Bottom‐Up Preparation of Fully sp2‐Bonded Porous Carbons with High Photoactivities

Porous carbons, possessing exceptional stability, high surface area, and electric conductivity, are broadly used as superior adsorbent, supporter, or electrode material for environmental protection, industrial catalysis, and energy storage and conversion. The construction of such kinds of materials with designable structures and properties will extremely extend their potential applications, but remains a huge synthetic challenge. Herein, a bottom‐up approach is presented to synthesize one type of fully sp² carbon–bonded frameworks by transition metal–catalyzed cross‐coupling of different polyphenylenes with electron‐withdrawing 9,9′‐bifluorenylidene (9,9′‐BF) through its 2,7‐position. The resulting porous polymeric carbons exhibit substantial semiconducting properties, such as strong light‐harvesting capabilities in the visible light region, likely due to their π‐extended backbones with donor–acceptor characters. Their electronic and porous structures can be finely tuned via the polyphenylene spacers. The intriguing properties allow these porous carbons to efficiently catalyze dye degradation under visible light or even natural sunlight with high reusability. Meanwhile, associated with their intrinsic structures, these porous carbons also exhibit highly selective degradation activities toward different dyes. In particular, the photodegradation mechanism involving oxygen and electron is elucidated for the first time for such kinds of materials, related to the presence of specific 9,9′‐BF units in their π‐conjugated skeletons.     

Laser‐Induced Direct Lithography for Patterning of Carbon with sp3 and sp2 Hybridization

A new method of laser‐induced lithography for direct writing of carbon on a glass surface is described, in which deposition occurs from a transparent precursor solution. At the glass–solution interface where the laser spot is focused, a micro‐explosion process takes place, leading to the deposition of pure carbon on the glass surface. Transmission electron microscopy (TEM) analysis shows two distinct co‐existing phases. The dominant one shows a mottled morphology with diffraction typical of cubic (sp³) diamond. The other region shows an ordered array of graphene sheets with diffraction pattern typical of sp²‐bonded carbon. The sp³ crystallites range in size from 9 to 30 Å and are scattered randomly throughout the sample. A UV Raman spectrum shows a broad band at the location of the expected diamond peak, together with a peak corresponding to the graphite region. We conclude that the patterned carbon is composed of a mixture of nanocrystalline sp³ and sp² carbon forms.     

Substantial Cyano‐Substituted Fully sp2‐Carbon‐Linked Framework: Metal‐Free Approach and Visible‐Light‐Driven Hydrogen Evolution

Polymeric semiconductors are emerging as a kind of competitive photocatalysts for hydrogen evolution due to their well‐tunable structures, versatile functionalization, and low‐cost processibility. In this work, a series of conjugated porous polymers with substantial cyano‐substituted fully sp²‐carbon frameworks are efficiently synthesized by using electron‐deficient tricyanomesitylene as a key building block to promote an organic base‐catalyzed Knoevenagel condensation with various aldehyde‐substituted arenes. The resulting porous polymers feature donor‐acceptor structures with π‐extended conjugation, rendering them with distinct semiconducting properties. They possess hierarchically porous structures, nanoscale morphologies, and intriguing wettability. These promising physical characters, finely tailorable by varying the arene units, are essentially relevant to the abundant cynao substituents over the whole frameworks. The as‐prepared porous polymers exhibit excellent visible‐light‐driven photocatalytic activity for water‐splitting hydrogen evolution with apparent quantum yield up to 2.0% at 420 nm or 1.9% at 470 nm, among the highest values yet reported for porous polymer‐based photocatalysts, also representing the first example of such kinds of catalysts formed through a metal‐free‐catalyzed carbon–carbon coupling reaction.     

