Molecular Design of Porous Organic Polymer-Derived Carbonaceous Electrocatalysts for Pinpointing Active Sites in Oxygen Reduction Reaction.

The widespread application of fuel cells is hampered by the sluggish kinetics of the oxygen reduction reaction (ORR), which traditionally necessitates the use of high-cost platinum group metal catalysts. The indispensability of these metal catalysts stems from their ability to overcome kinetic barriers, but their high cost and scarcity necessitate alternative strategies. In this context, porous organic polymers (POPs), which are built up from the molecular level, are emerging as promising precursors to produce carbonaceous catalysts owning to their cost-effectiveness, high electrical conductivity, abundant active sites and extensive surface area accessibility. To enhance the intrinsic ORR activity and optimize the performance of these electrocatalysts, recognizing, designing, and increasing the density of active sites are identified as three crucial steps. These steps, which form the core of our review, serve to elucidate the link between the material structure design and ORR performance evaluation, thereby providing valuable insights for ongoing research in the field. Leveraging the precision of polymer skeletons based on molecular units, POP-derived carbonaceous catalysts provide an excellent platform for in-depth exploration of the role and working mechanism for the specific active site during the ORR process. In this review, the recent advances pertaining to the synthesis techniques and electrochemical functions of various types of active sites, pinpointed from POPs, are systematically summarized, including heteroatoms, surficial substituents and edge/defects. Notably, the structure-property relationship, between these active sites and ORR performance, are discussed and emphasized, which creates guidelines to shed light on the design of high-performance ORR electrocatalysts.

Chemically Induced Compatible Interface in Pyrolyzed Bacterial Cellulose/Graphene Sandwich for Electrochemical Energy Storage.

Herein, a three-step approach toward a multi-layered porous PBC/graphene sandwich has been developed, in which the chemical bonding interactions have been successfully enhanced via esterification between the layers of pyrolyzed bacterial cellulose (PBC) and graphene. Such a chemically induced compatible interface has been demonstrated to contribute significantly to the mass transfer efficiency when the PBC/graphene sandwich is deployed as electrode material for both supercapacitors and lithium-sulfur batteries. The high specific capacitance of the supercapacitors has been increased by three times, to 393 F g-1 at 0.1 A g-1. A high initial discharge specific capacity (~1100 mAhg-1) and high coulombic efficiency (99% after 300 cycles) of the rPG/S-based lithium-sulfur batteries have been achieved.

A template oriented one-dimensional Schiff-base polymer: towards flexible nitrogen-enriched carbonaceous electrodes with ultrahigh electrochemical capacity.

Lithium-ion capacitors (LICs) have attracted much attention considering their efficient combination of high energy density and high-power density. However, to meet the increasing requirements of energy storage devices and the flexible portable electronic equipment, it is still challenging to develop flexible LIC anodes with high specific capacity and excellent rate capability. Herein, we propose a delicate bottom-up strategy to integrate unique Schiff-base-type polymers into desirable one-dimensional (1D) polymeric structures. A secondary-polymerization-induced template-oriented synthesis approach realizes the 1D integration of Schiff-base porous organic polymers with appealing characteristics of a high nitrogen-doping level and developed pore channels, and a further thermalization yields flexible nitrogen-enriched carbon nanofibers with high specific capacity and fast ion transport. Remarkably, when used as the flexible anode in LICs, the NPCNF//AC LIC demonstrates a high energy density of 154 W h kg-1 at 500 W kg-1 and a high power density of 12.5 kW kg-1 at 104 W h kg-1. This work may provide a new scenario for synthesizing 1D Schiff-base-type polymer derived nitrogen-enriched carbonaceous materials towards promising free-standing anodes in LICs.

Construction of imine-linked covalent organic framework as advanced adsorbent for the sensitive determination of chlorophenols.

