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The separation, transfer and recombination of charge often affect the rate of photocatalytic reduction of CO2. Schottky junctions can promote the rapid separation of space charge. Therefore, in this paper, Pd nanosheets were grown on the surface of DUT-67 by a hydrothermal method, and a Schottky junction was constructed between DUT-67 and Pd. Under the action of the Schottky junction, the CO yield of 0.3-Pd/DUT-67 reached 12.15 μmol/g/h, which was 17 times higher than that of DUT-67. Efficient charge transfer was demonstrated in photochemical experiments. The large specific surface area and the increased light utilization rate also contributed to the increase in the CO2 reduction efficiency. In addition, the mechanism of Pd/DUT-67 photocatalytic reduction of CO2 was proposed.

Zn–Atz, CaSt2 and TP synergistically stabilize PVC with high efficiency.

Construction of carbon nitride based 3D/0D intramolecular DA catalysts with enhanced optical and electrical properties for efficient photoreduction of CO2.

PVC materials grafted with ricinoleic acid-derived phosphate ester (PVC-AR-g, g = 1 ~ 4, where ricinoleic acid-derived phosphate ester grafts are abbreviated as AR) were prepared via a green and effective synthetic method. These materials were developed with the aim of overcoming the toxicity limits and environmental pollution issues caused by toxic dioctyl phthalate, which is traditionally used for plasticizing PVC materials. In this study, 3-aminopropyltri ethoxysilane (APTES) and AR, which contains phosphate ester groups, hydroxyl groups, linear alkyl groups, highly flexible long carbon chains and siloxane were introduced into the chains of PVC to efficiently plasticize PVC materials. Dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) were used to investigate the mechanical and plasticization properties, respectively, of the plasticized PVC films. Meanwhile, the leaching properties were also examined. The good plasticization behavior of the PVC-AR-g materials was attributed to the numerous hydroxyl, ester, linear siloxane and highly flexible long carbon chain present simultaneously in the branched segments, which formed strong hydrogen bonding and dipole–dipole interactions with the PVC main chains. Moreover, the PVC-AR-g materials showed improved thermal stability and outstanding anti-migration ability because of the covalent bonds between the PVC and graft intermediate.

Photocatalytic conversion of CO2 into hydrocarbon fuels is an ideal technology of mitigating greenhouse effect caused by excessive emission of CO2. However, the high recombination rate of electron-hole pairs and limited charge carriers transport speed constrained the catalytic performance of many semiconductor catalysts. In this contribution, a series of carbon nitride (g-CN) samples with intramolecular donor-acceptor (D-A) system were successfully prepared by introducing organic donor into their structures. Characterization results confirmed that carbazole was successful connected to the structure of g-CN via chemical bond. The formation of intramolecular D-A system greatly enlarged the light response region of g-CN-xDbc. In addition, a new charge transfer transition mode was formed in g-CN-0.01Dbc due to the incorporation carbazole, which enable it to use light with energy lower than the intrinsic absorption of g-CN. Meanwhile, the D-A structure led to the spatial separation of electrons and holes in g-CN-xDbc and significantly decreased the recombination rate of electron-hole pairs. The g-CN-0.01Dbc presented the best catalytic performance and the CO evolution rate was 9.6 times higher than that of g-CN. Moreover, the reaction was performed in water without any additive, which made it green and sustainable. DFT simulation confirmed the D-A structure and charge carrier migration direction in the prepared samples.

Photocatalytic technology provides a new strategy for mitigating energy crisis. The development of photocatalytic materials with high efficiency and stable visible light response has always been the direction of researchers in the field of photocatalysis. Graphite carbon nitride (g-CN) has attracted ever increasing attention in the field of photocatalysis due to its special characteristics (such as visible light response, high stability, and low cost). However, the low separation efficiency of photogenerated electrons and holes limits its catalytic activity. In this paper, a novel g-CN-based intramolecular donor–acceptor (D–A) system was prepared to promote the separation efficiency of light-induced charge carriers. The catalyst is prepared from g-CN and 1,2-dibromobenzene (Bz) through a simple calcination method. Characterization results confirmed that Bz was successfully introduced into the g-CN (g-CN-Bz (x)) framework. The formation of the D–A structure leads to the spatial separation of electrons and holes pairs, which significantly accelerates the separation efficiency of charge carriers. Moreover, the D–A structure plays an important role in adjusting the width of band gap, which can increase the light absorption capacity of the catalyst. The D–A system also leads to the formation of a built-in electric field, which significantly accelerates the migration speed of electrons. Among the prepared catalysts, g-CN-Bz (0.01) has the best photocatalytic CO2 reduction performance, and the evolution rate of CO is 5.2 times higher than that of CN (3.64 μmol g−1). In addition, the reaction is carried out in water without any sacrificial agent, which makes it green and environmentally friendly. The charge carrier excitation-recombination process between donor and acceptor, and photocatalytic reduction of CO2 to CO over the CN based DA composites.

