Zeolitic imidazolate frameworks (ZIFs) are a class of metal-organic frameworks (MOFs) with large porosity and high surface area. Although nanoscale ZIFs have various applications in targeted drug delivery, water purification, gas storage, and etc, their toxicity is not well studied yet. In the present study, the nanoscale zeolitic imidazolate framework-8 (ZIF-8), constructed from zinc ions and 2-methyl imidazole in ambient conditions and characterized using TEM, FESEM, XRD, DLS, EDS, and BET. Based on the SEM results, the average particle size of produced ZIFs was about 103.95 nm. Also based on the BET results, the mean pore diameter of this product was 2.51 nm. Aquatic toxicity of as-synthesized ZIF-8 nanoparticles was assessed using adult zebrafish (Danio rerio) in accordance with OECD test guideline No 203. Fish were exposed to increasing concentrations of ZIF-8 NPs including 0 (control), 1, 10, 20, 40, 60, 80, 100, 140, and 200 mg/L in 1000 mL glass vessels under 16 h light: 8 h dark. The numbers of dead animals were recorded at 24, 48, 72, and 96 hours and lethal concentrations (LCs) were estimated using Probit analysis program. The median effective concentration (LC50) of ZIF-8 NPs was calculated as 165.229 mg/L. Although this result reveals low acute toxicity of ZIF-8 NPs for freshwater fish, D. rerio, more experiments are necessary to investigate long term effects of this nanostructure material on aquatic species.

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