Eco-sustainable and recyclable porous carbons are reported as metal-free catalysts for the synthesis of benzodiazepines for the first time. The porous carbons were able to efficiently catalyse the synthesis of benzodiazepine 1 from o-phenylendiamine 2 and acetone 3 under mild conditions. Both acidic functions and the porosity of the catalysts were determinant features. High conversion values were obtained when using HNO3 oxidized carbons. The highest selectivity to benzodiazepine 1 was obtained in the presence of the most microporous catalyst N-N, which is indicative of the great influence of porous properties. Stronger acid sites and high microporosity of the carbon treated with H2SO4 yield benzodiazepine 1 with total selectivity.

Chromium is one of the most important raw materials for the European Union. Adsorption has become an important process for the recovery of metals from wastewaters, which has led to a demand for low-cost and eco-friendly adsorbents. The objective of this work was to use new and renewable carbon-based adsorbents from rice wastes in the removal/recovery of Cr(III) from synthetic and real wastewaters. Rice wastes were submitted to co-pyrolysis and the resulting char was optimized through physical and/or chemical activations/treatments. A commercial activated carbon was used for comparison purposes. All adsorbents were characterized (including an ecotoxicity test for the char precursor) and submitted to Cr(III) removal assays from a synthetic solution, in which two solid/liquid ratios (S/L) were tested (5 and 10 g/L). The CO2 activated carbon at a S/L = 5 g/L was the biomass-derived adsorbent that performed better, obtaining a maximum Cr(III) uptake capacity of 9.23 mg/g comparable to the one obtained by the commercial adsorbent at the same S/L (9.80 mg/g). The good results on this biomass-derived carbon were due to the effective volatile matter removal during the activation (from 22.7 to 4.25% w/w), which increased both surface area (from <5.0 to 325 m2/g) and ash content (from 30.0 to 40.4% w/w), allowing an increase in Cr(III) removal due to ion exchange mechanism and porosity development. The best adsorbent, under optimized conditions, was also applied to a chromium rich industrial wastewater. The results obtained in this real case application demonstrated a competition effect due to the presence of other ions.

The present work aims to assess the efficiency of chars, obtained from the gasification and co-pyrolysis of rice wastes, as adsorbents of Cr3+ from aqueous solution. GC and PC chars, produced in the gasification and co-pyrolysis, respectively, of rice husk and polyethylene were studied. Cr3+ removal assays were optimised for the initial pH value, adsorbent mass, contact time and Cr3+ initial concentration. GC showed a better performance than PC with about 100% Cr3+ removal, due to the pH increase that caused Cr precipitation. Under pH conditions in which the adsorption prevailed (pH<5.5), GC presented the highest uptake capacity (21.1mg Cr3+ g−1 char) for the following initial conditions: 50mg Cr3+ L−1; pH 5; contact time: 24h;L/S ratio: 1000mLg−1. The pseudo-second order kinetic model showed the best adjustment to GC experimental data. Both the first and second order kinetic models fitted well to PC experimental data. The ion exchange was the dominant phenomenon on the Cr3+ adsorption by GC sample. Also, this char significantly reduced the ecotoxicity of Cr3+ solutions for the bacterium Vibrio fischeri. GC char proved to be an efficient material to remove Cr3+ from aqueous solution, without the need for further activation.

