Multivariate Metal–Organic Frameworks Ranging from a Homogeneous Uniform Distribution to Heterogeneous 1D, 2D, and 3D Distributions of Mixed Building Blocks

Post-synthetic exchange serves as a potent technique to craft multivariate metal–organic frameworks (MOFs). These MOFs outperform in properties beyond the mere fusion of individual components. The post-synthetic ligand exchange (PLE) process in anisotropic 3D MOFs, which have pillared 2D layers, can cause a 1D contraction of the framework structure. This process can be effectively regulated by manipulating the temperature. At lower temperatures, the mixed building blocks form a microstructural MOF, which is homogeneous with a uniform distribution. However, as the temperature increases, the distribution transforms. It becomes heterogeneous, featuring a 2D concentric distribution of mixed building blocks. The reverse PLE process triggers a 1D expansion of the framework structure. This can create a heterogeneous microstructural MOF characterized by a 1D sandwiched distribution due to varying exchange kinetics between the layers. However, as temperatures increase, this layer selectivity diminishes, leading to a change of the building block distribution in the MOF structure. It evolves into another form of a heterogeneous microstructural MOF, this time exhibiting a 3D core–shell distribution.