Mechanochemical Synthesis of New Praziquantel Cocrystals: Solid-State Characterization and Solubility

New cocrystals of praziquantel with suberic, 3-hydroxybenzoic, benzene-1,2,4,5-tetracarboxylic, trimesic, and 5-hydroxyisophthalic acids were obtained through ball milling experiments. The optimal conditions for the milling process were chosen by changing the solvent volume and the mechanical action time. Supramolecular interactions in the new cocrystals are detailed based on single-crystal X-ray diffraction analysis, confirming the expected formation of hydrogen bonds between the praziquantel carbonyl group and the carboxyl (or hydroxyl) moieties of the coformers. Different structural characterization techniques were performed for all samples, but the praziquantel:suberic acid cocrystal includes a wider range of investigations such as thermal analysis, infrared and X-ray photoelectron spectroscopies, and SEM microscopy. The stability for up to five months was established by keeping it under extreme conditions of temperature and humidity. Solubility studies were carried out for all the new forms disclosed herein and compared with the promising cocrystals previously reported with salicylic, 4-aminosalicylic, vanillic, and oxalic acids. HPLC analyses revealed a higher solubility for most of the new cocrystal forms, as compared to pure praziquantel.

Mechanism of NCNTs Growth on Foamed Nickel and Thus-Prepared PS Hydrogenation High-Performance Carrier NCNTs@FN

Traditional heterogeneous catalysts are affected in the catalytic hydrogenation of PS by the scale effect, viscosity effect, adhesion effect, and conformational effect, resulting in poor activity and stability. Monolithic Pd-CNTs@FN catalysts could eliminate or weaken the impact of these negative effects. We grew nitrogen-doped carbon nanotubes (NCNTs) on monolithic-foamed nickel (FN) and investigate their growth mechanism. Meanwhile, the feasibility of using the NCNTs@FN carrier for PS hydrogenation reaction was also verified. The growth of NCNTs on FN can be divided into 3 stages: initial growth stage, stable growth stage, and supersaturation stage. Finally, a three-layer structure of NCNT layer, dense carbon layer, and FN skeleton is formed. Two types of structures, nickel-doped carbon nanotubes (NiCNTs) and C-Ni alloy, are formed by combining C and Ni, while four nitrogen-doped structures, NPD, NPR, NG, and NO, are formed by C and N. The prepared carrier exhibited an extremely outstanding specific surface area (2.829 × 106 cm2/g) and strength (no NCNTs falling off after 24 h 500 rpm agitation), as well as high catalytic activity for PS hydrogenation after loaded with Pd (2.13 ± 0.95 nm), with a TOF of up to 27.6 gPS/(gPd•h). After 8 repetitions of the catalyst, there was no significant decrease in activity. This proves the excellent performance of Pd-NCNTs@FN in polymer hydrogenation reactions, laying a solid foundation for further research on the mechanism of NCNTs promoting PS hydrogenation and regulating the growth of NCNTs.

Pyridinic nitrogen dominated doping on Pd/carbon catalysts for enhanced hydrogenation performance

The hydrogenation of 4-carboxylbenzaldehyde over Pd catalysts is a crucial process during the production of pure terephthalic acid. Herein, ZIF-8 derived carbon materials (NC) with adjustable N types were synthesized and used as the supports of Pd catalysts. Pd supported on NC with 50.5% of pyridinic N exhibited best hydrogenation activity with a TOF value of 4.1 min-1. The microstructures of NC support and electronic structures of Pd in Pd/NC were investigated by techniques such as XRD, N2 physisorption, XPS, H2-O2 titration and TEM. The nitrogen species in CN surface not only can adjust chemical state and dispersion of Pd nanoparticles (NPs), but also promote the adsorption and activation capability of H2 molecular. Besides, the ratio of Pd0/Pd2+ and Pd dispersion were closely correlated with pyridinic nitrogen content. The improvement in hydrogenation activity and stability of Pd/CN catalyst in relative to Pd/C were ascribed to the synergistic effect of pyridinic nitrogen and active site Pd0.

