N-containing Groups Research Articles

Spirulina platensis Immobilized Alginate Beads for Removal of Pb(II) from Aqueous Solutions.

Microalgae contain a diversity of functional groups that can be used as environmental adsorbents. Spirulina platensis is a blue-green microalga that comprises protein-N, which is advantageous for use in nitrogen-containing biomass as adsorbents. This study aimed to enhance the adsorption properties of alginate hydrogels by employing Spirulina platensis. Spirulina platensis was immobilized on sodium alginate (S.P@Ca-SA) via crosslinking. The results of field-emission scanning electron microscopy, Fourier-transform infrared, and X-ray photoelectron spectroscopy analyses of the N-containing functional groups indicated that Spirulina platensis was successfully immobilized on the alginate matrix. We evaluated the effects of pH, concentration, and contact time on Pb(II) adsorption by S.P@Ca-SA. The results demonstrated that S.P@Ca-SA could effectively eliminate Pb(II) at pH 5, reaching equilibrium within 6 h, and the maximum Pb(II) sorption capacity of S.P@Ca-SA was 87.9 mg/g. Our results indicated that S.P@Ca-SA fits well with the pseudo-second-order and Freundlich models. Compared with Spirulina platensis and blank alginate beads, S.P@Ca-SA exhibited an enhanced Pb(II) adsorption efficiency. The correlation implies that the amino groups act as adsorption sites facilitating the elimination of Pb(II).

Adsorption mechanism of quaternary ammonium corrosion inhibitor on carbon steel surface using ToF-SIMS and XPS

ToF-SIMS and XPS are combined to study the adsorption of tetradecyl-benzyldimethyl-ammonium (BDA-C14) bromide corrosion inhibitor on carbon steel surface. BDA-C14 forms a protective layer with N-containing polar head group interacting with carbon steel surface. The adsorbed inhibitor surface coverage strongly depends on immersion time and inhibitor concentration. A maximum and uniform coverage is found for sufficiently long exposure times at a critical inhibitor concentration of about 25 ppmw. The uniform adsorbed inhibitor layer formed on the surface mitigates the formation of iron chloride/hydroxide intermediates and thus enhances the corrosion protection of carbon steel in aggressive environment.

In situ-synthesized Co and N-doped mesoporous hollow silica spheres for the selective oxidation of ethylbenzene.

Transition metal and nitrogen co-doped carbon materials (M-N-C) have attracted great attention in the field of catalysis due to their high atomic utilization and outstanding catalytic performance. Herein, a series of Co and N-doped carbon catalysts (Co-N-C@mSiO2-x) were successfully prepared by pyrolysis of cobalt porphyrins in situ synthesized in the cavity of mesoporous hollow silica spheres according to a ship-in-bottle method. The optimal catalyst exhibited excellent catalytic performance for the selective oxidation of ethylbenzene, with 95.5% conversion for ethylbenzene and 98.9% selectivity toward acetophenone. In combination with characterization techniques, acid treatment experiments and KSCN poisoning tests, the successful synthesis of cobalt-porphyrins in hollow silica spheres was demonstrated, and the excellent performance of Co-N-C@mSiO2-0.10 was attributed to the more acid-resistant Co-Nx species as the main metal active center. In addition, the N-containing groups could significantly facilitate the conversion of ethylbenzene. This work is expected to provide a straightforward and green approach to design metal and N co-doped carbon materials.

Reactions of main group compounds with azides forming organic nitrogen-containing species.

Since the seminal discovery of phenyl azide by Grieß in 1864, a variety of organic azides (R-N3) have been developed and extensively studied. The amenability of azides to a number of reactions has expanded their utility as building blocks not only in organic synthesis but also in bioorthogonal chemistry and materials science. Over the decades, it has been demonstrated that the reactions of main group compounds with azides lead to diverse N-containing main group molecules. In view of the pronounced progress in this area, this review summarizes the reactions of main group compounds with azides, emphatically introducing their reaction patterns and mechanisms. The reactions of forming inorganic nitrogen species are not included in this review.

Highly dispersed Pd nanoparticles anchored on carbon nitride for hydrogen production from formic acid

A carbon nitride supported Pd catalyst was prepared by a wet reduction method. The addition of water can change the type and content of N-containing groups. The catalytic activity is dependent on the surface electronic properties of Pd.

