Herein, a hollow spherical pillar[5]arene-based polymer (P5-AO) adsorbent was synthesized. The P5-AO adsorbent was capable of effectively capturing uranium from simulated seawater (139.5 mg g -1 ) and real seawater (8.1 mg g -1 ). We also elucidated the uranium adsorption mechanism of P5-AO via extended X-ray absorption fine structure (EXAFS). This study provides a novel direction for the development of uranium capture adsorbents.