Metal‐free heteroatom‐doped carbocatalysts with a high surface area are desirable for catalytic reactions. In this study, we found an efficient strategy to prepare nitrogen, phosphorus, and sulfur ...co‐doped hollow carbon shells (denote as NPS‐HCS) with a surface area of 1020 m2 g−1. Using a poly(cyclotriphosphazene‐co‐4,4′‐sulfonyldiphenol) (PZS) shell as carbon source and N, P, S‐doping source, and the ZIF‐67 core as structural template as well as extra N‐doping source, NPS‐HCS were obtained with a high surface area and superhydrophilicity. All these features render the prepared NPS‐HCS a superior metal‐free carbocatalyst for the selective oxidation of aromatic alkanes in aqueous solution. This study provides a reliable and facile route to prepare doped carbocatalysts with enhanced catalytic properties.
Highly efficient and selective: A synthetic route was developed to produce nitrogen, phosphorus, and sulfur co‐doped hollow carbon shells which were used as a metal‐free carbocatalyst. The carbocatalyst had a high surface area and showed superior activity in the selective oxidation of aromatic alkanes in aqueous solution.
Benzene-ring doped g-C3N4 nanosheets (BS-CN) exhibited extended light adsorption and enhanced separation/transfer of photoinduced holes and electrons, which promoted it an excellent ...visible-light-driven hydrogen evolution catalyst by 12-fold improvement.
Display omitted
•Homogeneous benzene-ring doped g-C3N4 nanosheets for photocatalytic hydrogen evolution.•Enhanced photocatalytic hydrogen evolution rate of 12.3 mmol h−1 g−1.•High quantum efficiency of 17.7% at 420 nm.
Solar-to-chemical energy conversion by photocatalytic hydrogen evolution (PHE) is critical for reduction of the pollution and storage of clean energy. To improve the solar conversion efficiency, it is highly imperative to accelerate the photocarrier separation and transportation through materials design. Herein, we describe a highly effective PHE catalyst based on in-plane benzene-ring doped g-C3N4 nanosheets heterostructure through the thermal co-polymerization of urea and 4, 4'-sulfonyldiphenol (BPS) followed by a controlled heat-etching step. The solid-state 13C NMR confirms the existence of benzene-ring structure in g-C3N4 nanosheets. Experimental results and theoretical calculations show that the energy and electronic structure of the catalyst are optimally regulated, inducing increased light absorption and effectively accelerated separation of the photo-driven charge carriers. It exhibits enhanced photocatalytic hydrogen evolution efficiency with a PHE rate of 12.3 mmol h−1 g−1 (almost 12 times higher than that of pure g-C3N4 nanosheets) and the quantum efficiency of 17.7% at 420 nm.
Abstract
Transition metal single atom catalysts (SACs) with M
1
-N
x
coordination configuration have shown outstanding activity and selectivity for hydrogenation of nitroarenes. Modulating the atomic ...coordination structure has emerged as a promising strategy to further improve the catalytic performance. Herein, we report an atomic Co
1
/NPC catalyst with unsymmetrical single Co
1
-N
3
P
1
sites that displays unprecedentedly high activity and chemoselectivity for hydrogenation of functionalized nitroarenes. Compared to the most popular Co
1
-N
4
coordination, the electron density of Co atom in Co
1
-N
3
P
1
is increased, which is more favorable for H
2
dissociation as verified by kinetic isotope effect and density functional theory calculation results. In nitrobenzene hydrogenation reaction, the as-synthesized Co
1
-N
3
P
1
SAC exhibits a turnover frequency of 6560 h
−1
, which is 60-fold higher than that of Co
1
-N
4
SAC and one order of magnitude higher than the state-of-the-art M
1
-N
x
-C SACs in literatures. Furthermore, Co
1
-N
3
P
1
SAC shows superior selectivity (>99%) toward many substituted nitroarenes with co-existence of other sensitive reducible groups. This work is an excellent example of relationship between catalytic performance and the coordination environment of SACs, and offers a potential practical catalyst for aromatic amine synthesis by hydrogenation of nitroarenes.
