Title : Conjugated porous polymers: Potential testbed for platinum free electrocatalysis for oxygen reduction reaction
Background: Starting from the grand old activated charcoal to zeolites, porous materials have been utilized for environmental and technological benefits for mankind. Of late, porous organic polymers (POPs) have emerged as a new class of functional materials with applications ranging from gas adsorption, gas/liquid separations, catalysis, light harvesting, energy storage to chemo/biosensing.
Objective: A combination of porosity and π-electron conjugation leads to the development of a new field of conjugated porous polymers (CPPs) and utilization of platinum free electrocatalysis for oxygen reduction reaction.
Methods: In this context, we have synthesized a monomer of 2,3-bis(4-bromophenyl) pyrido[3,4-b] pyrazine, and fabricated CPP in the form of solid powder, which is not soluble in common organic solvents.
Results: The synthesized polymer CPP was characterized by solid state 13C (CP-TOSS) NMR spectroscopy and Fourier transform infra-red spectroscopy (FTIR) spectra. The CPP polymer is an excellent catalyst for oxygen reduction reaction.
Conclusion: We created a conjugated porous polymer using 2,3-bis(4-bromophenyl) pyrido[3,4-b] pyrazine. We utilized the polymer as a heterogeneous catalyst to reduce oxygen. DFT simulations revealed a precise mechanism for the four-electron ORR. The oxygen molecule may decompose on the closest pyrazine site, converting N=O to N-OH. Also, fewer densely packed structures have a smaller free energy of the ORR steps.