Highly Efficient Electrocatalysts for Oxygen Reduction Reaction Based on 1D Ternary Doped Porous Carbons Derived from Carbon Nanotube Directed Conjugated Microporous Polymers

One‐dimensional (1D) porous materials have shown great potential for gas storage and separation, sensing, energy storage, and conversion. However, the controlled approach for preparation of 1D porous materials, especially porous organic materials, still remains a great challenge due to the poor dispersibility and solution processability of the porous materials. Here, carbon nanotube (CNT) templated 1D conjugated microporous polymers (CMPs) are prepared using a layer‐by‐layer method. As‐prepared CMPs possess high specific surface areas of up to 623 m² g^?1 and exhibit strong electronic interactions between p‐type CMPs and n‐type CNTs. The CMPs are used as precursors to produce heteroatom‐doped 1D porous carbons through direct pyrolysis. As‐produced ternary heteroatom‐doped (B/N/S) 1D porous carbons possess high specific surface areas of up to 750 m² g^?1, hierarchical porous structures, and excellent electrochemical‐catalytic performance for oxygen reduction reaction. Both of the diffusion‐limited current density (4.4 mA cm^?2) and electron transfer number (n = 3.8) for three‐layered 1D porous carbons are superior to those for random 1D porous carbon. These results demonstrate that layered and core–shell type 1D CMPs and related heteroatom‐doped 1D porous carbons can be rationally designed and controlled prepared for high performance energy‐related applications.     

Unexpected Sole Enol‐Form Emission of 2‐(2′‐Hydroxyphenyl)oxazoles for Highly Efficient Deep‐Blue‐Emitting Organic Electroluminescent Devices

Considerable efforts have been devoted to the development of highly efficient blue light‐emitting materials. However, deep‐blue fluorescence materials that can satisfy the Commission Internationale de l'Eclairage (CIE) coordinates of (0.14, 0.08) of the National Television System Committee (NTSC) standard blue and, moreover, possess a high external quantum efficiency (EQE) over 5%, remain scarce. Here, the unusual luminescence properties of triphenylamine‐bearing 2‐(2′‐hydroxyphenyl)oxazoles ( 3a–3c ) and their applications in organic light‐emitting diodes (OLEDs) are reported as highly efficient deep‐blue emitters. The 3a ‐based device exhibits a high spectral stability and an excellent color purity with a narrow full‐width at half‐maximum of 53 nm and the CIE coordinates of (0.15, 0.08), which is very close to the NTSC standard blue. The exciton utilization of the device closes to 100%, exceeding the theoretical limit of 25% in conventional fluorescent OLEDs. Experimental data and theoretical calculations demonstrate that 3a possesses a highly hybridized local and charge‐transfer excited state character. In OLEDs, 3a exhibits a maximum luminance of 9054 cd m^?2 and an EQE up to 7.1%, which is the first example of highly efficient blue OLEDs based on the sole enol‐form emission of 2‐(2′‐hydroxyphenyl)azoles.     

High‐Performance Cathode Based on Self‐Templated 3D Porous Microcrystalline Carbon with Improved Anion Adsorption and Intercalation

Dual‐ion batteries (DIBs) have attracted much attention due to their advantages of low cost and especially environmental friendliness. However, the capacities of most DIBs are still unsatisfied (≈100 mAh g^?1) ascribed to the limited capacity of anions intercalation for conventional graphite cathode. In this study, 3D porous microcrystalline carbon (3D‐PMC) was designed and synthesized via a self‐templated growth approach, and when used as cathode for a DIB, it allows both intercalation and adsorption of anions. The microcrystalline carbon is beneficial to obtain capacity originated from anions intercalation, and the 3D porous structure with a certain surface area contributes to anions adsorption capacity. With the synergistic effect, this 3D‐PMC is utilized as cathode and tin as anode for a sodium‐based DIB, which has a high capacity of 168.0 mAh g^?1 at 0.3 A g^?1, among the best values of reported DIBs so far. This cell also exhibits long‐term cycling stability with a capacity retention of ≈70% after 2000 cycles at a high current rate of 1 A g^?1. It is believed that this work will provide a strategy to develop high‐performance cathode materials for DIBs.     