Display omitted
•Mg/Fe-CLDH adsorbent was synthesized for simultaneous removal of F and As(V).•There was no competitive adsorption between F and As(V) on Mg/Fe-CLDH adsorbent.•Mg/Fe-CLDH adsorbent ...can achieve the simultaneous removal of F and As(V).•Effect of mixed oxides formed on adsorbent was more obvious than BET on adsorption.•Adsorption mechanisms of F and As(V) on Mg/Fe-CLDH were analyzed in detail.
The present study evaluated calcined Mg/Fe layered double hydroxide (Mg/Fe-CLDH) as an adsorbent for simultaneous removal of fluoride and arsenate from aqueous solution. The Mg/Fe layered double hydroxide (Mg/Fe-LDH) was synthesized by co-precipitation method. A series of batch experiments were performed under various conditions, such as M2+/M3+ ratio, calcination temperature, initial anions concentrations, contact time, solution pH and competitive adsorption, for the adsorption of fluoride and arsenate on Mg/Fe-CLDH. It was found that the Mg/Fe-CLDH adsorbent with a M2+/M3+ ratio of 5, calcined at 400°C and pH 7, had the largest adsorption capacity of 50.91 and 50.24mg/g for fluoride and arsenate, respectively. Data of equilibrium experiments were fitted well to Langmuir isotherm model and pseudo-second-order kinetic model. Competitive adsorption experiments indicated that the Mg/Fe-CLDH adsorbents can achieve the simultaneous removal of fluoride and arsenate. The adsorbents were characterized by BET, SEM, XRD, FT-IR and XPS, and the analysis results demonstrated that the adsorption mechanism involved surface adsorption, ion exchange interaction and original LDH structure reconstruction by rehydration of mixed metal oxides and concomitant intercalation of fluoride and arsenate ions into the interlayer region.
A novel nanoadsorbent for the removal of heavy metal ions is reported.Cotton was first hydrolyzed to obtain cellulose nanocrystals（CNCs）.CNCs were then chemically modified with succinic anhydride to ...obtain SCNCs.The sodic nanoadsorbent（NaSCNCs） was further prepared by treatment of SCNCs with saturated NaHCO 3 aqueous solution.Batch experiments were carried out with SCNCs and NaSCNCs for the removal of Pb 2＋ and Cd 2＋.The effects of contact time,pH,initial adsorption concentration,coexisting ions and the regeneration performance were investigated.Kinetic studies showed that the adsorption equilibrium time of Pb 2＋ and Cd 2＋ was reached within 150 min on SCNCs and 5 min on NaSCNCs.The adsorption capacities of Pb 2＋ and Cd 2＋ on SCNCs and NaSCNCs increased with increasing pH.The adsorption isotherm was well fitted by the Langmuir model.The maximum adsorption capacities of SCNCs and NaSCNCs for Pb 2＋ and Cd 2＋ were 367.6 mg/g,259.7 mg/g and 465.1 mg/g,344.8 mg/g,respectively.SCNCs and NaSCNCs showed high selectivity and interference resistance from coexisting ions for the adsorption of Pb 2＋.NaSCNCs could be efficiently regenerated with a mild saturated NaCl solution with no loss of capacity after two recycles.The adsorption mechanisms of SCNCs and NaSCNCs were discussed.
Single atom catalysts (SACs) with metal
1
-N
x
sites have shown promising activity and selectivity in direct catalytic oxidation of benzene to phenol. The reaction pathway is considered to be ...involving two steps, including a H
2
O
2
molecule dissociated on the metal single site to form the (metal
1
-N
x
)=O active site, and followed by the dissociation of another H
2
O
2
on the other side of metal atom to form O=(metal
1
-N
x
)=O intermediate center, which is active for the adsorption of benzene molecule via the formation of a C-O bond to form phenol. In this manuscript, we report a Cu SAC with nitrogen and oxygen dual-coordination (Cu
1
-N
3
O
1
moiety) that doesn’t need the first H
2
O
2
activation process, as verified by both experimental and density function theory (DFT) calculations results. Compared with the counterpart nitrogen-coordinated Cu SAC (denoted as Cu
1
/NC), Cu SAC with nitrogen and oxygen dual-coordination (denoted as Cu
1
/NOC) exhibits 2.5 times higher turnover frequency (TOF) and 1.6 times higher utilization efficiency of H
2
O
2
. Particularly, the coordination number (CN) of Cu atom in Cu
1
/NOC maintains four even after H
2
O
2
treatment and reaction. Combining DFT calculations, the dynamic evolution of single atomic Cu with nitrogen and oxygen dual-coordination in hydroxylation of benzene is proposed. These findings provide an efficient route to improve the catalytic performance through regulating the coordination environments of SACs and demonstrate a new reaction mechanism in hydroxylation of benzene to phenol reaction.