Food safety is a great concern of the general public. Chlorophenols (CPs) as organic pollutant can be found in drinking water and foods, causing serious harm to human health. Herein, imine-linked covalent organic frameworks (COFs), named as TAPT-AN-COF, was synthesized by aniline modulation strategy through condensation of 1,3,5-triformylphoroglucinol and 4,4',4''-(1,3,5-Triazine-2,4,6-triyl)trianiline with aniline as modulator. The prepared TAPT-AN-COF possesses good crystallinity and regular morphology, displaying excellent adsorption capability towards CPs pollutants. Thus, the TAPT-AN-COF was used as novel adsorbent for off-line solid-phase extraction of four CPs (2-CP, 3-CP, 2,3-CPs, 2,4-CPs) from bottled water, tea drink and honey samples before high performance liquid chromatography-ultraviolet detection. Under optimal conditions, wide linear range, low detection limits and satisfactory extraction recovery were gained. The π-stacking and hydrophobic interactions between the TAPT-AN-COF and the analytes played an important role in the adsorption. The established method has a great potential in determining other hydrophobic aromatic compounds.

Rational integration of porous organic polymer and multiwall carbon nanotube for the microextraction of polycyclic aromatic hydrocarbons.

By integration of benzene-constructed porous organic polymer (KBF) and multiwalled carbon nanotube (MWCNT), a MWCNT-KBF hybrid material was constructed through in situ knitting benzene with formaldehyde dimethyl acetal in the presence of MWCNTs to form a network. MWCNT-KBF was then adopted as a novel solid-phase microextraction (SPME) fiber coating. Coupled to gas chromatography-flame ionization detection, the MWCNT-KBF-assisted SPME method showed large enhancement factors (483-2066), low limits of detection (0.04-0.12 µg L-1), good linearity (0.13-50 µg L-1), and acceptable reproducibility (4.2-10.2%) for the determination of polycyclic aromatic hydrocarbons (PAHs). The method recoveries of seven PAHs were in the range 80.1-116.3%, with relative standard deviations (RSDs) ranging from 3.5 to 11.9%. The SPME method was successfully applied to the determination of PAHs in river, pond, rain, and waste water, providing a good alternative for monitoring trace level of PAHs in environmental water. Graphical abstract Schematic representation of the rational integration of porous organic polymer (KBF) and multiwalled carbon nanotube (MWCNT) to form a MWCNT-KBF hybrid material through in situ knitting benzene with formaldehyde dimethyl acetal at the presence of MWCNT.

Band Structure Engineering of Schiff-Base Microporous Organic Polymers for Enhanced Visible-Light Photocatalytic Performance.

Schiff-base networks (SBNs), as typical examples of nitrogen-doped microporous organic polymers (MOPs), exhibit promising application prospects owing to their stable properties and tunable chemical structures. However, their band structure engineering, which plays a key role in optical properties, remains elusive due to the complicated mechanisms behind energy level adjustment. In this work, a series of SBNs are fabricated by tailoring the ratio of p-phthalaldehyde and o-phthalaldehyde in the Schiff-base chemistry reaction with melamine, resulting in a straightforward as well as continuous tuning of their band gaps ranging from 4.4 to 1.4 eV. Consequently, SBNs can be successfully used as photocatalysts with excellent visible-light photocatalytic activity even under metal-free conditions. Significantly, electronic structures of SBNs are systematically studied by electrochemical and spectroscopic characterizations, demonstrating that the enhanced performance is ascribed to proper band structure and improved charge separation ability. More importantly, in combination with theoretical calculations, the band structure regulation mechanism and band structure-photocatalytic property relationship are deeply disclosed. The results obtained from this study will not only furnish SBN materials with excellent performance for solar energy conversion, but also open up elegant protocols for the molecular engineering of MOPs with desirable band structures.

Rational Design of Carbon-Rich Materials for Energy Storage and Conversion.

