Synergistic Porosity and Charge Effects in a Supramolecular Porphyrin Cage Promote Efficient Photocatalytic CO2 Reduction

Lun An; Patricia De La Torre; Peter T Smith; Mina R Narouz; Christopher J Chang

doi:10.1002/anie.202209396

Synergistic Porosity and Charge Effects in a Supramolecular Porphyrin Cage Promote Efficient Photocatalytic CO₂ Reduction

Angew Chem Int Ed Engl. 2023 Jan 26;62(5):e202209396. doi: 10.1002/anie.202209396. Epub 2022 Dec 20.

Authors

Lun An^{1

2}, Patricia De La Torre^{1

2}, Peter T Smith^{1

2}, Mina R Narouz^{1

2}, Christopher J Chang^{1

2

3}

Affiliations

¹ Department of Chemistry, University of California, Berkeley, 94720-1460, Berkeley, CA, USA.
² Chemical Sciences Division, Lawrence Berkeley National Laboratory, 94720-1460, Berkeley, CA, USA.
³ Department of Molecular and Cell Biology, University of California, Berkeley, 94720-1460, Berkeley, CA, USA.

Abstract

We present a supramolecular approach to catalyzing photochemical CO₂ reduction through second-sphere porosity and charge effects. An iron porphyrin box (PB) bearing 24 cationic groups, FePB-2(P), was made via post-synthetic modification of an alkyne-functionalized supramolecular synthon. FePB-2(P) promotes the photochemical CO₂ reduction reaction (CO₂ RR) with 97 % selectivity for CO product, achieving turnover numbers (TON) exceeding 7000 and initial turnover frequencies (TOF_max ) reaching 1400 min^-1 . The cooperativity between porosity and charge results in a 41-fold increase in activity relative to the parent Fe tetraphenylporphyrin (FeTPP) catalyst, which is far greater than analogs that augment catalysis through porosity (FePB-3(N), 4-fold increase) or charge (Fe p-tetramethylanilinium porphyrin (Fe-p-TMA), 6-fold increase) alone. This work establishes that synergistic pendants in the secondary coordination sphere can be leveraged as a design element to augment catalysis at primary active sites within confined spaces.

Keywords: Carbon Dioxide Reduction; Electrocatalysis; Photocatalysis; Porous Cage; Second-Sphere.

Abstract

Grants and funding