Search

Ionic liquids (ILs) are prized for their selective dissolution of carbon dioxide (CO 2 ), leading to their widespread use in ionogel membranes for gas separation. Despite their advantages, creating sustainable ionogel membranes with high IL contents poses challenges due to limited mechanical strength, leakage risks, and poor recyclability. Herein, we leverage copolymerized and supramolecularly bound ILs to develop ionogel membranes with high mechanical strength, zero leakage, and excellent self-healing and recycling capabilities. These membranes exhibit superior ideal selectivity for gas separation compared to other reported ionogel membranes, achieving a CO 2 /nitrogen selectivity of 61.7 and a CO 2 /methane selectivity of 24.6, coupled with an acceptable CO 2 permeability of 186.4 Barrer. Additionally, these gas separation ionogel membranes can be upcycled into ionic skins for sensing applications, further enhancing their utility. This research outlines a strategic approach to molecularly engineer ionogel membranes, offering a promising pathway for developing sustainable, high-performance materials for advanced gas separation technologies., (© 2024 Wiley-VCH GmbH.)

Vinylene-linked two-dimensional polymers (V-2DPs) and their layer-stacked covalent organic frameworks (V-2D COFs) featuring high in-plane π-conjugation and robust frameworks have emerged as promising candidates for energy-related applications. However, current synthetic approaches are restricted to producing V-2D COF powders that lack processability, impeding their integration into devices, particularly within membrane technologies reliant upon thin films. Herein, we report the novel on-water surface synthesis of vinylene-linked cationic 2DPs films (V-C2DP-1 and V-C2DP-2) via Knoevenagel polycondensation, which serve as the anion-selective electrode coating for highly-reversible and durable zinc-based dual-ion batteries (ZDIBs). Model reactions and theoretical modeling revealed the enhanced reactivity and reversibility of the Knoevenagel reaction on the water surface. On this basis, we demonstrated the on-water surface 2D polycondensation towards V-C2DPs films that show large lateral size, tunable thickness, and high chemical stability. Representatively, V-C2DP-1 presents as a fully crystalline and face-on oriented film with in-plane lattice parameters of a=b≈43.3 Å. Profiting from its well-defined cationic sites, oriented 1D channels, and stable frameworks, V-C2DP-1 film possesses superior bis(trifluoromethanesulfonyl)imide anion (TFSI - )-transport selectivity (transference, t_=0.85) for graphite cathode in high-voltage ZDIBs, thus triggering additional TFSI - -intercalation stage and promoting its specific capacity (from ~83 to 124 mAh g -1 ) and cycling life (>1000 cycles, 95 % capacity retention)., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Conjugated coordination polymers (c-CPs) are unique organic-inorganic hybrid semiconductors with intrinsically high electrical conductivity and excellent charge carrier mobility. However, it remains a challenge in tailoring electronic structures, due to the lack of clear guidelines. Here, we develop a strategy wherein controlling the redox state of hydroquinone/benzoquinone (HQ/BQ) ligands allows for the modulation of the electronic structure of c-CPs while maintaining the structural topology. The redox-state control is achieved by reacting the ligand TTHQ (TTHQ=1,2,4,5-tetrathiolhydroquinone) with silver acetate and silver nitrate, yielding Ag 4 TTHQ and Ag 4 TTBQ (TTBQ=1,2,4,5-tetrathiolbenzoquinone), respectively. In spite of sharing the same topology consisting of a two-dimensional Ag-S network and HQ/BQ layer, they exhibit different band gaps (1.5 eV for Ag 4 TTHQ and 0.5 eV for Ag 4 TTBQ) and conductivities (0.4 S/cm for Ag 4 TTHQ and 10 S/cm for Ag 4 TTBQ). DFT calculations reveal that these differences arise from the ligand oxidation