Direct radiative heating at 200 °C quantitatively converts sulfoxide-tags to desirable vinyl groups on a porous zinc(ii) metal-organic framework analogue of IRMOF-9. The transformation results in an expansion of the pore volume of the framework and a higher surface area. The framework topology and crystallinity are preserved during thermolysis, as established by powder X-ray diffraction, thermal analysis and computational studies. Importantly, the volatile by-product is chemically benign and escapes without damaging the framework. In this way, the post-synthetic thermolysis yields a material with identical properties to that prepared by direct synthesis. This work expands the repertoire of post-synthetic thermochemistry for MOFs and demonstrates that high-temperature processes can be compatible with the retention of important framework properties.