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1.
Nat Mater ; 2024 Jun 07.
Artículo en Inglés | MEDLINE | ID: mdl-38849556

RESUMEN

Surface terminations profoundly influence the intrinsic properties of MXenes, but existing terminations are limited to monoatomic layers or simple groups, showing disordered arrangements and inferior stability. Here we present the synthesis of MXenes with triatomic-layer borate polyanion terminations (OBO terminations) through a flux-assisted eutectic molten etching approach. During the synthesis, Lewis acidic salts act as the etching agent to obtain the MXene backbone, while borax generates BO2- species, which cap the MXene surface with an O-B-O configuration. In contrast to conventional chlorine/oxygen-terminated Nb2C with localized charge transport, OBO-terminated Nb2C features band transport described by the Drude model, exhibiting a 15-fold increase in electrical conductivity and a 10-fold improvement in charge mobility at the d.c. limit. This transition is attributed to surface ordering that effectively mitigates charge carrier backscattering and trapping. Additionally, OBO terminations provide Ti3C2 MXene with substantially enriched Li+-hosting sites and thereby a large charge-storage capacity of 420 mAh g-1. Our findings illustrate the potential of intricate termination configurations in MXenes and their applications for (opto)electronics and energy storage.

2.
J Am Chem Soc ; 146(4): 2574-2582, 2024 Jan 31.
Artículo en Inglés | MEDLINE | ID: mdl-38231138

RESUMEN

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have attracted increasing interest in electronics due to their (semi)conducting properties. Charge-neutral 2D c-MOFs also possess persistent organic radicals that can be viewed as spin-concentrated arrays, affording new opportunities for spintronics. However, the strong π-interaction between neighboring layers of layer-stacked 2D c-MOFs annihilates active spin centers and significantly accelerates spin relaxation, severely limiting their potential as spin qubits. Herein, we report the precise tuning of the charge transport and spin dynamics in 2D c-MOFs via the control of interlayer stacking. The introduction of bulky side groups on the conjugated ligands enables a significant dislocation of the 2D c-MOFs layers from serrated stacking to staggered stacking, thereby spatially weakening the interlayer interactions. As a consequence, the electrical conductivity of 2D c-MOFs decreases by 6 orders of magnitude, while the spin density achieves more than a 30-fold increase and the spin-lattice relaxation time (T1) is increased up to ∼60 µs, hence being superior to the reference 2D c-MOFs with compact stackings whose spin relaxation is too fast to be detected. Spin dynamics results also reveal that spinless polaron pairs or bipolarons play critical roles in the charge transport of these 2D c-MOFs. Our strategy provides a bottom-up approach for enlarging spin dynamics in 2D c-MOFs, opening up pathways for developing MOF-based spintronics.

3.
J Am Chem Soc ; 146(1): 1026-1034, 2024 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-38117539

RESUMEN

Graphene nanoribbons (GNRs) have garnered significant interest due to their highly customizable physicochemical properties and potential utility in nanoelectronics. Besides controlling widths and edge structures, the inclusion of chirality in GNRs brings another dimension for fine-tuning their optoelectronic properties, but related studies remain elusive owing to the absence of feasible synthetic strategies. Here, we demonstrate a novel class of cove-edged chiral GNRs (CcGNRs) with a tunable chiral vector (n,m). Notably, the bandgap and effective mass of (n,2)-CcGNR show a distinct positive correlation with the increasing value of n, as indicated by theory. Within this GNR family, two representative members, namely, (4,2)-CcGNR and (6,2)-CcGNR, are successfully synthesized. Both CcGNRs exhibit prominently curved geometries arising from the incorporated [4]helicene motifs along their peripheries, as also evidenced by the single-crystal structures of the two respective model compounds (1 and 2). The chemical identities and optoelectronic properties of (4,2)- and (6,2)-CcGNRs are comprehensively investigated via a combination of IR, Raman, solid-state NMR, UV-vis, and THz spectroscopies as well as theoretical calculations. In line with theoretical expectation, the obtained (6,2)-CcGNR possesses a low optical bandgap of 1.37 eV along with charge carrier mobility of ∼8 cm2 V-1 s-1, whereas (4,2)-CcGNR exhibits a narrower bandgap of 1.26 eV with increased mobility of ∼14 cm2 V-1 s-1. This work opens up a new avenue to precisely engineer the bandgap and carrier mobility of GNRs by manipulating their chiral vector.

