From Anisotropic Aluminum-MOF Rods to Oriented Membranes: Stepwise Coordination-Editing for Geometry-Governed Isomer Separation

Oriented metal-organic framework (MOF) membranes featuring one-dimensional (1D) channels are highly sought after for molecular separations due to minimal transport tortuosity. Nevertheless, realizing such oriented architectures, particularly for Al-MOFs, is challenged by high coordination barriers and anisotropic crystal growth, often compromising the membrane integrity and obscuring the anticipated transport advantages. Here, we report a stepwise coordination-editing synthesis strategy that circumvents these limitations by redirecting the formation of oriented Al-MOF membranes from conventional "nucleation-growth" to an endogenous pathway within a prestructured coordination (PSC) scaffold. The PSC scaffold, established under a mild kinetic trapping regime, forms a coordination-saturated Al-carboxylate network that predefined membrane continuity prior to crystallization. Subsequent thermal activation triggers terminal-to-bridging bond rearrangement within this scaffold, initiating the propagation of Al-O-Al connectivity and enabling its collective directional development across the membrane. Because this endogenous process does not rely on external nucleation or lateral intergrowth, it simultaneously achieves highly aligned 1D channels, compact grain boundaries, and robust interfacial adhesion to the support. As a demonstration, we fabricated the first highly 1D channel-oriented Al-bttotb membranes, enabling direct and efficient liquid-phase separation of C6 isomers relevant to light naphtha processing. The membranes exhibit high permeation fluxes for linear alkanes and favorable separation factors in both binary and multicomponent systems, outperforming state-of-the-art membranes. This work establishes endogenous crystallization as an alternative pathway for translating anisotropic Al-MOFs into functional membrane beyond conventional growth-based approaches.