N-ethyl Carbazole Research Articles

Role of hydrogen spillover on the hydrogenation of N-ethylcarbazole over in-situ Encapsulation of Ru within zeolite for hydrogen storage

Hydrogen spillover plays a crucial role in heterogeneous catalysis, significantly enhancing the activity of catalysts. However, the promotion mechanism of hydrogen spillover on non-reducible oxide supports (such as zeolite) is rarely reported. Herein, we prepared Ru@Beta sample by in-situ approach, effectively encapsulating Ru species into Beta zeolite. Additionally, three samples (Ru/SiO2, Ru@Naβ, and Ru@Hβ) with different hydrogen spillover effect were prepared. The optimal concentration of Ru was 0.5 wt%, and the Ru@Hβ sample with the strongest hydrogen spillover has 100 % conversion rate of N-ethylcarbazole (NEC) and 98 % selectivity towards to 12H-NEC. In contrast, the Ru/SiO2 with weak hydrogen spillover has only 89.5 % conversion rate and 28.9 % selectivity of 12H-NEC. Notably, the Ru@Hβ can still completely convert NEC even after 7 cycles, thereby exhibiting its remarkable activity and stability. Various characterizations (HAADF-STEM, XPS, EXAFS, in-situ DRIFT, and H2-TPD) indicate the superior catalytic performance of Ru@Hβ with strong hydrogen spillover effect, originating from the presence of more hydroxyl (–OH) and Brønsted acid on the surface, while Lewis acid act as hydrogen acceptors and NEC hydrogenation sites. This work not only expands our understanding of the hydrogen spillover, but also paves the way onto the potential applications in heterogeneous catalysis for efficient hydrogenation.

Catalysts for Liquid Organic Hydrogen Carriers (LOHCs): Efficient Storage and Transport for Renewable Energy.

Restructuring the current energy industry towards sustainability requires transitioning from carbon based to renewable energy sources, reducing CO2 emissions. Hydrogen, is considered a significant clean energy carrier. However, it faces challenges in transportation and storage due to its high reactivity, flammability, and low density under ambient conditions. Liquid organic hydrogen carriers offer a solution for storing hydrogen because they allow for the economical and practical storage of organic compounds in regular vessels through hydrogenation and dehydrogenation. This review evaluates several hydrogen technologies aimed at addressing the challenges associated with hydrogen transportation and its economic viablity. The discussion delves into exploring the catalysts and their activity in the context of catalysts' development. This review highlights the pivotal role of various catalyst materials in enhancing the hydrogenation and dehydrogenation activities of multiple LOHC systems, including benzene/cyclohexane, toluene/methylcyclohexane (MCH), N-ethylcarbazole (NEC)/dodecahydro-N-ethylcarbazole (H12-NEC), and dibenzyltoluene (DBT)/perhydrodibenzyltoluene (H18-DBT). By exploring the catalytic properties of noble metals, transition metals, and multimetallic catalysts, the review provides valuable insights into their design and optimization. Also, the discussion revolved around the implementation of a hydrogen economy on a global scale, with a particular focus on the plans pertaining to Saudi Arabia and the GCC (Gulf Cooperation Council) countries. The review lays out the challenges this technology will face, including the need to increase its H2 capacity, reduce energy consumption by providing solutions, and guarantee the thermal stability of the materials.

Synthesis of furo[2,3-c]carbazoles as potent α-glucosidase and α-amylase inhibitors

The carbazole-3-carbaldehyde 2, produced by N-ethyl carbazole via Vilsmeier-Haack reaction, was subjected to Dakin type oxidation with H2O2 and H2SO4 in methanol to produce the carbazole-3-ol 3. The reaction of 3 with a range of commercially available α-haloketones 4a–f in the presence of Al2O3 as catalyst in xylene led to their regio-selective cyclization to afford the furo[2,3-c]carbazoles 5a–f. Identification of the furo[2,3-c]carbazoles 5a–f were performed through 1H NMR,13C NMR, FT-IR and high resolution mass spectrometry. Single crystal X-ray diffraction analysis was employed to further confirm the structures of the some of the targeted compounds. In vitro antidiabetic activities of the newly synthesized furocarbazoles 5a–e were investigated utilizing α-glucosidase and α-amylase enzymes. The biological evaluation revealed the obvious efficiencies of the targeted molecules toward the α-glucosidase enzyme inhibition with the potent IC50 values compared to the standard acarbose. In the case of α-glucosidase inhibition, the furo[2,3-c]carbazoles chloro substituted 5c and nitro substituted 5f were found to be more potent than acarbose with the values of 215.0 and 162.70 μM, respectively. On the other hand, the compound 5f was found to be only promising candidate for α-amylase enzyme but not as effective as the standard acarbose.