Modulation of Structure and Optical Property of Nitrogen-Incorporated VO2 (M1) Thin Films by Polyvinyl Pyrrolidone

VO2, as a promising material for smart windows, has attracted much attention, and researchers have been continuously striving to optimize the performance of VO2-based materials. Herein, nitrogen-incorporated VO2 (M1) thin films, using a polyvinylpyrrolidone (PVP)-assisted sol-gel method followed by heat treatment in NH3 atmosphere, were synthesized, which exhibited a good solar modulation efficiency (ΔTsol) of 4.99% and modulation efficiency of 37.6% at 2000 nm (ΔT2000 nm), while their visible integrated transmittance (Tlum) ranged from 52.19% to 56.79% after the phase transition. The crystallization, microstructure, and thickness of the film could be regulated by varying PVP concentrations. XPS results showed that, in addition to the NH3 atmosphere-N doped into VO2 lattice, the pyrrolidone-N introduced N-containing groups with N-N, N-O, or N-H bonds into the vicinity of the surface or void of the film in the form of molecular adsorption or atom (N, O, and H) filling. According to the Tauc plot, the estimated bandgap of N-incorporated VO2 thin films related to metal-to-insulator transition (Eg1) was 0.16-0.26 eV, while that associated with the visible transparency (Eg2) was 1.31-1.45 eV. The calculated Eg1 and Eg2 from the first-principles theory were 0.1-0.5 eV and 1.4-1.6 eV, respectively. The Tauc plot estimation and theoretical calculations suggested that the combined effect of N-doping and N-adsorption with the extra atom (H, N, and O) decreased the critical temperature (τc) due to the reduction in Eg1.

Oxygen-enriched lignin-derived porous carbon nanosheets promote Zn2+ storage

Carbon-based zinc-ion capacitors (ZICs) have sparked intense research enthusiasm because of large power density, good rate capability and cycling stability. However, there is still a long way to go before they achieve commercial applications. Herein, oxygen-enriched lignin-derived porous carbon nanosheets (OLCKs) were prepared by one-step carbonization-activation method, and more O-containing functional groups were generated on the surface of the porous carbon by post-surface functionalization strategy. The self-doped N can change the electron distribution of carbon skeleton and decrease energy barrier of chemical absorption of Zn2+/H+. Meanwhile, the carbonyl group can significantly enhance the wettability of OLCKs. Furthermore, the diffusion-controlled reactions mainly exist at high and low potential ranges in CV curves, which demonstrates the occurred Faradaic reaction. Consequently, the assembled aqueous ZICs based on OLCKs demonstrate a capacity of 121.7 mAh/g at 0.3 A/g, energy density of 94.3 Wh kg−1 and good cyclic stability. Besides, the assembled Zn//PVA/LiCl/ZnCl2(gel)//OLCK4 ZIC can also achieve energy density of 134.4 Wh kg−1 at 0.1 A/g. This work provides a novel design strategy by incorporating abundant O and N-containing functional groups to enhance energy density.

Gaseous formaldehyde adsorption by eco-friendly, porous bamboo carbon microfibers obtained by steam explosion, carbonization, and plasma activation

To develop an eco-friendly biomass adsorbent for indoor formaldehyde, porous bamboo carbon microfibers (BCMFs) with different types and contents of oxygen (O)-containing and nitrogen (N)-containing functional groups were firstly prepared by combining high-pressure steam explosion, carbonization, and plasma activation. The BCMF adsorbents were characterized, and their adsorption performance and mechanism were evaluated and theoretically calculated. BCMF carbonized at 800 °C (BCMF-800) showed the highest specific surface area of 526.862 m2 g−1. The surfaces of the BCMFs were etched, with many additional micro/nanoscale pores and cavities. Functional groups, including O–CO, CO, CO, quaternary N, oxidized N, pyridinic N, amine N, and pyrrolic N were successfully introduced by plasma activation at various powers and atmospheres. BCMF-800 samples activated by O2 plasma at 240 W (BCMF-800-O-240) and by N2 at 120 W (BCMF-800-N-120) exhibited the highest formaldehyde adsorption capacities (179.53 mg g−1 and 205.28 mg g−1), which were 85.90 % and 112.50 % higher than that of BCMF-800, respectively. The samples introduced by carboxyl and pyrrolic N showed the highest adsorption energies (−14.54 kcal mol−1 and −11.58 kcal mol−1) with an increase of 83.82 % and 46.40 %, respectively, compared with the control, which were proved to be the optimal O-containing and N-containing functional groups for enhancing formaldehyde adsorption. This work provides a new insight into the natural biomass-based adsorbents for gaseous formaldehyde with a clean and eco-friendly preparation and modification process.

