The modifications of framework metal ions and ligands were investigated in metal–organic frameworks (MOFs). The transmetalated MOFs were obtained by soaking an MOF in the solution of a new replacing metal ion. By simply controlling the soaking time, not only fully transmetalated isostructural framework structure but also selectively transmetalated core-shell bimetallic structure could be prepared. The ligand exchanged MOFs were obtained via soaking an MOF in the solution of a new replacing ligand. When a 3-D pillared MOF with bipy as a pillaring ligand, [Ni(HBTC)(bipy)], was soaked in another potential pillaring ligand, dabco, new MOFs, [Ni(HBTC)(dabco)] and [Ni2(HBTC)2(bipy)(dabco)] (where H3BTC = 1,3,5-benzenetricarboxylic acid, dabco = 1,4-diazabicyclo[2.2.2]octane and bipy = 4,4'-bipyridine) were prepared via postsynthetic ligand exchanges. By controlling the concentration of dabco, not only entropically favorable [Ni(HBTC)(dabco)] with completely exchanged dabco but also enthalpically favorable [Ni2(HBTC)2(bipy)(dabco)] with selectively exchanged bipy/dabco in the alternating layers could be obtained. In addition, isoreticular and polymorphic 3-D MOFs were prepared via the combination of direct solvothermal reactions using Ni(II) ion and H3BTC as building components and bipy or pyrazine as a pillar between the sheets, postsynthetic ligand exchanges of the MOFs prepared via the direct solvothermal reactions and postsynthetic ligand insertions into a 2-D MOF. While there is no significant structural rearrangement of the framework during the replacement of the framework metal ion, the ligand exchanges and insertions led to the significant structural reorganizations of the framework.

Postsynthetic modifications of metal-organic frameworks

251st National Meeting (2016)

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