Highly Active and Stable Fe/Co/N Co-doped Carbon-Anchored Pd Nanoparticles for Oxygen Reduction Reaction

A highly active and stable electrocatalyst based on Pd nanoparticles anchored on zeolitic imidazolate framework-derived Fe/Co/N co-doped carbon (Pd/FeCoNC) is prepared. FeCo alloy nanoparticles are uniformly dispersed and wrapped by graphene layers in Fe/Co/N co-doped carbon (FeCoNC). The influences of carbonization temperature on the structure and catalytic activity of FeCoNC toward oxygen reduction reaction (ORR) are investigated. The FeCoNC prepared at 800 °C (FeCoNC-800) has a favorable ORR catalytic activity as a consequence of the synergistic effect of Fe/Co/N co-doping and hierarchical pore structures of coexisting micropores and mesopores. Pyridinic N in FeCoNC is a preferential adsorption site for anchoring Pd nanoparticles. Pd/FeCoNC exhibits both superior activity and durability to 40 wt % Pt/C at the same level of metallic mass loading, which shows a 44 mV higher half-wave potential (0.88 V) than Pt/C and a 91% remaining current of the initial after 10,000 s. The Fe/Co/N co-doping and hierarchical pores of FeCoNC contribute a large diffusion current, and the introduction of Pd realizes more positive onset and half-wave potentials. This work provides an easy way for preparing low-cost and high-efficiency catalysts for ORR.

MOF-derived Ru@ZIF-8 catalyst with the extremely low metal Ru loading for selective hydrogenolysis of C–O bonds in lignin model compounds under mild conditions

A MOF-derived Ru@ZIF-8 catalyst with extremely low Ru loading effectively cleaved the C–O bonds of lignin model compounds under mild conditions.

Nitrogen doped carbon for Pd-catalyzed hydropurification of crude terephthalic acid: roles of nitrogen species

The purification of crude terephthalic acid was performed by the hydrogenation of 4-carboxybenzaldehyde (4-CBA) over activated carbon (AC) supported Pd catalysts in industry. However, traditional Pd/AC catalysts usually suffer from low hydrogenation activity and poor thermal stability. Herein, nitrogen was incorporated into AC via a simple hydrothermal treatment of AC with urea as the nitrogen resource. The N doped AC contained pyridinic N, pyrrolic N, graphitic N and oxidized N. Wide characterizations revealed that N doping not only effectively improved the dispersion of Pd NPs but also increased the proportion of Pd⁰. In addition, N doping also enhanced the dissociative adsorption capacity of molecular hydrogen. More importantly, the resistance to sintering of Pd NPs was efficiently suppressed after N doping. As a result, N doped AC supported Pd showed both higher activity and better thermal stability than the N-free one.

Pd on N doped activated carbon exhibited increased activity and stability in 4-CBA hydrogenation relative to Pd catalysts without N doping. Higher dispersion of Pd⁰ and facile activation of H₂ accounted for the better activity of Pd/NC.

Electrocatalytic hydrogenation of benzoic acids in a proton-exchange membrane reactor

The highly efficient chemoselective electrocatalytic hydrogenation of benzoic acids (BAs) to cyclohexanecarboxylic acids (CCAs) was carried out in a proton-exchange membrane reactor under mild conditions without hydrogenation of the carboxyl group. Among the investigated catalysts, the PtRu alloy catalyst was found to be the most suitable for achieving high current efficiencies for production of CCAs. An electrochemical spillover mechanism on the PtRu alloy catalyst was also proposed.

A novel Co-based MOF/Pd composite: synergy of charge-transfer towards the electrocatalytic oxygen evolution reaction

A novel Co-based MOF/Pd composite (LEEL-037/Pd-C) presented an electronic transference (Co 3d orbital → linkers π* → Pd 5S orbital) promoting an enhanced OH⁻ adsorption, thus improving the oxygen evolution reaction (OER) in alkaline medium.

Bimetallic RuPd nanoparticles in ionic liquids: selective catalysts for the hydrogenation of aromatic compounds

Bimetallic RuPd nanoparticles are effective catalysts for the hydrogenation of aromatic compounds and the activity and selectivity depend on the Ru : Pd ratio.

Microcalorimetric adsorption and infrared spectroscopic studies of supported Pd, Ru and Pd–Ru catalysts for the hydrogenation of aromatic rings with carboxyl groups

Pd–Ru/SiO₂ showed special surface chemical properties that were totally different from those of Pd/SiO₂ and Ru/SiO₂ and exhibited high activity and selectivity for the hydrogenation of benzoic acid to cyclohexanecarboxylic acid.

Complete dechlorination of lindane over N-doped porous carbon supported Pd catalyst at room temperature and atmospheric pressure

Transfer hydrogenation is highly effective for dechlorinating priority organic pollutants in wastewater. Lindane could be completely dechlorinated at room temperature and atmospheric pressure via transfer hydrogenation, in which Pd (3.1 wt%) supported on chitosan-derived porous carbon (3.1Pd@A600) and formic acid (FA) were used as catalyst and hydrogen source, respectively. Favorable catalytic activity of 3.1Pd@A600 is attributed to pyridinic N of the support that allowed Pd nanoparticles to be well-dispersed in the solid and to pyridinic N-Pd interactions that enhanced FA decomposition over that observed for commercial carbon supported Pd catalyst (5Pd@AC). In the reaction system containing 3.1Pd@A600 and FA, 99.7% lindane conversion and 100% dechlorination efficiency could be achieved at 25 °C and atmospheric pressure within 60 min. Benzene and cyclohexane were identified as end-products of lindane dechlorination. The transfer hydrogenation strategy developed in this study has wide application to chlorinated organic pollutants contained in actual waste streams.

