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Graphitic carbon nitride (g-C 3 N 4 ) is an emerging visible-light-responsive photocatalyst that has been explored since 2009. This photocatalyst has highly tailorable structures and properties that enable potential utilization of a large portion of solar energy. This material is also synthesized from earth-abundant precursors, is chemically and thermally stable, and is biocompatible with no reported toxicity to date. The merits and pioneering performance evaluation of g-C 3 N 4 indicate that this photocatalyst holds promise for the degradation of persistent and emerging contaminants, including chemicals and pathogens, for sustainable water purification with reduced energy and chemical footprint. In this perspective, we propose and answer five questions that are most relevant to the development and application of g-C 3 N 4 for photocatalytic water purification, including both benefits and current barriers, from molecular-scale mechanistic understanding of g-C 3 N 4 properties and photocatalytic performance to industrial-scale photoreactor design for g-C 3 N 4 implementation in practice.
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Mechanistic Investigation of a Photocatalyst Model Reveals Function by Perylene-Like Closed Shell Super-Photoreductant Capable of Reducing Unactivated Arenes
Benzo[ghi]perylene monoimides (BPIs) have recently been employed as organic photocatalysts for challenging reductions. In probing their function, we identify a thermal degradation product involving imide ring opening, and this in turn motivates the development and synthesis of a high-symmetry model systema benzo[ghi]perylene diester (BPDE)whose structural simplicity is useful for mechanistic exploration relevant to the broader photocatalyst class. Using electrochemical and spectroscopic tools, we probe both the singly and doubly reduced states of BPDE and report the generation of [BP-H]−, a twoelectron, one-proton activated closed-shell super-reductant. This catalytically active species, after visible photon absorption, operates from its singlet excited state, where the motions of the added proton are coupled to an electron transfer event, which enables direct reduction of inert substrates like benzene and fluorobenzene. Traditional Birch chemistry on benzene has been previously realized only by solvated electrons or electrochemistry. The function of this model system uncovered in these mechanistic explorations suggests modes of operation for this photocatalyst class that will enable future optimizations.
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- Award ID(s):
- 2016557
- PAR ID:
- 10514111
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- ACS Catalysis
- ISSN:
- 2155-5435
- Page Range / eLocation ID:
- 2252 to 2263
- Subject(s) / Keyword(s):
- Birch reduction, photoredox catalysis, quenching, super reductant, excited-state redox, aryl−fluoride bond activation, defluorination, proton-coupled electron transfer
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acscatal.3c05386
