Electroactive covalent organic frameworks: a new choice for organic electronics

Covalent organic frameworks (COFs) with implemented electroactive moieties and coherent conduction channels are found to be competent for the transport of charges, in a similar manner as conventional (semi)conductors.Unlike densely packed polymer layers that used electronics, crystallinity COFs is mostly supported by covalent bonds potentially boost communication stability.The voids inside framework structure enable encapsulation mass transport, allowing space guest components such external electron donors/acceptors well diffusion-based functions sensing switching. feature bond-supported along high encapsulating abilities. Together ease chemical addition moieties, these properties have recently raised interest this class material electronics. In review, we systematically summarize utilization advantageous characteristics fulfill different electronic processes, resulting various applications. Broadly, been successfully conductive or semiconductive devices, photodetector photovoltaics, transistors, light-emitting sensor memory devices. Simultaneously, general tactics provide functionalities discussed, providing open considerations inspiration future design. porous, crystalline polymers periodically organized networks connected between light atoms C, N, O. Directed reticular chemistry, 2D 3D constructed selecting building blocks bonding linkages predefined orientations [1.Lyle S.J. et al.Covalent frameworks: chemistry extended into two three dimensions.Trends Chem. 2019; 1: 172-184Abstract Full Text PDF Scopus (124) Google Scholar]. extends dimensions, forming sheets stack together intermolecular interactions, whereas reach out all directions therefore an isotropic structure. The predesigned bottom-up synthesis (see Glossary) rigid architecture endows ultrahigh surface area, lightweight, precisely controlled pore atom distribution, stability wide range solvents conditions [2.Liu R. ideal platform designing ordered materials advanced applications.Chem. Soc. Rev. 2021; 50: 120-242Crossref PubMed Scholar,3.Geng K. design, synthesis, functions.Chem. 2020; 120: 8814-8933Crossref (774) Intrigued their unique features, race among researchers explore applications COF-based has started. Organic electronics discipline uses small molecules functional elements devices [4.Pron A. al.Electroactive electronics: preparation strategies, structural aspects characterization techniques.Chem. 2010; 39: 2577-2632Crossref (407) This interdisciplinary research area including device engineering. Focusing on act electrically transfer charges under certain conditions. Compared inorganic equivalents, usually advantages being highly diverse, flexible, having low energy consumption when fabricated, solution processable [5.Yang Y. al.The effects side chains charge mobilities semiconducting conjugated beyond solubilities.Adv. Mater. 311903104Crossref (93) electrical conductance can ductile transparent electrodes flexible circuits, applied field-effect transistors (OFETs), diodes (OLEDs), photovoltaics (OPVs), lasers, others. As emerging material, now designed electroactivity, releasing new choice (Box 1) [6.Yusran applications.Adv. 322002038Crossref (66) Scholar,7.Allendorf M.D. al.Electronic using materials.Chem. 8581-8640Crossref (82) materials, show some remedy traditional limitations might even lead innovations. First, vastly surpasses intermolecular-force-supported molecules/polymers, considering enhanced long-range higher stability. behavior profoundly affected allow stable, long range, priori predictable crystallinity. Second, porous within tunnels layers, which uncommon conductive/semiconductive too diffusion molecules. Furthermore, pores (e.g., dopants), could interact COF host property modification integrate multiple functionalities. Considering benefits, attractive