Developing lauraldehyde-derived Mannich base grafted PVC materials (PVC-ML-g, g = 1, 2, 3, 4, where the lauraldehyde-derived Mannich base is abbreviated as ML) via clean and efficient strategies is an effective way to resolve the increasing diseases in humans and environmental pollution caused by toxic dioctyl phthalate (DOP) traditionally used to plasticize PVC materials. Thus, in this study, the lauraldehyde-derived Mannich base, which contains both phosphate ester groups and highly flexible long carbon chains, was grafted onto PVC chains to efficiently plasticize PVC materials. The PVC-ML-g materials displayed a lower glass transition temperature than pure PVC and were comparable to conventional DOP plasticized PVC. The good plasticization behavior in the PVC-ML-3 materials was due to the simultaneous introduction of more ester groups and mobile, unentangled longer alkyl chains into the structure of PVC, which decreased the molecular interactions between the PVC chains. Moreover, the PVC-ML-g materials showed improved thermal stability and outstanding anti-migration ability because of the covalent bonds between PVC and lauraldehyde-derived Mannich base grafts.

Carbon nitride (CN) has attracted increasing attention in the field of photocatalysis due to its special properties such as visible light response, high stability, and low cost. However, the low separation efficiency of photogenerated electrons and holes limits its catalytic activity. Herein, a novel kind of CN based intramolecular donor–acceptor (DA) system was prepared to facilitate the separation efficiency of photoinduced charge carriers. The catalysts were prepared from CN and 4,7-dibromo-2,1,3-benzothiadiazole (Dbbt) by a simple calcination method. A series of characterization results confirmed that Dbbt is successfully introduced into the framework of CN (CN–Dbbt-x). It was found that the formation of the DA structure leads to the spatial separation of electrons and holes which significantly accelerate the separation efficiency of charge carriers. Moreover, the DA structure played an important role in regulating the bandgap structure, which can increase the optical absorption ability of the catalysts. Also, the DA system led to the formation of a built-in electric field, which remarkably accelerates the migration speed of electrons. CN–Dbbt-0.01 displayed the best photocatalytic CO2 reduction performance, and the CO evolution rate was 4.9 times higher than that of CN. Moreover, the reaction was carried out in water without any sacrificial agents, which makes it a green and environmentally friendly reaction. DFT simulation and experimental results showed that Dbbt and CN respectively serve as the donor and acceptor in CN–Dbbt-0.01.

Defect structure is one of the crucial factors for enhancing the catalytic activities of photocatalysts. However, rational design and construction of defect structures in catalysts to meet the aim of enhancing photocatalytic performance in a simple and cost-effective way is still a challenge. In this contribution, we report a strategy to construct defect structures in graphitic carbon nitride (g-CN) by simple copolymerizing of urea with polyethyleneimine (PEI). Among the prepared catalysts, u-0.05PEI presents the best photocatalytic activity for CO2 reduction, with CO and CH4 yields of 32.86 and 1.68 μmol g-1 in 4 h, which is about 3.2 and 2.5 times higher than that of g-CN, respectively. Characterization results show that both C and N defects are formed in the newly prepared catalysts. The C defects on the surface of u-xPEI result in the formation of more amino groups which are beneficial for CO2 adsorption. Meanwhile, the N defects inside the samples lead to the generation of midgap states between the valance band and conduction band of u-xPEI. The midgap states greatly enlarge the light absorption extent, and enable the use of light with energy lower than the intrinsic absorption of g-CN in the photoreduction of CO2. As confirmed by DRS, EPR, PL analysis, the excellent catalytic activity of u-0.05PEI is mainly attributed to the remarkably improved light utilization efficiency and fast charge transfer. Moreover, the reaction is performed in water without any additive or organic solvent, which makes it environmentally friendly.

In this article, we successfully prepared the WO3/g-C3N4 (WO/CN) heterojunction photocatalyst with high photocatalytic CO2 reduction performance by the simple impregnation–calcination process. Tran...

Bimetal mixed MOFs of [CoZn][(BDC)(DABCO)0.5] (CZ-BDO), [CoNi][(BDC)(DABCO)0.5] (CN-BDO), and [NiZn][(BDC)(DABCO)0.5] (NZ-BDO) were prepared under solvothermal conditions and further employed as highly active accelerants for converting carbon dioxide into cyclic carbonates. The characteristics of the bimetal compounds were revealed via various techniques, including ICP-OES, XRD, FT-IR, Raman, XPS, SEM, EDS maps, N2 adsorption, TG-DTG, and CO2/NH3-TPD. The catalytic results revealed that CZ-BDO is superior to the other samples for obtaining a satisfactory chloropropene carbonate (CPC) yield. The excellent catalytic activity may be owing to the presence of a solid solution within the Co and Zn bimetal sample, which provides synergistic catalysis in the carbon dioxide cycloaddition. In addition, the synergistic catalysis was further confirmed by the NH3-TPD profiles, whereby the amount of CZ-BDO basic sites was obviously enhanced compared to the other samples. Furthermore, DFT calculations were also performed to reveal the synergistic catalysis between Co and Zn for the coupling reaction. Additionally, when the coupling reaction was carried out at 100 °C for 5 h in the presence of 0.5 wt% epichlorohydrin (ECH) as a catalyst at 3.0 MPa, 99.31% conversion of ECH and 97.05% yield of CPC were obtained over the optimal CZ-BDO sample. Moreover, the bimetal sample can also efficiently convert other epoxides into the corresponding cyclic carbonates.