Background The awareness of environmental and socio-economic impacts caused by greenhouse gas emissions from the livestock sector leverages the adoption of strategies to counteract it. Feed supplements can play an important role in the reduction of the main greenhouse gas produced by ruminants—methane (CH\textsubscript{4}). In this context, this study aims to assess the effect of two biochar sources and inclusion levels on rumen fermentation parameters \textit{in vitro}. Methods Two sources of biochar (agro-forestry residues, AFB, and potato peel, PPB) were added at two levels (5 and 10%, dry matter (DM) basis) to two basal substrates (haylage and corn silage) and incubated 24-h with rumen inocula to assess the effects on CH\textsubscript{4} production and main rumen fermentation parameters \textit{in vitro}. Results AFB and PPB were obtained at different carbonization conditions resulting in different apparent surface areas, ash content, pH at the point of zero charge (pHpzc), and elemental analysis. Relative to control (0% biochar), biochar supplementation kept unaffected total gas production and yield (mL and mL/g DM, \textit{p} = 0.140 and \textit{p} = 0.240, respectively) and fermentation pH (\textit{p} = 0.666), increased CH\textsubscript{4}production and yield (mL and mL/g DM, respectively, \textit{p} = 0.001) and ammonia-N (NH\textsubscript{3}-N, \textit{p} = 0.040), and decreased total volatile fatty acids (VFA) production (\textit{p} < 0.001) and H\textsubscript{2} generated and consumed (\textit{p} ≤ 0.001). Biochar sources and inclusion levels had no negative effect on most of the fermentation parameters and efficiency. Acetic:propionic acid ratio (\textit{p} = 0.048) and H\textsubscript{2} consumed (\textit{p} = 0.019) were lower with AFB inclusion when compared to PPB. Biochar inclusion at 10% reduced H\textsubscript{2} consumed (\textit{p} < 0.001) and tended to reduce total gas production (\textit{p} = 0.055). Total VFA production (\textit{p} = 0.019), acetic acid proportion (\textit{p} = 0.011) and H\textsubscript{2} generated (\textit{p} = 0.048) were the lowest with AFB supplemented at 10%, no differences being observed among the other treatments. The basal substrate affected most fermentation parameters independently of biochar source and level used. Discussion Biochar supplementation increased NH\textsubscript{3}-N content, \textit{iso}-butyric, \textit{iso}-valeric and valeric acid proportions, and decreased VFA production suggesting a reduced energy supply for microbial growth, higher proteolysis and deamination of substrate N, and a decrease of NH\textsubscript{3}-N incorporation into microbial protein. No interaction was found between substrate and biochar source or level on any of the parameters measured. Although AFB and PPB had different textural and compositional characteristics, their effects on the rumen fermentation parameters were similar, the only observed effects being due to AFB included at 10%. Biochar supplementation promoted CH\textsubscript{4} production regardless of the source and inclusion level, suggesting that there may be other effects beyond biomass and temperature of production of biochar, highlighting the need to consider other characteristics to better identify the mechanism by which biochar may influence CH\textsubscript{4} production.

The work reports the impregnation of naproxen into locust bean gum mesoporous matrixes with different textural properties. The matrixes were prepared through the dissolution of the biopolymer in water and in two ionic liquids (ILs): [bmim][Cl] and [C2OHmim][Cl] and dried with scCO2. The poor water-soluble pharmaceutical drug naproxen was loaded into the matrixes and the composites were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy and by differential scanning calorimetry; the results were compared with neat ILs and drug. The naproxen release from the matrixes was attempted at pH 7.4. Sustained release of naproxen in the different composites occurs, and consequently the naproxen release has lower rates compared with neat crystalline naproxen dissolution. Nevertheless, it was possible to observe small differences on release profiles for the studied composites. The higher release rate was observed for the composite where [bmim][Cl] was used as solvent, for which the calorimetric analysis revealed full amorphization of the incorporated drug. Cytotoxicity assays reveal that cellular viability in Caco-2 cells is preserved. This fact allied with the biocompatibility of locust bean gum allow for the composites potential application as naproxen controlled/sustained delivery systems with higher drug bioavailability achieved through naproxen amorphization.

Biodiesel production generates low particle size rapeseed waste (recovered from warehouse air filtration systems) that was herein explored as promising biomass precursor of chemically activated carbons. The influence of several experimental parameters on the porosity development was investigated. No benefit was observed when solution impregnation was made nor a significant dependence of the biomass : K2CO3 ratio was observed and{,} as expected{,} high porosity development was obtained only for treatments at 700 [degree]C. Microporous materials with apparent surface area around 1000 m2 g-1 were obtained comparing favorably with literature data regarding activated carbons from rapeseed processing by-products. A selected lab-made sample and two commercial carbons were tested as adsorbents of caffeine from aqueous solution. Although commercial materials present a quicker adsorption rate{,} regarding adsorption capacity the lab-made sample reaches the same value attained by a benchmark material. The regeneration tests made over the rapeseed derived carbon through heat treatments at 600 [degree]C for 1 hour under N2 flow proved that at least two exhaustion-regeneration cycles can be made since the material retains a caffeine adsorption capacity similar to that of the fresh carbon. Therefore{,} a waste management problem of biodiesel industry - rapeseed residue - can be transformed in a valuable material with promising properties for environmental remediation processes.

