Roughly　4　billion　tons　of　uranium　exists　in　the　oceans,　which　equates　to　a　nearly　inexhaustible　supply　for　nuclear　power　production.　However,　the　extraction　of　uranium　from　seawater　is　highly　challenging　due　the　background　high　salinity　and　uranium＇s　relatively　low　concentration　(similar　to　3　mg　L-1).　Current　approaches　are　generally　limited　by　either　their　selectivity,　sustainability,　or　their　economic　competitiveness.　Here　we　engineered　a　biomass-derived　microporous　membrane,　based　on　the　interfacial　formation　of　robust　metalphenolic　networks　(MPNs),　for　uranium　capture　from　seawater.　These　membranes　displayed　advantages　in　terms　of　selectivity,　kinetics,　capacity,　and　renewability　in　both　laboratory　settings　and　marine　field-testing.　The　MPN-based　membranes　showed　a　greater　than　ninefold　higher　uranium　extraction　capacity　(27.81　mg)　than　conventional　methods　during　a　long-term　cycling　extraction　of　10　L　of　natural　seawater　from　the　East　China　Sea.　These　results,　coupled　with　our　techno-economic　analysis,　demonstrate　that　MPN-based　membranes　are　promising　economically　viable　and　industrially　scalable　materials　for　real-world　uranium　extraction.