Ru/g-C3N4 as an efficient catalyst for selective hydrogenation of aromatic diamines to alicyclic diamines

A series of Ru/g-C3N4 materials with highly dispersed Ru were firstly prepared by an ultrasonic impregnation method using carbon nitride as a support. The catalysts were characterized by various techniques including BET and elemental analysis, ICP-AES, XPS, XRD, CO2-TPD and TEM. The results demonstrated that Ru/g-C3N4 materials with a mesoporous structure and highly dispersed Ru were successfully prepared. The chemo-selective hydrogenation of p-phenylenediamine (PPDA) to 1,4-cyclohexanediamine (CHDA) over Ru/g-C3N4 as a model reaction was investigated in detail. PPDA conversion of 100% with a CHDA selectivity of more than 86% could be achieved under mild conditions. It can be inferred that the carbon nitride support possessed abundant basic sites and the Ru/g-C3N4-T catalysts provided suitable basicity for the aromatic ring hydrogenation. Compared to the N-free Ru/C catalyst, the involvement of nitrogen species in Ru/g-C3N4 remarkably improved the catalytic performance. In addition, the recyclability of the catalyst demonstrated that the aggregation of Ru nanoparticles was responsible for the decrease of the catalytic activity. Furthermore, this strategy also could be expanded to the selective hydrogenation of other aromatic diamines to alicyclic diamines.

N-doped porous carbon supported Ni catalysts derived from modified Ni-MOF-74 for highly effective and selective catalytic hydrodechlorination of 1,2-dichloroethane to ethylene

Metal-organic frameworks (MOFs) have received significant attention as promising precursors or sacrificial templates in the preparation of porous carbon supported catalysts. In this study, N-doped porous carbon supported Ni catalysts (denoted as Ni/NC) were prepared using furfuryl alcohol (FA) loaded Ni-MOF-74 as the precursor followed by NH₄OH treatment and pyrolysis under N₂ atmosphere. For comparison purpose, Ni catalysts supported on porous carbon (denoted as Ni/C) were also prepared by direct pyrolysis of Ni-MOF-74. The selective gas phase catalytic hydrodechlorination of 1,2-dichloroethane to ethylene was carried out to evaluate the catalytic performances of the catalysts. It was found that for Ni catalysts prepared at the same pyrolysis temperature, Ni particle sizes in Ni/NC catalysts were significantly smaller (20-40% smaller) than that of Ni/C. This reflected that pre-modification of Ni-MOF-74 using FA and NH₄OH could effectively increase Ni dispersion in Ni catalysts derived from Ni-MOF-74. Moreover, Ni/NC had a markedly stronger ability to form spillover H₂ owing to the enhanced metal-support interactions by N-doping. Accordingly, Ni/NC catalysts exhibited much higher catalytic activities than Ni/C catalysts. The turnover frequencies of Ni/NC catalysts were found to be 1.22-1.65 times higher than Ni/C catalysts. Increasing pyrolysis temperature led to decreased catalytic activities of both Ni/C and Ni/NC catalysts, due to the aggregation of Ni particles at higher treatment temperature. The findings from this study demonstrate that the MOF-mediated synthesis method offers a promising way to prepare Ni-based catalysts for catalytic hydrodechlorination of chlorinated hydrocarbons.

Pt/Al2O3 coated with N-doped carbon as a highly selective and stable catalyst for catalytic hydrogenation of p-chloronitrobenzene to p-chloroaniline

