► Solvent exchange method was used to activate Zr-MOF. ► Nanosize Zr-MOF exhibits high surface area and thermal stability. ► Nanosize Zr-MOF presents high adsorption of H2 and CO2. ► The heat of H2 adsorption is low and was estimated to be 6–12kJmol−1. A nanosize Zr-metal organic framework (Zr-MOF, UiO-66) with a uniformed particle size around 100nm was solvothermally synthesized and activated by solvent exchange method, vacuum drying and heating. The activation process with an exchangeable guest solvent produced the Zr-MOF with a high surface area by removal almost all guest and free terephthalic acid molecules from the pores enhancing its capacity for adsorption. The nanosize Zr-MOF also showed strong thermal stability up to 753K. The Zr-MOF was tested for hydrogen and carbon dioxide adsorption at varying pressures and temperatures and it exhibited adsorption capacity of 1.6wt% (H2) at 1atm, 77K and 79cc (CO2)g−1 at 1atm, 273K, respectively. The heat of H2 adsorption was estimated to be 6–12kJmol−1 while the heat of CO2 adsorption was determined to be around 28kJmol−1.