MIL-100 (Fe, Cr) and MIL-101 (Fe, Cr), metal-organic frameworks (MOFs), have been assessed in solvent-free isomerization of dicyclopentadiene (DCPD) from the endo- to exo-form. In the isomerization reaction, the conversion of endo-DCPD and selectivity for the exo-dimer strongly depend on the nature of the active metal center. The MIL-100 (Fe) catalyst possessing more acid sites shows the highest catalytic activity among the MILs and it was readily recoverable and reusable in subsequent reaction cycles for the isomerization. The effects of reaction parameters such as temperature, reaction time, and catalyst loading on the reactivity were also investigated.