Schiff Base Functionalized Cellulose: Towards Strong Support-Cobalt Nanoparticles Interactions for High Catalytic Performances

A new hybrid catalyst consisting of cobalt nanoparticles immobilized onto cellulose was developed. The cellulosic matrix is derived from date palm biomass waste, which was oxidized by sodium periodate to yield dialdehyde and was further derivatized by grafting orthoaminophenol as a metal ion complexing agent. The new hybrid catalyst was characterized by FT-IR, solid-state NMR, XRD, SEM, TEM, ICP, and XPS. The catalytic potential of the nanocatalyst was then evaluated in the catalytic hydrogenation of 4-nitrophenol to 4-aminophenol under mild experimental conditions in aqueous medium in the presence of NaBH4 at room temperature. The reaction achieved complete conversion within a short period of 7 min. The rate constant was calculated to be K = 8.7 × 10-3 s-1. The catalyst was recycled for eight cycles. Furthermore, we explored the application of the same catalyst for the hydrogenation of cinnamaldehyde using dihydrogen under different reaction conditions. The results obtained were highly promising, exhibiting both high conversion and excellent selectivity in cinnamyl alcohol.

Inserting Single-Atom Zn by Tannic Acid Confinement To Regulate the Selectivity of Pd Nanocatalysts for Hydrogenation Reactions

Precisely controlling the selectivity of nanocatalysts has always been a hot topic in heterogeneous catalysis but remains difficult owing to their complex and inhomogeneous catalytic sites. Herein, an effective strategy to regulate the chemoselectivity of Pd nanocatalysts for selective hydrogenation reactions by inserting single-atom Zn into Pd nanoparticles is reported. Taking advantage of the tannic acid coating-confinement strategy, small-sized Pd nanoparticles with inserted single-atom Zn are obtained on the O-doped carbon-coated alumina. Compared with the pure Pd nanocatalyst, the Pd nanocatalyst with single-atom Zn insertion exhibits prominent selectivity for the hydrogenation of p-iodonitrobenzene to afford the hydrodeiodination product instead of nitro hydrogenation ones. Further computational studies reveal that the single-atom Zn on Pd nanoparticles strengthens the adsorption of the nitro group to avoid its reduction and increases the d-band center of Pd atoms to facilitate the reduction of the iodo group, which leads to enhanced selectivity. This work provides new guidelines to tune the selectivity of nanocatalysts with guest single-atom sites.

Effect of Morphological Modification over g-C3N4 on Photocatalytic Hydrogen Evolution Performance of g-C3N4-Pt Photocatalysts

In this study, the morphological properties of g-C3N4 in g-C3N4-Pt photocatalysts were modified by a simple hydrothermal treatment for photocatalytic hydrogen evolution. In addition, the morphological modification effect of g-C3N4 on the hydrogen evolution performance was investigated. The long-time hydrothermal treatment clearly changed the morphology of g-C3N4 by building extended melem units with more oxygen functional groups at the defect edges of the extended melem units, which was evidenced by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) measurements. The different morphological features of g-C3N4 resulted in lower photoluminescence (PL) emission intensity in PL spectra and a smaller semicircle radius in electrochemical impedance spectroscopy (EIS) data. This indicates the more efficient charge separation of the g-C3N4-Pt photocatalyst with a modified morphology. Consequently, morphologically modified g-C3N4-Pt showed a higher photocatalytic hydrogen evolution rate due to the better charge separation efficiency.

Highly stable Pt-Co bimetallic catalysts prepared by atomic layer deposition for selective hydrogenation of cinnamaldehyde

Pt-Co bimetallic catalysts were deposited onγ-Al₂O₃nanoparticles by atomic layer deposition (ALD) and were used for selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL). High resolution transmission electron microscopy, hydrogen temperature-programmed reduction, x-ray diffraction, and x-ray photoelectron spectroscopy were used to identify the strong interaction between Pt and Co. The obtained catalysts with an optimal Pt/Co ratio achieved a COL selectivity of 81.2% with a CAL conversion of 95.2% under mild conditions (i.e., 10 bar H₂and 80 °C). During the CAL hydrogenation, the addition of Co on Pt significantly improved the activity and selectivity due to the synergetic effects of Pt-Co bimetallic catalysts, resulted from the transfer of electrons from Co to Pt, which can stabilize the carbonyl groups. The obtained Pt-Co bimetallic catalysts also showed excellent stability due to the strong interaction between the metal nanoparticles and the alumina support. Negligible losses in the activity and selectivity were observed during the recycling experiments, showing the potential for practical applications.

