Zeolitic imidazolate framework-8 (ZIF-8) is regarded in this study as a simple and lowcost alternative catalyst for the isomerization of glucose and the production of 5-hydroxymethyl furfural (HMF). Two methods of preparing ZIF-8 catalysts were investigated: room temperature and hydrothermal synthesis at 140 °C. The hydrothermal synthesis method yields a material with a very large surface area (1967 m 2 g -1 ). When used as a catalyst, the ZIF-8 materials produced excellent fructose yields. ZIF-8 prepared by hydrothermal synthesis had a fructose selectivity of 65% and a glucose conversion of 24% at 100 °C in aqueous reaction medium. The selectivity dropped dramatically when the reactions were repeated at higher temperatures (140 °C). Surprisingly, higher temperatures resulted in higher levels of mannose production. Due to a lack of strong Brnsted acidity, ZIF-8 materials had low HMF yields. Despite the excellent performance of ZIF-8 catalysts in batch reactions, their activity did not translate well to the flow reactor during an 8-hour continuous run with a residence time of 6 minutes. The activity of ZIF-8 in the flow reactor at 100 °C was halved in 3 hours, implying that the catalyst's stability was not maintained in the long run.