Nanoarchitectonics of Metal-Free Porous Polyketone as Photocatalytic Assemblies for Artificial Photosynthesis.

The main component of natural gas is methane, whose combustion contributes to global warming. As such, sustainable, energy-efficient, nonfossil-based methane production is needed to satisfy current energy demands and chemical feedstocks. In this article, we have constructed a metal-free porous polyketone ( TPA-DPA PPK ) with donor-acceptor (D-A) groups with an extensive π-conjugation by facile Friedel-Crafts acylation reaction between triphenylamine ( TPA ) and pyridine-2,6-dicarbonyl dichloride ( DPA ). TPA-DPA PPK is a metal-free catalyst for visible-light-driven CO 2 photoreduction to CH 4 , which can be used as a solar fuel in the absence of any cocatalyst and sacrificial agent. CH 4 production (152.65 ppm g -1 ) is ∼5 times greater than that of g-C 3 N 4 under the same test conditions. Charge-density difference plots from excited-state time-dependent density functional theory (TD-DFT) calculations indicate a depletion and accumulation of charge density among the donor/acceptor functional groups upon photoexcitation. Most notably, binding energies from DFT demonstrate that H 2 O is more strongly bound with the pyridinic nitrogen group than CO 2, which shed insight into mechanistic pathways for photocatalytic CO 2 reduction.