<p>Natural aquatic systems harbour the world’s largest uranium reserves, a pivotal raw material underpinning the nuclear industry, sufficient to sustain global nuclear energy demand for millennia into the future. However, uranium extraction remains extremely challenging, attributed that uranium species form stable complexes with interfering substances (for example, CO₃²⁻, Ca²⁺), whereas conventional active moieties (adsorptive, catalytic) fail to interact effectively with the uranium core. Here we report a series of stable, selective and tunable adsorptive porous polymers that feature triangular binding pockets fabricated with metalloporphyrin as the wall components. The resulting adsorbent exhibits high uranium extraction capability with a removal efficiency over 96% in 1,500 min by robust micropore confinement and multi-coordination between CO₃²⁻ and the porphyrin cation. We demonstrate highly efficient uranium extraction from various natural waters (lake, salt lake brine and seawater) with a capacity as high as 79.8 mg g⁻¹ (24 days). This binding pocket design concept holds broad applicability for the rational design of versatile adsorbent materials, spanning electrochemical devices and precise molecular separation.</p>