Facile Tuned TSCT-TADF in Donor-Acceptor MOF for Highly Adjustable Photonic Modules based on Heterostructures Crystals

Tandem Four-Component Reaction to Access Fused Polycycles Exhibiting Aggregation-Enhanced Through-Space Charge Transfer Emission

Rapid construction of new fluorescence emitters is essential in advancing synthetic luminescent materials. This study illustrated a piperidine-promoted reaction of chiral dialdehyde with benzoylacetonitrile and malonitrile, leading to the formation of the 6/6/7 fused cyclic product in good yield. The proposed reaction mechanism involves a dual condensation/cyclization process, achieving the formation of up to six bonds for fused polycycles. The single crystal structure analysis revealed that the fused cyclic skeleton contains face-to-face naphthyl and cyanoalkenyl motifs, which act as the electronic donor and acceptor, respectively, potentially resulting in through-space charge transfer (TSCT) emission. While the TSCT emissions were weak in solution, a notable increase in luminescence intensity was observed upon aggregation, indicating bright fluorescent light. A series of theoretical analyses further supported the possibility of spatial electronic communication based on frontier molecular orbitals, the distance of charge transfer, and reduced density gradient analysis. This work not only provides guidance for the one-step synthesis of complex polycycles, but also offers valuable insights into the design of aggregation-enhanced TSCT emission materials.

Dynamic Reversible Full-Color Piezochromic Fluorogens Featuring Through-Space Charge-Transfer Thermally Activated Delayed Fluorescence and their Application as X-Ray Imaging Scintillators

Thermally activated delayed fluorescence (TADF) emitters featuring through-space charge transfer (TSCT) can be excellent candidates for piezochromic luminescent (PCL) materials due to their structural dynamics. Spatial donor-acceptor (D-A) stacking arrangements enable the modulation of inter- and intramolecular D-A interactions, as well as spatial charge transfer states, under varying pressure conditions. Herein, we demonstrate an effective approach toward dynamic reversible full-color PCL materials with TSCT-TADF characteristics. Their single crystals exhibit a full-color-gamut PCL process spanning a range of 170 nm. Moreover, the TSCT-TADF-PCL emitters display a unity photoluminescence quantum yield, and show promising application in X-ray scintillator imaging.

Recent progress on charge transfer engineering in reticular framework for efficient electrochemiluminescence

Electrochemiluminescence (ECL) is a luminescence production technique triggered by electrochemistry, which has emerged as a powerful analytical technique in bioanalysis and clinical diagnosis. During ECL, charge transfer (CT) is an important process between electrochemical excitation and luminescent emission, and dramatically affects the efficiency of exciton generation, playing a pivotal role in the light-emitting properties of nanomaterials. Reticular framework materials with intramolecular/intermolecular interactions offer a promising platform for regulating CT pathways and enhancing luminescence efficiency. Deciphering the role of intramolecular/intermolecular CT processes in reticular framework materials allows for the targeted design and synthesis of emitters with precisely controlled CT properties. This sheds light on the microscopic mechanisms of electro-optical conversion in ECL, propelling advancements in their efficiency and breakthrough applications. This mini-review focuses on recent advancements in engineering CT within reticular frameworks to boost ECL efficiency. We summarized strategies including intra-reticular charge transfer, CT between the metal and ligands, and CT between guest molecules and frameworks within reticular frameworks, which holds promise for developing next-generation ECL devices with enhanced sensitivity and light emission.

In Situ-Generated Hollow CoFe-LDH/Co-MOF Heterostructure Nanorod Arrays for Oxygen Evolution Reaction

Assembling a heterostructure is an effective strategy for enhancing the electrocatalytic activity of hybrid materials. Herein, CoFe-layered double hydroxide and Co-metal-organic framework (CoFe-LDH/Co-MOF) hollow heterostructure nanorod arrays are synthesized. First, [Co(DIPL)(H3BTC)(H2O)2]n [named as Co-MOF, DIPL = 2,6-di(pyrid-4-yl)-4-phenylpyridine, H3BTC = 1,3,5-benzenetricarboxylic acid] crystalline materials with a uniform hollow structure were prepared on the nickel foam. The CoFe-LDH/Co-MOF composite perfectly inherits the original hollow nanorod array morphology after the subsequent electrodeposition process. Optimized CoFe-LDH/Co-MOF hollow heterostructure nanorod arrays display excellent performance in oxygen evolution reaction (OER) with ultralow overpotentials of 215 mV to deliver current densities of 10 mA cm-2 and maintain the electrocatalytic activity for a duration as long as 220 h, ranking it one of the non-noble metal-based electrocatalysts for OER. Density functional theory calculations validate the reduction in free energy for the rate-determining step by the synergistic effect of Co-MOF and CoFe-LDH, with the increased charge density and noticeable electron transfer at the Co-O site, which highlights the capability of Co-MOF to finely adjust the electronic structure and facilitate the creation of active sites. This work establishes an experimental and theoretical basis for promoting efficient water splitting through the design of heterostructures in catalysts.

