Polystyrene-Supported Cu/2,2,6,6-Tetramethyl-1-piperidine-N-oxyl Catalytic Systems Constructed by Nanoprecipitation and Their Cooperative Catalysis for Benzyl Alcohol Oxidation

Abstract

Transformation of multifunctional homogeneous catalysts to the corresponding heterogeneous catalytic systems makes catalytic reactions interesting from both economic and environmental points of view. Here, we have devised a controllable and efficient strategy for the preparation of supported multifunctional catalysts by taking the Cu/2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) catalytic system as an example. Polystyrene-supported Cu/TEMPO catalysts were, for the first time, prepared via nanoprecipitation of polymers in water and efficient for aerobic oxidation of benzyl alcohol (BnOH). Cooperative behaviors could be regulated by precise control of local concentrations of functional groups. We have demonstrated that the incorporation of functional groups into polystyrene supports can make better use of catalytic components, resulting from confinement-enhanced cooperation. This strategy provides access to build more efficient multifunctional heterogeneous catalysts through establishing structure–activity relationships.

Engineering of polystyrene-supported acid–base catalysts for aldol condensation in water

“…2). In agreement with reported results, 26,32 spherical nanoparticles with small size (o100 nm, Fig. 2A and C) were successfully prepared.…”

“…Furthermore, the dilute effect of styrene units has also been confirmed in other catalytic systems based on nanoprecipitation of the polymers. 26 Taken together, we demonstrated that the rational engineering of polymer-supported acid-base catalysts constructed by nanoprecipitation can control their catalytic performance.…”

“…More importantly, the coil-globule collapse of the flexible polymer chains makes the formation of well-matched catalytic centers possible. To prepare polystyrene-supported acid–base catalysts, benzylamine-containing copolymers and catechol-containing copolymers were dissolved in DMF, and the resulting solutions were added to aqueous solutions of Triton X-100, 26 which was used to improve the stability of the catalysts. The morphologies and size distributions of these nanoparticle catalysts were investigated by TEM and DLS (Fig.…”

“…By altering the proximity effect, catalytic performance shall be regulated by tuning the local concentrations of functional groups. [26][27][28][29] The aldol reaction of 4nitrobenzaldehyde (4NBA) with acetone is chosen as a model reaction to evaluate these catalysts. The effect of polymer composition and effective constituent ratio on catalytic performance were examined.…”

Pyrene-Containing Polymer-Supported Cu/TEMPO Catalytic Systems: Aromatic Stacking-Enhanced Cooperative Catalysis

“…24 To control the morphology of catalysts, our group developed a strategy to construct polymer-supported multifunctional catalytic systems exemplified by the Cu/2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) catalytic system. 25 The polymer-supported Cu/ TEMPO catalytic systems were prepared via nanoprecipitation of copolymers containing catalytic components, in which the coil−globule collapse of copolymer chains contributes to the formation of cooperative catalytic centers. Moreover, cooperative behaviors can be effectively regulated by varying local concentrations of functional groups within polymer-supported catalysts.…”