Scalable Hollow Fiber Adsorbents for Metal Ion Recovery via Selective In-Pore MOF-808 Growth under Aqueous Conditions

Selective in situ growth of metal-organic frameworks (MOFs) within polymeric supports under mild, aqueous conditions remains a synthetic challenge due to interfacial instability, uncontrolled crystallization, and MOF leaching. Here, this study reports a binding-assisted strategy for the selective in-pore growth of MOF-808 within polyacrylonitrile (PAN)/polyvinyl pyrrolidone (PVP) hollow fibers at 30 °C. Alkaline hydrolysis of PAN introduces anchoring sites for zirconium clusters, while ethanol-assisted solvation promotes MOF crystallization under ambient conditions. The spatial distribution and surface charge of hydrolyzed PVP suppress MOF nucleation on the outer surface, enabling uniform in-pore growth with 34 wt.% loading and > 99% retention after ultrasonication. Post-synthetic functionalization with ethylenediaminetetraacetic acid (EDTA) imparts a strong affinity for Pb²⁺, Ni²⁺, and Co²⁺ ions. The EDTA-modified composite exhibits a 2.5-fold increase in Pb²⁺ adsorption kinetics compared to physically blended counterparts. A modularized 105 cm fiber unit effectively treats 1 L of a mixed-metal solution (10 ppm each), underscoring the scalability and process compatibility of this approach. This work demonstrates a mild, scalable, and leaching-resistant route for fabricating MOF-polymer hybrid sorbents through spatially controlled in-pore crystallization, offering a robust platform for water treatment and metal recovery applications.