Enhanced Cr (VI) reduction and removal by Fe/Mn oxide biochar composites under acidic simulated wastewater.

Chromium (Cr (VI)) can cause severe damage to the ecosystem and humans because of its toxicity. In this paper, the adsorbed Fe/Mn ions Bacillus cereus ZNT-03, lotus seeds, and graphene oxide were co-cultured as the raw materials. Fe/Mn oxide biochar composite (FMBC) was prepared to treat Cr (VI) by one-step pyrolysis. FMBC has high-density micropores, and the average pore size is about 0.82nm. Fe (II), Mn (II), and N-containing functional groups could serve as electron donors for Cr (VI) reduction. The removal of Cr (VI) is monolayer chemisorption and pH-dependent. The maximum adsorption capacity of FMBC is 21.25mgg-1. Cr (VI) is reduced and adsorbed on FMBC by physical adsorption, reduction, complexation, electrostatic attraction, and coprecipitation. The contribution ratio of the reduction mechanism to Cr (VI) is 72.25%. The packed column and regeneration experiments indicated that FMBC had excellent adsorption stability even after soaking in acidic simulated wastewater after 180days (pH 1.5). These results indicate that FMBC can provide rapid reduction and efficient adsorption for Cr (VI), making it possible to apply in water treatment.

Machine learning predicting and engineering the yield, N content, and specific surface area of biochar derived from pyrolysis of biomass

Biochar produced from pyrolysis of biomass has been developed as a platform carbonaceous material that can be used in various applications. The specific surface area (SSA) and functionalities such as N-containing functional groups of biochar are the most significant properties determining the application performance of biochar as a carbon material in various areas, such as removal of pollutants, adsorption of CO2 and H2, catalysis, and energy storage. Producing biochar with preferable SSA and N functional groups is among the frontiers to engineer biochar materials. This study attempted to build machine learning models to predict and optimize specific surface area of biochar (SSA-char), N content of biochar (N-char), and yield of biochar (Yield-char) individually or simultaneously, by using elemental, proximate, and biochemical compositions of biomass and pyrolysis conditions as input variables. The predictions of Yield-char, N-char, and SSA-char were compared by using random forest (RF) and gradient boosting regression (GBR) models. GBR outperformed RF for most predictions. When input parameters included elemental and proximate compositions as well as pyrolysis conditions, the test R2 values for the single-target and multi-target GBR models were 0.90–0.95 except for the two-target prediction of Yield-char and SSA-char which had a test R2 of 0.84 and the three-target prediction model which had a test R2 of 0.81. As indicated by the Pearson correlation coefficient between variables and the feature importance of these GBR models, the top influencing factors toward predicting three targets were specified as follows: pyrolysis temperature, residence time, and fixed carbon for Yield-char; N and ash for N-char; ash and pyrolysis temperature for SSA-char. The effects of these parameters on three targets were different, but the trade-offs of these three were balanced during multi-target ML prediction and optimization. The optimum solutions were then experimentally verified, which opens a new way for designing smart biochar with target properties and oriented application potential.Graphical

Tunable morphology of strontium titanate nanocubes controlled by tert-butylamine-assisted solvothermal method and their enhanced electrical conductivity

The exploration of the size and shape of well-defined strontium titanate (SrTiO3) nanocubes remains challenging despite the increasing interest in this material, owing to its remarkable morphology-dependent electron and phonon transport abilities. This paper discusses the controllable solvothermal synthesis of SrTiO3 nanocube with tunable morphology in the ethanol-water solvent, using cetyltrimethylammonium bromide (CTAB) as a capping agent and tert-butylamine (TBA) as a mineralizer. The SrTiO3 nanocubes crystallization can be described as the dissolution-precipitation process, and the addition of CTAB and TBA affects the transformation of oriented attachment in forming a well-defined nanocube. In this study, the X-Ray Diffraction (XRD) data supported by the Le Bail refinement analysis revealed the shape-dependent tuning in lattice parameters of polycrystalline samples. The electrostatic interaction of CTAB and TBA on the particle surface of SrTiO3 was proven by the appearance of specific absorption peaks in the IR spectrum. XPS spectra show the chemical shift toward higher binding energy confirming the attraction of the nitrogen N-containing groups from CTAB and TBA with SrTiO3 through the synergistic capping effect. Meanwhile, HRTEM images showed that the nanocube particles have a uniform shape, sharp edges and vertices, flat faces, and narrow size distribution. In addition, the electrical conductivity in the bulk samples with uniform nanocubes increases three-fold compared to non-uniform nanocubes. These findings can potentially set a foundation for establishing synthesis techniques for producing morphologically-distinct particles based on surface interactions through the selective adsorption of additives.

