Abstract
ABSTRACT
Selective K
+
over Li
+
separation is indispensable for lithium recovery from salt‐lake brines, whereas simultaneous high‐efficiency separation of K
+
from interfering Na
+
and Mg
2+
cations remains challenging for pristine MOF membranes. Herein, an ultrathin
b
‐oriented Co‐gallate MOF membrane is fabricated using a gas–liquid interfacial soft‐template approach. The membrane possesses 3D interconnected zigzag subnanochannels (≈3.7 Å) that impose geometry‐confined ion dehydration, hindering the transport of Li
+
, Na
+
, and Mg
2+
far more significantly than K
+
, as corroborated by molecular dynamics simulations. Under a concentration gradient driving force, the u
b
‐CoG membrane achieves a prominent K
+
/Li
+
selectivity of 13.5, as well as excellent K
+
/Na
+
and K
+
/Mg
2+
sieving capability. The recorded K
+
/Li
+
selectivity stands as the highest value among MOF ion‐sieving membranes. This interfacial orientation strategy provides a promising pathway to advanced ion‐sieving membranes for multicomponent industrial brine lithium extraction.