Metal-Ion Metathesis in Metal-Organic Frameworks: A Synthetic Route to New Metal-Organic Frameworks

A porous metal–organic framework, Mn(H3O)[(Mn4Cl)3(hmtt)8] (POST‐65), was prepared by the reaction of 5,5′,10,10′,15,15′‐hexamethyltruxene‐2,7,12‐tricarboxylic acid (H3hmtt) with MnCl2 under solvothermal conditions. POST‐65(Mn) was subjected to post‐synthetic modification with Fe, Co, Ni, and Cu according to an ion‐exchange method that resulted in the formation of three isomorphous frameworks, POST‐65(Co/Ni/Cu), as well as a new framework, POST‐65(Fe). The ion‐exchanged samples could not be prepared by regular solvothermal reactions. The complete exchange of the metal ions and retention of the framework structure were verified by inductively coupled plasma–atomic emission spectrometry (ICP‐AES), powder X‐ray diffraction (PXRD), and Brunauer–Emmett–Teller (BET) surface‐area analysis. Single‐crystal X‐ray diffractions studies revealed a single‐crystal‐to‐single‐crystal (SCSC)‐transformation nature of the ion‐exchange process. Hydrogen‐sorption and magnetization measurements showed metal‐specific properties of POST‐65. Please Mr. POST‐65 man: Ion exchange in metal‐ion frameworks was demonstrated to be a useful post‐synthesis modification method of MOFs to produce a series of isomorphous frameworks and a new framework that were difficult to synthesize directly (see figure).