Semiconductor Porous Hydrogen-Bonded Organic Frameworks Based on Tetrathiafulvalene Derivatives

Abstract

Herein, we report on the use of tetrathiavulvalenetetrabenzoic acid, H 4 TTFTB, to engender semiconductivity in porous hydrogen-bonded organic frameworks (HOFs). By tuning the synthetic conditions, three different polymorphs have been obtained, denoted MUV-20a, MUV-20b, and MUV-21, all of them presenting open structures (22, 15, and 27%, respectively) and suitable TTF stacking for efficient orbital overlap. Whereas MUV-21 collapses during the activation process, MUV-20a and MUV-20b offer high stability evacuation, with a CO 2 sorption capacity of 1.91 and 1.71 mmol g −1 , respectively, at 10 °C and 6 bar. Interestingly, both MUV-20a and MUV-20b present a zwitterionic character with a positively charged TTF core and a negatively charged carboxylate group. First-principles calculations predict the emergence of remarkable charge transport by means of a through-space hopping mechanism fostered by an efficient TTF π−π stacking and the spontaneous formation of persistent charge carriers in the form of radical TTF •+ units. Transport measurements confirm the efficient charge transport in zwitterionic MUV-20a and MUV-20b with no need for postsynthetic treatment (e.g., electrochemical oxidation or doping), demonstrating the semiconductor nature of these HOFs with record experimental conductivities of 6.07 × 10 −7 (MUV-20a) and 1.35 × 10 −6 S cm −1 (MUV-20b).

Zwitterionic hydrogen-bonded organic framework (ZHOF): a metal-free water oxidation proton relay in alkaline and neutral media

“…Indeed, the simultaneous positioning of the positively and negatively charged groups on SSPCs may result in multiple advantages like tuneable charge density in the framework, the concurrent attraction of oppositely charged counterions with the lowest repulsion, and accessibility for de-/protonating H-bond donors/acceptors. 23 After introducing the cationic 25 and anionic 26 COFs, the first example of ionic HOF (anionic) was synthesized in 2020 by Liu et al 27 It should be noted that concurrent with our experimental studies, the first reports on the forerunners of the reticulate zwitterionic COF 23 and zwitterionic HOF 28 have been published.…”

Recent advancements of photo- and electro-active hydrogen-bonded organic frameworks

“…However, the TTF cores have nearly no π-π interactions, resulting in poor framework stability for these HOFs, and the redox properties of the TTF cores were only verified during phase transitions between these HOFs. In 2022, Vicent-Morales et al [118] provides a new idea that the synthesis of HOF with deprotonated H 4 TTFTB can exhibit semi- conducting properties. In 2021, Kirlikovali et al [94] reported a stable TTF-based HOF (called HOF-110) constructed with tetrathiafulvalene tetranaphthoic acid (H 4 TTFTN), which also has high conductivity and colorchanging properties upon the inclusion of iodine within the framework (Figure 5c).…”

Eu(iii)-Functionalized HOFs based on machine learning-assisted fluorescence sensing: discrimination of quinolonesviaPCA and BPNN models

“…6–8 Among these materials, hydrogen-bonded organic frameworks (HOFs) are gradually being probed in the design of advanced functional luminescent sensors due to their excellent fluorescence and phosphorescence properties. 9–11 HOFs, 12–15 as a remarkable type of polymeric porous material, are self-assembled through hydrogen bonds between organic linkers, in which the framework can be further enhanced through framework interpenetration and other types of weak intermolecular interactions such as π⋯π interactions, van der Waals interactions, and C–H⋯π interactions. 16–19 They are generally fabricated to feature highly rigid aromatic moieties in a large π-conjugated system to achieve permanent porosity, indicating that HOFs are very promising luminescent materials.…”