Linker functionalization in MIL-47(V)-R metal-organic frameworks: understanding the electronic structure

Abstract

Metal–organic frameworks (MOFs) have gained much interest due to their intrinsic tunable nature. In this work, we study how linker functionalization modifies the electronic structure of the host MOF, more specifically, the MIL-47­(V)-R (R = −F, −Cl, −Br, −OH, −CH3, −CF3, and −OCH3). It is shown that the presence of a functional group leads to a splitting of the π orbital on the linker. Moreover, the upward shift of the split-off π-band correlates well with the electron-withdrawing/donating nature of the functional groups. For halide functional groups the presence of lone-pair back-donation is corroborated by calculated Hirshfeld-I charges. In the case of the ferromagnetic configuration of the host MIL-47­(V+IV) material a half-metal to insulator transition is noted for the −Br, −OCH3, and −OH functional groups, while for the antiferromagnetic configuration only the hydroxy group results in an effective reduction of the band gap.