CdIn2S4 micro-flower spheres modified with Au NPs and rGO have been designed for CO2 photoreduction. The photoproduction yields of CO and CH4 were 4 and 5 times higher than that of pure CdIn2S4, respectively. The photoproduction of CO and CH4 from the photocatalytic CO2 reduction process has been evidenced by 13C isotope tracer tests. Au NPs act as both the acceptor of photogenerated electrons and the donor of hot electrons at the CdIn2S4 and rGO interface. Three electron transfer channels: CdIn2S4 → Au → rGO, CdIn2S4 → Au, and Au → rGO, efficiently improve the transfer efficiency of electrons. Meanwhile, CO2 adsorption is largely improved, as confirmed by DFT calculations which indicate that the CO2 adsorption ability of the C sites from rGO has been enhanced by Au NPs. In situ FTIR has been carried out to research the CO2 photoreduction process. This work demonstrates the importance of efficient electron transfer and excellent CO2 adsorption in improving the efficiency of CO2 photoreduction, providing an inspiring concept for future advancement in this area.

Photocatalytic reduction of CO2 by semiconductors is of great significance in generating value-added fuels. Here, we construct a novel S–C–S heterojunction constituted of MoS2/SnS2/r-GO by a simple...

Photocatalytic technology provides a new strategy for the treatment of water pollution and energy crisis. Developing photocatalytic materials with high efficiency and stable visible light response has always been the direction of scientific researchers in the photocatalytic field. In this paper, we designed and prepared an efficient and stable rGO-modifited type-I Ag2S/g-C3N4 heterojunction photocatalyst (rGO/Ag2S/CN). The TEM (Transmission electron microscope) technology shows that the morphology of rGO/Ag2S/CN is a sandwich-like structure. UV–Vis DRS (UV–visible diffuse-reflectance spectrum) shows that the loading of Ag2S NPs and the modification of rGO effectively enhance the light response performance of nanocomposite materials in visible light. PL (Photoluminescence) and PEC (Photoelectrochemical) results prove that the photogenerated carriers transport and separation efficiency of rGO/Ag2S/CN have been improved. The photodegradation of RhB and the photoreduction of CO2 results confirmed that this ternary nanocomposite has great photocatalytic activity. The photodegradation efficiency of the RhB aqueous solution is about 98.5% after 30 min under the visible light irradiation. The photoreduction experiments showed that the yields of CO and CH4 are 178.05 μmol/g and 121.11 μmol/g, respectively after 8 h under the UV light irradiation. The results of cyclic photocatalytic experiments and the XRD pattern after those processes further revealed that the modification of rGO not only enhanced the photocatalytic performance of the nanocomposite photocatalyst, but also effectively improved the stability of Ag2S in the photocatalytic process. The possible photocatalytic reaction mechanisms were discussed in detail.

[(CH3)2NH2][Co3(BTC)(HCOO)4(H2O)]·H2O (Co-BTC) was synthesized under solvothermal conditions, further used as the precursor for the synthesis of 2-methylimidazole modified Co-BTC (2MeIm@Co-BTC-x). The characteristics of 2MeIm@Co-BTC-x were systematically characterized by various technologies including XRD, FESEM, FT-IR, XPS, N2-adsorption, TG-DTG and CO2/NH3-TPD. It was found that except for the crystal faces (0 1 1) and (− 1 0 2) corresponding to ZIF-67 and Co-BTC, a new crystal phase appeared at 12.22o for the modified Co-BTC, which may be attributed to the coordination between 2MeIm and unsaturated Co ions of Co-BTC. Interestingly, a new structure of hexagonal prisms together with hierarchical porous were also formed for the modified Co-BTC. Besides, when this composite was explored as a heterogeneous catalyst for catalytic conversion of carbon dioxide with epichlorohydrin (ECH) as probe, an obvious enhancement in catalytic activity was obtained compared with the fresh Co-BTC, suggesting that 2MeIm ligands within the modified Co-BTC played a great role on the coupling process. Furthermore, 97.21% of ECH conversion and 98.79% of chloropropene carbonate selectivity were gained over 2MeIm@Co-BTC-1.0 under optimal conditions (3.0 MPa, 90 °C, 5 h, 0.75 wt% catalyst of ECH). Additionally, only a slight decrease in catalytic activity was found after the optimal sample was reused three times. Finally, a mechanism for interpreting the coupling process of carbon dioxide cycloaddition with epoxide was proposed. One-pot catalytic conversion of CO2 into cyclic carbonate over 2-methylimidazole modified Co-BTC