Significantly improved dehydrogenation of dodecyl-N-ethylcarbazole over supported PdFe bimetallic nanocatalysts via polydopamine surface modification of Al2O3

N-ethylcarbazole (NEC) has great application prospects in hydrogen storage due to its ability to dehydrogenate at lower energy and high hydrogen storage performance. Developing supported metal catalysts with high catalytic activity and stability is key to achieving large-scale application of LOHC hydrogen storage technology. In this paper, bimetallic FePd/Al2O3@PDA-GR catalysts used for the dehydrogenation process of 12H-NEC were prepared by stepwise reduction methods, including chemical reduction and galvanic replacement, using PDA-coated Al2O3 as the support. The characterization results showed that adding PDA could anchor the metal particles, improve the dispersion of metal particles on the support surface, and reduce the agglomeration phenomenon. The nanoparticles of bimetallic catalysts prepared by the galvanic replacement were small, with the particle size distribution of 0.86 nm-2.78 nm, and an average size of 1.52 nm. The large number of exposed active sites enabled the catalysts to reduce the dosage of Pd while still possessing excellent catalytic performance. And part of Pd was coated on Fe NPs in the Fe5Pd1/Al2O3@PDA-GR catalysts prepared by galvanic replacement, which improved the atom utilization of Pd. And there is an obvious electronic interaction between Fe and Pd. In the dehydrogenation process of 12H-NEC to NEC, The prepared FePd/Al2O3@PDA-GR catalyst exhibited excellent catalytic performance and had a significantly greater dehydrogenation efficiency than found in the literature, 95% for 1 h and 100% for 3 h at 180 °C. The temperature drop to 160 °C did not affect the dehydrogenation efficiency, which remained at 98.1% for 3 h. The prepared catalyst had good stability, and the dehydrogenation efficiency was 93.1% after five successive cycles.

Theoretical investigation on hydrogen storage into N-ethylcarbazole catalyzed by electron-rich Ni4/TiO2-Al2O3

Liquid organic hydrogen strorage (LOHC) technique is a promising safe long-term storage and long-distance transportation at ambient conditions whose bottleneck is the development of catalyst with outstanding hydrogen storage performance and relative low cost. Here, we report a promising Ni4 clusters supported on TiO2-Al2O3 composite oxides (Ni4/TA) as the hydrogen storage catalyst. The effect of TiO2 on the geometry and electron structures of the catalyst, the adsorption behaviors of N-ethylcarbazole (NEC) and its intermediates as well as the hydrogen storage mechanism are investigated via DFT calculations. The results indicate that the electron density around the loaded Ni4 clusters accumulated and the d-band center of Ni4 cluster is modulated due to the excellent electron migration performance of TiO2 species. Thus strengthened the capture and adsorption of NEC at the active region but weakened the adsorption strength of 4H-NEC and 8H-NEC which benefit the desorption-resorption transformation process. A declination of about 60 kJ·mol−1 in the required energy for the rate controlling step demonstrate TiO2 profoundly promoted the startup of hydrogen storage reaction. Moreover, the protonation effect caused by introduction of TiO2 makes it possible to further storage hydrogen into the second aromatic ring of NEC, thus makes the fully hydrogen storage into NEC easy and controllable. This study provides a theoretical guidance for the developing of non-noble metal supported hydrogen storage catalyst with excellent performance.