Maize Cob Waste (MCW) is available worldwide in high amounts, as maize is the most produced cereal in the world. MCW is generally left in the crop fields, but due to its low biodegradability it has a negligible impact in soil fertility. Moreover, MCW can be used as substrate to balance the C/N ratio during the Anaerobic co-Digestion (AcoD) with other biodegradable substrates, and is an excellent precursor for the production of Activated Carbons (ACs). In this context, a biorefinery is theoretically discussed in the present review, based on the idea that MCW, after proper pre-treatment is valorised as precursor of ACs and as co-substrate in AcoD for biomethane generation. This paper provides an overview on different scientific and technological aspects that can be involved in the development of the proposed biorefinery; the major topics considered in this work are the following ones: (i) the most suitable pre-treatments of MCW prior to AcoD; (ii) AcoD process with regard to the critical parameters resulting from MCW pre-treatments; (iii) production of ACs using MCW as precursor, with the aim to use these ACs in biogas conditioning (H2S removal) and upgrading (biomethane production), and (iv) an overview on biogas upgrading technologies.

A char produced from spent tire rubber showed very promising results as an adsorbent of Remazol Yellow (RY) from aqueous solutions. Spent tire rubber was submitted to a pyrolysis process optimized for char production. The obtained char was submitted to chemical, physical, and textural characterizations and, subsequently, applied as a low-cost adsorbent for dye (RY) removal in batch adsorption assays. The obtained char was characterized by relatively high ash content (12.9% wt), high fixed-carbon content (69.7% wt), a surface area of 69 m2/g, and total pore volume of 0.14 cm3/g. Remazol Yellow kinetic assays and modelling of the experimental data using the pseudo-first and pseudo-second order kinetic models demonstrated a better adjustment to the pseudo-first order model with a calculated uptake capacity of 14.2 mg RY/g char. From the equilibrium assays, the adsorption isotherm was fitted to both Langmuir and Freundlich models; it was found a better fit for the Langmuir model to the experimental data, indicating a monolayer adsorption process with a monolayer uptake capacity of 11.9 mg RY/g char. Under the experimental conditions of the adsorption assays, the char presented positive charges at its surface, able to attract the deprotonated sulfonate groups (SO3−) of RY; therefore, electrostatic attraction was considered the most plausible mechanism for dye removal.

Blends of rice waste streams were submitted to co-gasification assays. The resulting chars (G1C and G2C) were characterized and used in Cr(III) removal assays from a synthetic solution. A Commercial Activated Carbon (CAC) was used for comparison purposes. The chars were non-porous materials mainly composed by ashes (68.3–92.6% w/w). The influences of adsorbent loading (solid/liquid ratio – S/L) and initial pH in Cr(III) removal were tested. G2C at a S/L of 5 mg L−1 and an initial pH of 4.50 presented an uptake capacity significantly higher than CAC (7.29 and 2.59 mg g−1, respectively). G2C was used in Cr(III) removal assays from an industrial wastewater with Cr(III) concentrations of 50, 100 and 200 mg L−1. Cr(III) removal by precipitation (uptake capacity ranging from 11.1 to 14.9 mg g−1) was more effective in G2C, while adsorption (uptake capacity of 16.1 mg g−1) was the main removal mechanism in CAC.

Abstract This work reports for the first time a new series of promising porous catalytic carbon materials, functionalized with Lewis and Brønsted acid sites useful in the green synthesis of 2,3-dihydro-1H-1,5-benzodiazepine – nitrogen heterocyclic compounds. Benzodiazepines and derivatives are fine chemicals exhibiting interesting therapeutic properties. Carbon materials have been barely investigated in the synthesis of this type of compounds. Two commercial carbon materials were selected exhibiting different textural properties: i) Norit RX3 (N) as microporous sample and ii) mesoporous xerogel (X), both used as supports of ZrO2 (Zr) and ZrO2/SO42− (SZr). The supported SZr led to higher conversion values and selectivities to the target benzodiazepine. Both chemical and textural properties influenced significantly the catalytic performance. Particularly relevant are the results concerning the non-sulfated samples, NZr and XZr, that were able to catalyze the reaction leading to the target benzodiazepine with high selectivity (up to 80 %; 2 h). These results indicated an important role of the carbon own surface functional groups, avoiding the use of H2SO4. Even very low amounts of SZr supported on carbon reveal high activity and selectivity. Therefore, the carbon materials herein reported can be considered an efficient and sustainable alternative bifunctional catalysts for the benzodiazepine synthesis.

