ZIF-8/LDH Nanohybrids for Dye Adsorption: LDH Composition-Dependent Structure and Adsorption Performance

The development of nanoscale hybrid adsorbents with tunable surface properties is important for the efficient removal of organic pollutants from water. In this study, ZIF-8/LDH nanohybrids (ZIF-8/MgAl-LDH and ZIF-8/CaAl-LDH) were synthesized through an in situ growth strategy and evaluated for the adsorption of representative organic dyes. Structural characterization confirmed the successful formation of hybrid architectures with preserved crystallinity, high porosity, and strong interfacial integration between the MOF and LDH components. Comparative adsorption studies revealed that ZIF-8/CaAl-LDH exhibited superior performance, achieving approximately 94% removal of malachite green (MG) within 60 min under optimized conditions. Adsorption behavior was further investigated through kinetic, equilibrium, pH-dependent, pHPZC, and thermodynamic analyses. The results indicated that MG adsorption is governed by a combination of electrostatic attraction, hydrogen-bonding interactions, pore-filling within the porous ZIF-8 framework, and surface adsorption at the MOF-LDH interface. The enhanced adsorption performance of ZIF-8/CaAl-LDH is attributed to the synergistic combination of the high surface area and hierarchical porosity of ZIF-8 with the charge-regulated surface chemistry of the LDH component. In addition, the nanohybrid exhibited good structural stability and reusability during repeated adsorption–desorption cycles. These findings demonstrate that LDH composition plays a critical role in controlling the nanoscale interfacial structure and adsorption behavior of MOF-LDH nanohybrids and highlight the potential of ZIF-8/CaAl-LDH as an efficient adsorbent for dye-contaminated wastewater.