Scale‐Up Biomass Pathway to Cobalt Single‐Site Catalysts Anchored on N‐Doped Porous Carbon Nanobelt with Ultrahigh Surface Area

Porous Co? N? C catalysts with ultrahigh surface area are highly required for catalytic reactions. Here, a scale‐up method to synthesize gram‐quantities of isolated Co single‐site catalysts anchored on N‐doped porous carbon nanobelt (Co‐ISA/CNB) by pyrolysis of biomass‐derived chitosan is reported. The usage of ZnCl₂ and CoCl₂ salts as effective activation–graphitization agents can introduce a porous belt‐like nanostructure with ultrahigh specific surface area (2513 m² g^?1) and high graphitization degree. Spherical aberration correction electron microscopy and X‐ray absorption fine structure analysis reveal that Co species are present as isolated single sites and stabilized by nitrogen in CoN₄ structure. All these characters make Co‐ISA/CNB an efficient catalyst for selective oxidation of aromatic alkanes at room temperature. For oxidation of ethylbenzene, the Co‐ISA/CNB catalysts yield a conversion up to 98% with 99% selectivity, while Co nanoparticles are inert. Density functional theory calculations reveal that the generated Co?O centers on isolated Co single sites are responsible for the excellent catalytic efficiency.     

Reversible Thermochromic Polymeric Thin Films Made of Ultrathin 2D Crystals of Coordination Polymers Based on Copper(I)‐Thiophenolates

A one‐pot reaction between Cu(BF₄)₂·xH₂O and 4‐mercaptobenzoic acid in acetone or methanol gives rise to the formation of lamellar microcrystals of two Cu(I)‐thiophenolate‐based coordination polymers (CPs) with the formulas [CuCT] _n ( 1 ) (CT = 4‐carboxy‐thiophenolate) and [CuMCT]_n ( 2 ) (MCT = 4‐methoxycarbonyl‐thiophenolate). Both 1 and 2 show a reversible luminescent thermochromic behavior upon cooling, changing their color from pale yellow to green to orange in the case of 1 , and from pale orange to green in the case of 2 . It is shown that the lamellar character of these crystals, which exhibit micrometer lateral dimensions and sub‐micrometer/nanometer thicknesses, allows processing them with an organic polymer such as polyvinylidene difluoride (PVDF) to form thermochromic 1 @PVDF and 2 @PVDF thin films. These thermal stimuli‐responsive thin films are freestanding, free of macroscopic defects, and robust under mechanical bending stress, opening up the possibility to use them in, for example, 2D imaging sensor films.     

Highly Stable Nanoporous Sulfur‐Bridged Covalent Organic Polymers for Carbon Dioxide Removal

Carbon dioxide capture and separation requires robust solids that can stand harsh environments where a hot mixture of gases is often found. Herein, the first and comprehensive syntheses of porous sulfur‐bridged covalent organic polymers (COPs) and their application for carbon dioxide capture in warm conditions and a wide range of pressures (0–200 bar) are reported. These COPs can store up to 3294 mg g^?1 of carbon dioxide at 318 K and 200 bar while being highly stable against heating up to 400 °C. The carbon dioxide capacity of the COPs is also not hindered upon boiling in water for at least one week. Physisorptive binding is prevalent with isosteric heat of adsorptions around 24 kJ mol^?1. M06–2X and RIMP2 calculations yield the same relative trend of binding energies, where, interestingly, the dimer of triazine and benzene play a cooperative role for a stronger binding of CO₂ (19.2 kJ mol^?1) as compared to a separate binding with triazine (13.3 kJ mol^?1) or benzene (11.8 kJ mol^?1).     

Uniformly Confined Germanium Quantum Dots in 3D Ordered Porous Carbon Framework for High‐Performance Li‐ion Battery

Although abundant germanium (Ge)‐based anode materials have been explored to obtain high specific capacity, high rate performance, and long charge/discharge lifespans for lithium‐ion batteries (LIBs), their performances are still far from satisfactory due to the intrinsic defects of Ge and the relatively intricate anode structure. To work out these issues, a 3D ordered porous N‐doped carbon framework with Ge quantum dots uniformly embedded (3DOP Ge@N? C) as a binder‐free anode for LIBs via a facile polystyrene colloidal nanospheres template‐confined strategy is proposed. This unique structure not only facilitates Li‐ion diffusion and electron transport that can guarantee rapid de/alloying reaction, but also alleviates the huge volume changes during reactions and improves cycling stability. Notably, the resulting anode delivers a high specific reversible capacity (≈1160 mA h g^?1 at 1 A g^?1), superior rate properties (exceeding 500 mA h g^?1 at 40 A g^?1), and excellent cycling stability (over 90% capacity retention after 1200 cycles even at 5 A g^?1). Furthermore, both the 3DOP Ge@N? C anode with high areal mass loading (up to 8 mg cm^?2) and the full cell coupled with LiFePO₄ cathode display high capacity and cycling stability, further indicative of the favorable real‐life application prospects for high‐energy LIBs.     