Carbon-rich materials have drawn tremendous attention toward a wide spectrum of energy applications due to their superior electronic mobility, good mechanical strength, ultrahigh surface area, and more importantly, abundant diversity in structure and components. Herein, rationally designed and bottom-up constructed carbon-rich materials for energy storage and conversion are discussed. The fundamental design principles are itemized for the targeted preparation of carbon-rich materials and the latest remarkable advances are summarized in terms of emerging dimensions including sp2 carbon fragment manipulation, pore structure modulation, topological defect engineering, heteroatom incorporation, and edge chemical regulation. In this respect, the corresponding structure-property relationships of the resultant carbon-rich materials are comprehensively discussed. Finally, critical perspectives on future challenges of carbon-rich materials are presented. The progress highlighted here will provide meaningful guidance on the precise design and targeted synthesis of carbon-rich materials, which are of critical importance for the achievement of performance characteristics highly desirable for urgent energy deployment.

A facile and processable integration strategy towards Schiff-base polymer-derived carbonaceous materials with high lithium storage performance.

Herein, a novel in situ concentrated-solution-induced polymerization strategy is developed towards the integration of Schiff-base networks into graphene foam with processable and moldable characteristics. This bottom-up design process endows the resultant composites with a high nitrogen content (9.6 at%) and abundant porosity and accordingly demonstrates high lithium storage properties.

Nitrogen-Enriched Carbon/CNT Composites Based on Schiff-Base Networks: Ultrahigh N Content and Enhanced Lithium Storage Properties.

To improve the electrochemical performance of carbonaceous anodes for lithium ion batteries (LIBs), the incorporation of both well-defined heteroatom species and the controllable 3D porous networks are urgently required. In this work, a novel N-enriched carbon/carbon nanotube composite (NEC/CNT) through a chemically induced precursor-controlled pyrolysis approach is developed. Instead of conventional N-containing sources or precursors, Schiff-base network (SNW-1) enables the desirable combination of a 3D polymer with intrinsic microporosity and ultrahigh N-content, which can significantly promote the fast transport of both Li+ and electron. Significantly, the strong interaction between carbon skeleton and nitrogen atoms enables the retention of ultrahigh N-content up to 21 wt% in the resultant NEC/CNT, which exhibits a super-high capacity (1050 mAh g-1 ) for 1000 cycles and excellent rate performance (500 mAh g-1 at a current density of 5 A g-1 ) as the anode material for LIBs. The NEC/CNT composite affords a new model system as well as a totally different insight for deeply understanding the relationship between chemical structures and lithium ion storage properties, in which chemistry may play a more important role than previously expected.

A collaborative strategy for stable lithium metal anodes by using three-dimensional nitrogen-doped graphene foams.

A collaborative strategy is developed for constructing stable lithium metal anodes by using self-supporting three-dimensional nitrogen-doped graphene foams as the multifunctional host matrix. The resultant electrode shows impressive electrochemical performances, attributable to the three-dimensional porous architecture and nitrogen-doping nature of such a unique host matrix.

Caging tin oxide in three-dimensional graphene networks for superior volumetric lithium storage.

Tin and its compounds hold promise for the development of high-capacity anode materials that could replace graphitic carbon used in current lithium-ion batteries. However, the introduced porosity in current electrode designs to buffer the volume changes of active materials during cycling does not afford high volumetric performance. Here, we show a strategy leveraging a sulfur sacrificial agent for controlled utility of void space in a tin oxide/graphene composite anode. In a typical synthesis using the capillary drying of graphene hydrogels, sulfur is employed with hard tin oxide nanoparticles inside the contraction hydrogels. The resultant graphene-caged tin oxide delivers an ultrahigh volumetric capacity of 2123 mAh cm-3 together with good cycling stability. Our results suggest not only a conversion-type composite anode that allows for good electrochemical characteristics, but also a general synthetic means to engineering the packing density of graphene nanosheets for high energy storage capabilities in small volumes.

Disassembly-Reassembly Approach to RuO2 /Graphene Composites for Ultrahigh Volumetric Capacitance Supercapacitor.