4.
J Am Chem Soc ; 2024 Jul 02.
Artículo en Inglés | MEDLINE | ID: mdl-38953716

RESUMEN

Oscillations in the chemical or physical properties of materials, composed of an odd or even number of connected repeating methylene units, are a well-known phenomenon in organic chemistry and materials science. So far, such behavior has not been reported for the important class of materials, perovskite semiconductors. This work reports a distinct odd-even oscillation of the molecular structure and charge carrier transport properties of phenylalkylammonium two-dimensional (2D) Sn-based perovskites in which the alkyl chains in the phenylalkylammonium cations contain varying odd and even carbon numbers. Density functional theory calculations and grazing-incidence wide-angle X-ray scattering characterization reveal that perovskites with organic ligands containing an alkyl chain with an odd number of carbon atoms display a disordered crystal lattice and tilted inorganic octahedra accompanied by reduced mobilities. In contrast, perovskites with cations of an even number of carbon atoms in the alkyl chain form more ordered crystal structures, resulting in improved charge carrier mobilities. Our findings disclose the importance of minor changes in the molecular conformation of organic cations have an effect on morphology, photophysical properties, and charge carrier transport of 2D layered perovskites, showcasing alkyl chain engineering of organic cations to control key properties, of layered perovskite semiconductors.

5.
J Am Chem Soc ; 146(22): 15479-15487, 2024 Jun 05.
Artículo en Inglés | MEDLINE | ID: mdl-38780095

RESUMEN

The development of efficient and low-cost catalysts is essential for photocatalysis; however, the intrinsically low photocatalytic efficiency as well as the difficulty in using and recycling photocatalysts in powder morphology greatly limit their practical performance. Herein, we describe quasi-homogeneous photocatalysis to overcome these two limitations by constructing ultrastiff, hierarchically porous, and photoactive aerogels of conjugated microporous polymers (CMPs). The CMP aerogels exhibit low density but high stiffness beyond 105 m2 s-2, outperforming most low-density materials. Extraordinary stiffness ensures their use as robust scaffolds for scaled photocatalysis and recycling without damage at the macroscopic level. A challenging but desirable reaction for direct deaminative borylation is demonstrated using CMP aerogel-based quasi-homogeneous photocatalysis with gram-scale productivity and record-high efficiency under ambient conditions. Combined terahertz and transient absorption spectroscopic studies unveil the generation of high-mobility free carriers and long-lived excitonic species in the CMP aerogels, underlying the observed superior catalytic performance.

6.
Small ; 20(16): e2308951, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38010120

RESUMEN

CdSe nanoplatelets (NPLs) are promising 2D semiconductors for optoelectronic applications, in which efficient charge transport properties are desirable. It is reported that thermal annealing constitutes an effective strategy to control the optical absorption and electrical properties of CdSe NPLs by tuning the inter-NPL distance. Combining optical absorption, transmission electron microscopy, and thermogravimetric analysis, it is revealed that the thermal decomposition of ligands (e.g., cadmium myristate) governs the inter-NPL distance and thus the inter-NPL electronic coupling strength. Employing ultrafast terahertz spectroscopy, it is shown that this enhanced electronic coupling increases both the free carrier generation efficiency and the short-range mobility in NPL solids. The results show a straightforward method of controlling the interfacial electronic coupling strength for developing functional optoelectronic devices through thermal treatments.

7.
Nat Mater ; 22(11): 1361-1369, 2023 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-37709929

RESUMEN

Evidence shows that charge carriers in organic semiconductors self-localize because of dynamic disorder. Nevertheless, some organic semiconductors feature reduced mobility at increasing temperature, a hallmark for delocalized band transport. Here we present the temperature-dependent mobility in two record-mobility organic semiconductors: dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]-thiophene (DNTT) and its alkylated derivative, C8-DNTT-C8. By combining terahertz photoconductivity measurements with atomistic non-adiabatic molecular dynamics simulations, we show that while both crystals display a power-law decrease of the mobility (µ) with temperature (T) following µ ∝ T -n, the exponent n differs substantially. Modelling reveals that the differences between the two chemically similar semiconductors can be traced to the delocalization of the different states that are thermally accessible by charge carriers, which in turn depends on their specific electronic band structure. The emerging picture is that of holes surfing on a dynamic manifold of vibrationally dressed extended states with a temperature-dependent mobility that provides a sensitive fingerprint for the underlying density of states.