Liquid organic hydrogen carriers: Process design and economic analysis for manufacturing N‐ethylcarbazole

AbstractThis paper revisits the economics of manufacturing N‐ethylcarbazole (NEC), a strong candidate for large‐scale liquid organic hydrogen carrier (LOHC) supply chains, because of its high H2 storage capacity (6 wt%), selective hydrogenation and dehydrogenation reactions, and favorable reaction enthalpy and reaction temperatures compared to other LOHC systems. Two different process routes for producing NEC from industrial chemicals are selected out of 10 possible options: one using aniline and the other using cyclohexanone and nitrobenzene as feedstock. The required capital and operational costs are estimated to determine a NEC break‐even cost for a capacity of 225 ktpa. NEC break‐even costs of $3.0 and $2.6 per kg LOHC are found for the routes. This is significantly less than the $40/kg cost that has generally been reported in literature for NEC, thus improving the economic viability of using NEC as LOHC. The total fixed capital costs are estimated to be $200 MM and $250 MM. Furthermore, the prices of the feedstock show the largest influence (76% and 72%) on the final NEC break‐even costs. The overall LOHC price contribution to the levelized H2 cost is estimated to be $0.77–$0.90 per kg H2 for a 60‐day roundtrip and $0.09–$0.10 per kg H2 for a 7‐day roundtrip. It is important to note that both routes rely heavily on laboratory scale data and the corresponding assumptions that stem from this limitation. Therefore, this research can serve as a guide to future experimental studies into validating the key assumptions made for this analysis.

Strong metal-support interactions of TiO2 interface-loaded Pt constructed under different atmospheres for adjusting the hydrogen storage reaction performance of N-ethylcarbazole.

In this study, two series of samples (rT-Pt/TiO2 prepared with a hydrogen pretreatment and Tr-Pt/TiO2 prepared with an oxygen pretreatment) were prepared by treating commercial TiO2 supports in different atmospheres to establish different TiO2 interfacial structures, followed by the addition of platinum nanoparticles (NPs) for the catalyzed hydrogenation/dehydrogenation cycle of N-ethylcarbazole (NEC). The kinetic analysis and reaction mechanism were investigated by combining XRD, Raman, CO-DRIFT, HRTEM, XPS, H2-TPD and DFT calculations. It was found that the performance of the samples for the NEC system's cyclic hydrogen storage could be modulated by treating the TiO2 interfacial structure with different atmospheres varying the extent of strong metal-support interaction (SMSI). In addition, a turnover frequency (TOF) of 191.52 min-1 for dehydrogenation was achieved at 170 °C, which is better than the previously reported catalysts. Experimental studies (characterization and kinetic studies) and DFT calculations confirmed that the SMSI of the Tr-Pt/TiO2 series samples promoted the escape of H2 and enhanced the catalytic activity for 4H-NEC in the 12H-NEC dehydrogenation reaction. In the NEC hydrogenation reaction, the rT-Pt/TiO2 series samples were pretreated with H2 before loading platinum metal, which led to the early activation of Ti4+ in their carriers, and thus suppressed the SMSI effect of the reduction process after loading platinum. This process caused the interface formed by rT-Pt/TiO2 to have a higher energy barrier to 6H-NEC, which is an intermediate product of the NEC hydrogenation process, and this interrupted the hydrogenation process of 6H-NEC.

Exploring the potential of liquid organic hydrogen carrier (LOHC) system for efficient hydrogen storage and Transport: A Techno-Economic and energy analysis perspective

Despite its potential as an environmentally clean fuel and energy source, hydrogen storage and utilization has been significantly hampered by its extremely low volumetric density (0.08988 g/L at 1 atm), making it inefficient to store and transport. Therefore, liquid organic hydrogen carrier (LOHC) systems are being recently investigated as potential alternatives for hydrogen storage and transport. However, as a budding research area, the selection of a suitable LOHC, its deployment in hydrogen fuel stations, and its economic viability are not well established. Therefore, this study proposes a comprehensive investigation of four different LOHCs [Methylcyclohexane (MCH), Dibenzyltoluene (DBT), N-ethylcarbazole (NEC) and Naphthalene (NAP)] via Aspen HYSYS simulations. The LOHCs were compared and contrasted using their physiochemical properties, techno-economic analysis and heat network integration. The techno-economic analysis revealed that NAP-based hydrogen storage has the lowest cost among the LOHC options, while NEC shows the highest cost. However, when considering the breakeven point, the order changes to DBT, MCH, NAP, and NEC with 3, 3.8, 5.1 and 5.9, respectively. This result is attributed to the different hydrogen uptakes of the LOHCs, resulting in a longer breakeven period for NEC. Internal rate of return and net present value analysis also demonstrated the superior economic feasibility of the proposed systems. In terms of heat integration, the DBT process outperformed the other LOHCs as the most heat-efficient process with 80 % utility reduction, while the NEC process exhibited the lowest heat integration potential of 66.7 % utility reduction. Combining these findings with the physiochemical properties of the LOHCs, DBT emerges as the most attractive due to its favorable performance across multiple categories, such as toxicities, prices, energy consumptions, and material handling, using a spiderweb diagram.