Fullerene-Derived Porous and Defective N-Doped Carbon Nanosheets as Advanced Trifunctional Metal-Free Electrocatalysts.

Dopants and defects are crucial for multifunctional carbon-based metal-free electrocatalysts, but the rational design and facile production remain as a big challenge. Herein, we report a novel strategy using salt-assisted pyrolysis of derivatized fullerenes to fabricate defect-rich and N-doped carbon nanosheets. Molecular level modification of C60 via amination and hydroxylation gives rise to well-defined fullerol molecules bearing N-containing groups (FNG). Subsequent calcination of FNG and NaCl at 750 °C generates porous carbon nanosheets (FNCNs-750) and turns the N-containing groups into high-level N dopants (12.43 at.%). Further pyrolysis of FNCNs-750 at 900 °C (FNCNs-900) leads to a reduced N content populated by graphitic-N. Meanwhile, abundant intrinsic defects (e. g., topological defects and edges) are created due to the breakdown of fullerene cages and partial removal of edged N atoms. These structural features endow FNCNs-900 with outstanding trifunctional catalytic performance, better than or close to the noble metal-based benchmark catalysts.

Facile ultrasonic-assisted one-step preparation of sugarcane bagasse carbon sorbent for bio-based odor removal cat litter formulation

To reduce the cost of adsorbents for the removal of cat urine odor there has been concerted research efforts to produce functionalized porous carbon from waste biomass. In this work, a cost-effective and environmentally friendly method was used to prepare a carbon adsorbent (AC-SNP) from sugarcane bagasse through ultrasonic-assisted impregnation of mixed HNO3/H3PO4 on bagasse prior to carbonization. Ultrasonication enhanced structural deformation of bagasse and enriched the N and O-containing groups prior to cabonization which allowed the final carbon material to have increased specific surface area of 1603.1 m2/g and porosity of 1.3858 cm3·g−1 (including micro- and meso-pores), and increased surface functionality of -COOH, -OH, pyrrolic N, and pyridinic N groups. The adsorption capacity of the carbon material for 3-mercapto-3-methyl-1-butanol (MMB), a volatile cat urine component, was up to 207.12 mg/g at 25 °C, and the heterogenous multi-layer Freundlich model and Pseudo-second-order model were used to explain the adsorption mechanism. Density functional theory (DFT) calculations showed that there are electrostatic interactions and hydrogen bonding between the O- and N-containing groups and MMB molecules. AC-SNP was found to be nontoxic in a cat litter formulation, and removes 99.87% volatile MMB at a low loading ratio of 2 wt%. The fabricated sugarcane bagasse-based cat litter (SB_CL) formulation also has anti-bacterial properties, and so has significant commercialization prospects.

In Situ Separator Modification with an N-Rich Conjugated Microporous Polymer for the Effective Suppression of Polysulfide Shuttle and Li Dendrite Growth.

Lithium-sulfur (Li-S) batteries are very promising high-energy-density electrochemical energy storage devices, but suffer from serious Li polysulfide (LiPS) shuttle and uncontrollable Li dendrite growth. Here, we show in situ polyolefin separator modification with an N-rich conjugated microporous polymer (NCMP) for advanced Li-S battery. In situ polymerization generates an ultrathin NCMP coating on the whole external surface and the internal surface of the separator, which is substantially different from the conventional approaches with thick coatings only on the external surface. The NCMP coating with abundant N-containing groups (-NH2 and -N═), uniform nanopores (12.294 Å), and π-conjugated structure can simultaneously inhibit LiPS shuttle and regulate uniform nucleation and growth of Li dendrites. Consequently, the NCMP-based separator endows the Li-S battery with significantly enhanced cycling stability at high S loading (5.4 mg cm-2), lean electrolyte (E/S = 6.3 μL mg-1), and limited Li excess (50 μm).