Digestate from a biogas plant that uses solely biomass for biogas production was used as precursor material for the production of activated carbon as an alternative to increase its added value. The digestate was converted into hydrochar by hydrothermal carbonization varying the temperature (190–250°C), residence time (3 and 6h), and pH (5 and 7). Temperature followed by residence time had the strongest influence on the chemical composition and thermal stability of the hydrochars. A significant effect of the pH was not observed. The hydrochars were chemically activated to enhance the surface area and use them as activated carbon. As a consequence, the surface areas increased from 8 to 14m2/g (hydrochars) to 930–1351m2/g (activated carbons). Furthermore, large micropore volumes were measured (0.35–0.50cm3/g). The activated carbons were studied as adsorbents in gas phase applications, showing that the product of digestate is a very effective adsorbent for carbon dioxide (CO2). Especially the activated carbon obtained from the hydrochar produced at 250°C for 6h, which adsorbed 8.80mol CO2/kg at 30°C and 14.8bar. Additionally, the activated carbons showed a stronger affinity towards CO2 compared to methane (CH4), which makes this material suitable for the upgrading of raw biogas to biomethane.

Twelve biochars from forest and agri-food wastes (pruning of Quercus ilex, Eucalyptus grandis, Pinus pinaster, Quercus suber, Malus pumila, Prunus spinosa, Cydonia oblonga, Eriobotrya japonica, Juglans regia, Actinidia deliciosa, Citrus sinensis and Vitis vinifera) were investigated as potential low-cost and renewable adsorbents for removal of a commonly used pharmaceutical, fluoxetine. Preliminary adsorption experiments allowed to select the most promising adsorbents, Quercus ilex, Cydonia oblonga, Eucalyptus, Juglans regia and Vitis vinifera pruning material. They were characterized by proximate, elemental and mineral analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy, determination of specific surface area and pH at the point of zero charge. Batch and equilibrium studies were performed, and the influence of pH was evaluated. The equilibrium was reached in less than 15 min in all systems. The maximum adsorption capacity obtained was 6.41 mg/g for the Eucalyptus biochar, which also demonstrated a good behavior in continuous mode (packed column).

In the present study, a novel porous carbon obtained by K2CO3 activation of potato peel waste under optimized conditions was applied for the first time as liquid-phase adsorbent of sodium diclofenac in parallel with a commercial activated carbon. The biomass-activated carbon presented an apparent surface area of 866 m2 g−1 and well-developed microporous structure with a large amount of ultramicropores. The obtained carbon presented leaching and ecotoxicological properties compatible with its safe application to aqueous medium. Kinetic data of laboratory-made and commercial sample were best fitted by the pseudo-second-order model. The commercial carbon presented higher uptake of diclofenac, but the biomass carbon presented the higher adsorption rate which was associated with its higher hydrophilic nature which favoured external mass transfer. Both adsorbents presented adsorption isotherms that were best fitted by Langmuir model. The biomass carbon and the commercial carbon presented adsorption monolayer capacities of 69 and 146 mg g−1, and Langmuir constants of 0.38 and 1.02 L mg−1, respectively. The better performance of the commercial sample was related to its slightly higher micropore volume, but the most remarkable effect was the competition of water molecules in the biomass carbon.

In the present work, the enhancement of biogas and methane yields through anaerobic co-digestion of the pre-hydrolised Organic Fraction of Municipal Solid Wastes (hOFMSW) and Maize Cob Wastes (MCW) in a lab-scale thermophilic anaerobic reactor was tested. In order to increase its biodegradability, MCW were submitted to an initial pre-treatment screening phase as follows: (i) microwave (MW) irradiation catalysed by NaOH, (ii) MW catalysed by glycerol in water and alkaline water solutions, (iii) MW catalysed by H2O2 with pH of 9.8 and (iv) chemical pre-treatment at room temperature catalysed by H2O2 with 4 h reaction time. The pre-treatments cataysed by H2O2 were performed with 2% MCW (wMCW/v alkaline water) at ratios of 0.125, 0.25, 0.5 and 1.0 (wH2O2/wMCW). The pre-treatment that presented the most favourable balance between sugars, lignin, cellulose and hemicellulose solubilisations, as well as low production of phenolic compound and furfural (inhibitors), was the chemical pre-treatment catalysed by H2O2, at room temperature, with a ratio of 0.5 wH2O2/wMCW (Pre1). This Pre1 was then optimised testing reaction times of 1, 2 and 3 days at a different pH (11.5) and MCW percentage (10% w/v). The optimised pre-treatment that presented the best results, considering the same criteria defined above, was the one carried out during 3 days, at pH 9.8 and 10% MCW w/v (Pre2). The anaerobic reactor was initially fed with the hOFMSW obtained from the hydrolysis tank of an industrial AD plant. The hOFMSW was than co-digested with MCW submitted to the pre-treatment Pre1. In another assay, hOFMSW was co-digested with MCW submitted pre-treatment Pre 2. The co-digestion of hOFMSW + Pre1 increased the biogas yield by 38.9% and methane yield by 29.7%, when compared to the results obtained with hOFMSW alone. The co-digestion of hOFMSW + Pre2 increased biogas yield by 46.0% and CH4 yield by 36.3%. In both cases, the methane content obtained in the biogas streams was above 66% v/v. These results show that pre-treatment with H2O2, at room temperature, is a promising low cost way to valorize MCW through co-digestion with hOFMSW.