state inhibiting energy band formation near the Fermi level in Ag 4 TTHQ. Consequently, Ag 4 TTHQ displays a high Seebeck coefficient of 330 μV/K and a power factor of 10 μW/m ⋅ K 2 , surpassing Ag 4 TTBQ and the other reported silver-based c-CPs. Furthermore, terahertz spectroscopy demonstrates high charge mobilities exceeding 130 cm 2 /V ⋅ s in both Ag 4 TTHQ and Ag 4 TTBQ., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) are emerging as a unique subclass of layer-stacked crystalline coordination polymers that simultaneously possess porous and conductive properties, and have broad application potential in energy and electronic devices. However, to make the best use of the intrinsic electronic properties and structural features of 2D c-MOFs, the controlled synthesis of hierarchically nanostructured 2D c-MOFs with high crystallinity and customized morphologies is essential, which remains a great challenge. Herein, we present a template strategy to synthesize a library of 2D c-MOFs with controlled morphologies and dimensions via insulating MOFs-to-c-MOFs transformations. The resultant hierarchically nanostructured 2D c-MOFs feature intrinsic electrical conductivity and higher surface areas than the reported bulk-type 2D c-MOFs, which are beneficial for improved access to active sites and enhanced mass transport. As proof-of-concept applications, the hierarchically nanostructured 2D c-MOFs exhibit a superior performance for electrical properties related applications (hollow Cu-BHT nanocubes-based supercapacitor and Cu-HHB nanoflowers-based chemiresistive gas sensor), achieving over 225 % and 250 % improvement in specific capacity and response intensity over the corresponding bulk type c-MOFs, respectively., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Electrochemical proton storage plays an essential role in designing next-generation high-rate energy storage devices, e.g., aqueous batteries. Two-dimensional conjugated covalent organic frameworks (2D c-COFs) are promising electrode materials, but their competitive proton and metal-ion insertion mechanisms remain elusive, and proton storage in COFs is rarely explored. Here, we report a perinone-based poly(benzimidazobenzophenanthroline) (BBL)-ladder-type 2D c-COF for fast proton storage in both a mild aqueous Zn-ion electrolyte and strong acid. We unveil that the discharged C-O - groups exhibit largely reduced basicity due to the considerable π-delocalization in perinone, thus affording the 2D c-COF a unique affinity for protons with fast kinetics. As a consequence, the 2D c-COF electrode presents an outstanding rate capability of up to 200 A g -1 (over 2500 C), surpassing the state-of-the-art conjugated polymers, COFs, and metal-organic frameworks. Our work reports the first example of pure proton storage among COFs and highlights the great potential of BBL-ladder-type 2D conjugated polymers in future energy devices., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) are emerging as a unique class of electronic materials. However, 2D c-MOFs with band gaps in the Vis-NIR and high charge carrier mobility are rare. Most of the reported conducting 2D c-MOFs are metallic (i.e. gapless), which largely limits their use in logic devices. Herein, we design a phenanthrotriphenylene-based, D 2h -symmetric π-extended ligand (OHPTP), and synthesize the first rhombic 2D c-MOF single crystals (Cu 2 (OHPTP)). The continuous rotation electron diffraction (cRED) analysis unveils the orthorhombic crystal structure at the atomic level with a unique slipped AA stacking. The Cu 2 (OHPTP) is a p-type semiconductor with an indirect band gap of ≈0.50 eV and exhibits high electrical conductivity of 0.10 S cm -1 and high charge carrier mobility of ≈10.0 cm 2  V -1  s -1 . Theoretical calculations underline the predominant role of the out-of-plane charge transport in this semiquinone-based 2D c-MOF., (© 2023 Wiley-VCH GmbH.)