Engineering the Pore Structure and Functionality of Ionic Porous Polymers for Separating Acetylene over Carbon Dioxide

Precise engineering of organic porous polymers to realize the selective separation of structurally similar gases presents a great challenge. In this study, a new class of ionic porous polymers P(Ph3Im-Br-nDVB) with a high ionic density and microporous surface area are constructed through a facile copolymerization strategy, providing an efficient path to rational control over pore structure and functionality. The first example of ionic porous organic polymers is reported to address the challenge of discriminating the subtle difference of C₂H₂ and CO₂, which have almost identical molecular sizes and similar physicochemical properties, which achieve the highest C₂H₂/CO₂ selectivity (17.9) among porous organic polymers. These ionic porous polymers exhibit high stability and excellent dynamic breakthrough performance for binary C₂H₂/CO₂ mixtures, indicating their practical feasibility. Modeling studies reveal that anions are the specific binding sites for preferential C₂H₂ capture because of Br⁻···HCCH interactions. This study not only demonstrates an efficient strategy to build novel ionic porous polymers integrating abundant micropores and ionic sites but also sheds some light on the development of functionalized materials for the separation of structurally similar gas molecules.     

Stimuli‐Responsive DNA‐Gated Nanoscale Porous Carbon Derived from ZIF‐8

Stimuli‐responsive nanoscale porous carbon derived from ZIF‐8 (NCZIF) gated by DNA capping units is reported. The NCZIF is first obtained by calcination of nano‐ZIF‐8 crystals under an inert atmosphere. It is further conjugated with amine‐modified single‐stranded DNA after carboxylation (DNA/NCZIF). The guest molecules are sealed in the pore of NCZIF by the formation of a DNA duplex structure on the surface of NCZIF. As proof of principle, two systems that can be, respectively, used for controlled drug delivery and biosensing are introduced. In the first system, the drug model (rhodamine 6G, Rh6G) is locked in the NCZIF by the DNA capping units composed of rich‐G sequences and its complementary DNA strand. The in vitro cellular experiments reveal that DNA/NCZIF has good biocompatibility and can controllably release Rh6G upon the K⁺‐stimuli in cells. In the second system, the signal probe (methylene blue, MB) is locked in the NCZIF and then released after the unlocking of the pores triggered by the dissociation of the aptamer‐hybrid capping units. The MB‐loaded DNA/NCZIF can linearly respond to target molecules in the range from 1 × 10^?9 to 10 × 10^?6 m and has good specificity.     

Self‐Assembly of Flexible Free‐Standing 3D Porous MoS2‐Reduced Graphene Oxide Structure for High‐Performance Lithium‐Ion Batteries

Flexible freestanding electrodes are highly desired to realize wearable/flexible batteries as required for the design and production of flexible electronic devices. Here, the excellent electrochemical performance and inherent flexibility of atomically thin 2D MoS₂ along with the self‐assembly properties of liquid crystalline graphene oxide (LCGO) dispersion are exploited to fabricate a porous anode for high‐performance lithium ion batteries. Flexible, free‐standing MoS₂–reduced graphene oxide (MG) film with a 3D porous structure is fabricated via a facile spontaneous self‐assembly process and subsequent freeze‐drying. This is the first report of a one‐pot self‐assembly, gelation, and subsequent reduction of MoS₂/LCGO composite to form a flexible, high performance electrode for charge storage. The gelation process occurs directly in the mixed dispersion of MoS₂ and LCGO nanosheets at a low temperature (70 °C) and normal atmosphere (1 atm). The MG film with 75 wt% of MoS₂ exhibits a high reversible capacity of 800 mAh g^?1 at a current density of 100 mA g^?1. It also demonstrates excellent rate capability, and excellent cycling stability with no capacity drop over 500 charge/discharge cycles at a current density of 400 mA g^?1.     