8.
Nat Mater ; 22(7): 880-887, 2023 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-37337069

RESUMEN

Two-dimensional conjugated polymers (2DCPs), composed of multiple strands of linear conjugated polymers with extended in-plane π-conjugation, are emerging crystalline semiconducting polymers for organic (opto)electronics. They are represented by two-dimensional π-conjugated covalent organic frameworks, which typically suffer from poor π-conjugation and thus low charge carrier mobilities. Here we overcome this limitation by demonstrating two semiconducting phthalocyanine-based poly(benzimidazobenzophenanthroline)-ladder-type 2DCPs (2DCP-MPc, with M = Cu or Ni), which are constructed from octaaminophthalocyaninato metal(II) and naphthalenetetracarboxylic dianhydride by polycondensation under solvothermal conditions. The 2DCP-MPcs exhibit optical bandgaps of ~1.3 eV with highly delocalized π-electrons. Density functional theory calculations unveil strongly dispersive energy bands with small electron-hole reduced effective masses of ~0.15m0 for the layer-stacked 2DCP-MPcs. Terahertz spectroscopy reveals the band transport of Drude-type free carriers in 2DCP-MPcs with exceptionally high sum mobility of electrons and holes of ~970 cm2 V-1 s-1 at room temperature, surpassing that of the reported linear conjugated polymers and 2DCPs. This work highlights the critical role of effective conjugation in enhancing the charge transport properties of 2DCPs and the great potential of high-mobility 2DCPs for future (opto)electronics.


Asunto(s)
Estructuras Metalorgánicas , Polímeros , Electrónica , Electrones , Indoles
9.
Nano Lett ; 23(5): 1850-1857, 2023 Mar 08.
Artículo en Inglés | MEDLINE | ID: mdl-36799492

RESUMEN

Bond-free integration of two-dimensional (2D) materials yields van der Waals (vdW) heterostructures with exotic optical and electronic properties. Manipulating the splitting and recombination of photogenerated electron-hole pairs across the vdW interface is essential for optoelectronic applications. Previous studies have unveiled the critical role of defects in trapping photogenerated charge carriers to modulate the photoconductive gain for photodetection. However, the nature and role of defects in tuning interfacial charge carrier dynamics have remained elusive. Here, we investigate the nonequilibrium charge dynamics at the graphene-WS2 vdW interface under electrochemical gating by operando optical-pump terahertz-probe spectroscopy. We report full control over charge separation states and thus photogating field direction by electrically tuning the defect occupancy. Our results show that electron occupancy of the two in-gap states, presumably originating from sulfur vacancies, can account for the observed rich interfacial charge transfer dynamics and electrically tunable photogating fields, providing microscopic insights for optimizing optoelectronic devices.

10.
Angew Chem Int Ed Engl ; 63(8): e202312123, 2024 Feb 19.
Artículo en Inglés | MEDLINE | ID: mdl-38010868

RESUMEN

A critical step in photocatalytic water dissociation is the hole-mediated oxidation reaction. Molecular-level insights into the mechanism of this complex reaction under realistic conditions with high temporal resolution are highly desirable. Here, we use femtosecond time-resolved, surface-specific vibrational sum frequency generation spectroscopy to study the photo-induced reaction directly at the interface of the photocatalyst TiO2 in contact with liquid water at room temperature. Thanks to the inherent surface specificity of the spectroscopic method, we can follow the reaction of solely the interfacial water molecules directly at the interface at timescales on which the reaction takes place. Following the generation of holes at the surface immediately after photoexcitation of the catalyst with UV light, water dissociation occurs on a sub-20 ps timescale. The reaction mechanism is similar at pH 3 and 11. In both cases, we observe the conversion of H2 O into Ti-OH groups and the deprotonation of pre-existing Ti-OH groups. This study provides unique experimental insights into the early steps of the photo-induced dissociation processes at the photocatalyst-water interface, relevant to the design of improved photocatalysts.

