Organic Linker Defines the Excited‐State Decay of Photocatalytic MIL‐125(Ti)‐Type Materials

Abstract

Recently, MIL-125(Ti) and NH2 -MIL-125(Ti), two titanium-based metal-organic frameworks, have attracted significant research attention in the field of photocatalysis for solar fuel generation. This work reveals that the differences between these structures are not only based on their light absorption range but also on the decay profile and topography of their excited states. In contrast to MIL-125(Ti), NH2 -MIL-125(Ti) shows markedly longer lifetimes of the charge-separated state, which improves photoconversion by the suppression of competing decay mechanisms. We used spectroelectrochemistry and ultrafast spectroscopy to demonstrate that upon photoexcitation in NH2 -MIL-125(Ti) the electron is located in the Ti-oxo clusters and the hole resides on the aminoterephthalate unit, specifically on the amino group. The results highlight the role of the amino group in NH2 -MIL-125(Ti), the electron donation of which extends the lifetime of the photoexcited state substantially.

Understanding metal–organic frameworks for photocatalytic solar fuel production

“…52 Obviously, this is just an approximate estimation, and detailed experimental protocols should be described for electrochemistry with MOFs. In addition, DFT calculations have also proven to be effective in shedding light on this issue.…”

“…73,74 Regarding ultrafast measurements in absorbance mode, the ultrafast study done on the MIL-125IJTi) series is one of the clearest examples. 52 Here, MOF suspensions were excited at their wavelength absorption maxima. By separating the large MOF particles (>100 nm) from the suspension, the experiments could be done in transmittance fashion, avoiding light scattering and following the decay kinetics with a picosecond time resolution.…”

Engineering oxygen-containing and amino groups into two-dimensional atomically-thin porous polymeric carbon nitrogen for enhanced photocatalytic hydrogen production

“…21,22 Furthermore, the -NH 2 group can act as hole-stabilizers and thus prolong the lifetime of the excited states in photocatalysts. 23,24 The strong With the current high energy consumption, the development of efficient cheap materials for energy conversion and storage is a pertinent challenge. Photocatalytic hydrogen evolution is a promising technology that paves the way for a clean and renewable source for hydrogen fuel.…”

Photocatalytic hydrogen generation from a visible-light responsive metal–organic framework system: the impact of nickel phosphide nanoparticles

“…2), thus allowing effective charge separation. 42,45 Such charge separation provides an efficient stabilization of the photoexcited species; a key element for allowing the electrons to reach the surface of MIL-125-NH2, before their recombination with the holes.…”