Dual‐Ligand Metal‐Organic Frameworks via In Situ Amidoxime Engineering for Selective Ion Separation

Metal‐organic frameworks (MOFs) are attractive candidates for ion extraction due to their ordered porous architectures. However, their inert surfaces with few binding sites limit their use in selective ion separation. Herein, inspired by the dual‐ligand coordination of oxime groups in biological carriers, a precise in situ amidoxime surface functionalization strategy (MOFs‐AO) is reported that preserves MOFs architecture while enabling high‐density controlled functionalization of amidoxime moieties for selective Ga(III) extraction. Density functional theory (DFT) calculations and molecular force measurements reveal that, unlike conventional monodentate with low electron density, amidoxime groups provide reinforced interactions with Ga(III) through spatially optimized N,O dual‐ligand coordination configuration. As a result, MOFs‐AO achieve a Ga(III) capacity of 205.13 mg g −1 and a Ga(III)/V(V) ratio exceeding 7.0 in challenging Bayer liquor, nearly one order of magnitude higher than comparable materials. When integrated into a polymeric network, the MOFs‐AO form a flow‐through reactor exhibiting high water flux (>1250 L m −2 h −1 ) and continuous Ga(III) recovery efficiency above 90% through successive in situ adsorption–desorption cycles. This work demonstrates a robust and generalizable surface‐engineering strategy for MOFs functionalization, advancing sustainable and selective ion separation.