Partial Metalation of Porphyrin Moieties in Hydrogen-Bonded Organic Frameworks Provides Enhanced CO2 Photoreduction Activity.

ABSTRACT

In natural photosynthesis, the architecture of multiproteins integrates more chromophores than redox centers and simultaneously creates a well-controlled environment around the active site. Herein, we demonstrate that these features can be emulated in a prototype hydrogen-bonded organic framework (HOF) through simply varying the proportion of metalated porphyrin in the structure. Further studies demonstrate that changing the metalloporphyrin content not only realizes a fine tuning of the photosensitizer/catalyst ratio, but also alters the microenvironment surrounding the active site and the charge separation efficiency. As a result, the obtained material achieves the challenging overall CO2 reduction with a high HCOOH production rate (29.8 µmol g-1 h-1 , scavenger free), standing out from existing competitors. This work unveils that the degree of metalation is vital to the catalytic activity of the porphryinic framework, presenting as a new strategy to optimize the performance of heterogeneous catalysts.