Two activated carbons (ACs) were prepared by physical activation of Maize Cob Waste (MCW) with CO2, during 2 and 3 h (MCW(PA)2h and MCW(PA)3h, respectively). Two other ACs were prepared by chemical activation: a) MCW(LD) – MCW was impregnated with anaerobic liquid digestate (LD) and carbonized under N2 atmosphere; and b) CAR-MCW(LD) – previously carbonized MCW was impregnated with LD and carbonized under N2 atmosphere. All ACs were fully characterized for textural and chemical properties, and then used in dynamic H2S removal assays from real biogas samples. Regarding H2S removal, the ACs that were physically activated behaved much better than the impregnated ones: MCW(PA)3h and MCW(PA)2h showed H2S uptake capacities of 15.5 and 0.65 mg g−1, respectively, while MCW(LD) and CAR-MCW(LD) showed values of 0.47 and 0.25 mg g−1, respectively. This may indicate that textural properties (surface area and microporosity) are more important than mineral content in H2S removal. Effectively, both surface area and micropore volume were much higher for the samples of MCW(PA)3h (SBET = 820 m2 g−1 and Vmicro = 0.32 cm3 g−1) and MCW(PA)2h (SBET = 630 m2 g−1 and Vmicro = 0.21 cm3 g−1) than for the ACs that were chemically activated (SBET = 38.0 m2 g−1 and Vmicro = 0.01 cm3 g−1 for MCW(LD); SBET = 8.0 m2 g−1 and Vmicro = 0.01 cm3 g−1 for CAR-MCW(LD)). High oxygen content in MCW(PA)3h favoured the catalytic oxidation reaction of H2S, promoting its removal. The use of MCW as precursor and LD as activating agent of the ACs may contribute for the integrated management of maize wastes and to diversify the applications of anaerobic digestate.

The efficiency of porous carbons in fine chemical synthesis, among other application fields, has been demonstrated since both the porous structure and chemical surface provide the appropriated chemical environment favoring a great variety of relevant chemical transformations. In recent years, metal organic frameworks (MOFs) and covalent organic frameworks (COFs) have emerged as interesting opportunities in the preparation of porous carbons with improved physico-chemical properties. Direct calcination of MOFs or COFs, in the presence or not of others carbon or heteroatom sources, could be considered an easy and practical approach for the synthesis of highly dispersed heteroatom-doped porous carbons but also new porous carbons in which single atoms of metallic species are present, showing a great development of the porosity; both characteristics of supreme importance for catalytic applications. The goal of this review is to provide an overview of the traditional methodologies for the synthesis of new porous carbon structures together with emerging ones that use MOFs or COFs as carbon precursors. As mentioned below, the catalytic application in fine chemical synthesis of these kinds of materials is at present barely explored, but probably will expand in the near future.

Recent studies show the incorporation of graphene oxide (GO) in cement composites. But these composites are frequently incompatible with original materials for building rehabilitation. To overcome this limitation, natural hydraulic lime mortars were used as matrix, and the influence of GO percentage and type of mixing was investigated. The influence on the microstructure, mechanical and physical properties was assessed. The best results were obtained with dispersed GO at concentrations of 0.05% and 0.1%. A slight improvement of mechanical and physical characteristics was achieved. This could lead to new mortars with improved properties that can be used for building rehabilitation.