Ultra‐High Surface Area Nitrogen‐Doped Carbon Aerogels Derived From a Schiff‐Base Porous Organic Polymer Aerogel for CO2 Storage and Supercapacitors

Nitrogen‐doped carbon aerogels (NCAs) have received great attention for a wide range of applications, from thermal electronics to waste water purification, heavy metal or gas adsorption, energy storage, and catalyst supports. Herein NCAs are developed via the synthesis of a Schiff‐base porous organic polymer aerogel followed by pyrolysis. By controlling the pyrolysis temperature, the polymer aerogel can be simply converted into porous NCAs with a low bulk density (5 mg cm^?3), high surface area (2356 m² g^?1), and high bulk porosity (70%). The NCAs containing 1.8–5.3 wt% N atoms exhibit remarkable CO₂ uptake capacities (6.1 mmol g^?1 at 273 K and 1 bar, 33.1 mmol g^?1 at 323 K and 30 bar) and high ideal adsorption solution theory selectivity (47.8) at ambient pressure. Supercapacitors fabricated with NCAs display high specific capacitance (300 F g^?1 at 0.5 A g^?1), fast rate (charge to 221 F g^?1 within only 17 s), and high stability (retained >98% capacity after 5000 cycles). Asymmetric supercapacitors assembled with NCAs also show high energy density and power density with maximal values of 30.5 Wh kg^?1 and 7088 W kg^?1, respectively. The outstanding CO₂ uptake and energy storage abilities are attributed to the ultra‐high surface area, N‐doping, conductivity, and rigidity of NCA frameworks.     

Light‐Coded Digital Crystallinity Patterns Toward Bioinspired 4D Transformation of Shape‐Memory Polymers

Spatially heterogeneous distribution of active components is key to the diverse shape‐morphing behaviors of biological species and their associated functions. Artificial morphing materials employing similar strategies have widened the design space for advanced functional devices. Typically, the spatial heterogeneity is introduced during the material synthesis/fabrication step and cannot be altered afterward. An approach that allows spatio‐selective programming of crystallinity in a shape‐memory polymer (SMP) by a digital photothermal effect is reported. The light‐patternable crystallinity affects greatly the shape morphing behavior. Consequently, a pre‐stretched 2D film with spatial heterogeneity in crystallinity can morph with time into designable 3D permanent shapes, achieving the 4D transformation. This approach utilizes a reprocessible thermoplastic SMP (polylactide) and the programming relies on a physical phase transformation (crystallization) instead of chemical heterogeneity. This allows repeated erasing and reprogramming using the same material, suggesting a versatile and sustainable means for manufacturing advanced morphing devices.     

Versatile Crystal Structures and (Opto)electronic Applications of the 2D Metal Mono‐, Di‐, and Tri‐Chalcogenide Nanosheets

Emerging 2D metal chalcogenides present excellent performance for electronic and optoelectronic applications. In contrast to graphene and other 2D materials, 2D metal chalcogenides possess intrinsic bandgaps, versatile band structures, and superior atmospheric stability. The many categories of 2D metal chalcogenides ensure that they can be applied to various practical scenarios. 2D metal monochalcogenides, dichalcogenides, and trichalcogenides are the three main categories of these materials. They have distinct crystal structures resulting in different characteristics. Some basic device characteristics, such as the charge carrier characteristics, scattering mechanisms, interfacial contacts, and band alignments of heterojunctions, are vital factors for practical device applications that ensure that the desired properties can be achieved. Various electronic, optoelectronic, and photonic applications based on 2D metal chalcogenides have been extensively investigated. 2D metal chalcogenides are considered as competitive candidates for future electronic and optoelectronic applications.     

A Reusable Interface Constructed by 3‐Aminophenylboronic Acid‐Functionalized Multiwalled Carbon Nanotubes for Cell Capture,Release, and Cytosensing

A newly developed electrochemical cell sensor for the determination of K562 leukemia cells using 3‐aminophenylboronic acid (APBA)‐functionalized multiwalled carbon nanotubes (MWCNTs) films is demonstrated. The films are generated by the covalent coupling between the ? NH₂ groups in APBA and the ? COOH group in the acid‐oxidized MWCNTs. As a result of the sugar‐specific affinity interactions, the K562 leukemia cells are firmly bound to the APBA‐functionalized MWCNTs film via boronic acid groups. Compared to electropolymerized APBA films, the presence of MWCNTs not only provides abundant boronic acid domains for cell capture, their high electrical conductivity also makes the film suitable for electrochemical sensing applications. The resulting modified electrodes are tested as cell detection sensors. This work presents a promising platform for effective cell capture and constructing reusable cytosensors.     