Inter-site interaction in densely populated single-atom catalysts has been demonstrated to have a crucial role in regulating the electronic structure of metal atoms, and consequently their catalytic ...performances. We herein report a general and facile strategy for the synthesis of several densely populated single-atom catalysts. Taking cobalt as an example, we further produce a series of Co single-atom catalysts with varying loadings to investigate the influence of density on regulating the electronic structure and catalytic performance in alkene epoxidation with O
. Interestingly, the turnover frequency and mass-specific activity are significantly enhanced by 10 times and 30 times with increasing Co loading from 5.4 wt% to 21.2 wt% in trans-stilbene epoxidation, respectively. Further theoretical studies reveal that the electronic structure of densely populated Co atoms is altered through charge redistribution, resulting in less Bader charger and higher d-band center, which are demonstrated to be more beneficial for the activation of O
and trans-stilbene. The present study demonstrates a new finding about the site interaction in densely populated single-atom catalysts, shedding insight on how density affects the electronic structure and catalytic performance for alkene epoxidation.
D
etection of a trace amount of NO
2
at room temperature has very important applications in air quality monitoring, protection of human health and medical diagnose. However, the existing NO
2
sensors ...often suffer from low sensitivity when the concentration at the ppb-level. Here, we report a new kind of materials based on graphdiyne(GDY) for highly sensitive detection of ppb-level(ppb: part per billion) NO
2
at room temperature. After thermal treatment of the as-prepared GDY at 600 °C under argon atmosphere for 2 h(the obtained sample denoted as GDY-600), the prepared sensor with GDY-600 displays excellent sensitivity with a response value of 6.2% towards 250 ppb NO
2
at room temperature, which is better than most of reported sensing materials. In addition, the sensor exhibits significantly high selectivity to NO
2
against typical interfering gases including CO, CO
2
, NH
3
, H
2
, H
2
S and toluene. Moreover, the sensor shows remarkable stability after repetitive measurements. The superior sensing performance of GDY-600 can be ascribed to the highly
π
-conjugated structure with special acetylenic bonds and abundant oxygen-containing functional groups, which are all beneficial for the gas adsorption and redox reaction on the surface.
► A multi-amino-functionalized cellulose was synthesized for the removal of arsenic. ► The aminated cellulose has relative high nitrogen content. ► The adsorbent has a high adsorption capacity for ...As(V). ► The adsorption capacities of arsenic were less affected by coexisting ions. ► The adsorbent can be efficiently regenerated with NaOH solution.
A multi-amino adsorbent for arsenic adsorption was reported in this paper. Glycidyl methacrylate (GMA) was first grafted onto the surface of cotton cellulose using ceric ammonium nitrate (CAN) as the initiator, and then the introduced epoxy groups reacted with tetraethylenepentamine (TEPA) to obtain a multi-amino adsorbent. The adsorbent was characterized by FTIR, elemental analysis, 13C NMR and SEM. Then, the adsorption of arsenic for this adsorbent was investigated. The results showed that the GMA and TEPA were successfully grafted onto the surface of cellulose, and the modification improved the arsenic adsorption performances. Kinetic study suggested that the chemisorptions were the rate-limiting step. Among the three adsorption isotherm models used, Langmuir model fitted the experimental data best. The adsorption capacities of arsenic were less affected by coexisting ions. The adsorbent could be effectively regenerated for four cycles with 0.1mol/L NaOH solution.
PDF