Metal-organic frameworks (MOFs) have attracted increasing interest for broad applications in catalysis and gas separation due to their high porosity. However, the insulating feature and the limited active sites hindered MOFs as photocathode active materials for application in photoelectrocatalytic hydrogen generation. Herein, we develop a layered conductive two-dimensional conjugated MOF (2D c-MOF) comprising sp-carbon active sites based on arylene-ethynylene macrocycle ligand via CuO 4 linking, named as Cu 3 HHAE 2 . This sp-carbon 2D c-MOF displays apparent semiconducting behavior and broad light absorption till the near-infrared band (1600 nm). Due to the abundant acetylene units, the Cu 3 HHAE 2 could act as the first case of MOF photocathode for photoelectrochemical (PEC) hydrogen generation and presents a record hydrogen-evolution photocurrent density of ≈260 μA cm -2 at 0 V vs. reversible hydrogen electrode among the structurally-defined cocatalyst-free organic photocathodes., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

2D conjugated metal-organic frameworks (2D c-MOFs) are emerging as electroactive materials for chemiresistive sensors, but selective sensing with fast response/recovery is a challenge. Phthalocyanine-based Ni 2 [MPc(NH) 8 ] 2D c-MOF films are presented as active layers for polarity-selective chemiresisitors toward water and volatile organic compounds (VOCs). Surface-hydrophobic modification by grafting aliphatic alkyl chains on 2D c-MOF films decreases diffused analytes into the MOF backbone, resulting in a considerably accelerated recovery progress (from ca. 50 to ca. 10 s) during humidity sensing. Toward VOCs, the sensors deliver a polarity-selective response among alcohols but no signal for low-polarity aprotic hydrocarbons. The octadecyltrimethoxysilane-modified Ni 2 [MPc(NH) 8 ] based sensor displays high-performance methanol sensing with fast response (36 s)/recovery (13 s) and a detection limit as low as 10 ppm, surpassing reported room-temperature chemiresistors., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Two-dimensional polymers (2DPs) are a class of atomically/molecularly thin crystalline organic 2D materials. They are intriguing candidates for the development of unprecedented organic-inorganic 2D van der Waals heterostructures (vdWHs) with exotic physicochemical properties. In this work, we demonstrate the on-water surface synthesis of large-area (cm 2 ), monolayer 2D polyimide (2DPI) with 3.1-nm lattice. Such 2DPI comprises metal-free porphyrin and perylene units linked by imide bonds. We further achieve a scalable synthesis of 2DPI-graphene (2DPI-G) vdWHs via a face-to-face co-assembly of graphene and 2DPI on the water surface. Remarkably, femtosecond transient absorption spectroscopy reveals an ultra-fast interlayer charge transfer (ca. 60 fs) in the resultant 2DPI-G vdWH upon protonation by acid, which is equivalent to that of the fastest reports among inorganic 2D vdWHs. Such large interlayer electronic coupling is ascribed to the interlayer cation-π interaction between 2DP and graphene., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Despite the recent progress in the synthesis of crystalline boronate ester covalent organic frameworks (BECOFs) in powder and thin-film through solvothermal method and on-solid-surface synthesis, respectively, their applications in electronics, remain less explored due to the challenges in thin-film processability and device integration associated with the control of film thickness, layer orientation, stability and crystallinity. Moreover, although the crystalline domain sizes of the powder samples can reach micrometer scale (up to ≈1.5 μm), the reported thin-film samples have so far rather small crystalline domains up to 100 nm. Here we demonstrate a general and efficient synthesis of crystalline two-dimensional (2D) BECOF films composed of porphyrin macrocycles and phenyl or naphthyl linkers (named as 2D BECOF-PP or 2D BECOF-PN) by employing a surfactant-monolayer-assisted interfacial synthesis (SMAIS) on the water surface. The achieved 2D BECOF-PP is featured as free-standing thin film with large single-crystalline domains up to ≈60 μm 2 and tunable thickness from 6 to 16 nm. A hybrid memory device composed of 2D BECOF-PP film on silicon nanowire-based field-effect transistor is demonstrated as a