van der Waals Metal‐Organic Framework as an Excitonic Material for Advanced Photonics

Abstract

Synergistic combination of organic and inorganic nature in van der Waals metal-organic frameworks supports different types of robust excitons that can be effectively and independently manipulated by light at room temperature, and opens new concepts for all-optical data processing and storage.

On the Existence of Excitonic Signatures in the Optical Response of Metal–Organic Frameworks: Comment on “van der Waals Metal–Organic Framework as an Excitonic Material for Advanced Photonics”

“…It was claimed that proposed classification of the peaks follows from the polarization dependence of the measured spectra.In light of the experimental findings and their interpretation proposed in by Milichko et al [6] our Comment here has several goals. The first one corresponds to the bound electron-hole pairs for which quasiparticles of the opposite charge are situated in the neighbor 2D layers, while the second one corresponds to the situation when an electron and a hole placed in the same layer forming a bound state.…”

“…In light of the experimental findings and their interpretation proposed in by Milichko et al [6] our Comment here has several goals. First, as we will demonstrate below, the data presented in by Milichko et al [6] can be persuasively explained as resulting from single-particle excitations only, without any necessity for the formation of excitons.…”

“…

Lorentzians attributed by the authors to inter-and intralayer excitons. First, as we will demonstrate below, the data presented in by Milichko et al [6] can be persuasively explained as resulting from single-particle excitations only, without any necessity for the formation of excitons. It was claimed that proposed classification of the peaks follows from the polarization dependence of the measured spectra.

In light of the experimental findings and their interpretation proposed in by Milichko et al [6] our Comment here has several goals.

…”

“…The first one corresponds to the bound electron-hole pairs for which quasiparticles of the opposite charge are situated in the neighbor 2D layers, while the second one corresponds to the situation when an electron and a hole placed in the same layer forming a bound state. The claim of Milichko et al [6] that they "demonstrated for the first time the prospect of metal-organic frameworks as excitonic materials for simultaneous all-optical data processing and storage" thus remains not supported. First, as we will demonstrate below, the data presented in by Milichko et al [6] can be persuasively explained as resulting from single-particle excitations only, without any necessity for the formation of excitons.…”

“…The claim of Milichko et al [6] that they "demonstrated for the first time the prospect of metal-organic frameworks as excitonic materials for simultaneous all-optical data processing and storage" thus remains not supported. [2][3][4][5] In the recent report, [6] it was suggested that one particular type of MOF, namely the Zn-based van der Waals metal-organic framework [{Zn 2 (TBAPy)(H 2 O) 2 }*3.5DEF] n , where TBAPy = 1,3,6,8-tetrakis(p-benzoate)pyrene and DEF is a diethylformamide (MOF-Zn below), reveals strong signatures of excitonic response at room temperatures. They may look very similar to those appearing due to excitonic effects, but have a completely different physical origin.…”