Programmable MOF–CNC Nanohybrid Networks Enabling Ion Transport Sensing and Efficient Water Purification

The development of processable adsorbent materials that combine high capacity, fast transport, and structural stability remains a key challenge for water treatment applications. Here, a dispersible ZIF-cellulose nanocrystal (ZIF-CNC) nanohybrid platform is introduced and integrated within a poly(vinyl alcohol)-carboxymethylcellulose (PVA-CMC) matrix to form architecture-tunable materials with controlled transport properties. The nanohybrid enables uniform dispersion of ZIF-8 domains while preserving accessible porosity and interfacial functionality. By varying processing routes, the same composition is reconfigured into hydrogels and cryogels, allowing decoupling of composition from structure. In the hydrogel state, NaCl conditioning promotes ion enrichment and high ionic conductivity (up to 8.3 S·m^-1), while in the cryogel state, freeze casting generates a highly porous and interconnected architecture (91% porosity, 0.14 g·cm^-3 density) that enhances mass transport. The freeze-cast cryogel exhibits superior adsorption performance, achieving 97.6% removal of methylene blue and a maximum Cu²⁺ adsorption capacity of 154.5 mg·g^-1 with 89.6% removal efficiency. Adsorption follows pseudo-second-order kinetics (R² = 0.999) and is dominated by coordination and interfacial interactions at ZIF-CNC domains. The improved pore connectivity and accessibility in freeze-cast structures reduce mass transfer limitations and enhance utilization of active sites. Practical applicability is demonstrated through seed germination assays, where treated water restores plant growth to near-reference conditions. This work highlights a scalable strategy for coupling MOF nanohybrids with architecture-directed processing to control transport and adsorption performance, providing a versatile platform for high-efficiency water treatment.