alternative vast number applications.Box 1The branches processesDepending processes (shown rectangles Figure I), categorized colored boxes I). If bias voltage, it defined COF. Conductive most basic widely researched aspect materials. thermally activated at room temperature, intrinsically conductive. Light chemicals (dopants) also source activation, corresponding activation doping respectively. if triggered gate voltage from third electrode, belongs scope three-terminal OFETs. For photoactivated current change illumination large, shows photoresponsive utilized photodetectors. formed excitons dissociate accumulate phases followed extraction electrodes, exploited solar cells. showing conduction, COFs: (i) reversibly trap ions/charges switching, behaves signal storage; (ii) causing change, acts detection; (iii) absorption due electrochemical redox reaction, EC device. emissive integrated active layer OLED. Depending Being conductive, meaning fundamental Considerable effort devoted construct COFs, achievements marked continuously increasing conductivities (Table 1). From recent research, design rules extracted 2). following section, expand strategies.Table 1Comparison reported date representative MOFs polymersMaterial typeMaterialConductivity (S m−1)MethodSample typeRefs2D COFI2@TTF-Ph-COFI2@TTF-Py-COF10−310−4Two probePellet[10.Jin S. al.Two-dimensional tetrathiafulvalene towards latticed salts.Chem. Eur. J. 2014; 20: 14608-14613Crossref (115) Scholar][email protected] × 10−4Two probePellet[8.Ding H. al.A tetrathiafulvalene-based framework.Chem. 14614-14618Crossref (123) Scholar][email protected] 10−40.28Two probeFilm[9.Cai S.-L. al.Tunable conductivity oriented thin films Sci. 5: 4693-4700Crossref Scholar]TTF-DMTA1.8 probeFilm[25.Cai al.Reversible interlayer sliding changes adaptive frameworks.ACS Appl. Interfaces. 12: 19054-19061Crossref (24) Scholar][email protected] 10−3~1Four probePellet[12.Meng Z. chemiresistive intrinsic conductivity.J. Am. 141: 11929-11937Crossref (164) Scholar][email protected] 10−91.52 10−5Two probePellet[15.Nath B. azodioxy-linked porphyrin-based I2 doping-enhanced photoconductivity.CrystEngComm. 2016; 18: 4259-4263Crossref Scholar]TAPP−TFPP−COFI2@TAPP−TFPP−COF1.12 10−81.46 probePellet[26.Xu X. al.Semiconductive sensitive near-infrared detection.ACS 37427-37434Crossref (35) Scholar]I2@TANG-COF1Four probePellet[18.Lakshmi V. two-dimensional poly(azatriangulene) paramagnetic states.J. 142: 2155-2160Crossref (40) Scholar]WBDT[email protected]2.70 10−43.67vdPaAbbreviation: vdP, van der Pauw.Pellet[19.Rotter J.M. al.Highly conducting Wurster-type twisted frameworks.Chem. 11: 12843-12853Crossref Scholar]1-S1-Se1-Te3.7(± 0.4) 10−88.4 (± 3.8) 10−71.3 0.1) probePellet[20.Duhović Dincă M. Synthesis heavy chalcogens.Chem. 2015; 27: 5487-5490Crossref (77) Scholar]BDT-COF1~5 probeFilm[21.Medina D.D. al.Directional charge-carrier benzodithiophene films.ACS Nano. 2017; 2706-2713Crossref (87) Scholar][email protected] 10−2Two probePellet[23.Jin E. sp2 carbon-conjugated frameworks.Science. 357: 673-676Crossref (533) Scholar]PyVg-COF0.4Two probeFilm[27.Wang L. soluble, compatible implementation.Chem. 10: 1023-1028Crossref Scholar][email protected]110Two probePellet[5.Yang Scholar]3D [email protected] 10−2 (25oC)1.4 (120oC)Two probePellet[11.Li al.Three-dimensional tunable 13324-13329Crossref protected]3.4Two probeFilm[29.Yang all-carbon linked film.Small. 17e2103152Crossref (2) Scholar]2D MOF{[Cu2(6-Hmna)(6-mn)]NH4}n1096Four probeCrystal[33.Pathak al.Integration (–Cu–S–)n plane metal–organic affords conductivity.Nat. Commun. 