Relief of forbidden catenation in a metal-organic framework: Network conversion from interpenetration-frustrated gra to interpenetration-allowed hms topology

Abstract

Controlling the interpenetration in MOFs is important, because the degree of interpenetration affects not only their porosity but also their stability. MOFs thermodynamically prefer to have a densely packed interpenetrated structure when the net topology and dimensions of building blocks allow for interpenetration. When the net topology of a MOF does not allow interpenetration because of collision, even MOFs with extremely large porosity can be prepared. Here, we report for the first time a thermal conversion from a less densely packed noninterpenetrated MOF with an interpenetration-frustrated topology to a more densely packed twofold interpenetrated analogue with an interpenetration-allowed topology. We prepared a MOF with an interpenetrationfrustrated gra topology via postsynthetic ligand insertion into a 2D MOF of hcb topology. The MOF with forbidden catenation was thermally converted into a MOF with an interpenetration-allowed topology. The topology conversion from an interpenetration-frustrated gra net into an interpenetration-allowed hms net was accompanied by an increase in the packing density of the MOF. The resultant MOF had superior thermal stability and crystallinity compared with its parent crystal because of enhanced long range ordering in the interpenetrated network.