Kinetics of the reaction of H2 with Pt0-nanoparticles in aqueous suspensions monitored by the catalytic reduction of PW12O403−

The mechanism of the reaction between Pt⁰ nanoparticles and Hydrogen was measured in the absence of an electric field via following the formation of PW₁₂O₄₀^4−/5−.

Hydrogenation of pentenal over supported Pt nanoparticles: influence of Lewis-acid sites in the conversion pathway

The superb TOF and high selectivity of Pt/CeAl are associated with the surface properties (e.g. medium Lewis acidic site). The unsaturated Ce4+/Al3+ cations pairs act as the acid sites and electron acceptors to polarize the CO bonds.

Regulating Hydrogenation Chemoselectivity of α,β-Unsaturated Aldehydes by Combination of Transfer and Catalytic Hydrogenation

Two hydrogenation mechanisms, transfer and catalytic hydrogenation, were combined to achieve higher regulation of hydrogenation chemoselectivity of cinnamyl aldehydes. Transfer hydrogenation with ammonia borane exclusively reduced C=O bonds to get cinnamyl alcohol, and Pt-loaded metal-organic layers efficiently hydrogenated C=C bonds to synthesize phenyl propanol with almost 100 % conversion rate. The hydrogenation could be performed under mild conditions without external high-pressure hydrogen and was applicable to various α,β-unsaturated aldehydes.

A magnetic CoRu-CoOX nanocomposite efficiently hydrogenates furfural to furfuryl alcohol at ambient H2 pressure in water

A one-pot synthesized CoRu-CoOX nanocomposite was reported as a magnetically recoverable catalyst for selective hydrogenation of furfural to furfuryl alcohol in water at ambient H2 pressure.

Synthesis of α,β-unsaturated carbonyl compounds by carbonylation reactions

Carbonylation reactions represent one of the most important tool box for the synthesis of α,β-unsaturated carbonyl compounds which are key building blocks in organic chemistry. This paper summarizes the most important advances in this field.

Highly selective hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran at low temperature over a Co–N–C/NiAl-MMO catalyst

Currently there is tremendous interest in the discovery of catalysts which can selectively hydrogenate biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF).

Selective hydrogenation of 2-pentenal using highly dispersed Pt catalysts supported on ZnSnAl mixed metal oxides derived from layered double hydroxides

Highly dispersed Pt catalysts supported on ZnSnAl mixed metal oxides showed high selectivity for 2-pentenol in selective hydrogenation of 2-pentenal.

Inorganic Perovskite-Induced Synergy on Highly Selective Pd-Catalyzed Hydrogenation of Cinnamaldehyde

The transformation of various organic molecules into value-added chemicals has been driven by the success in development of highly active catalytic systems. Heterogeneous catalysts have found use in many industrial processes by virtue of their ease of separation and high activities in various reactions. However, many processes employing heterogeneous catalysts in the transformation of organic molecules suffer significantly when it comes to product selectivity. Herein, we report on the synthesis of highly selective palladium nanoparticle (Pd NP)-containing catalysts. The heterogeneous catalysts reported herein consist of active mixed-metal oxides, in the form of perovskites as catalysts, and as catalytic supports for Pd NPs. The activity of pure perovskites when applied as catalysts in the hydrogenation of cinnamaldehyde is 3 factors lower compared with Pd NPs immobilized on them. However, considering the fact that perovskites achieved percentage conversions between 18 and 25% in a short period of time makes them perfect candidates to replace platinum group metals in the future. In addition to being earmarked as the future of catalysis, perovskites induced a synergistic effect on the conversion of the substrate compared to when Pd NPs are immobilized on the silica support. Furthermore, these catalysts are 100% selective to hydrocinnamaldehyde and stable for up to five catalytic cycles. With regard to reusability of the catalysts, Pd/LaFeO₃ was used as a benchmark catalyst and revealed the need for surface restructuring of the catalyst for optimum activity.

Pt nanoparticles supported on YCoxFe1−xO3 perovskite oxides: highly efficient catalysts for liquid-phase hydrogenation of cinnamaldehyde

The Pt/YCo_0.3Fe_0.7O₃ catalyst furnished ca. 95% selectivity to cinnamyl alcohol at nearly full conversion for the selective hydrogenation of cinnamaldehyde.

A route to support Pt sub-nanoparticles on TiO2 and catalytic hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline at room temperature

We report a method to support Pt sub-nanoparticles on TiO₂.