The present work is aimed to investigate the catalytic activities of various Mn-based MOFs for carbon dioxide coupling with epoxides. The metal organic frameworks, [(CH3NH3][Mn(COOH)3] (MA-MnF), [(CH3CH2NH3][Mn(COOH)3] (EA-MnF), and [C3H5N2][Mn(COOH)3] (Im-MnF) were studied via several characterizations such as XRD, FT-IR, XPS, N2-adsorption, TG-DSC, CO2-adsorption and NH3-TPD. Interestingly, Im-MnF compound was observed to possess the highest catalytic activity among the studied compounds, which is associated not only with the amounts of basic sites, but also related to the nitrogen-containing species. 97.27% conversion of allyl-glycidyl ether (AGE, TOF: 36.78 h−1) and 97.66% selectivity to allyl-glycidyl carbonate (AGC) were obtained under the explored optimized conditions (100 °C, 15 bar, 6 h, 1.0 wt% of AGE). In addition, only a slight downward in catalytic activity was found when the sample was reused twice. Furthermore, coupling reactions of CO2 with various epoxides were also performed, of which, the yield of the cyclic carbonates followed the order: Epichlorohydrin > Allyl glycidyl ether > Styrene oxide > Cyclohexene oxide > Propylene oxide. Finally, a mechanism was proposed, which is in good agreement with the DFT calculation.

A highly active and stable Zn@C/HZSM-5 catalyst with active Zn species and intra-crystalline mesopores for glycerol to aromatics (GTA) was prepared by addition of a Zn@C porous carbon template derived from ZIF-8 into the zeolite synthesis process. XRD, UV-vis DRS, ICP-OES, XPS, TEM, BET, TPD, Py-IR, TGA, and TPO were used to elucidate the correlation between the physicochemical properties and the catalytic performances of the resultant catalysts. The introduced Zn species significantly improved the catalytic activity of Zn@C/HZSM-5 due to the formed Zn-Lewis acid (ZnOH+), which could enhance the aldol condensation and dehydrogenation–aromatization steps in the GTA reaction. Furthermore, the catalytic stability of Zn@C/HZSM-5 was also obviously improved for the simultaneous incorporation of intra-crystalline mesopores. Compared with the inherent micropores in bare HZSM-5, the introduced intra-crystalline mesopores in Zn@C/HZSM-5 not only promoted the diffusion of bulky molecules in zeolite channels and further slowed down coke formation, but also provided more mesopore volume to resist coke deposition, which finally slowed down the catalyst deactivation. Moreover, the Zn introduction methods had significant influences on the Zn state, acidic properties and subsequent catalytic performances of the Zn-modified catalysts. In Zn/HZSM-5(IM) prepared by impregnation, majority of Zn species existed as ZnOH+, and this only remarkably enhanced the aldol condensation step (liquid route), which only resulted in an obvious improvement of the C9 aromatic yield. Whereas in Zn/HZSM-5(PM) prepared by physical mixing, a small fraction of Zn species existed as ZnOH+, which only significantly enhanced the oligomerization step (gas route), leading to a large improvement in the BTX yield. In comparison, Zn@C/HZSM-5 possessed the appropriate ZnOH+ species, which could obviously enhance both the aldol condensation step and oligomerization step in GTA, thus resulting in a superior total aromatics yield for the simultaneous improvements of the BTX yield and C9 aromatic yield. Finally, nearly 100% carbon conversion and 54.7% total aromatics yield were obtained over the stable Zn@C/HZSM-5 with an 8.5 h lifetime due to the synergy between the Zn-Lewis acid (ZnOH+), intra-crystalline mesopores and HZSM-5 zeolite.

Zn2(C9H3O6)(C4H5N2)(C4H6N2)3 (Zn-BTC-2MeIm) was hydrothermally synthesized and employed as a highly efficient catalyst for CO2 coupling with epichlorohydrin (ECH). Various techniques such as XRD, FT-IR, XPS, TG-DTG, NH3/CO2-TPD were employed for characterizing the compound. Interestingly, TG profile illustrated the Zn-BTC-2MeIm was stable above 200 °C. The highest catalytic activity of 98.93% conversion of ECH and 98.32% selectivity to chloropropene carbonate was observed under the optimum conditions (100 °C, 120 mesh, 1000 rpm, 3.0 MPa, 6 h, 0.75 wt.% of ECH). Besides, the recyclability results exhibited Zn-BTC-2MeIm compound could be reused no less than three times with a slight reduction in its catalytic ability. Moreover, coupling results of CO2 with other epoxides showed this compound could efficiently convert various epoxides into cyclic carbonates. Finally, the investigation of the kinetic exhibited the law of CO2 coupling with ECH was coincident with the first order kinetic and the activation energy (Ea) was to be 113.38 kJ/mol.

