Carbon-based aerogels, composed of interconnected threedimensional (3D) networks, have attracted intensive attention because of their unique physical properties, such as low density, high electrical conductivity, porosity, and specific surface area. [1][2][3] As a result, carbon-based aerogels are promising materials used as catalyst supports, [4] artificial muscles, [5] electrodes for supercapacitors, [6] absorbents, [7] and gas sensors. [8] Especially, ultralight or flexible carbon-based aerogels have many potential applications. For example, ultralight nitrogen-doped graphene framework, used as an absorbent for organic liquids or the active electrode material, exhibits a high absorption capacity and specific capacitance; [9] stretchable conductors, fabricated by infiltrating flexible graphene foam with elastic polymers, show high stability of electronic conductivity even under high stretching and bending strain. [10] Traditionally, to fabricate carbon aerogels, resorcinolformaldehyde organic aerogels were pyrolyzed in an inert atmosphere to form a highly cross-linked carbon structure. [11,12] The carbon aerogels always have a high density (100-800 mg cm À3 ) [11,13] and tend to break under compression. Carbon nanotube (CNT) sponges, [7] graphene foam, [10] and CNT forests [14] have been prepared through chemical vapor deposition (CVD). Meanwhile, CNTs and graphene can be employed as building blocks and assembled into macroscopic 3D architectures. [15][16][17][18] However, the harmful and expensive precursors or complex equipments involved in these syntheses dramatically hamper the large-scale production of these carbon-based aerogels for industry application. Recently, we have developed a template-directed hydrothermal carbonization process for synthesis of carbonaceous nanofiber hydrogels/aerogels on macroscopic scale by using glucose as precursors. [19] However, the use of expensive nanowire templates in this synthesis pushes us to explore a facile, economic, and environmentally friendly method to produce carbon-based nanostructured aerogels.Nowadays, there is a trend to produce carbon-based materials from biomass materials, as they are very cheap, easy to obtain, and nontoxic to humans, etc. [20] Bacterial cellulose (BC), a typical biomass material, is composed of interconnected networks of cellulose nanofibers, [21,22] and can be produced in large amounts in a microbial fermentation process. [22] Recently, we reported a highly conductive and stretchable conductor, fabricated from BC, shows great electromechanical stability under stretching and bending strain. [23] Herein, we report a facile route to produce ultralight, flexible, and fire-resistant carbon nanofiber (CNF) aerogels in large scale from BC pellicles. When used as absorbents, the CNF aerogels can absorb a wide range of organic solvents and oils with excellent recyclability and selectivity. The absorption capacity can reach up to 310 times the weight of the pristine CNF aerogels. Besides, the electrical conductivity of the CNF aerogel is highly s...

Robust nanofiber gels: Monolithic hydrogels and aerogels consisting of uniform carbonaceous nanofibers (CNFs) were fabricated on a macroscopic scale (12 L, see picture) by a simple template‐directed, hydrothermal carbonization process. The high surface reactivity of the CNFs and high porosity and robust nature of the gels can be exploited in applications such as selective adsorbents and templates for creating functional composite gels.

5104 www.MaterialsViews.com wileyonlinelibrary.comof heteroatom-doped carbon nanomaterials. In the past decades, there has been certain success in developing effective approaches for synthesizing heteroatomdoped carbon nanomaterials. [ 10,12,[16][17][18][19][20][21] However, despite great progress has been made, the preparation of different heteroatom-doped carbon materials is rarely a general strategy; furthermore, the preparation of these existing heteroatomdoped carbon materials, specifi cally 3D network monolith, usually involves either complicated and expensive instruments, or harsh, complex, and time-consuming synthesis routes, or hazardous chemicals (e.g., concentrated sulfuric acid), all that have seriously restricted their practical applications. Accordingly, it is highly desirable to exploit a simple, renewable, scalable, but multifunctional and general strategy to effectively engineer 3D heteroatom-doped carbon nanomaterials, which is crucial for widespread implementation and commercialization.Bacterial cellulose (BC), a bio-product produced from fermentation, has attracted much attention due to its wide availability, low cost, renewability, and porous nature. [ 6,14,22,23 ] Herein, we demonstrate a highly effi cient, convenient, lowcost, and general strategy to fabricate heteroatom-doped carbon nanomaterials based on the characteristic abundant surface functional groups (hydroxy/carboxylic groups) of BC, [ 24 ] in which the BC serves as an excellent platform for introducing different heteroatoms into the framework of carbon nanomaterials. Specifi cally, P-doped, N,P-co-doped, and B,P-co-doped carbon nanofi bers were successfully prepared by impregnating H 3 PO 4 , NH 4 H 2 PO 4 , and H 3 BO 3 / H 3 PO 4 into the BC pellicle, respectively, followed by carbonization in an inert atmosphere at 800 °C. Compared with previous reports, our approach has three signifi cant advantages for constructing 3D macroscopic heteroatom-doped carbon materials, namely, i) the raw materials are abundant and cheap, ii) the preparation process is easy handling, versatile, and general, and iii) the fabrication is generally suitable for an industrial scale-up. To demonstrate the application potential of the as-prepared heteroatom-doped carbon nanomaterials, here we show the utilization of N,P-co-doped carbon nanofi bers in electrode materials of supercapacitor devices. The as-constructed supercapacitor exhibits high power density and excellent cycling stability.Recently, heteroatom-doped three-dimensional (3D) nanostructured carbon materials have attracted immense interest because of their great potential in various applications. Hence, it is highly desirable to exploit a simple, renewable, scalable, multifunctional, and general strategy to engineer 3D heteroatom-doped carbon nanomaterials. Herein, a simple, eco-friendly, general, and effective way to fabricate 3D heteroatom-doped carbon nanofi ber networks on a large scale is reported. Using this method, 3D P-doped, N,Pco-doped, and B,P-co-doped carbon nanofi ber networks are...