalline phases, specific surface areas and other physicochemical properties. Meanwhile, the lanthanum adsorption performance of the two materials was systematically investigated. Static adsorption experimental results reveal that both materials exhibit outstanding adsorption capacity toward La³⁺. The maximum adsorption capacities of DHDPDA-TAPB-P and DHDPDA-TAPA-P reach 197.51 mg/g and 165.85 mg/g, respectively. Such performance difference originates from the structural modulation of amine monomer backbones. XPS results confirm that the adsorption process is dominated by the coordination interaction between phosphate groups and La³⁺. This study offers a new strategy for the recovery of La³⁺ and provides a valuable reference for the structural design of rare earth adsorption materials.