Photoexcited state properties of N-ethylcarbazole-functionalized carbon dots in solution and in PVK polymer matrix

The adducts of N-ethylcarbazole (NEC) to small carbon nanoparticles prepared by microwave-assisted thermal processing are carbon dots (CDots) with NEC for the dot surface functionalization, thus NEC-CDots, which were shown previously for their high stability in the dot structure and properties. In this study, the optical absorptions and photoexcited state properties of NEC-CDots in solution and in poly(N-vinylcarbazole) (PVK) film matrix were evaluated by using optical spectroscopy methods, including those for fluorescence decays and lifetimes. The results suggest that the properties are largely unchanged from solution phase to the polymer matrix environment, very positive to their expected optoelectronic applications.

PdRu/SBA15 catalysts for hydrogen storage by reversible N-ethylcarbazole hydrogenation/dehydrogenation reactions

In this work, a stable double complex salt (DCS) on the surface of SBA-15 is constructed by phase transfer-assisted electrostatic adsorption method. DCS was then reduced by glow discharge plasma to obtain SBA-15 loaded PdRu bimetallic catalysts (PdRu/SBA15). The catalysts were characterized by nitrogen adsorption–desorption, TEM, FT-IR, XPS, H2-TPR and ICP-OES. The Pd anion dissolved by phase transfer is precisely adsorbed on the Ru cation, and this unique intimacy of two metals promotes the formation of stable structure. The synergistic effect of the DCS structure and the in-situ reduction of glow discharge plasma makes PdRu/SBA15 have highly dispersed and stable PdRu nanoparticles (NPs). PdRu/SBA15 is suitable for reversible hydrogen storage system. It not only catalyzed N-ethylcarbazole (NEC) hydrogenation efficiently, but also showed enhanced catalytic performance in the dehydrogenation of dodecahydro-N-ethylcarbazole (12H-NEC). The hydrogenation efficiency reached 99.8% for 80 min at 100 °C, H2 pressure of 5 Mpa and the dehydrogenation efficiency reached 100% for 6 h at 180 °C under the action of the same PdRu/SBA15 catalyst. Moreover, the catalytic activity of PdRu/SBA15 catalyst did not decrease obviously after seven cycles in reversible hydrogen storage. The reversible hydrogen storage PdRu catalysts with excellent activity has a very bright prospect in the practical application of fuel cells.

Preparation of SBA-15 supported Ru nanocatalysts by electrostatic adsorption-ultrasonic in situ reduction method and its catalytic performance for hydrogen storage of N-ethylcarbazole.