Achieving high yields of 5-hydroxymethylfurfural (HMF) from carbohydrates remains a challenge today. With the aim of developing an efficient and inexpensive catalyst for the production of HMF, manganese phosphate (MnPO4) was used as the sole catalyst for the catalytic conversion of biomass-derived carbohydrates into HMF in the H2O/tetrahydrofuran (THF) biphasic reaction system. The effects of various factors, including reaction temperature, reaction time, system, and catalyst dosage on the conversion of carbohydrates to HMF were explored. An impressing HMF yield of 59% was achieved with glucose as a feedstock at 160 °C for 90 min. Meanwhile, up to 44% of HMF was also obtained with microcrystalline cellulose as a feedstock at 170 °C for 120 min. In addition, MnPO4 catalyst also displayed outstanding catalytic activities for the conversion of other biomass-derived carbohydrates including monosaccharides and disaccharides. Combined with the dissolution characteristics of the MnPO4, a possible catalytic mechanism for the conversion of carbohydrates into HMF catalyzed by MnPO4 was proposed. The catalytic approach proposed in this paper exhibited a promising potential for HMF production via optimizing the catalytic process.

Photocatalytic conversion of CO

Graphitic carbon nitride (g-C3N4) has been widely investigated in photocatalysis due to its excellent semiconductor properties. Though various strategies have been used to optimize the catalytic activity of g-C3N4, the influence of thickness itself on the photoelectric properties and CO2 reduction activity of g-C3N4 is still unclear. In this work, g-C3N4 with various thickness were successfully prepared by high-temperature exfoliation, and applied for the photoreduction of CO2. It was found that the conduction band (CB) of g-C3N4 samples shifted to negative position with decreasing thickness due to quantum confinement effect. Meanwhile, the more negative CB position endowed g-C3N4 with higher reduction potential that favors the reduction of CO2. Moreover, the specific surface area remarkably increased with higher exfoliation degree accompanied by more exposed active sites. The thinner g-C3N4 thickness also led to the exposure of ample edge amino groups that are beneficial for CO2 adsorption. Furthermore, the high-temperature exfoliation were also benefit for optimizing the crystal structure of g-C3N4 and reducing defect structures, which significantly inhibits the recombination of electron-hole pairs and facilitates the migration of charge carriers. These merits of g-C3N4 with high exfoliation degree synergistically catalyze the photoreduction of CO2 with high efficiency.

In the present work, two dual-linker metal-organic frameworks (MOFs) were prepared with metal salts, terephthalic acid and 4, 4′-bipyridine as precursors, and subsequently used for preparing cyclic carbonates from carbon dioxide and epoxides. These two MOFs were characterized by a number of techniques. The two MOFs prepared showed superior catalytic performance under solventless and co-catalyst-free conditions. In this sense, Co(tp)(bpy) achieved epichlorohydrin (ECH) conversions as high as 95.75% and chloropropylene carbonate (CPC) yields of 94.18% under optimal reaction conditions. The high activity of Co(tp)(bpy) was attributed to the co-existence of Lewis acidic and basic active sites on the catalyst derived from incompletely coordinated metal cations and uncoordinated pyridine groups, respectively. In addition, Co(tp)(bpy) maintained this high catalytic performance after five consecutive reaction cycles. A possible reaction mechanism was proposed based on the experimental results.

Bimetal mixed MOFs of [CoZn][(BDC)(DABCO)0.5] (CZ-BDO), [CoNi][(BDC)(DABCO)0.5] (CN-BDO), and [NiZn][(BDC)(DABCO)0.5] (NZ-BDO) were prepared under solvothermal conditions and further employed as highly active accelerants for converting carbon dioxide into cyclic carbonates. The characteristics of the bimetal compounds were revealed via various techniques, including ICP-OES, XRD, FT-IR, Raman, XPS, SEM, EDS maps, N2 adsorption, TG-DTG, and CO2/NH3-TPD. The catalytic results revealed that CZ-BDO is superior to the other samples for obtaining a satisfactory chloropropene carbonate (CPC) yield. The excellent catalytic activity may be owing to the presence of a solid solution within the Co and Zn bimetal sample, which provides synergistic catalysis in the carbon dioxide cycloaddition. In addition, the synergistic catalysis was further confirmed by the NH3-TPD profiles, whereby the amount of CZ-BDO basic sites was obviously enhanced compared to the other samples. Furthermore, DFT calculations were also performed to reveal the synergistic catalysis between Co and Zn for the coupling reaction. Additionally, when the coupling reaction was carried out at 100 °C for 5 h in the presence of 0.5 wt% epichlorohydrin (ECH) as a catalyst at 3.0 MPa, 99.31% conversion of ECH and 97.05% yield of CPC were obtained over the optimal CZ-BDO sample. Moreover, the bimetal sample can also efficiently convert other epoxides into the corresponding cyclic carbonates.

