Lowering Band Gap of an Electroactive Metal–Organic Framework via Complementary Guest Intercalation

Abstract

A new honeycomb-shaped electroactive metal-organic framework (MOF) has been constructed from an electron deficient naphthalenediimide (NDI) ligand equipped with two terminal salicylic acid groups. π-Intercalation of electron-rich planar tetrathiafulvalene (TTF) guests between the NDI ligands stacked along the walls lowers the electronic band gap of the material by ca. 1 eV. An improved electron delocalization through the guest-mediated π-donor/acceptor stacks is attributed to the diminished band gap of the doped material, which forecasts an improved electrical conductivity.

Mechano-regulated metal–organic framework nanofilm for ultrasensitive and anti-jamming strain sensing

“…On one hand, the 3D long-range ordering of the repetitive building blocks may provide potential charge transport pathways with either through-bond or through-space conduction model; on the other hand, the mechanical flexibility of the organic–inorganic hybrids puts strain detection into a possibility by the deformation-induced electronic structure and conductivity change of the material. However, the low atomic density and strong localization of the electron wave function of MOFs lead to scarcity in the itinerant electrons and electronic communication between the metal cations and organic ligands, resulting in insulating behavior that can hardly be used for electronic devices 39 – 41 . Increasing MOFs’ conductivity to semiconductive level thus appears a direct necessarity for device applications.…”

A porous, electrically conductive hexa-zirconium(iv) metal–organic framework

“… 42 The basis for increase is the ligation of open Cu( ii ) sites by TCNQ nitrile groups such that a continuous charge-transfer pathway is formed (each TCNQ is thought to connect to four copper ions, with the overall Cu( ii )trimesate unit functioning as an electron donor, and TCNQ as an acceptor). 43 Among other D–A pairs incorporated within MOFs to study charge transfer are: (a) TTF/naphthalenetetracarboxydiimide (NDI), 44 , 45 (b) oligothiophene/[6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM), 44 , 46 and (c) N , N ′-bis(4-pyridyl)-2,6-dipyrrolidyl napthalenediimide/methylviologen. 47 However, only in case (c) has bulk electrical conductivity been investigated (with a 35-fold increase in conductivity accompanying viologen incorporation).…”

Tunable Crystallinity and Charge Transfer in Two‐Dimensional G‐Quadruplex Organic Frameworks

“…Interestingly,aweak EPR spectrum was observed for these hetero-GQFs ( Figure S15). Thef ield-modulated continuous-wave EPR spectra measured at approximately 9.5 GHz show as ingle first-derivative signal centered at g % 2c ontaining contributions from both PyrC + and NDIC À , where the hyperfine coupling is unresolved owing to orientation averaging in the powder samples.U sing pulse-EPR electron spin echo spectroscopy at around 34 GHz, the integrated Hahn echo intensity yields the spectrum showing two resolved signals of PyrC + and NDIC À at g % 2.0025 and 2.0031, respectively, [23] indicating that charge separation occurs within the hetero-GQF.A lthough electron-density shifts in CT complexes do not usually result in afull electron transfer and EPR activity, [24] such signals have been observed in metal-organic frameworks (MOF) [25] and CT complexes of small organic molecules having alternating donor-acceptor p stacks. [26] To our knowledge,the present examples are the first demonstration of isolable 2D organic frameworks,where the intrinsic p-stacking in the structure can be exploited for CT complex formation.…”