N-ethylcarbazole (NEC) is an ideal liquid organic hydrogen storage carrier. The development of efficient hydrogen storage catalysts can promote the large-scale application of this process. In this paper, SBA-15 supported Ru nanocatalysts (Ru/S15-SU) were synthesized by strong electrostatic adsorption (SEA)-ultrasonic in situ reduction method (UR). Ru/S15-SU was characterized by N2 adsorption-desorption, TEM, H2 temperature program reduction, FT-IR, XRD, and XPS analysis measures. The results showed that ultrafine Ru NPs were evenly distributed on the surface of SBA-15, and ultrasonic in situ reduction not only reduced Ru3+ to Ru0, but also produced a coordination effect between Ru and O, enhancing the interaction between Ru NPs and the carrier. Ru/S15-SU exhibited excellent catalytic performance in the hydrogenation reaction of NEC, and the hydrogen storage efficiency reached 99.31% at 130°C and 6 MPa H2 pressure, which is superior to that of commercial 5wt%Ru/Al2O3. The excellent catalytic hydrogenation performance can be attributed to the selective anchoring of ruthenium ions on the surface of SBA-15 via electrostatic adsorption, preventing the aggregation of Ru NPs and enhancing the interaction between SBA-15 and Ru NPs by ultrasonic in situ reduction. Ru/S15-SU had a lower NEC hydrogenation apparent activated energy (Ea) of 68.45 kJ/mol than 5wt%Ru/Al2O3 catalyst. This method provides a new approach for the green preparation of nanocatalysts without using any chemical reducing agents.

Preparation of MCM-41 supported Ni@Pd core-shell nanocatalysts by ultrasound-assisted galvanic replacement and their efficient catalytic dehydrogenation of dodecahydro-N-ethylcarbazole

N-ethylcarbazole (NEC) is one of the most promising liquid organic hydrogen carriers (LOHCs) due to its low dehydrogenation enthalpy. The development of an efficient catalyst for the dehydrogenation of dodecahydro-N-ethylcarbazole (H12-NEC) is the key to the large-scale application of LOHCs. In this paper, Ni/MCM-41 was prepared by chemical reduction method using MCM-41 as the carrier, and then MCM-41 loaded Nin@Pd1 core-shell nanocatalysts (Nin@Pd1/M41) were prepared by ultrasound-assisted galvanic replacement method using Ni as the templating agent and reducing agent. It was shown that there was electron transfer between Ni and Pd, and SMSI effect of Nin@Pd1 with MCM-41 by the characterization results of Nin@Pd1/M41, which promoted the catalytic performance. H12-NEC dehydrogenation efficiency over Ni6@Pd1/M41 reached 100% at 180 °C for 4 h and at 170 °C for 6 h, and 97.58% for 6 h at 160 ℃, and TOF was 5080.6 h−1, which was better than that reported in the literature. The excellent catalytic dehydrogenation performance of Ni6@Pd1/M41 can mainly be attributed to the synergistic effect of coordination and strain effects between the bimetals.

Boosting the dehydrogenation efficiency of dodecahydro-N-ethylcarbazole by assembling Pt nanoparticles on the single-layer Ti3C2Tx MXene

As the candidates for large-scale hydrogen storage, liquid organic hydrogen carriers (LOHCs) exhibit evident advantages in hydrogen storage density and convenience of storage and transportation. Among them, NECZ (N-ethylcarbazole)/12H-NECZ (dodecahydro-N-ethylcarbazole) is considered as a typical system with the lower hydrogenation/dehydrogenation temperature. However, the low dehydrogenation efficiency restrict its commercial applications. In this work, the single-layer Ti3C2Tx MXene was employed as the support to load the Pt nanoparticles for the 12H-NECZ dehydrogenation reaction. The effect of transition metals, loading amounts and morphologies of catalysts were analyzed. It was found that the 3 wt% Pt/S–Ti3C2Tx catalyst exhibited the best catalytic performance with 100% conversion, 91.55% selectivity of NECZ and 5.62 wt% hydrogen release amount at 453 K, 101.325 kPa for 7 h. The product distributions and kinetics analysis suggested that the elementary reaction from 4H-NECZ to NECZ was the rate-limiting step. The selectivity of NECZ is sensitive to the dehydrogenation temperature. Combined with the XRD, SEM, HRTEM, XPS, BET and FT-IR results, it could be indicated that the special two-dimension structure of S–Ti3C2Tx and electronic effect between Pt and S–Ti3C2Tx enhanced the dehydrogenation efficiency of 12H-NECZ. The measurements of cyclic dehydrogenation indicated that the Pt/S–Ti3C2Tx catalyst exhibited good stability after 42 h. This work brought a new strategy for the design of efficient catalysts using two-dimensional materials in the applications of the liquid organic storage hydrogen technology.

