When the Solvent Locks the Cage: Theoretical Insight into the Transmetalation of MOF-5 Lattices and Its Kinetic Limitations

Abstract

Transmetalation is an innovative postsynthetic strategy for tailoring the properties of metal−organic frameworks (MOFs), allowing stable unprecedented metal coordination environments. Although the experimental synthetic protocol is wellestablished, the underlying mechanism for transmetalation is still unknown. In this work, we propose two different solvent-mediated reaction paths for the Ni transmetalation in Zn-MOF-5 lattices through density functional theory simulations. In both mechanisms, the bond strength between the exchanged metal and the solvent is the key descriptor that controls the degree of transmetalation. We also show that the role of the solvent in this process is twofold: it initially promotes Zn exchange, but if the metal−solvent bond is too strong, it blocks the second transmetalation cycle by restricting the lattice flexibility. The competition between these two effects leads the degree of incorporation of metal into MOF-5 to display a volcano-type dependence with respect to the metal−solvent bond strength for different transition metal ions.

Dynamic DMF Binding in MOF-5 Enables the Formation of Metastable Cobalt-Substituted MOF-5 Analogues

“…Yet, the fact that only one Zn 2+ ion in each SBU may exhibit a coordination number above four at any given time is in line with our previous observation of cation exchange in MOF-5: when Ni 2+ ions replace Zn 2+ in this material, they assume octahedral geometry, and accordingly no more than one Ni 2+ ion can be inserted in each SBU. 29 , 30 Importantly, however, the experiments above demonstrate that DMF binding to MOF-5 clusters is dynamic . In other words, as long as the metal ions within the SBUs can support fast exchange between 4-, 5-, and 6-coordinate species, DMF could bind indiscriminately to any one of the four metal ions and exchange between these ions rapidly regardless of their identity.…”

Methane Storage: Molecular Mechanisms Underlying Room-Temperature Adsorption in Zn4O(BDC)3 (MOF-5)

“…In particular, identifying specific chemical or structural elements that govern optimal adsorption is of critical importance, as these could potentially be post-synthetically introduced, or alternatively, incorporated as a component in a specifically crafted adsorption system. The Zn4O(BDC)3 framework (where BDC 2-= 1,4benzenedicarboxylate), also known as MOF-5 or IRMOF-1, can be considered as a benchmark system for understanding gas-sorption processes in MOFs, [8][9][10] MOF chemistry 11,12 and CH4 adsorption [13][14][15] in particular. As seen in Figure 1, MOF-5 has a cubic crystalline structure which consists of tetrahedral Zn4O clusters coordinated by carboxylate-terminated BDC linkers.…”

Complete Transmetalation in a Metal–Organic Framework by Metal Ion Metathesis in a Single Crystal for Selective Sensing of Phosphate Ions in Aqueous Media

“…[12] Finally,after successive steps,the complete exchange of metal ion occurs (Figure 2c). In the present work, the metal exchange was successful only in DMF solvent, and it was found to fail in methanol and acetone.A dissociative mechanism is assumed to take place,s ince the bond between the metal and the organic linker in the MOF is not too strong and can be broken, especially if it is displaced by the solvent.…”

“…Thei nitial step involves the active participation of the DMF,a nd it induces the breaking of Ba À Ob ond resulting in as winging carboxylate group.T his group is then free to coordinate to anearby Tb(DMF) n 3+ .The replacement of one of the carboxylate unit at the Ba center by DMF yielding an intermediate,then the COO À moiety successively coordinates to Tb(DMF) n 3+ ,l eading to the next intermediate. [12] Finally,after successive steps,the complete exchange of metal ion occurs (Figure 2c).…”