Effects of ligand functionalization on the photocatalytic properties of titanium-based MOF: A density functional theory study

Abstract

The first principle calculations have been performed to investigate the geometries, band structures and optical absorptions of a series of MIL-125 MOFs, in which the 1,4-benzenedicarboxylate (BDC) linkers are modified by different types and amounts of chemical groups, including NH2, OH, and NO2. Our results indicate that new energy bands will appear in the band gap of pristine MIL-125 after introducing new group into BDC linker, but the components of these band gap states and the valence band edge position are sensitive to the type of functional group as well as the corresponding amount. Especially, only the incorporation of amino group can obviously decrease the band gap of MIL-125, and the further reduction of the band gap can be observed if the amount of NH2 is increased. Although MIL-125 functionalized by NH2 group exhibits relatively weak or no activity for the photocatalytic O2 evolution by splitting water, such ligand modification can effectively improve the efficiency in H2 production because now the optical absorption in the visible light region is significantly enhanced. Furthermore, the adsorption of water molecule becomes more favorable after introducing of amino group, which is also beneficial for the water-splitting reaction. The present study can provide theoretical insights to design new photocatalysts based on MIL-125.

Effect of Ligand Functionalization on the Rate of Charge Carrier Recombination in Metal–Organic Frameworks: A Case Study of MIL-125

“…The top of the valence band in the original compound MIL-125 is represented by the ligand-centered orbitals, mainly constructed from the contributions of C and O atoms. Substitution of hydrogen in the benzene ring by the NH 2 -, OH-, or SH- side group leads to the appearance of additional ligand-centered bands with a substantial contribution from the N, O, or S atoms at the top of the valence band, in agreement with previously reported results. ,− The position of these bands is shifted upward in energy with respect to the rest of the valence band manifold by approximately 1.5 eV in the case of NH 2 and SH side groups and 1 eV in the case of the OH group. The conduction band edge is mainly composed of the Ti, C, and O atomic orbitals and, as expected, ,, stays practically intact upon ligand modification.…”

Cerium Metal–Organic Framework for Photocatalysis

“…Porous metal–organic framework (MOF) materials with inorganometallic nodes and tailorable organic ligands find widespread applications such as catalysis, gas storage, and gas separation . Recently, the use of MOFs as photocatalysts has aroused great interest. , An important promoter of this interest is that MOFs can facilitate the diffusion of reactants to the active sites to potentially overcome the low charge mobility of many nonporous semiconductors. In addition, some MOFs are effective at adsorbing gas molecules; thus a single MOF has the potential to act as a dual-functional material in both capturing and converting reactants (e.g., CO 2 ), thereby reducing the complexity of the photocatalytic system.…”

Metal–Organic Frameworks: Molecules or Semiconductors in Photocatalysis?

“…[74][75][76] We think dispersion can be engineered in larger "0D" clusters as well;e ven MIL-125 brings some visible dispersion to its CBM in computed band structures. [31] We do note here that MOFs with large unit cells have correspondingly low Brillouin zones (in reciprocal space). This renders an actual calculation of effective masses necessary for even qualitative measures of the dispersion around the edges.…”

“…[15] Overall, grafting may be just as effective as metal Figure 5. Band alignment of several ZIF, [28] UiO, [29] and MIL-125 [31] variants (with different linkers).…”