1721Crossref (83) Scholar]Ni3(HITP)25540Four probePellet[34.Chen T. al.Continuous variation M3(hexaiminotriphenylene)2 (M = Co, Ni, Cu) MOF alloys.J. 12367-12373Crossref (76) Scholar][Ag5(C6S6)]n25 000Four probePellet[35.Huang neutral coordination infinite silver–sulfur networks.J. 2018; 140: 15153-15156Crossref (68) Scholar]PolymerPEDOT:PSS(H2SO4 treated)438 probeFilm[37.Kim N. PEDOT:PSS nanofibrils induced solution-processed crystallization.Adv. 26: 2268-2272Crossref (677) Scholar]PBTTT(FeCl3 doped)100 000vdPaAbbreviation: Pauw.Film[38.Jacobs, I.E. al. High-efficiency ion-exchange polymers. Adv. Published online August 21, 2021. https://onlinelibrary.wiley.com/doi/full/10.1002/adma.202102988Google Scholar]a Abbreviation: Pauw. Open table tab Box 2Key COFsAs category common bandgap large electrons promoted valence band ambient conditions, thus insulating properties. To endow metallic conductivity, important: (Figure IA), activating factors IB), IC). Specifically, introduced sites ready produce mobile carriers. These further heat, light, dopants) form charges. Finally, need efficient transportation. optimization cooperatively contributes conductivity. bulk material. Efficient easily oxidized reduced stable shell species (i.e., radical cation anion), serves Due construction density order 1 examples). synthesized activated. involves removal and/or band. Methods include thermal excitation, photoexcitation, doping. Among factors, way create amount Tetrathiafulvalene (TTF) block make its strong electron-donating ability [8.Ding When TTF cations dopant [9.Cai Scholar,10.Jin Scholar], partially filled necessary behavior. TTF-based Scholar] 1A) [11.Li 1B) both after doping, indicated linear I–V characteristics, 1.4 S m−1 120°C Phthalocyanines porphyrins cyclic conjugation involving 18e− belong Phthalocyanine/porphyrin-based excited [12.Meng Scholar,13.Wan carrier mobility.Chem. 2011; 23: 4094-4097Crossref (510) photoexcited [14.Ding al.Synthesis metallophthalocyanine exhibit mobility photoconductivity.Angew. Int. Ed. 1289-1293Crossref (387) [15.Nath gain Interestingly, type changing coordinated central metal phthalocyanine/porphyrin 1C) [16.Feng al.High-rate porphyrin switching hole ambipolar conduction.Angew. 2012; 51: 2618-2622Crossref (289) Scholar,17.Ding al.Conducting role metals controlling π-electronic 48: 8952-8954Crossref (107) There other excellent [18.Lakshmi Scholar, 19.Rotter 20.Duhović 21.Medina give TANG 1D) WBDT 1E) [19.Rotter 3.67 m−1, respectively, improve efficiency selection matching important. It generally difficult predict will best result. Dopant screening instance, dopants SbCl5, I2, F4TCNQ, latter WBTD Having uptake important ensure doped. Fortunately, natural advantage porosity, exemplified TANG-COF close-to-complete respect, potential achieve capture they greater porosity than 1F) [22.Wang C. exceptionally iodine capability.Chem. 24: 585-589Crossref (151) worth mentioning types sometimes overlapped generate better performance Scholar,15.Nath Once formed, needed transfer. Within occurs through 2 1C). bond channel in-plane individual layers. Thus, enhancing overall delocalization facilitates through-bond [23.Jin Scholar,24.Kim Choi H.C. Light-promoted highly-conjugated framework.Commun. 2: 60Crossref (49) An example sp2c-COF 1G), solely comprising hybridized carbons, 7.1 π–π stacking 1H). interactions reducing distance avoiding configuration through-space [10.Jin eclipsed mode staggered [25.Cai self-sorting align π-overlapped [26.Xu do not contribute equally anisotropic Scholar,27.Wang Scholar,28.Thomas al.Design four-arm cores: prediction remarkable charge-transport properties.Mater. Horiz. 6: 1868-1876Crossref because interplane π-orbital overlap channels, hopping mechanisms, major antagonists channels. First lack continuity. Pressing powders pellets results numerous boundaries, cracks, gaps inside, scatter impede solved exploring technologies continuous [21.Medina SBFdiyne-COF fabricated continuous-flow system extremely film quality reaching 3.4 TCNQ [29.Yang Second amorphous less-ordered regions [30.Ghosh Paesani F. Unraveling effect defects, domain size, photophys