Postsynthesis Annealing of MOF‑5 Remarkably Enhances the Framework Structural Stability and CO₂ Uptake

Structural stability and porosity characteristics of metal–organic frameworks (MOFs) are of great importance for practical applications, such as gas sorption/storage and catalytic support. By means of a simple and effective method of postsynthesis thermal annealing below its framework decomposition temperature, the annealed MOF-5 shows unexpectedly high CO₂ uptake up to 2 mmol g^–1 at 25 °C and 1 bar, which is more than double the capacity of the untreated counterpart (0.8 mmol g^–1). Structural characterizations reveal that the annealed MOFs are very active with local vacancy sites due to partial decomposition of the bridging carboxylates of the framework linker. The annealed MOFs also show high stability for cyclic CO₂ uptake and air/moisture. Such an approach may be effectively applied to other MOF structures or MOF based membranes to enhance their gas uptake or separation.