Photocatalytic reduction of CO

The present work aimed to investigate the law of the conversion of glycerol with diethyl carbonate (DEC) over the highly efficient Ce–NiO catalyst prepared by co-precipitation method. The thermodynamic and kinetics parameters of this reaction for glycerol carbonate synthesis were studied. The reaction equilibrium constants were investigated experimentally in the temperature region of 338–358 K, and the standard molar properties (at 298 K) were obtained (△H0= 115.71 kJ mol−1, △G0= 13.523 kJ mol−1, △S0= 0.343 kJ mol−1). Effects of various experimental conditions including stirring speed, reaction temperature, catalyst amount, reactant mole ratio on the reaction kinetics were also studied. Different order kinetic equations were used to simulate law of the transesterification process. The result shows a three-order equation of glycerol (two orders) and DEC (one order) was more appropriate to interpret the law of glycerol transesterification with diethyl carbonate. The activation energy of this reaction was obtained with 87.90 kJ mol−1. Finally, the microstructure and physicochemical properties of the Ce–NiO samples were studied by XRD, SEM, TEM, and CO2-TPD. One-pot catalytic conversion of glycerol into glycerol carbonate over Ce–NiO catalyst.

A series of Ce1-xCdxO mixed oxide catalysts prepared by co-precipitation method were tested for synthesis of glycerol carbonate (GC) from glycerol and diethyl carbonate (DEC). The microstructural and physicochemical properties of the bimetal catalysts were characterized by XRD, SEM, TEM, XPS, CO2-TPD, N2-adsorption, TG-DSC and 1H NMR. The results show that the spherical particles of CdO were uniformly dispersed on the surface of lamellar CeO2. Besides, a noticeable increase was observed in the moderate basic sites concentration, because more oxygen atoms were adsorbed on the bimetal sample surface which was attributed to Ce4+ doped into CdO lattice. The Ce0.7Cd0.3O sample annealed at 500 °C was observed with the highest catalytic activity. 96.84% of glycerol conversion and 100% selectivity to GC were obtained over this catalyst under the optimized conditions (5 wt.% catalyst of glycerol, 90 °C, 180 min, glycerol/DEC molar ratio of 1:3). Besides, it was found that the conversion of glycerol carbonate was synergistically accelerated by the moderate and strong basic sites.

As important glycerol derivatives, glycerol carbonate (GC) and glycidol (GD) have attracted increasing attention in recent years. In the present work, a series of new solid base catalysts were developed to catalyze the conversion of glycerol to afford GC and GD. These catalysts were prepared by loading KF on the porous La-Zr solid base catalyst and characterized using a series of methods. A large number of various basic sites were generated upon loading KF onto the La-Zr-600 support. The weak basic sites were assigned to the surface hydroxyl groups produced during the formation of LaOF, while the strong and super basic sites were related to the Lewis base produced due to the interaction between KF and the La-Zr-600 support. A glycerol conversion of 91.77% and a GC selectivity of 99% were obtained over 0.3KF/La-Zr, which displayed the best catalytic performance under the optimal reaction conditions. The excellent activity of these catalysts was attributed to the presence of the strong and super basic sites, which favor the transesterification of glycerol with dimethyl carbonate. The production of GD from GC decarbonylation was unfeasible at low temperature using the newly developed catalysts. A plausible reaction mechanism has been proposed based on the experimental results and characterization.

We present here a study of the production of furfural from xylose and wheat straw using the chromium phosphate (CrPO4) with Lewis and Bronsted acidity as a highly efficient catalyst in the water/tetrahydrofuran (THF) biphasic system. The effects of various reaction parameters including reaction temperature, reaction time, system, and catalyst dosage were explored to evaluate the product yield. Under CrPO4 catalysis, an excellent furfural yield could reach 88% from the xylose at 160 °C for 60 min. Meanwhile, 67% furfural and 32% 5‑hydroxymethylfurfura (HMF) were simultaneously achieved from wheat straw at 180 °C for 90 min. Mechanistic studies suggested that the perfect catalytic activity of CrPO4 was due to its inherent bifunctional catalysis activity. It was found that the CrPO4 was easily to be recovered and a great catalytic activity was available after four cycles, which not only contributed to a sustainably reduced energy consumption on catalyst recovery, but also reduced the concerns associated with toxic chromium element.

