Strain‐Mediated Anisotropic Growth of Metal–Organic Framework Belts

ABSTRACT Metal–organic frameworks (MOFs), such as zeolitic imidazolate framework‐L (ZIF‐L), are organized porous materials that are sensitive to synthesis and processing conditions. Here, we report a one‐pot, purely aqueous route that couples pH‐controlled anisotropic growth of ZIF‐L platelets to unique belt morphologies and surface functionalization with citric‐acid‐capped Fe 3 O 4 magnetic nanoparticles. This interfacial stabilization control of originally metastable layered MOF phases yields magnetically responsive nanomaterials without organic solvents, surfactants, or post‐synthetic processing. By adjusting the basicity of the 2‐methylimidazole environment, conventional ZIF‐L leaf platelets reproducibly evolve into high‐aspect‐ratio, elongated, belt‐like platelets with an aspect ratio of ∼10, while retaining the layered organization of the original ZIF‐L phase. Plane‐resolved x‐ray peak shifts (Δd/d ratio) show distinct, anisotropic lattice distortions, suggesting a stabilization mechanism in which interfacial coordination of carboxylate groups to under‐coordinated surface Zn 2+ sites moderates layer relaxation and reconstruction pathways during synthesis and nanoparticle addition. This approach provides unique MOF belt morphology with enhanced phase stability and may be suggested as a scalable strategy for producing stable, anisotropic, magnetically responsive MOF‐based nanocomposites with non‐traditional shapes.