A porous, yet compact, RuO2 /graphene hybrid is successfully prepared by using a disassembly-reassembly strategy, achieving effective and uniform loading of RuO2 nanoparticles inside compact graphene monolith. The disassembly process ensures the uniform loading of RuO2 nanoparticles into graphene monolith, while the reassembly process guarantees a high density yet simultaneously unimpeded ion transport channel in the composite. The resulting RuO2 /graphene hybrid possesses a density of 2.63 g cm-3 , leading to a record high volumetric capacitance of 1485 F cm-3 at the current density of 0.1 A g-1 . When the current density is increased to 20 A g-1 , it remains a high volumetric capacitance of 1188 F cm-3 . More importantly, when the single electrode mass loading is increased to 12 mg cm-2 , it still delivers a high volumetric capacitance of 1415 F cm-3 at the current density of 0.1 A g-1 , demonstrating the promise of this disassembly-reassembly approach to create high volumetric performance materials for energy storage applications.

High-Performance Silicon Battery Anodes Enabled by Engineering Graphene Assemblies.

We propose a novel material/electrode design formula and develop an engineered self-supporting electrode configuration, namely, silicon nanoparticle impregnated assemblies of templated carbon-bridged oriented graphene. We have demonstrated their use as binder-free lithium-ion battery anodes with exceptional lithium storage performances, simultaneously attaining high gravimetric capacity (1390 mAh g(-1) at 2 A g(-1) with respect to the total electrode weight), high volumetric capacity (1807 mAh cm(-3) that is more than three times that of graphite anodes), remarkable rate capability (900 mAh g(-1) at 8 A g(-1)), excellent cyclic stability (0.025% decay per cycle over 200 cycles), and competing areal capacity (as high as 4 and 6 mAh cm(-2) at 15 and 3 mA cm(-2), respectively). Such combined level of performance is attributed to the templated carbon bridged oriented graphene assemblies involved. This engineered graphene bulk assemblies not only create a robust bicontinuous network for rapid transport of both electrons and lithium ions throughout the electrode even at high material mass loading but also allow achieving a substantially high material tap density (1.3 g cm(-3)). Coupled with a simple and flexible fabrication protocol as well as practically scalable raw materials (e.g., silicon nanoparticles and graphene oxide), the material/electrode design developed would propagate new and viable battery material/electrode design principles and opportunities for energy storage systems with high-energy and high-power characteristics.

Chloridobis(1,10-phenanthroline-κN,N')copper(II) tetra-kis-(nitrato-κO,O')(1,10-phenanthroline-κN,N')terbate(III).

The title complex salt, [CuCl(C(12)H(8)N(2))(2)][Tb(NO(3))(4)(C(12)H(8)N(2))], consists of discrete [CuCl(phen))(2)](+) cations and [Tb(NO(3))(4)(phen)](-) anions (phen is 1,10-phenanthroline). The [CuCl(phen))(2)](+) cation contains a five-coordinate Cu(2+) ion, ligated by two bidentate phen ligands and one Cl(-) ion, exhibiting a distorted CuN(4)Cl trigonal-bipyramidal geometry. In the [Tb(NO(3))(4)(phen)](-) anion, the Tb(3+) ion is coordinated by one chelating phen ligand and four chelating nitrates, forming a distorted TbN(2)O(8) bicapped dodeca-hedral configuration. The anions and cations are assembled into a three-dimensional network by weak C-H⋯Cl and C-H⋯O hydrogen bonds. There is also a significant π-π stacking inter-action, with a centroid-centroid distance of 3.635 (2) Å.

5-Chloro-1-(4-meth-oxy-benz-yl)indoline-2,3-dione.

In the title compound, C(16)H(12)ClNO(3), an arm-like 4-meth-oxy-benzene links to 5-chloro-indoline-2,3-dione through a methyl-ene group, with a dihedral angle between the mean planes of the benzene ring and the indole moiety of 88.44 (8)°. In the crystal, weak inter-molecular C-H⋯O and π-π stacking inter-actions [centroid-centroid distance = 3.383 (3) Å] link the mol-ecules together to form a three-dimensional framework.