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RESEARCH PRODUCT

MIL-53(Al) under reflux in water: Formation of γ-AlO(OH) shell and H2BDC molecules intercalated into the pores

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Abstract It is shown that treatment of MIL-53(Al) (Al(OH)BDC·H2O, BDC = 1,4-benzene dicarboxylate) under reflux in water results in a progressive transformation of the solid into a new well crystallized phase. After reflux for 10 h or more the new phase is obtained in a pure form and its XRD pattern was indexed in a monoclinic system with the following cell parameters: a = 19.47 A, b = 8.98 A, c = 6.60 A, β = 107.7°. Characterization of the obtained solid by TGA, FT-IR, NMR, TEM and XRD has revealed that its composition is [0.8Al(OH)BDC·0.2H2BDC] + 0.2γ-AlO(OH). Formation of this material indicates that under reflux in water a partial hydrolysis of the MOF network occurs producing H2BDC molecules (occluded in the pores) and γ-AlO(OH) species. The latter is shown to form a thick shell (100–200 nm) consisting of strongly crumpled sheets of 3 nm of thickness. Formation of γ-AlO(OH) under reflux in water allows to use such treatment as an easy way to modify the surface properties of MIL-53(Al). We showed that treatment of MIL-53(Al) under reflux in water for a short time (