11.
Angew Chem Int Ed Engl ; 63(20): e202320091, 2024 May 13.
Artículo en Inglés | MEDLINE | ID: mdl-38488855

RESUMEN

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 Ag4TTHQ and Ag4TTBQ (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 Ag4TTHQ and 0.5 eV for Ag4TTBQ) and conductivities (0.4 S/cm for Ag4TTHQ and 10 S/cm for Ag4TTBQ). DFT calculations reveal that these differences arise from the ligand oxidation state inhibiting energy band formation near the Fermi level in Ag4TTHQ. Consequently, Ag4TTHQ displays a high Seebeck coefficient of 330 µV/K and a power factor of 10 µW/m ⋅ K2, surpassing Ag4TTBQ and the other reported silver-based c-CPs. Furthermore, terahertz spectroscopy demonstrates high charge mobilities exceeding 130 cm2/V ⋅ s in both Ag4TTHQ and Ag4TTBQ.

12.
J Am Chem Soc ; 145(16): 8979-8987, 2023 Apr 26.
Artículo en Inglés | MEDLINE | ID: mdl-37067179

RESUMEN

Conductive metal-organic frameworks (c-MOFs) with outstanding electrical conductivities and high charge carrier mobilities are promising candidates for electronics and optoelectronics. However, the poor solubility of planar ligands greatly hinders the synthesis and widespread applications of c-MOFs. Nonplanar ligands with excellent solubility in organic solvents are ideal alternatives to construct c-MOFs. Herein, contorted hexabenzocoronene (c-HBC) derivatives with good solubility are adopted to synthesize c-MOFs. Three c-MOFs (c-HBC-6O-Cu, c-HBC-8O-Cu, and c-HBC-12O-Cu) with substantially different geometries and packing modes have been synthesized using three multitopic catechol-based c-HBC ligands with different symmetries and coordination numbers, respectively. With more metal coordination centers and increased charge transport pathways, c-HBC-12O-Cu exhibits the highest intrinsic electrical conductivity of 3.31 S m-1. Time-resolved terahertz spectroscopy reveals high charge carrier mobilities in c-HBC-based c-MOFs, ranging from 38 to 64 cm2 V-1 s-1. This work provides a systematic and modular approach to fine-tune the structure and enrich the c-MOF family with excellent charge transport properties using nonplanar and highly soluble ligands.

13.
J Am Chem Soc ; 145(4): 2430-2438, 2023 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-36661343

RESUMEN

Electrically conductive coordination polymers and metal-organic frameworks are attractive emerging electroactive materials for (opto-)electronics. However, developing semiconducting coordination polymers with high charge carrier mobility for devices remains a major challenge, urgently requiring the rational design of ligands and topological networks with desired electronic structures. Herein, we demonstrate a strategy for synthesizing high-mobility semiconducting conjugated coordination polymers (c-CPs) utilizing novel conjugated ligands with D2h symmetry, namely, "4 + 2" phenyl ligands. Compared with the conventional phenyl ligands with C6h symmetry, the reduced symmetry of the "4 + 2" ligands leads to anisotropic coordination in the formation of c-CPs. Consequently, we successfully achieve a single-crystalline three-dimensional (3D) c-CP Cu4DHTTB (DHTTB = 2,5-dihydroxy-1,3,4,6-tetrathiolbenzene), containing orthogonal ribbon-like π-d conjugated chains rather than 2D conjugated layers. DFT calculation suggests that the resulting Cu4DHTTB exhibits a small band gap (∼0.2 eV), strongly dispersive energy bands near the Fermi level with a low electron-hole reduced effective mass (∼0.2m0*). Furthermore, the four-probe method reveals a semiconducting behavior with a decent conductivity of 0.2 S/cm. Thermopower measurement suggests that it is a p-type semiconductor. Ultrafast terahertz photoconductivity measurements confirm Cu4DHTTB's semiconducting nature and demonstrate the Drude-type transport with high charge carrier mobilities up to 88 ± 15 cm2 V-1 s-1, outperforming the conductive 3D coordination polymers reported till date. This molecular design strategy for constructing high-mobility semiconducting c-CPs lays the foundation for achieving high-performance c-CP-based (opto-)electronics.

