Assembly immobilized palladium(0) on carboxymethylcellulose/Fe3 O4 hybrid: An efficient tailor-made magnetically catalyst for the Suzuki-Miyaura couplings

Preparation of recyclable magnetic palladium nanocatalysts by dispersion strategy based on sodium alginate for reduction of p-nitrophenol and Suzuki-Miyaura coupling

Palladium (Pd) has excellent catalytic performance, its application is seriously limited by low atomic utilization and weak recovery capacity. To solve these problems, we report a universal palladium nanocatalysts preparation strategy by taking advantage of the rich chemistry of sodium alginate (SA). SA units not only self-assemble into a cross-linked porous carboxyl and hydroxyl framework but also can coat different substrates. Benefiting from the distinguished chelation of SA, metallic nanocatalysts can be achieved. As a proof-of-concept demonstration, Pd loading on nano-Fe3O4 modified with SA and investigated their catalytic capabilities. The catalyst was Fe3O4 nanoparticles encapsulated by SA film loaded with 0.4 wt% of Pd. It has a particle size around 100 nm and has good superparamagnetism with a saturation strength of 76.26 emu/g. It exhibited good catalytic activity at TOF = 660 h-1 and TOF = 4311 h-1 in typical Suzuki-Miyaura coupling reaction and the reduction of p-nitrophenol, respectively, and showed appreciable recyclability in the test of recyclability. Thus, our findings demonstrate that recyclable magnetic palladium nanocatalysts have several attractive features, such as easy preparation, outstanding catalytic activity and reusability. This work lays the foundation for the preparation of palladium nanocatalysts and the potential application of SA in the field of catalysts.

Carboxymethyl cellulose nanocolloids anchored Pd(0) nanoparticles (CMC@Pd NPs): synthesis, characterization, and catalytic application in transfer hydrogenation

Herein, we report on the preparation of novel colloidal system based on carboxymethyl cellulose (CMC) and Pd nanoparticles (CMC@Pd NPs) via an ecofriendly auto-reduction process under mild conditions. In the first step, the follow-up of reduction and preparation of CMC anchored palladium nanoparticles (Pd NPs) in aqueous solution was carried out using UV-Vis spectroscopy. Thereafter, the monodispersed colloids were fully characterized by advanced analytical, structural, and morphological techniques. Based on Scherrer equation, the as-synthesized CMC@Pd NPs crystallite size was about 10.88 nm. Accordingly, the detailed microscopic study revealed CMC nanocolloids anchored uniform distribution of Pd NPs and the presence of CMC nanofilm as protective monolayer. To the best of our knowledge, the observed nanoscale properties are reported for the first time for CMC-M system. The performance of the as-synthesized CMC@Pd nanocolloids was first investigated in the reduction of 4-nitrophenol, as a model substrate, to 4-aminophenol using NaBH4 as a hydrogen source. Moreover, the catalytic reduction of various nitroarenes bearing electron withdrawing or donating substituents was carried out and monitored by UV-Vis spectroscopy. The chemo- and regioselectivity of the catalytic reduction in presence of CMC@Pd NPs were also studied. Consequently, the prepared CMC@Pd nanocolloids exhibit remarkable activity, good heterogeneity, and higher reusability and stability for the catalytic reduction reaction under mild conditions.

An environment-friendly dip-catalyst with xylan-based catalytic paper coatings

Replacing catalyst supports with sustainable and degradable materials is an urgent task. Xylan is a type of abundant natural polymers with potential applications in dispersing, anchoring, and coating materials, but its material values have always been underestimated. In this study, polyethyleneimine modified dialdehyde xylan (DAX-PEI) was used as a dispersing and anchoring agent to bind Pd nanoparticles onto paper surface to produce a DAX-PEI-Pd coated paper, which was used to catalyze Suzuki-Miyaura reactions. The catalytic coated paper exhibited a good catalytic activity with a yield of 91% and a high turnover frequency (TOF) of 3300 h^-1. Besides, it showed an excellent recyclability with the same catalytic coated paper being used 15 times and still having a yield of nearly 90%. This environment-friendly catalytic coated paper owns its great prospect in organic synthesis.