Postsynthetic Improvement of the Physical Properties in a Metal-Organic Framework through a Single Crystal to Single Crystal Transmetallation

A single crystal to single crystal transmetallation process takes place in the three-dimensional (3D) metal-organic framework (MOF) of formula Mg-2(II){Mg-4(II)[Cu-2(II)(Me(3)mpba)(2)](3)}45H(2)O (1; Me(3)mpba(4-)=N,N-2,4,6-trimethyl-1,3-phenylenebis(oxamate)). After complete replacement of the Mg-II ions within the coordination network and those hosted in the channels by either Co-II or Ni-II ions, 1 is transmetallated to yield two novel MOFs of formulae Co-2(II){Co-4(II)[Cu-2(II)(Me(3)mpba)(2)](3)}56H(2)O (2) and Ni-2(II){Ni-4(II)[Cu-2(II)(Me(3)mpba)(2)](3)} 54H(2)O (3). This unique postsynthetic metal substitution affords materials with higher structural stability leading to enhanced gas sorption and magnetic properties.