Figure 3. Schematic illustration of fabrication of (a) individual spherical porous polymers from solid spherical nanoparticle templates, (b) tubular porous polymers from tubular porous templates, such as AAO, and (c) ordered macroporous polymers from colloidal crystal templates.

Exceptionally large surface area and well-defined nanostructure are both critical in the field of nanoporous carbons for challenging energy and environmental issues. The pursuit of ultrahigh surface area while maintaining definite nanostructure remains a formidable challenge because extensive creation of pores will undoubtedly give rise to the damage of nanostructures, especially below 100 nm. Here we report that high surface area of up to 3,022 m2 g−1 can be achieved for hollow carbon nanospheres with an outer diameter of 69 nm by a simple carbonization procedure with carefully selected carbon precursors and carbonization conditions. The tailor-made pore structure of hollow carbon nanospheres enables target-oriented applications, as exemplified by their enhanced adsorption capability towards organic vapours, and electrochemical performances as electrodes for supercapacitors and sulphur host materials for lithium–sulphur batteries. The facile approach may open the doors for preparation of highly porous carbons with desired nanostructure for numerous applications.

Organic batteries free of toxic metal species could lead to a new generation of consumer energy storage devices that are safe and environmentally benign. However, the conventional organic electrodes remain problematic because of their structural instability, slow ion-diffusion dynamics, and poor electrical conductivity. Here, we report on the development of a redox-active, crystalline, mesoporous covalent organic framework (COF) on carbon nanotubes for use as electrodes; the electrode stability is enhanced by the covalent network, the ion transport is facilitated by the open meso-channels, and the electron conductivity is boosted by the carbon nanotube wires. These effects work synergistically for the storage of energy and provide lithium-ion batteries with high efficiency, robust cycle stability, and high rate capability. Our results suggest that redox-active COFs on conducting carbons could serve as a unique platform for energy storage and may facilitate the design of new organic electrodes for high-performance and environmentally benign battery devices.

have triggered serious threats to the survival and development of mankind. Consequently, exploring novel materials with task-specific applications is of fundamental importance for the sustainable development of economy and society. The burgeoning progress of nanomaterials in recent years has demonstrated that porosity is one of the essential factors in determining material properties for possible breakthroughs in their applications. Therefore, porous materials are playing important roles in many well-established applications and emerging technologies for challenging social and economic issues due to their intrinsic characteristics of large surface areas, open channels, and the possible control over the pore environment. According to International Union of Pure and Applied Chemistry, the pores of porous materials are classified into three categories by their pore sizes: micropores are smaller than 2 nm, mesopores are in the range of 2-50 nm, and macropores are larger than 50 nm. [1] Their pore walls include the organic skeleton (e.g., porous polymers, organic porous cages, and supramolecular organic frameworks), the inorganic skeleton (e.g., zeolites, porous carbons, and mesoporous silica), and the hybrid skeleton (e.g., metal-organic frameworks (MOFs)).Among the developed porous materials, porous polymers have attracted an increasing level of research interest owing to their potential to integrate the advantages of both porous materials and polymers. [2,3] Table 1 lists the characteristic structural features and properties of porous polymers, and gives a systematic comparison to other typical porous materials, such as zeolites, porous carbons, and MOFs. Porous polymers, zeolites, porous carbons, and MOFs share a number of features such as high permanent porosities, large surface areas, and designable pores and voids. However, they are different in several important aspects. The major advantages of porous polymers over many other porous materials are their chemical diversity and easy processability. Compared to zeolites and porous carbons, the synthesis of porous polymers is generally more versatile and can be approached in a way that conforms to the concept of rational materials design. Similar to MOFs, porous polymers inherit the excellent chemical and physical tunability afforded by the versatility of organic chemistry. Furthermore, Exploring advanced porous materials is of critical importance in the development of science and technology. Porous polymers, being famous for their all-organic components, tailored pore structures, and adjustable chemical components, have attracted an increasing level of research interest in a large number of applications, including gas adsorption/storage, separation, catalysis, environmental remediation, energy, optoelectronics, and health. Recent years have witnessed tremendous research breakthroughs in these fields thanks to the unique pore structures and versatile skeletons of porous polymers. Here, recent milestones in the diverse applications of porous polymers are presented, ...

Ordered π-columns and open nanochannels found in covalent organic frameworks (COFs) could render them able to store electric energy. However, the synthetic difficulty in achieving redox-active skeletons has thus far restricted their potential for energy storage. A general strategy is presented for converting a conventional COF into an outstanding platform for energy storage through post-synthetic functionalization with organic radicals. The radical frameworks with openly accessible polyradicals immobilized on the pore walls undergo rapid and reversible redox reactions, leading to capacitive energy storage with high capacitance, high-rate kinetics, and robust cycle stability. The results suggest that channel-wall functional engineering with redox-active species will be a facile and versatile strategy to explore COFs for energy storage.

Lithium metal batteries have been considerably limited by the problems of uncontrolled dendritic lithium formation and the highly reactive nature of lithium with electrolytes. Herein, we have developed functional porous bilayer composite separators by simply blade-coating polyacrylamide-grafted graphene oxide molecular brushes onto commercial polypropylene separators. Our functional porous bilayer composite separators integrate the lithiophilic feature of hairy polyacrylamide chains and fast electrolyte diffusion pathways with the excellent mechanical strength of graphene oxide nanosheets and thus enable molecular-level homogeneous and fast lithium ionic flux on the surfaces of electrodes. As a result, dendrite-free uniform lithium deposition with a high Coulombic efficiency (98%) and ultralong-term reversible lithium plating/stripping (over 2600 h) at a high current density (2 mA cm−2) are achieved for lithium metal anodes. Remarkably, lithium metal anodes with an unprecedented stability of more than 1900 h cycling at an ultrahigh current density of 20 mA cm−2 are demonstrated.

Lithium-sulfur (Li-S) batteries, based on the redox reaction between elemental sulfur and lithium metal, have attracted great interest because of their inherently high theoretical energy density. However, the severe polysulfide shuttle effect and sluggish reaction kinetics in sulfur cathodes, as well as dendrite growth in lithium-metal anodes are great obstacles for their practical application. Herein, a two-in-one approach with superhierarchical cobalt-embedded nitrogen-doped porous carbon nanosheets (Co/N-PCNSs) as stable hosts for both elemental sulfur and metallic lithium to improve their performance simultaneously is reported. Experimental and theoretical results reveal that stable Co nanoparticles, elaborately encapsulated by N-doped graphitic carbon, can work synergistically with N heteroatoms to reserve the soluble polysulfides and promote the redox reaction kinetics of sulfur cathodes. Moreover, the high-surface-area pore structure and the Co-enhanced lithiophilic N heteroatoms in Co/N-PCNSs can regulate metallic lithium plating and successfully suppress lithium dendrite growth in the anodes. As a result, a full lithium-sulfur cell constructed with Co/N-PCNSs as two-in-one hosts demonstrates excellent capacity retention with stable Coulombic efficiency.

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