bio-inspired system to mimic neuronal synapses, displaying a learning-erasing-forgetting memory process., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Single-layer and multi-layer 2D polyimine films have been achieved through interfacial synthesis methods. However, it remains a great challenge to achieve the maximum degree of crystallinity in the 2D polyimines, which largely limits the long-range transport properties. Here we employ a surfactant-monolayer-assisted interfacial synthesis (SMAIS) method for the successful preparation of porphyrin and triazine containing polyimine-based 2D polymer (PI-2DP) films with square and hexagonal lattices, respectively. The synthetic PI-2DP films are featured with polycrystalline multilayers with tunable thickness from 6 to 200 nm and large crystalline domains (100-150 nm in size). Intrigued by high crystallinity and the presence of electroactive porphyrin moieties, the optoelectronic properties of PI-2DP are investigated by time-resolved terahertz spectroscopy. Typically, the porphyrin-based PI-2DP 1 film exhibits a p-type semiconductor behavior with a band gap of 1.38 eV and hole mobility as high as 0.01 cm 2  V -1  s -1 , superior to the previously reported polyimine based materials., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Layered two-dimensional (2D) conjugated metal-organic frameworks (MOFs) represent a family of rising electrocatalysts for the oxygen reduction reaction (ORR), due to the controllable architectures, excellent electrical conductivity, and highly exposed well-defined molecular active sites. Herein, we report a copper phthalocyanine based 2D conjugated MOF with square-planar cobalt bis(dihydroxy) complexes (Co-O 4 ) as linkages (PcCu-O 8 -Co) and layer-stacked structures prepared via solvothermal synthesis. PcCu-O 8 -Co 2D MOF mixed with carbon nanotubes exhibits excellent electrocatalytic ORR activity (E 1/2 =0.83 V vs. RHE, n=3.93, and j L =5.3 mA cm -2 ) in alkaline media, which is the record value among the reported intrinsic MOF electrocatalysts. Supported by in situ Raman spectro-electrochemistry and theoretical modeling as well as contrast catalytic tests, we identified the cobalt nodes as ORR active sites. Furthermore, when employed as a cathode electrocatalyst for zinc-air batteries, PcCu-O 8 -Co delivers a maximum power density of 94 mW cm -2 , outperforming the state-of-the-art Pt/C electrocatalysts (78.3 mW cm -2 )., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

To bridge the gap between laboratory-scale studies and commercial applications, mass production of high quality graphene is essential. A scalable exfoliation strategy towards the production of graphene sheets is presented that has excellent yield (ca. 75 %, 1-3 layers), low defect density (a C/O ratio of 21.2), great solution-processability, and outstanding electronic properties (a hole mobility of 430 cm 2  V -1  s -1 ). By applying alternating currents, dual exfoliation at both graphite electrodes enables a high production rate exceeding 20 g h -1 in laboratory tests. As a cathode material for lithium storage, graphene-wrapped LiFePO 4 particles deliver a high capacity of 167 mAh g -1 at 1 C rate after 500 cycles., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

On-chip micro-supercapacitors (MSCs) are important Si-compatible power-source backups for miniaturized electronics. Despite their tremendous advantages, current on-chip MSCs require harsh processing conditions and typically perform like resistors when filtering ripples from alternating current (AC). Herein, we demonstrated a facile layer-by-layer method towards on-chip MSCs based on an azulene-bridged coordination polymer framework (PiCBA). Owing to the good carrier mobility (5×10 -3  cm 2  V -1  s -1 ) of PiCBA, the permanent dipole moment of azulene skeleton, and ultralow band gap of PiCBA, the fabricated MSCs delivered high specific capacitances of up to 34.1 F cm -3 at 50 mV s -1 and a high volumetric power density of 1323 W cm -3 . Most importantly, such MCSs exhibited AC line-filtering performance (-73° at 120 Hz) with a short resistance-capacitance constant of circa 0.83 ms., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Despite the availability of numerous two-dimensional (2D) materials with structural ordering at the atomic or molecular level, direct construction