Longitudinally grown pyrolyzed quinacridones for sodium-ion battery anode

Carbonaceous materials have been actively investigated as anode materials for sodium-ion batteries (SIBs). However, the development of carbonaceous materials that can effectively accommodate large sodium ions within carbon microstructures is highly challenging. In this study, quinacridones (QAs) are used to prepare SIB anode materials via pyrolysis. Among QAs, 2,9-dimethylquinacridone (2,9-DMQA) exhibits prominent morphological development with a high char yield of 61 % at 600 °C. Additionally, we reveal that the pyrolysis mechanism and microstructure are significantly affected by the crystal orientation of the precursor. As the 2,9-DMQA has a parallel-oriented crystal structure, the pyrolyzed 2,9-DMQAs grow polycyclic aromatic hydrocarbons with longitudinal microstructures through thermal polymerization initiated by methyl substituents. In addition, the evolution of gas from the 2,9-DMQA precursor induces the reorganization of the carbon framework to form a disordered structure. The anodes fabricated with the 2,9-DMQA pyrolyzed at 600 °C (2,9-DMQA-600) show sodium-ion storage performance with a high rate capability (290 mAh/g at a current density of 0.05 A/g) and excellent cycle stability (247 mAh/g at 0.1 A/g after 200 cycles and 134 mAh/g at 5 A/g after 1000 cycles). The well-developed carbon microstructures and surface-confined sodium-ion storage derived from the remaining N-containing and O-containing functional groups provide superior electrochemical performance.

Drug repurposing strategy part 1: from approved drugs to agri-bactericides leads.

Phytopathogenic bacteria are a major cause of crop mortality and yield reduction, especially in field cultivation. The lack of effective chemistry agri-bactericides is responsible for challenging field prevention and treatment, prompting the development of long-lasting solutions to prevent, reduce, or manage some of the most devastating plant diseases facing modern agriculture today and in the future. Therefore, there is an urgent need to find lead drugs preventing and treating phytopathogenic bacterial infection. Drug repurposing, a strategy used to identify novel uses for existing approved drugs outside of their original indication, takes less time and investment than Traditional R&D Strategies in the process of drug development. Based on this method, we conduct a screen of 700 chemically diverse and potentially safe drugs against Xanthomonas oryzae PV. oryzae ACCC 11602 (Xoo), Xanthomonas axonopodis PV. citri (Xac), and Pectobacterium atrosepticum ACCC 19901 (Pa). Furthermore, the structure-activity relationship and structural similarity analysis of active drugs classify potent agri-bactericides into 8 lead series: salicylanilides, cationic nitrogen-containing drugs, azole antifungals, N-containing group, hydroxyquinolines, piperazine, kinase inhibitor and miscellaneous groups. MIC values were evaluated as antibacterial activities in this study. Identifying highly active lead compounds from the screening of approved drugs and comparison with the currently applied plant pathogenic bactericide to validate the bactericidal activity of the best candidates and assess if selected molecules or scaffolds lead to develop new antibacterial agents in the future. In conclusion, this study provides a possibility for the development of potent and highly selective agri-bactericides leads.

N-doped carbon materials produced by CVD with the compounds derived from LDHs

Layered double hydroxides (LDHs) of various compositions, i.e. Mg–Al, Mg–Mn–Al, are applied as the precursors of metal oxides for the preparation of N-doped carbon materials via chemical vapour deposition (CVD) with acetonitrile (as carbon and nitrogen source) at 600 and 700 °C. The use of Mn-containing LDHs for the preparation of the carbon materials is a novelty. The impact of transition metal species, i.e. MnxOy, in a blend of metal oxides derived from LDHs on the amount of carbon deposit and its composition, morphology, textural and capacitive properties is investigated. Mn-containing species occurring in a mixture of metal oxides enhance the quantity of carbonaceous product compared to those derived from Mg–Al LDHs. Thermally heated Mg–Mn–Al LDHs contain structural defects due to manganese oxides, which promote the formation of carbon deposit, especially higher production of amorphous carbons. The addition of Mn into Mg–Al LDHs matrix leads to carbon particles with increased N-doping and enhanced volume of mesopores. Furthermore, graphitic domains occurring in the carbon materials obtained with Mg–Mn–Al LDHs are thicker than those in the corresponding samples obtained with Mg–Al LDHs as Mn-containing species influence the concentration and location of N-containing groups in graphitic array. The specific capacitance of the carbon materials produced by CVD with the compounds derived from Mg–Al LDHs or Mg–Mn–Al LDHs is comparable (20–25 μF cm−2). The formation of electrical double layer at electrode/electrolyte interface is easier for the carbon materials prepared at 700 °C than for the carbon materials prepared at 600 °C. The maximum charge is stored either in the shallow parts of carbon particles for the former, as they contain bottleneck mesopores, or in the deep parts of carbon particles for the latter, as they contain slit-shaped mesopores.Graphical abstract

