Tailoring the Oxygen Reduction Activity of Hemoglobin through Immobilization within Microporous Organic Polymer-Graphene Composite

A facile one-pot, bottom-up approach to construct composite materials of graphene and a pyrimidine-based porous-organic polymer (PyPOP), as host for immobilizing human hemoglobin (Hb) biofunctional molecules, is reported. The graphene was selected because of its excellent electrical conductivity, while the PyPOP was utilized because of its pronounced permanent microporosity and chemical functionality. This approach enabled enclathration of the hemoglobin within the microporous composite through a ship-in-a-bottle process, where the composite of the PyPOP@G was constructed from its molecular precursors, under mild reaction conditions. The composite-enclathrated Fe-protoporphyrin-IX demonstrated electrocatalytic activity toward oxygen reduction, as a functional metallocomplex, yet with a distinct microenvironment provided by the globin protein. This approach delineates a pathway for platform microporous functional solids, where fine-tuning of functionality is facilitated by judicious choice of the active host molecules or complexes, targeting specific application.