Single Rh1Co catalyst enabling reversible hydrogenation and dehydrogenation of N-ethylcarbazole for hydrogen storage

N-ethylcarbazole (NEC) has been considered one of the most prospective liquid organic hydrogen carriers (LOHCs) for hydrogen storage. However, designing single catalyst capable of driving both hydrogenation of NEC and dehydrogenation of dodecahydro-NEC (12 H-NEC) is of a big challenge. Herein, we develop an atomic-dispersion of Rh with the Co nanoparticles (NPs) to form a Rh1Co structure maximizing the Rh utilization, which boosts the reversible (de)hydrogenation of NEC, and enables multiple cycles of reversible hydrogen uptake and release. Significantly, a low temperature of 90 °C is realized for the complete hydrogenation (100%), representing one of the lowest temperatures yet reported for the total hydrogenation of NEC. The remarkable catalytic performance of Rh1Co catalysts is the result of the optimal electronic structure between atomic-dispersion of Rh and Co NPs confirmed by structural characterizations and density functional theory (DFT) calculations, which allowed fast interfacial electron transfer to intermediates.

Coumarinacyl Anilinium Salt: A Versatile Visible and NIR Photoinitiator for Cationic and Step-Growth Polymerizations

A coumarinacyl anilinium (CAA) salt, facilely synthesized via a one-pot reaction, is shown to be a versatile visible and NIR photoinitiator for cationic and step-growth polymerizations. CAA salt exhibits superior photoinitiation performance as compared to commercial iodonium salt in cationic polymerization. Upon visible-light irradiation, this salt undergoes hemolytic and heterolytic cleavage and subsequent electron transfer and hydrogen abstraction reactions, forming reactive species capable of initiating cationic polymerization of epoxides and vinyl monomers. After a short irradiation period, polymerization also proceeds in the dark due to the non-nucleophilic nature of the counteranion. NIR-induced polymerizations were successfully conducted based on upconversion photochemistry. CAA salt can also initiate step-growth polymerization of N-ethyl carbazole (NEC) by oxidation of the monomer by the photochemically formed anilium radical cations. Subsequent proton release and radical coupling reactions essentially yield polycarbazole. CAA salt, featuring straightforward synthesis and long-wavelength sensitivity as well as versatile photoinitiating performance, has great potential in various applications.

Isomerization pathway of N-ethylcarbazole hydrogenation products affected by metal-support interactions

N-ethylcarbazole (NEC) is a widely studied liquid organic hydrogen carrier, and a large number of catalysts with excellent reactivity has been designed and developed thus far. However, the phenomenon of isomeric transformation of 12H-NEC products during the reaction was not explained. Here, we studied the process based on three different Ru catalysts supported on zirconium-based supports, and based on the experimental results, we identified that supported metal-support strong interaction (SMSI), metal-support anion interaction (MSAI) and hydrogen spillover will have coupling effect on the hydrogenation reaction path and the occurrence of isomerization in 12H-NEC product. Higher 12 [H] B content in 12H-NEC under Ru/ZrN catalyst was caused by the large number of secondary active centers on the surface of the support reacting in the hydrogenation reaction. The active site for the isomerization of 12 [H] B to 12 [H] A may be the electronegativity interface formed by Ru and the support, while the electroneutral or electropositive interface rich in hydrogen is not conducive to the catalytic conversion. To sum up, an image model for the isomeric transformation of 12H-NEC products was proposed.

Trace ultrafine Ru nanoparticles on Ni/Al hydrotalcite-derived oxides supports as extremely active catalysts for N-ethylcarbazole hydrogenation

