This study highlights ZIF-8's potential as an effective mRNA delivery platform, building upon its established role in biomedical applications. Our work demonstrates the ethanol-based coprecipitation of mRNA and ZIF-8 which achieves both stability during synthesis and efficient loading of mRNA. Addressing concerns of mRNA leakage from ZIF-8, we introduced PEI into the synthesis process, enhancing mRNA stability and protection against nucleases and biological media exposure. Characterization analyses confirmed the successful integration of mRNA-PEI within ZIF-8, establishing the resultant mRPZ as a robust delivery system with high loading efficiency and capacity. In vitro experiments demonstrated mRPZ's superior performance over conventional mRNA-PEI complexes, showcasing enhanced cellular uptake, minimal toxicity, and significant protein expression across diverse cell lines. Notably, mRPZ exhibited delayed but strong and sustained expression kinetics, indicative of prolonged mRNA release. Our in vivo work confirms our findings in vitro are translatable and the interesting properties demonstrated in vitro, like delayed release and improved expression compared to PEI alone, are consistent. We also noted interesting particle trafficking as the ZIF-8 coating increased particle uptake and expression in the lungs.