Bioinspired Design of Hybrid Polymer Catalysts with Multicopper Sites for Oxygen Reduction

Abstract

Cu-containing metalloenzymes are known to catalyze oxygen activation through cooperative catalysis. In the current work, we report the design of synthetic polymer Cu catalysts using pyrene-labelled poly(2-hydroxy-3-dipicolylamino) propyl methacrylate (Py-PGMADPA) to coordinate multiple Cu sites along polymer chains. The catalysts feature a pyrene end group that can form supramolecular π-π stacking with conductive carbon to allow efficient immobilization of catalysts to the graphite electrode. Cu-containing Py-PGMADPA was examined for electrocatalytic oxygen reduction. The hybrid catalyst showed an onset potential of 0.5 V (vs. RHE) at pH 7 and 0.79 V at pH 13. The kinetic study indicated that the catalyst had a 2e À reduction of oxygen mainly mediated by Cu + centers. We demonstrated the importance of cooperative catalysis among Cu sites which did not exist for other transition metal ions, like Mn 2 + , Fe 2 + , Co 2 + , and Ni 2 +. The confinement of polymer chains promotes the activity and stabilizes Cu catalysts even at an extremely low Cu loading. The rational design of bioinspired polymer catalysts offers an alternative way to prepare synthetic mimics of metalloenzymes.

Single-Atom Cobalt Catalysts Coupled with Peroxidase Biocatalysis for C–H Bond Oxidation

“…In the electrochemical reduction of O 2 , H 2 O 2 can be synthesized by a two-electron transfer process: O 2 + 2H + + 2e – → H 2 O 2 , E ° = 0.695 V vs the reversible hydrogen electrode (RHE). While an oxygen reduction reaction (ORR) on metal catalysts often involves a four-electron transfer, controlling the spatial distribution of noble metals like isolated Pd sites has shown to be very selective in reducing O 2 by a two-electron transfer. , A similar perspective is demonstrated in earth-abundant metal-based catalysts, e.g., molecular Cu catalysts. , It has been reported that H 2 O 2 production can be stimulated by changing the surrounding atomic structure of the metal center . By fine-tuning the environment and the local interactions of the metal site, highly active early transition metal catalysts have been reported for H 2 O 2 production. , …”

“…On top of the typical time-consuming separation and recycling of anthraquinone, the long-term storage of relatively unstable H 2 O 2 is problematic. There are a number of catalytic and noncatalytic processes to produce H 2 O 2 in controlled quantitative yield. − For example, electrochemical synthesis of H 2 O 2 from O 2 is effective, controllable, and, more importantly, can be done on demand . In the electrochemical reduction of O 2 , H 2 O 2 can be synthesized by a two-electron transfer process: O 2 + 2H + + 2e – → H 2 O 2 , E ° = 0.695 V vs the reversible hydrogen electrode (RHE).…”

“…15,16 A similar perspective is demonstrated in earth-abundant metalbased catalysts, e.g., molecular Cu catalysts. 13,14 It has been reported that H 2 O 2 production can be stimulated by changing the surrounding atomic structure of the metal center. 17 site, highly active early transition metal catalysts have been reported for H 2 O 2 production.…”

Chiral Biocatalytic Oxidations at 90 °C in Microemulsions Driven by Electrocatalytic Oxygen Reduction to Hydrogen Peroxide

“…[18] In this paper we report a cascade reaction using electrocatalytically produced hydrogen peroxide that activates HRP to drive biocatalytic oxidation with high chiral selectivity. A synthetic catalyst, Cu 2 + -containing pyrene-labelled poly(2hydroxy-3-dipicolylamino) propyl methacrylate (PyÀ PGMA 49 DPA) that we recently synthesized, [19] electrochemically reduces oxygen in solution to hydrogen peroxide (Scheme 1). HRP crosslinked with polylysine in LbL films on 1 μm carboxylated magnetic beads (MPs) was activated by hydrogen peroxide to drive the epoxidation of styrene and the CÀ H bond oxidations of ethylbenzene and methyl phenylacetate.…”

Hydrophobic pockets built in polymer micelles enhance the reactivity of Cu2+ions

“…The utilization of natural enzymes for many organic reactions, however, is very limited due to low stability, poor recyclability, and solubility under non-aqueous and high-temperature conditions. 11 As inspired by nature, extensive efforts have been contributed to create synthetic metallopolymer catalysts with a microenvironment for catalytic sites (often metal ions or nanoparticles), such as micelles, [12][13][14][15][16][17] single-chain polymer nanoparticles (SCNPs), [18][19][20][21][22][23][24][25][26][27][28][29] and dendrimers. [30][31][32][33] Among those, polymer micelles have unique nanostructures derived from amphiphilic block polymers (BCPs), of which the hydrophobic segment spontaneously aggregates to form core-shell assemblies in water.…”