Selective catalytic hydrogenation of p-chloronitrobenzene on Pt-based catalysts is a green and high-efficient way for p-chloroaniline production. However, supported monometallic Pt catalysts often exhibit undesirable p-chloroaniline selectivity. We herein reported supported Pt catalysts with N-doped carbon (NC) as an overcoating (Pt/Al₂O₃@NC) to overcome the disadvantage. Three Pt/Al₂O₃@NC catalysts with different NC coating amounts were prepared by in situ carbonization of an ionic liquid. For comparison, Al₂O₃ coated by NC and Pt/Al₂O₃ coated by SiO₂ were also prepared. A combination characterization confirmed that the NC overcoating was successfully formed on Pt/Al₂O₃ surface and Pt particles were completely coated by NC layers when ion liquid amount increased to 25 μl per g catalyst. Due to the intimate contact of NC layers and Pt particles Pt-NC heterojunctions were effectively formed on the catalyst surface. For the catalytic hydrogenation of p-chloronitrobenzene, Pt/Al₂O₃@NC with 25 μl ionic liquid as the NC precursor exhibited 100% selectivity to p-chloroaniline at 100% conversion of p-chloronitrobenzene. A lower ionic liquid amount led to decreased selectivity to p-chloroaniline. Furthermore, no deactivation was observed on Pt/Al₂O₃@NC during 5 catalytic cycles. The findings in the study demonstrate that coating noble metal catalysts by N-doped carbon is a promising method to enhance the selectivity and stability for catalytic hydrogenation of p-chloronitrobenzene.

Pt/Al₂O₃ with N-doped carbon overcoating exhibited 100% selectivity to p-chloroaniline for catalytic hydrogenation of p-chloronitrobenzene.

Pd nanoparticles confined in mesoporous N-doped carbon silica supports: a synergistic effect between catalyst and support

Palladium nanoparticles of similar size were deposited on different supports, layers of carbon materials (with and without nitrogen doping) on the surface of a MCF (mesocellular foam) silica.

Spatial acid–base–Pd triple-sites of a hierarchical core–shell structure for three-step tandem reaction

We present a hierarchical single catalyst with spatial acid–base–Pd triple-sites showing high catalytic activity and stability for the three-step D–K–H tandem reaction.

Nitrogen-Doped Carbon Cages Encapsulating CuZn Alloy for Enhanced CO2 Reduction

CuZn alloy, regarded as the active sites, shows excellent catalytic activity for the reverse water gas shift reaction, whereas the incorporation of N atoms, especially pyridinic N, can greatly improve its catalytic properties because of the strong promotion capacity for adsorption and activation of CO₂ molecules. Herein, the synthesis strategy involving Cu-doped Zn-based metal-organic frameworks is utilized to prepare CuZn alloy coated in an N-doped carbon shell. The excellent catalytic ability for CO₂ transformation originates from the synergistic catalytic effect between CuZn alloy and pyridinic N. The strong adsorption and activation capacity for CO₂ of pyridinic N is ascribed to the lone pair of electrons on the N atom and the high electron density in its vicinity.

Synergistic Activation of Palladium Nanoparticles by Polyoxometalate-Attached Melem for Boosting Formic Acid Dehydrogenation Efficiency

Pd nanoparticles (NPs) anchored on a phosphotungstic acid attached melem porous hybrid (PW/melem) were prepared by hybridization of phosphotungstic acid Pd salt and melem, followed by chemical reduction. PW/melem was demonstrated to be an outstanding support that can stabilize and disperse small Pd NPs (2 nm), and significantly boost their efficiency for H₂ generation from the dehydrogenation of formic acid (FA). Experimental results and mechanistic investigations indicate that a strong electronic interaction exists between Pd NPs and the PW anions; the PW anions accept electrons from Pd first and, during FA dehydrogenation, the reduced blue PW donates electrons to Pd. Moreover, melem plays an important role in hydrogen transfer and can accelerate H₂ generation. The overall synergistic effect of PW and melem endows Pd NPs with extremely high activity and stability for complete FA conversion at 50 °C, achieving a high turnover frequency of 15 393 h^-1 .

Exceptional Electrocatalytic Activity and Selectivity of Platinum@Nitrogen-Doped Mesoporous Carbon Nanospheres for Alcohol Oxidation

Porous carbon materials have attracted considerable attention for their various applications such as catalyst supports for fuel cells. However, few studies focus on the effect of carbon pore structure on different alcohols electrooxidation. In this work, platinum@nitrogen-doped carbon nanospheres with tailored mesopores (Pt@NMCs) are fabricated and exhibit outstanding electrocatalytic activity and durability for alcohol oxidation because of the structural advantages such as adjustable mesopores, N-doped carbon, and embedded catalysts. More importantly, the pore size of NMCs (or called the size of the windows connecting the neighboring spherical cavities), which can be tuned simply by adjusting the diameter of colloidal silica nanospheres, has a great effect on the electrocatalytic activity and selectivity of Pt catalysts toward oxidation of alcohols (methanol, ethanol, and n-propanol). Accordingly, we can adopt optimal Pt@NMCs with appropriate pore size based on different requirements and applications.

Synthesis and functionalization of ordered mesoporous carbons supported Pt nanoparticles for hydroconversion of n-heptane

Reaction pathway of n-heptane hydroconversion.