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　(∼3　μg　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　metal-phenolic　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　μg)　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.　©　2019　The　Royal　Society　of　Chemistry.