Influence of reaction conditions on the channel shape of 3d-4f heterometallic metal–organic framework

Abstract

Three structural kinds of 3d-4f metal–organic-frameworks (MOFs), {[Ln₄(ox)₃(Ni(IDA)₂)₃(H₂O)₆]}_n·xnH₂O (Type I: LnLa, Nd, Eu, Gd; IDA = iminodiacetate, ox = oxalate), {[Ln₂ (ox)(Ni(IDA)₂)₂(H₂O)₂]}_n·2nH₂O (Type II: LnLa, Pr, Nd, Eu) and {[Dy₂(ox)₂Ni(IDA)₂(H₂O)₂]}_n·2nH₂O (Type III), have been synthesized under hydrothermal condition. The crystal structures consist of Ln-oxalate tetramers for Type I, dimers for Type II and one-dimensional polymers for Type III bridged by the metalloligand [Ni(IDA)₂]²⁻. While Type I contains a mixture of “Ln₆Ni₄-parallelogram” (A-Type) and “Ln₆Ni₂-parallelogram” (B-Type) channels, Type II and Type III contain only A-type and B-type channels, respectively. A fairly high stability of the MOFs is indicated by thermogravimetric analyses and reversible dehydration and rehydration of guest water molecules, which is confirmed by single crystal-to-single crystal transformation of 1 and 5.