Symmetry-guided syntheses of mixed-linker Zr metal–organic frameworks with precise linker locations

Abstract

While the one-pot reaction of zirconium metal ions with a mixture of two dicarboxylate heterolinkers yielded a 12-c fcu Zr MOF with randomly distributed linkers, the symmetry-guided stepwise reaction produced the same MOF with both linkers precisely located in the framework. In the latter method, linear terephthalic acid (H₂BDC) derivatives with mmm symmetry were inserted into the mmm-symmetry sites of the flexible Zr MOF with 8-c bcu topology (ZRN-bcu), which is composed of zigzag 2,6-naphthalenedicarboxylic acid with 2/m symmetry. Although the length of the symmetry-matching BDC²⁻ derivatives was much shorter than the distance between the unlinked nearest-neighbor Zr clusters in ZRN-bcu, induced fitting of the derivatives into the framework was possible, resulting in well-defined locations for the two different dicarboxylate linkers. Thus, controlled synthesis of MOFs with the desired topology and functionality can be achieved using a symmetry-guided approach.