14.
Small ; : e2306732, 2023 Dec 11.
Artículo en Inglés | MEDLINE | ID: mdl-38073322

RESUMEN

Currently, most reported 2D conjugated metal-organic frameworks (2D c-MOFs) are based on planar polycyclic aromatic hydrocarbons (PAHs) with symmetrical functional groups, limiting the possibility of introducing additional substituents to fine-tune the crystallinity and electrical properties. Herein, a novel class of wavy 2D c-MOFs with highly substituted, core-twisted hexahydroxy-hexa-cata-benzocoronenes (HH-cHBCs) as ligands is reported. By tailoring the substitution of the c-HBC ligands with electron-withdrawing groups (EWGs), such as fluorine, chlorine, and bromine, it is demonstrated that the crystallinity and electrical conductivity at the molecular level can be tuned. The theoretical calculations demonstrate that F-substitution leads to a more reversible coordination bonding between HH-cHBCs and copper metal center, due to smaller atomic size and stronger electron-withdrawing effect. As a result, the achieved F-substituted 2D c-MOF exhibits superior crystallinity, comprising ribbon-like single crystals up to tens of micrometers in length. Moreover, the F-substituted 2D c-MOF displays higher electrical conductivity (two orders of magnitude) and higher charge carrier mobility (almost three times) than the Cl-substituted one. This work provides a new molecular design strategy for the development of wavy 2D c-MOFs and opens a new route for tailoring the coordination reversibility by ligand substitution toward increased crystallinity and superior electric conductivity.

15.
Angew Chem Int Ed Engl ; 62(10): e202216795, 2023 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-36627239

RESUMEN

Targeted synthesis of kagome (kgm) topologic 2D covalent organic frameworks remains challenging, presumably due to the severe dependence on building units and synthetic conditions. Herein, two isomeric "two-in-one" monomers with different lengths of substituted arms based on naphthalene core (p-Naph and m-Naph) are elaborately designed and utilized for the defined synthesis of isomeric kgm Naph-COFs. The two isomeric frameworks exhibit splendid crystallinity and showcase the same chemical composition and topologic structure with, however, different pore channels. Interestingly, C60 is able to uniformly be encapsulated into the triangle channels of m-Naph-COF via in situ incorporation method, while not the isomeric p-Naph-COF, likely due to the different pore structures of the two isomeric COFs. The resulting stable C60 @m-Naph-COF composite exhibits much higher photoconductivity than the m-Naph-COF owing to charge transfer between the conjugated skeletons and C60 guests.

16.
Angew Chem Int Ed Engl ; 62(35): e202305978, 2023 Aug 28.
Artículo en Inglés | MEDLINE | ID: mdl-37271733

RESUMEN

Linear conjugated polymers have attracted significant attention in organic electronics in recent decades. However, despite intrachain π-delocalization, interchain hopping is their transport bottleneck. In contrast, two-dimensional (2D) conjugated polymers, as represented by 2D π-conjugated covalent organic frameworks (2D c-COFs), can provide multiple conjugated strands to enhance the delocalization of charge carriers in space. Herein, we demonstrate the first example of thiophene-based 2D poly(arylene vinylene)s (PAVs, 2DPAV-BDT-BT and 2DPAV-BDT-BP, BDT=benzodithiophene, BT=bithiophene, BP=biphenyl) via Knoevenagel polycondensation. Compared with 2DPAV-BDT-BP, the fully thiophene-based 2DPAV-BDT-BT exhibits enhanced planarity and π-delocalization with a small band gap (1.62 eV) and large electronic band dispersion, as revealed by the optical absorption and density functional calculations. Remarkably, temperature-dependent terahertz spectroscopy discloses a unique band-like transport and outstanding room-temperature charge mobility for 2DPAV-BDT-BT (65 cm2  V-1 s-1 ), which far exceeds that of the linear PAVs, 2DPAV-BDT-BP, and the reported 2D c-COFs in the powder form. This work highlights the great potential of thiophene-based 2D PAVs as candidates for high-performance opto-electronics.

17.
Angew Chem Int Ed Engl ; 62(28): e202303929, 2023 Jul 10.
Artículo en Inglés | MEDLINE | ID: mdl-37163208

RESUMEN

Two-dimensional van der Waals heterostructures (2D vdWHs) have recently gained widespread attention because of their abundant and exotic properties, which open up many new possibilities for next-generation nanoelectronics. However, practical applications remain challenging due to the lack of high-throughput techniques for fabricating high-quality vdWHs. Here, we demonstrate a general electrochemical strategy to prepare solution-processable high-quality vdWHs, in which electrostatic forces drive the stacking of electrochemically exfoliated individual assemblies with intact structures and clean interfaces into vdWHs with strong interlayer interactions. Thanks to the excellent combination of strong light absorption, interfacial charge transfer, and decent charge transport properties in individual layers, thin-film photodetectors based on graphene/In2 Se3 vdWHs exhibit great promise for near-infrared (NIR) photodetection, owing to a high responsivity (267 mA W-1 ), fast rise (72 ms) and decay (426 ms) times under NIR illumination. This approach enables various hybrid systems, including graphene/In2 Se3 , graphene/MoS2 and graphene/MoSe2 vdWHs, providing a broad avenue for exploring emerging electronic, photonic, and exotic quantum phenomena.