Liquid organic hydrogen carriers (LOHCs) is a promising hydrogen storage technology and has become a hot issue. However, there is still a shortage of LOHCs hydrogenation catalysts that can balance cost and catalytic performance. In this work, a series of Ni/Al hydrotalcite-derived oxides (LDOs) were prepared with different Ni/Al ratios and preparation methods, on which trace ultrafine Ru nanoparticles (0.5 wt%, 1 wt%, 1.5 wt%) were supported. The activities were investigated for the hydrogenation of N-ethylcarbazole (NEC), one of the most promising liquid organic hydrogen carriers. Characterizations including XRD, XPS, SEM, TEM and H2-TPR indicate the composition of Ni/Al-LDOs and reveal three kinds of Ni/Al interactions existed in Ni/Al-LDOs. The influences of Ni-Al interactions on the size of Ru NPs supported on Ni/Al-LDOs and on the NEC hydrogenation activity were also explored. The results show that 1.5 wt% Ru-Ni1Al2-LDO300 has the best catalytic performance for NEC hydrogenation, with which can achieve up to 5.5 wt% hydrogen absorption at 150℃ and 8 MPa for 12 min, and the yield of 12H-NEC can reach 100 % for 60 min. In other words, the catalytic performance of 1.5 wt% Ru supported catalyst is superior to 5 wt% Ru/Al2O3 catalyst commonly used for NEC hydrogenation. This work provides a new idea for preparing catalysts with low cost and high performance by tuning the structure of Ni/Al-LDO supports and the size of Ru NPs.

Stable Carbon Dots from Microwave-Heated Carbon Nanoparticles Generating Organic Radicals for In Situ Additions

Carbon dots (CDots) are small carbon nanoparticles with effective surface passivation by organic functionalization. In the reported work, the surface functionalization of preexisting small carbon nanoparticles with N-ethylcarbazole (NEC) was achieved by the NEC radical addition. Due to the major difference in microwave absorption between the carbon nanoparticles and organic species such as NEC, the nanoparticles could be selectively heated via microwave irradiation to enable the hydrogen abstraction in NEC to generate NEC radicals, followed by in situ additions of the radicals to the nanoparticles. The resulting NEC-CDots were characterized by microscopy and spectroscopy techniques including quantitative proton and 13C NMR methods. The optical spectroscopic properties of the dot sample were found to be largely the same as those of CDots from other organic functionalization schemes. The high structural stability of NEC-CDots benefiting from the radical addition functionalization is highlighted and discussed.

Alloying effect of Ni-Mo catalyst in hydrogenation of N-ethylcarbazole for hydrogen storage.

Liquid organic hydrogen storage with N-ethylcarbazole (NEC) as a carrier is a very promising method. The use of precious metal hydrogenation catalysts restricts the development in industrial grade. Efficient and low-cost hydrogen storage catalysts are essential for its application. In this work, a Ni-Mo alloy catalyst supported by commercial activated carbon was synthesized by impregnation method, and the Ni-Mo ratio and preparation conditions were optimized. The catalyst was characterized by XRD, XPS, H2-TPR, SEM, and TEM. The results showed that the doping of Mo could dramatically promote the catalytic hydrogenation of N-ethylcarbazole by the Ni-based catalyst. More than 5.75 wt% hydrogenation could be achieved in 4h using the Ni-Mo catalyst, and the selectivity of the fully hydrogenated product 12H-NEC could be effectively improved. This result reduces the cost of hydrogenation catalysts by more than 90% and makes liquid organic hydrogen storage a scaled possibility.

Interheteromolecular Hyperconjugation Boosts (De)hydrogenation for Reversible H2 Storage.

Interheteromolecular hyperconjugation is ubiquitous in organic systems, affecting bond length, dipole moments, conformations and so on, while its effect on (de)hydrogenation reactivity in a heterogeneous thermo-catalytic system has rarely been explored. Herein, the N-heterocycles containing a benzene ring and aliphatic chain [N-ethylcarbazole (NEC) and N-propylcarbazole (NPC)] were utilized to study the correlation between interheteromolecular hyperconjugation and catalytic (de)hydrogenation. Density functional theory calculations, variable-temperature 1 H nuclear magnetic resonance spectroscopy, and catalytic experiments showed that the presented hyperconjugation between NEC and NPC weakened the electron cloud density of aromatic rings and thus facilitated the reactivity with hydrogen featuring unpaired electrons. Therefore, an extremely low temperature of 80 °C was enough for the hydrogenation. Moreover, this interheteromolecular hyperconjugation was general in other N-heterocycles (e. g., N-methyindole and NPC) and was also effective to (de)deuterate as revealed by isotope experiments. This work expands the application of interheteromolecular hyperconjugation to heterogeneous thermocatalysis for reversible H2 storage.