of mesoscale-ordered superstructures within a 2D monolayer remains an enormous challenge. Here, we report the synergic manipulation of two types of assemblies in different dimensions to achieve 2D conducting polymer nanosheets with structural ordering at the mesoscale. The supramolecular assemblies of amphipathic perfluorinated carboxylic acids and block co-polymers serve as 2D interfaces and meso-inducing moieties, respectively, which guide the polymerization of aniline into 2D, free-standing mesoporous conducting polymer nanosheets. Grazing-incidence small-angle X-ray scattering combined with various microscopy demonstrates that the resulting mesoscale-ordered nanosheets have hexagonal lattice with d-spacing of about 30 nm, customizable pore sizes of 7-18 nm and thicknesses of 13-45 nm, and high surface area. Such template-directed assembly produces polyaniline nanosheets with enhanced π-π stacking interactions, thereby resulting in anisotropic and record-high electrical conductivity of approximately 41 S cm(-1) for the pristine polyaniline nanosheet based film and approximately 188 S cm(-1) for the hydrochloric acid-doped counterpart. Our moldable approach creates a new family of mesoscale-ordered structures as well as opens avenues to the programmed assembly of multifunctional materials., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

To achieve sustainable production of H2 fuel through water splitting, low-cost electrocatalysts for the hydrogen-evolution reaction (HER) and the oxygen-evolution reaction (OER) are required to replace Pt and IrO2 catalysts. Herein, for the first time, we present the interface engineering of novel MoS2 /Ni3 S2 heterostructures, in which abundant interfaces are formed. For OER, such MoS2 /Ni3 S2 heterostructures show an extremely low overpotential of ca. 218 mV at 10 mA cm(-2) , which is superior to that of the state-of-the-art OER electrocatalysts. Using MoS2 /Ni3 S2 heterostructures as bifunctional electrocatalysts, an alkali electrolyzer delivers a current density of 10 mA cm(-2) at a very low cell voltage of ca. 1.56 V. In combination with DFT calculations, this study demonstrates that the constructed interfaces synergistically favor the chemisorption of hydrogen and oxygen-containing intermediates, thus accelerating the overall electrochemical water splitting., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Limited strategies have been established to prepare monodisperse mesoporous carbon nanospheres (MCNs) with tailored pore sizes. In this work, a method is reported to synthesize MCNs by combining polymerization of aniline with co-assembly of colloidal silica nanoparticles. The controlled self-assembly behavior of colloidal silica enables the formation of uniform composite nanospheres and convenient modulation over mesopores. After carbonization and removal of sacrificial templates, the resultant MCNs possess tunable mesopores (7-42 nm) and spherical diameters (90-300 nm), as well as high surface area (785-1117 m(2)  g(-1) ), large pore volume (1.46-2.01 cm(3)  g(-1) ) and abundant nitrogen moieties (5.54-8.73 at %). When serving as metal-free electrocatalysts for the oxygen reduction reaction (ORR), MCNs with an optimum pore size of 22 nm, compared to those with 7 and 42 nm, exhibit the best ORR performance in alkaline medium., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The rational construction of covalent or noncovalent organic two-dimensional nanosheets is a fascinating target because of their promising applications in electronics, membrane technology, catalysis, sensing, and energy technologies. Herein, a large-area (square millimeters) and free-standing 2D supramolecular polymer (2DSP) single-layer sheet (0.7-0.9 nm in thickness), comprising triphenylene-fused nickel bis(dithiolene) complexes has been readily prepared by using the Langmuir-Blodgett method. Such 2DSPs exhibit excellent electrocatalytic activities for hydrogen generation from water with a Tafel slope of 80.5 mV decade(-1) and an overpotential of 333 mV at 10 mA cm(-2) , which are superior to that of recently reported carbon nanotube supported molecular catalysts and heteroatom-doped graphene catalysts. This work is promising for the development of novel free-standing organic 2D materials for energy technologies., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)