Ce⁴⁺/Ce³⁺ Redox Effect-Promoted CdS/CeO₂ Heterojunction Photocatalyst for the Atom Economic Synthesis of Imines under Visible Light

Abstract

The employment of stoichiometric alcohols and amines for imine synthesis under mild and green reaction conditions is still a challenge in the field. In this work, based on our research foundation in the thermocatalytic synthesis of imines over ceria, a CdS/CeO2 heterojunction photocatalyst was constructed and successfully realized the atom-economic synthesis of imines under visible light without additives at room temperature. Mechanistic experiments and corresponding characterizations indicated that the CdS/CeO2 heterojunction can improve the separation efficiency of photogenerated carriers, which can be further enhanced by the Ce4+/Ce3+ redox pair by rapidly combining photogenerated e–. The in situ-reduced Ce3+ can better activate O2 to form Ce–O–O·, which, together with h+, efficiently accelerates alcohol oxidation, which is the rate-determined step for the synthesis of imines via oxidative coupling reaction of alcohol and amine. In addition, our photocatalyst exhibited fairly decent reusability and substrate universality. This work solves problems of using base additives and excess amine or alcohol in the reported photocatalytic systems and provides new insight for designing CeO2-based photocatalytic oxidation catalysts.

Proceeding of catalytic water splitting on Cu/Ce@g-C3N4 photocatalysts: an exceptional approach for sunlight-driven hydrogen generation

“…The combined utilization of SPR mediated by Cu and the electron scavenging ability of the Ce 3+ /Ce 4+ redox couple manifest as a synergistic effect. 90,91 The Cu and Ce co-catalysts work synergistically to facilitate the transfer of electron–hole pairs of g-C 3 N 4 for enhancing the H 2 generation performances of g-C 3 N 4 . This synergistic effect is pivotal in affirming the substantial enhancement of the photocatalytic activity of dual metal loaded Cu/Ce@g-C 3 N 4 catalysts.…”

Synthesis and Catalytic Performance of Mo2C/MoS2 Composite Heterojunction Catalysts

“…Hydrogen has emerged as a paragon of clean energy carriers, embodying a prodigious potential for high energy yield per mass (142 MJ kg −1 ), dwarfing even the venerable fossil fuels, bolstering its prominence at the pinnacles of energy research. The gamut of prevalent hydrogen fabrication techniques encompasses photocatalytic [2,3] and electrolytic hydrogen generation [4][5][6], biomass enzymatic degradation [7,8], and conventional fossilfuel-based hydrogen extraction [9,10]. For example, Marjeta et al [11] synthesized efficient photocatalysts by epitaxial growth of SrTiO 3 on Bi 4 Ti 3 O 12 substrates.…”

Transamidation of secondary carboxamides and amidation of esters are facilitated by magnetic Co@NC nanoparticles, as a highly efficient and recyclable catalyst under neat conditions

“…[25][26][27] In the last few decades, nanoparticles as catalysts have garnered considerable interest because of their enhanced selectivity and strong catalytic activity in organic reactions. [28][29][30] Recently, a variety of new nano-catalysts, designed specifically for the transamidation of amides, have been developed, such as Fe(OH) 3 @Fe 3 O 4 nanoparticles, 31 guanidine acetic acid (GAA) nanoparticles, 32 magnetically separable Fe 3 O 4 nanoparticles, 33 mesoporous silica nanoparticles (MSNs), 34 a sulfated poly borate nanocatalyst, 35 an Fe 3 O 4 -OSO 3 H nanocatalyst, 36 a SiO 2 -CeO 2 hybrid nanocomposite, 37 and nanosized zeolite beta (MSNs) 38 are used for primary amides and citric acid-coated nanoparticles (Fe 3 O 4 -CA NPs) for transamidation of primary and secondary amides. 39 Despite their numerous advantages, all these nanoparticle-catalyzed transamidation reactions involving unactivated amides require high temperatures and longer time.…”