Graphene Oxide Gel‐Derived,Free‐Standing,Hierarchically Porous Carbon for High‐Capacity and High‐Rate Rechargeable Li‐O2 Batteries

Lithium‐oxygen (Li‐O₂) batteries are one of the most promising candidates for high‐energy‐density storage systems. However, the low utilization of porous carbon and the inefficient transport of reactants in the cathode limit terribly the practical capacity and, in particular, the rate capability of state‐of‐the‐art Li‐O₂ batteries. Here, free‐standing, hierarchically porous carbon (FHPC) derived from graphene oxide (GO) gel in nickel foam without any additional binder is synthesized by a facile and effective in situ sol‐gel method, wherein the GO not only acts as a special carbon source, but also provides the framework of a 3D gel; more importantly, the proper acidity via its intrinsic COOH groups guarantees the formation of the whole structure. Interestingly, when employed as a cathode for Li‐O₂ batteries, the capacity reaches 11 060 mA h g^?1 at a current density of 0.2 mA cm^?2 (280 mA g^?1); and, unexpectedly, a high capacity of 2020 mA h g^?1 can be obtained even the current density increases ten times, up to 2 mA cm^?2 (2.8 A g^?1), which is the best rate performance for Li‐O₂ batteries reported to date. This excellent performance is attributed to the synergistic effect of the loose packing of the carbon, the hierarchical porous structure, and the high electronic conductivity of the Ni foam.     

Highly Stretchable Conductors Integrated with a Conductive Carbon Nanotube/Graphene Network and 3D Porous Poly(dimethylsiloxane)

Here, a novel and facile method is reported for manufacturing a new stretchable conductive material that integrates a hybrid three dimensional (3D) carbon nanotube (CNT)/reduced graphene oxide (rGO) network with a porous poly(dimethylsiloxane) (p‐PDMS) elastomer (pPCG). This reciprocal architecture not only alleviates the aggregation of carbon nanofillers but also significantly improves the conductivity of pPCG under large strains. Consequently, the pPCG exhibits high electrical conductivity with a low nanofiller loading (27 S m^?1 with 2 wt% CNTs/graphene) and a notable retention capability after bending and stretching. The simulation of the mechanical properties of the p‐PDMS model demonstrates that an extremely large applied strain (ε_appl) can be accommodated through local rotations and bending of cell walls. Thus, after a slight decrease, the conductivity of pPCG can continue to remain constant even as the strain increases to 50%. In general, this architecture of pPCG with a combination of a porous polymer substrate and 3D carbon nanofiller network possesses considerable potential for numerous applications in next‐generation stretchable electronics.     

Excitons and Electron–Hole Liquid State in 2D γ‐Phase Group‐IV Monochalcogenides

Different dispersion near the electronic band edge of a semiconductor can have great influence on its transport, thermoelectric, and optical properties. Using first‐principles calculations, it is demonstrated that a new phase of group‐IV monochalcogenides (γ‐MX, M = Ge, Sn; X = S, Se, or Te) can be stabilized in monolayer limit. γ‐MXs are shown to possess a unique band dispersion—that is, camel's back like structure—in the top valence band. The band nesting effect near the camel's back region induces a large excitonic absorbance and significantly different exciton behaviors from other 2D materials. Importantly, the small effective mass and the indirect characteristics of lowest‐energy exciton render it advantageous for the generation of electron–hole liquid state. After careful evaluation of the electron–hole dissociation temperature and the Mott critical density, it is predicted that a high‐temperature exciton gas to electron–hole liquid phase transition can be achieved in these materials with a low excitation power density. The findings open up new opportunities for both the fundamental research on exciton physics and design of excitonic devices based on 2D materials with distinct band dispersion.