The electronic and optical properties of p-type copper oxides (CO) strongly depend on the production technique as it influences the obtained phases: cuprous oxide (Cu2O) or cupric oxide (CuO), the most common ones. Cu films deposited by thermal evaporation have been annealed in air atmosphere, with temperature between 225 and 375 °C and time between 1 and 4 h. The resultant CO films have been studied to understand the influence of processing parameters in the thermoelectric, electrical, optical, morphological, and structural properties. Films with a Cu2O single phase are formed when annealing at 225 °C, while CuO single phase films can be obtained at 375 °C. In between, both phases are obtained in proportions that depend on the film thickness and annealing time. The positive sign of the Seebeck coefficient (S), measured at room temperature (RT), confirms the p-type behavior of both oxides, showing values up to 1.2 mV·°C–1 and conductivity up to 2.9 (Ω·m)−1. A simple detector using Cu2O have been fabricated and tested with fast finger touch events.

Heterogeneous catalysis is an exciting field in constant development. New and improved catalysts that can both be effective and economical are always on demand. Activated carbons may well play an important role in this field, as they are a cheaper alternative while more environmentally benign. In this paper, a brief overview of the effort developed in the application of activated carbon as heterogeneous catalysts in various reactions is presented. Functionalised activated carbon has been used as catalyst for fine chemical reactions. Gas-phase reactions for NO, N2O and CO2 conversions were thoroughly studied using activated carbon as catalyst support. In situ characterization techniques proved to be valuable tools to understand carbon gasification mechanism.

Porous carbons from digestate-derived hydrochar were produced, characterized and their performance to reclaim phosphate from water was evaluated as a preliminary approach to demonstrate their practical application. In a first step, the digestate was converted into hydrochars through hydrothermal carbonization by using two different pH conditions: 8.3 (native conditions) and 3.0 (addition of H2SO4). The resulting hydrochars did not present significant differences. Consecutively, the hydrochars were activated with KOH to produce activated carbons with enhanced textural properties. The resulting porous carbons presented marked differences: the AC native presented a lower ash content (20.3 wt%) and a higher surface area (SBET = 1106 m2/g) when compared with the AC-H2SO4 (ash content = 43.7 wt% SBET = 503 m2/g). Phosphorus, as phosphate, is a resource present in significative amount in wastewater, causing serious problems of eutrophication. Therefore, the performance of the porous carbons samples to recover phosphate – P(PO43−) – from water was evaluated through exploitation assays that included kinetic studies. The lumped model presented a good fitting to the kinetic data and the obtained uptake capacities were the same for both carbons, 12 mg P(PO43−)/g carbon. Despite the poorer textural properties of AC-H2SO4, this carbon was richer in Ca, Al, Fe, K, and Mg cations which promoted the formation of mineral complexes with phosphate anions. The results obtained in this work are promising for the future development of P(PO43−) enriched carbons that can be used thereafter as biofertilizers in soil amendment applications.

We report herein for the first-time acid biomass-derived carbons from vegetal biomass, with high developed porosity, prepared through integrating method comprising pyrolysis and surface phosphonation, able to efficiently catalyze the synthesis of quinoxalines from 1,2-diamines and α-hydroxi ketones, under aerobic conditions. The obtained results indicate that the reaction is mainly driven by a combination of acid function strength and textural properties in terms of conversion and selectivity. Furthermore, our experimental and theoretical observations suggest that the preferred reaction pathway for this transformation, in the presence of the investigated acid carbon catalysts, involves cascade reactions including imination reaction between reactants, successive imine-enamine and keto-enol tautomerisms, heterocyclization followed by dehydration, and aromatization. While the acid sites seem to be a relevant role in each reaction step, the system formed by activated carbon and molecular oxygen could be behind the last oxidative reaction to give the corresponding nitrogen heterocycles.

We report herein for the first-time acid biomass-derived carbons from vegetal biomass, with high developed porosity, prepared through integrating method comprising pyrolysis and surface phosphonation, able to efficiently catalyze the synthesis of quinoxalines from 1,2-diamines and α-hydroxi ketones, under aerobic conditions. The obtained results indicate that the reaction is mainly driven by a combination of acid function strength and textural properties in terms of conversion and selectivity. Furthermore, our experimental and theoretical observations suggest that the preferred reaction pathway for this transformation, in the presence of the investigated acid carbon catalysts, involves cascade reactions including imination reaction between reactants, successive imine-enamine and keto-enol tautomerisms, heterocyclization followed by dehydration, and aromatization. While the acid sites seem to be a relevant role in each reaction step, the system formed by activated carbon and molecular oxygen could be behind the last oxidative reaction to give the corresponding nitrogen heterocycles.