A highly shape-selective H[Zn,Al]ZSM-5/SiO2 composite catalyst was prepared by direct incorporating Zn species via isomorphous substitution into the zeolite framework and subsequent SiO2 deposition on zeolite surface. Its catalytic performance in methanol to aromatics (MTA) was compared with Zn/HZSM-5/SiO2 prepared by impregnation of Zn species and subsequent SiO2 deposition. The textural properties and acidic properties as well as the subsequent catalytic performances of the resultant catalysts in MTA reaction were obviously influenced by the introduction method of Zn species. H[Zn,Al]ZSM-5/SiO2 prepared by isomorphous substitution contained more inter-crystalline voids, which provided much space to resist deposition of coke and avoided quick blockage of micropore entrances. In contrast, Zn/HZSM-5/SiO2 prepared by impregnation contained sub-nanometric ZnO clusters at the pore entrances, which might restrict large molecule products diffusion and deteriorated the catalyst deactivation. Moreover, the sum of strong and medium acid sites in H[Zn,Al]ZSM-5/SiO2 was more than that in Zn/HZSM-5/SiO2, which meant there were more active sites for cyclization and aromatization steps in MTA reaction in the former. As a result, the lifetime of H[Zn,Al]ZSM-5/SiO2 was almost twice that of Zn/HZSM-5/SiO2. In addition, the enhancement in catalytic activity by Zn introduction and the improvement in para-selectivity in xylene by SiO2 deposition were also studied. Finally, nearly 100% methanol conversion, 95.6% para-selectivity in xylene and 18.2% para-xylene yield were simultaneously obtained over the stable H[Zn,Al]ZSM-5/SiO2 (with 24 h lifetime) in MTA reaction.

A zeolitic imidazolate framework material (ZIF-8) was prepared from stoichiometric zinc nitrate and 2-methylimidazole at room temperature in the presence of ammonium hydroxide. The material was characterized by a series of methods and used as a thermal stabilizer for poly (vinyl chloride) (PVC) film. The properties of the stabilized PVC were investigated using Congo red test, thermal aging test and thermal gravimetric analysis (TGA). Compared with the stabilizing efficiencies of some commonly-used reference stabilizers (e.g. CaSt 2 and ZnSt 2 ), the stabilizers including ZIF-8 [such as CaSt 2 /ZnSt 2 /ZIF-8 and ZnSt 2 /ZIF-8] exhibit better initial color stability and long-term thermal stability for PVC. The static thermal stability time was significantly prolonged from 33.13 min for PVC/CaSt 2 /ZnSt 2 to about 128.92 min for PVC/ZIF-8/ZnSt 2 at 180 °C. The superior performance is attributed to the synergistic effect of ZIF-8 and ZnSt 2 . The imidazole ligand of ZIF-8 can strongly absorb hydrogen chloride and form complexes with ZnCl 2 generated from ZnSt 2 in the PVC degradation process. In addition, the double bonds of ZIF-8 may help to form stable compounds with polyenes to further retard the PVC degradation. Dynamic mechanical and tensile properties of the PVC films were also studied.

In the present work, melem based catalysts with various functional groups were developed by the modification of melem oligomers and tested for the chemical fixation of CO2 into cyclic carbonates. The characterization of these catalysts, by means of SEM, BET, XRD, IR, TG and XPS, verified the functional groups are successfully incorporated into the melem oligomers structure. Activity test demonstrated that melem oligomers grafted with both hydroxyl and quaternary ammonium groups (MOSB) presented the best catalytic performance. A propylene oxide conversion of 97.4% and propylene carbonate selectivity of 97.8% were obtained under the optimal reaction conditions. The simultaneous existence of edge defects, hydroxyl groups and quaternary ammonium groups in the structure of the catalyst are responsible for the high performance of MOSB. These three groups synergistically catalyzed the chemical fixation of CO2 to proceed with high efficiency. Moreover, moderate yield could still be obtained after five cycles. A possible reaction mechanism was proposed for the cycloaddition of CO2 with epoxides to form cyclic carbonates.

[(CH3)2NH2][M3(BTC)(HCOO)4(H2O)].H2O (M–BTC, M = Mn, Ni, Co) were prepared under hydrothermal conditions and used as highly efficient catalysts for cycloaddition of CO2 with epichlorohydrin (ECH). The microstructure and physicochemical properties of the compounds were determined by PXRD, FT-IR, XPS, N2-adsorption, TG–DSC, NH3–TPD and CO2–TPD. 98.01% conversion of ECH and 96.05% selectivity to chloropropene carbonate was obtained over the Mn–BTC under the optimized reaction conditions (105 °C, 3.0 MPa, 9 h, 1.5 wt.% of ECH). Besides, the recyclability result exhibited the Mn–BTC compound can be utilized as least three times with a slight reduction in its catalytic ability. In addition, cycloaddition of CO2 with other epoxides and DFT calculation were also performed. The result exhibited the yield followed the order: ECH > 1, 2-epoxybutane > propene oxide > Allyl glycidyl ether, which was mainly determined by the energy of reaction.

