Linker Functionalization in MIL-47(V)-R Metal-Organic Frameworks: Understanding the Electronic Structure

TL;DR

This study investigates how different linker functional groups in MIL-47(V)-R MOFs influence their electronic structure, revealing shifts in π-bands and magnetic state-dependent band gap modifications.

Contribution

It provides detailed insights into the electronic effects of various functional groups on MIL-47(V)-R MOFs, including band splitting and magnetic state-dependent electronic transitions.

Findings

Functional groups cause π-orbital splitting and band shifts.

Lone-pair back donation observed in halide groups.

Certain functional groups induce magnetic state-dependent band gap changes.

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, -CH$_3$, -CF$_3$, and -OCH$_3$). It is shown that the presence of a functional group leads to a splitting of the $\pi$-orbital on the linker. Moreover, the upward shift of the split-off $\pi$-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 case of the ferromagnetic configuration of the host MIL-47(V$^{\mathrm{+IV}}$) material a half-metal to insulator transition is noted for the -Br, -OCH$_3$, and -OH functional groups, while for the anti-ferromagnetic configuration only the hydroxy-group results in an effective reduction of the band gap.