A general supramolecular strategy for fabricating full-color-tunable thermally activated delayed fluorescence materials

Developing a facile and feasible strategy to fabricate thermally activated delayed fluorescence materials exhibiting full-color tunability remains an appealing yet challenging task. In this work, a general supramolecular strategy for fabricating thermally activated delayed fluorescence materials is proposed. Consequently, a series of host-guest cocrystals are prepared by electron-donating calix[3]acridan and various electron-withdrawing guests. Owing to the through-space charge transfer mediated by multiple noncovalent interactions, these cocrystals all display efficient thermally activated delayed fluorescence. Especially, by delicately modulating the electron-withdrawing ability of the guest molecules, the emission colors of these cocrystals can be continuously tuned from blue (440 nm) to red (610 nm). Meanwhile, high photoluminescence quantum yields of up to 87% is achieved. This research not only provides an alternative and general strategy for the fabrication of thermally activated delayed fluorescence materials, but also establishes a reliable supramolecular protocol toward the design of advanced luminescent materials.

Modular Gating of Ion Transport by Postsynthetic Charge Transfer Complexation in a Metal-Organic Framework

Nature's design of biological ion channels that demonstrates efficient gating and selectivity brings to light a very promising model to mimic and design for achieving selective and tunable ion transport. Functionalized nanopores that permit modulation of the pore wall charges are a compelling approach to gain control over the ion transport mechanism through the pores. This makes way for employing a noncovalent supramolecular approach for attaining charge reversal of the MOF pore walls using donor-acceptor pairs that can demonstrate strong charge transfer interactions. Herein, robust Zr4+-based mesoporous MOF-808 was postsynthetically modified into an anion-selective nanochannel (MOF-808-MV) by modification with dicationic viologen-based motifs. Charge modulation and even reversal of the MOF-808-MV pore walls were then explored taking advantage of strong charge transfer interactions between the grafted dicationic viologen acceptor moieties and anionic, π-electron-rich donor guest molecules such as pyranine (PYR) and tetrathiafulvalene tetrabenzoic acid (TTF-TA). Tunability of the MOF pore charge from positive to neutral to negative was achieved via simple methodologies such as diffusion control in case of guest molecule like PYR and by pH modulation for pH-responsive guest like TTF-TA. This results in a concomitant modulation in the selectivity of the nanochannel, rendering it from anion-selective to ambipolar to cation-selective. Furthermore, as a real-time application of this ion channel, Na+ ion conductivity (σ = 3.5 × 10-5 S cm-1) was studied at ambient temperature.

Spatially Resolved Organic Whispering-Gallery-Mode Hetero-Microrings for High-Security Photonic Barcodes

Whispering-gallery-mode (WGM) microcavities featuring distinguishable sharp peaks in a broadband exhibit enormous advantages in the field of miniaturized photonic barcodes. However, such kind of barcodes developed hitherto are primarily based on microcavities wherein multiple gain medias were blended into a single matrix, thus resulting in the limited and indistinguishable coding elements. Here, a surface tension assisted heterogeneous assembly strategy is proposed to construct the spatially resolved WGM hetero-microrings with multiple spatial colors along its circular direction. Through precisely regulating the charge-transfer (CT) strength, full-color microrings covering the entire visible range were effectively acquired, which exhibit a series of sharp and recognizable peaks and allow for the effective construction of high-quality photonic barcodes. Notably, the spatially resolved WGM hetero-microrings with multiple coding elements were finally acquired through heterogeneous nucleation and growth controlled by the directional diffusion between the hetero-emulsion droplets, thus remarkably promoting the security strength and coding capacity of the barcodes. The results would be useful to fabricate new types of organic hierarchical hybrid WGM heterostructures for optical information recording and security labels.