Hydroxyl and nitrogen rich group-containing tung-oil-based ester (GEHTMA-1, GEHTMA-2, GEHTMA-3 and GEHTMA-4) plasticizers were successfully synthesized from tung-maleic anhydride and utilized to plasticize poly(vinyl chloride) (PVC). In comparison to petroleum-based plasticizers (e.g. DOTP), the mechanical test shows that bio-based GEHTMA-3 displays better mechanical properties, which means that GEHTMA-3 could endow PVC resins with well-balanced properties of flexibility and strength. With the addition of GEHTMA-3 into DOTP, PVC/DOTP/GEHTMA-3 exhibits better mechanical properties, plasticization performance, migration resistance and thermal stability compared with the PVC/DOTP system. Above all, PVC/28DOTP/12GEHTMA-3 shows the highest tensile strength and elongation of 32.19 MPa and 345.20%, respectively. PVC/32DOTP/8GEHTMA-3 displays the best thermal stability. The superior performance is attributed to the molecular interaction of GEHTMA-3 and DOTP with PVC. The interaction originates from the simultaneous introduction of hydroxyl, epoxy, benzene ring, ester and nitrogen rich groups into GEHTMA-3 structures. Besides, GEHTMA-3 presented good miscibility with PVC resins, particularly when a mixture of DOTP and GEHTMA-3 was used. In addition, possible plasticization of the PVC/DOTP/GEHTMA-3 system was presented.

In this study, different acid-modified Co–Al catalysts were prepared and employed for glycerol hydrogenolysis by the addition of B, Ce, Zr, and heteropolyacids (HSiW, HPW, HPMo) to Co–Al catalysts. The catalysts prepared in this work were thoroughly examined by various characterization methods such as BET, ICP, SEM, H2 chemisorption, TEM, XRD, H2-TPR, NH3-TPD, XPS, and FTIR. The results showed an increase in the acid strength and Co dispersion on the catalytic surface for the modified Co–Al catalysts. This facilitated the conversion of glycerol. When ethanol was used as a solvent, the selectivity of 1,2-propanediol (1,2-PDO) by the acid-modified Co–Al catalysts decreased slightly, attributable to the enhanced etherification activity of glycerol with ethanol. However, when water was used as a solvent, the modified Co–Al catalyst with the B, Ce, and Zr species increased the selectivity of 1,2-PDO. Addition of heteropolyacids to the Co–Al catalyst enhanced the selectivity of 1,3-propanediol (1,3-PDO) as comp...

Hydroxyl and nitrogen rich groups-containing tung-oil-based Ca/Zn (Ca-HTMA-1, Zn-HTMA-1, Ca-HTMA-2 and Zn-HTMA-2) and polyol thermal stabilizers (HTMA-1 and HTMA-2) were successfully synthesized from tung-maleic anhydride (TMA). The thermal stability tests show that CaSt 2 /Zn-HTMA-2/HTMA-2 displays the best thermal stability for poly(vinyl chloride) (PVC). The superior performance is attributed to the synergistic effect of CaSt 2 , Zn-HTMA-2 and HTMA-2, which is originated from the simultaneous introduction of hydroxyl and nitrogen rich groups into the Zn-HTMA-2 and HTMA-2 structures. The nitrogen rich groups can absorb the hydrogen chloride released during the PVC degradation process, which helps to inhibit the “autocatalytic effect” and lead to better long term thermal stability. Besides, hydroxyl groups can form stable chelates with ZnCl 2 to avoid “zinc-burning” during the later PVC degradation. Besides the better stabilization performance, CaSt 2 /Zn-HTMA-2/HTMA-2 also displays comparable plasticization performance for PVC compared with other stabilizers. A possible stabilizing mechanism of PVC/CaSt 2 /Zn-HTMA-2/HTMA-2 system was presented.

Construction of multi-interface contact step-scheme (S-scheme) photocatalyst is a promising pathway to achieve high-electron transfer efficiency for photocatalytic CO2 reduction. In this paper, g-C3N4 nanosheets were selected as the main photocatalyst, rod-like CeO2 (R-CeO2) with unique Ce4+→Ce3+ conversion property and rGO were loaded on the g-C3N4 surface to construct 2D-1D-2D sandwich photocatalyst. The yields of CO and CH4 were about 63.18 and 32.67 μmol/g after 4 h when the rGO/R-CeO2/g-C3N4 was used as catalyst, which were about 4 and 6 times higher than that of pure CN, respectively. Cyclic experiments proved that the composite had excellent photocatalytic and material stability. Photoelectrochemical tests showed that the construction of S-scheme electron transfer model and the introduction of rGO can great enhance the electron transmission and separation of photogenerated electron-hole pairs. CO2 adsorption test identified that the loading of R-CeO2 and rGO obviously enhanced the CO2 adsorption ability of pure g-C3N4. Density functional theory (DFT) calculations used to analyze the electron transfer path and the formation of the build-in electric field at the semiconductor interface. In-situ FTIR and 13CO2 element-tracer detection carried out to research the process of CO2 photoreduction. A possible multi-interface contact S-scheme electron transfer mechanism for enhanced CO2 photoreduction activity has been discussed.