Heterogenization of Rh(II) porphyrin catalysts in a metal–organic framework is crucial for catalyst turnover in thermal olefin hydrosilylation and hydrogermylation. Unlike MOF-supported metalloradical catalysts, homogeneous analogues convert to closed shell species that obstruct catalytic turnover. Site-isolated Rh(II) metalloradicals are readily accessed via MOF synthesis with a linker containing