18.
Angew Chem Int Ed Engl ; 62(46): e202312610, 2023 Nov 13.
Artículo en Inglés | MEDLINE | ID: mdl-37750665

RESUMEN

Structurally defined graphene nanoribbons (GNRs) have emerged as promising candidates for nanoelectronic devices. Low band gap (<1 eV) GNRs are particularly important when considering the Schottky barrier in device performance. Here, we demonstrate the first solution synthesis of 8-AGNRs through a carefully designed arylated polynaphthalene precursor. The efficiency of the oxidative cyclodehydrogenation of the tailor-made polymer precursor into 8-AGNRs was validated by FT-IR, Raman, and UV/Vis-near-infrared (NIR) absorption spectroscopy, and further supported by the synthesis of naphtho[1,2,3,4-ghi]perylene derivatives (1 and 2) as subunits of 8-AGNR, with a width of 0.86 nm as suggested by the X-ray single crystal analysis. Low-temperature scanning tunneling microscopy (STM) and solid-state NMR analyses provided further structural support for 8-AGNR. The resulting 8-AGNR exhibited a remarkable NIR absorption extending up to ∼2400 nm, corresponding to an optical band gap as low as ∼0.52 eV. Moreover, optical-pump TeraHertz-probe spectroscopy revealed charge-carrier mobility in the dc limit of ∼270 cm2  V-1 s-1 for the 8-AGNR.

19.
J Am Chem Soc ; 144(11): 5042-5050, 2022 Mar 23.
Artículo en Inglés | MEDLINE | ID: mdl-35189061

RESUMEN

Two-dimensional (2D) covalent organic frameworks (COFs) are an emerging class of promising 2D materials with high crystallinity and tunable structures. However, the low electrical conductivity impedes their applications in electronics and optoelectronics. Integrating large π-conjugated building blocks into 2D lattices to enhance efficient π-stacking and chemical doping is an effective way to improve the conductivity of 2D COFs. Herein, two nonplanar 2D COFs with kagome (DHP-COF) and rhombus (c-HBC-COF) lattices have been designed and synthesized from distorted aromatics with different π-conjugated structures (flexible and rigid structure, respectively). DHP-COF shows a highly distorted 2D lattice that hampers stacking, consequently limiting its charge carrier transport properties. Conversely, c-HBC-COF, with distorted although concave-convex self-complementary nodes, shows a less distorted 2D lattice that does not interfere with interlayer π-stacking. Employing time- and frequency-resolved terahertz spectroscopy, we unveil a high charge-carrier mobility up to 44 cm2 V-1 s-1, among the highest reported for 2D COFs.

20.
J Am Chem Soc ; 144(16): 7489-7496, 2022 Apr 27.
Artículo en Inglés | MEDLINE | ID: mdl-35420808

RESUMEN

Two-dimensional covalent organic frameworks (2D COFs) represent a family of crystalline porous polymers with a long-range order and well-defined open nanochannels that hold great promise for electronics, catalysis, sensing, and energy storage. To date, the development of highly conductive 2D COFs has remained challenging due to the finite π-conjugation along the 2D lattice and charge localization at grain boundaries. Furthermore, the charge transport mechanism within the crystalline framework remains elusive. Here, time- and frequency-resolved terahertz spectroscopy reveals intrinsically Drude-type band transport of charge carriers in semiconducting 2D COF thin films condensed by 1,3,5-tris(4-aminophenyl)benzene (TPB) and 1,3,5-triformylbenzene (TFB). The TPB-TFB COF thin films demonstrate high photoconductivity with a long charge scattering time exceeding 70 fs at room temperature which resembles crystalline inorganic materials. This corresponds to a record charge carrier mobility of 165 ± 10 cm2 V-1 s-1, vastly outperforming that of the state-of-the-art conductive COFs. These results reveal TPB-TFB COF thin films as promising candidates for organic electronics and catalysis and provide insights into the rational design of highly crystalline porous materials for efficient and long-range charge transport.

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