Selective reduction of ketone/aldehydes to alcohols is of great importance in green chemistry and chemical engineering. Highly efficient catalysts are still demanded to work under mild conditions, especially at room temperature. Here we present a synergistic function of single-atom palladium (Pd 1 ) and nanoparticles (Pd NPs ) on TiO 2 for highly efficient ketone/aldehydes hydrogenation to alcohols at room temperature. Compared to simple but inferior Pd 1 /TiO 2 and Pd NPs /TiO 2 catalysts, more than twice activity enhancement is achieved with the Pd 1+NPs /TiO 2 catalyst that integrates both Pd 1 and Pd NPs on mesoporous TiO 2 supports, obtained by a simple but large-scaled spray pyrolysis route. The synergistic function of Pd 1 and Pd NPs is assigned so that the partial Pd 1 dispersion contributes enough sites for the activation of C=O group while Pd NPs site boosts the dissociation of H 2 molecules to H atoms. This work not only contributes a superior catalyst for ketone/aldehydes hydrogenation, but also deepens the knowledge on their hydrogenation mechanism and guides people to engineer the catalytic behaviors as needed.
Fenglian Hu,Leipeng Leng,Mingyang Zhang,Wenxing Chen,Yanlong Yu,Jun Wang,J. Hugh Horton,Zhijun Li
Heterogeneous catalysts with atomically precise metal sites have enabled unique insight into structure–property relationships in materials science. Herein, we report the construction and selective hydrogenation performance of a single-atom palladium catalyst by confining the palladium atoms into the six-fold N-coordinating cavities of graphitic carbon nitride (g-C3N4) through a facile spatial confinement-reduction approach under mild reducing conditions. Spherical aberration correction electron microscopy and extended X-ray absorption fine structure measurements confirm the presence of atomically dispersed palladium atoms stabilized by the g-C3N4 support. Its exceptional catalytic activity was demonstrated by the hydrogenation of styrene (98% conversion, 1.5 h) and furfural (conversion of 64% and selectivity of 99%, 4 h) and hydrodechlorination of 4-chlorophenol (99% conversion and 99% selectivity, 10 min). This palladium catalyst can be reused at least five times with negligible deterioration of its activity. Importantly, the palladium atoms retained their atomic dispersion following the thermal treatment. Moreover, this synthetic method can be scaled up while retaining similar catalytic activity. Fundamental insights are provided to elucidate how the material’s structure significantly impacts the catalytic performance at the atomic scale.
Hydrogen peroxide (H 2 O 2 ) photosynthesis from H 2 O and O 2 remains a significant challenge due to the sluggish hydrogen donation process, which stems from the high O–H bond dissociation energy of water. In this study, we propose an effective strategy to accelerate the water oxidation reaction (WOR) by anchoring single palladium atoms (Pd–CNO 2 ) onto a keto-anthraquinone covalent organic framework (KfAQ-Pd), achieving remarkable H 2 O 2 production rates of 3828 μmol h −1 g −1 under visible light irradiation ( λ > 420 nm) in neutral water. Both experimental observations and theoretical simulations reveal that the Pd–CNO 2 configuration induces an upward shift in the d-band center and enhances the hydrophilicity of KfAQ. This modification effectively disrupts the hydrogen-bond network within adsorbed water clusters, thereby promoting the cleavage of the dangling O–H bonds in H 2 O molecules and facilitating efficient hydrogen donation. The generated H 3 O + species are subsequently reduced in-situ by photogenerated electrons, leading to the hydrogenation of anthraquinone moieties and ultimately driving efficient H 2 O 2 photosynthesis. Overall, these findings highlight the pivotal role of single Pd atoms in enhancing water dissociation and hydrogen transfer, offering a promising new paradigm for solar-driven, environmentally friendly H 2 O 2 synthesis in neutral aqueous systems.
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