A thermally promoted postsynthetic rearrangement has been performed on a zinc IRMOF-9-type framework bearing dimethylthiocarbamate tag groups. The rearrangement was accomplished via conventional heating at 285 °C. Crucially, despite the high temperature, the MOF maintains its high accessible surface area and pore space following thermal treatment. The structures and physical properties of the frameworks were characterized by a combination of single-crystal X-ray diffraction, powder X-ray diffraction, differential thermal-thermogravimetric analysis, and gas sorption analysis. The rearrangement results in a slightly higher level of CO2 adsorption for the modified MOF but with equivalent heat of adsorption. This work offers new perspectives on postsynthetic rearrangements in MOFs and demonstrates that rearrangements that occur at relatively high temperatures are still compatible with the need to retain the structural integrity and porosity of the framework.