Lignite-Based N-Doped Porous Carbon as an Efficient Adsorbent for Phenol Adsorption

The treatment of phenolic-containing wastewater has received increased attention in recent years. In this study, the N-doped porous carbons were prepared from lignite with tripolycyanamide as the N source, and their phenol adsorption behaviors were investigated. Results clearly showed that the addition of tripolycyanamide largely improved the surface area, micropore volume, N content and thus the phenol adsorption capacity of lignite-based carbons. The N-doped sample prepared at 700 °C showed a surface area of 1630 m2/g and a phenol adsorption capacity as high as 182.4 mg/g at 20 °C, which were 2.0 and 1.6 times that of the lignite-based carbon without N-doping. Pseudo-second order and Freundlich adsorption isotherm models could better explain the phenol adsorption behaviors over lignite-based N-doped porous carbon. Theoretical calculations demonstrated that phenol adsorption energies over graphitic-N (−72 kJ/mol) and pyrrolic-N (−74 kJ/mol) groups were slightly lower than that over the N-free graphite layer (−71 kJ/mol), supporting that these N-containing groups contribute to enhance the phenol adsorption capacity. The adsorption mechanism of phenol over porous carbon might be interpreted by the π–π dispersion interactions between aromatic-ring and carbon planes, which could be enhanced by N-doping through increasing π electron densities in the carbon plane.

Synergistic Effect of Oxygen- and Nitrogen-Containing Groups in Graphene Quantum Dots: Red Emitted Dual-Mode Magnetic Resonance Imaging Contrast Agents with High Relaxivity.

Contrast agents (CAs) in magnetic resonance imaging generally involve the dissociative Gd3+. Because of the limited ligancy of Gd3+, the balance between Gd3+ coordination stability (reducing the concentration of dissociative Gd3+) and increases in the number of coordination water molecules (enhancing the relaxivity) becomes crucial. Herein, the key factor of the synergistic effect between the O- and N-containing groups of graphene quantum dots for the structural design of CAs with both high relaxivity and low toxicity was obtained. The nitrogen-doped graphene quantum dots (NGQDs) with an O/N ratio of 0.4 were selected to construct high-relaxivity magnetic resonance imaging (MRI)-fluorescence dual-mode CAs. The coordination stability of Gd3+ can be increased through the synergetic coordination of O- and N-containing groups. The synergetic coordination of O- and N-containing groups can result in the short residency time of the water ligand and achieve high relaxivity. The resulting CAs (called NGQDs-Gd) exhibit a high relaxivity of 32.04 mM-1 s-1 at 114 μT. Meanwhile, the NGQDs-Gd also emit red fluorescence (614 nm), which can enable the MRI-fluorescence dual-mode imaging as the CAs. Moreover, the bio-toxicity and tumor-targeting behavior of NGQDs-Gd were also evaluated, and NGQDs-Gd show potential in MRI-fluorescence imaging in vivo.

A review on N-doped biochar for enhanced water treatment and emerging applications

N-doped biochar as high efficiency adsorbent to mitigate heavy metal and organic pollutants from wastewater has received extensive attentions, because of its specific surface structure and advantages in low cost and environmental friendliness. In this review, we first summarized the preparation technologies of N-doped biochar from both N-rich and N-poor biomass, followed by discussions on the determinants of N content in N-doped biochar. The N content and the content of N-containing functional groups, the two most important factors of the N-doped biochar, can be regulated through the selection of biomass, activation agents and N dopants together with the controlling of the doping ratio of activation agent and N dopants, pyrolysis temperature and holding time. In addition, this review systemically discussed the application of N-doped biochar in adsorption of heavy metals and organic pollutants. Furthermore, the adsorption mechanisms and specific roles of N-containing functional groups were further explained. Also, several emerging applications of N-doped biochar were introduced, including supercapacitors, CO2 adsorption, catalysts, soil remediation and soil fertilizer. Finally, several challenges in the wastewater treatment by N-doped biochar were presented, and the future outlook on the precise regulate the N functional groups and synergistic effect between N and O functional groups were proposed.