Synthesis and Structural Evolution of Zn-Ni ZIF Materials: From Cubic to Lamellar Frameworks

Understanding metal-dependent structural phase transitions in zeolitic imidazolate frameworks (ZIFs) remains a key challenge for the rational design of functional materials, particularly in controlling the transformation between distinct polymorphs such as ZIF-8 and ZIF-L. Despite recent advances, the role of transition-metal incorporation in directing phase evolution and tuning physicochemical properties is still not fully understood. This study reports the synthesis and structural evolution of bimetallic Zn_1-x Ni _x (x = 0-0.8) zeolitic imidazolate frameworks prepared via a rapid methanolic precipitation route at room temperature. The results demonstrate that Ni incorporation drives a composition-dependent phase transition from the cubic ZIF-8 framework to the lamellar ZIF-L structure, revealing a controllable structural evolution in Zn-Ni ZIF systems. The effects of Ni incorporation on crystal structure, morphology, porosity, and thermal stability were systematically investigated by XRD, Raman spectroscopy, SEM/EDS, N₂ physisorption, and TGA analyses. XRD and Rietveld refinement indicate that low Ni incorporation (x ≤ 0.2) preserves the ZIF-8 topology, while higher Ni contents (x ≥ 0.4) induce lattice strain, peak broadening, and the emergence of the ZIF-L phase. Raman spectroscopy reveals increased structural disorder and the coexistence of different coordination environments. Physisorption results show a gradual decrease in surface area and microporosity, while thermal analysis indicates that Ni incorporation modulates framework stability. CO₂ adsorption results highlight the influence of phase evolution and morphology on adsorption performance. Overall, these findings demonstrate that Ni acts as a structural modulator and phase-directing agent, enabling controlled tuning of the ZIF-8 to ZIF-L transformation, with potential implications for the design of advanced materials for catalysis and gas adsorption.