Molecular approaches to the photocatalytic reduction of carbon dioxide for solar fuels

Amanda J. Morris, Gerald J. Meyer, Etsuko Fujita

Research output: Contribution to journalArticle

730 Citations (Scopus)

Abstract

the scientific community now agrees that the rise in atmospheric CO 2, the most abundant green house gas, comes from anthropogenic sources such as the burning of fossil fuels. This atmospheric rise in CO 2 results in global climate change. Therefore methods for photochemically transforming CO2 into a source of fuel could offer an attractive way to decrease atmospheric concentrations. One way to accomplish this conversion is through the light-driven reduction of carbon dioxide to methane (CH4(g)) or methanol (CH3OH (l)) with electrons and protons derived from water. Existing infrastructure already supports the delivery of natural gas and liquid fuels, which makes these possible CO2 reduction products particularly appealing. This Account focuses on molecular approaches to photochemical CO 2 reduction in homogeneous solution. The reduction of CO2 by one electron to form CO2- is highly unfavorable, having a formal reduction potential of -2.14 V vs SCE. Rapid reduction requires an overpotential of up to 0.6 V, due at least in part to the kinetic restrictions imposed by the structural difference between linear CO2 and bent CO2-. An alternative and more favorable pathway is to reduce CO2 though proton-assisted multiple-electron transfer. The development of catalysts, redox mediators, or both that efficiently drive these reactions remains an important and active area of research. We divide these reactions into two class types. In Type I photocatalysis, a molecular light absorber and a transition metal catalyst work in concert. We also consider a special case of Type 1 photocatalysis, where a saturated hydrocarbon links the catalyst and the light absorber in a supramolecular compound. In Type II photocatalysis, the light absorber and the catalyst are the same molecule. In these reactions, transition-metal coordination compounds often serve as catalysts because they can absorb a significant portion of the solar spectrum and can promote activation of small molecules. This Account discusses four classes of transition-metal catalysts: (A) metal tetraaza-macrocyclic compounds; (B) supramolecular complexes; (C) metalloporphyrins and related metallomacrocycles; (D) Re(CO)3(bpy) Xbased compounds where bpy ) =2,′-bipyridine. Carbon monoxide and formate are the primary CO2 reduction products, and we also propose bicarbonate/carbonate production. For comprehensiveness, we briefly discuss hydrogen formation, a common side reaction that occurs concurrently with CO 2 reduction, though the details of that process are beyond the scope of this Account. It is our hope that drawing attention both to current mechanistic hypotheses and to the areas that are poorly understood will stimulate research that could one day provide an efficient solution to this global problem.

Original languageEnglish
Pages (from-to)1983-1994
Number of pages12
JournalAccounts of Chemical Research
Volume42
Issue number12
DOIs
Publication statusPublished - Dec 21 2009

Fingerprint

Carbon Dioxide
Carbon Monoxide
Catalysts
Photocatalysis
Transition metals
formic acid
Electrons
Protons
Macrocyclic Compounds
Metalloporphyrins
Molecules
Gas fuels
Carbonates
Methane
Liquid fuels
Bicarbonates
Hydrocarbons
Fossil fuels
Greenhouse gases
Climate change

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Molecular approaches to the photocatalytic reduction of carbon dioxide for solar fuels. / Morris, Amanda J.; Meyer, Gerald J.; Fujita, Etsuko.

In: Accounts of Chemical Research, Vol. 42, No. 12, 21.12.2009, p. 1983-1994.

Research output: Contribution to journalArticle

@article{b29919616a404bd7882adee3183a3062,
title = "Molecular approaches to the photocatalytic reduction of carbon dioxide for solar fuels",
abstract = "the scientific community now agrees that the rise in atmospheric CO 2, the most abundant green house gas, comes from anthropogenic sources such as the burning of fossil fuels. This atmospheric rise in CO 2 results in global climate change. Therefore methods for photochemically transforming CO2 into a source of fuel could offer an attractive way to decrease atmospheric concentrations. One way to accomplish this conversion is through the light-driven reduction of carbon dioxide to methane (CH4(g)) or methanol (CH3OH (l)) with electrons and protons derived from water. Existing infrastructure already supports the delivery of natural gas and liquid fuels, which makes these possible CO2 reduction products particularly appealing. This Account focuses on molecular approaches to photochemical CO 2 reduction in homogeneous solution. The reduction of CO2 by one electron to form CO2 •- is highly unfavorable, having a formal reduction potential of -2.14 V vs SCE. Rapid reduction requires an overpotential of up to 0.6 V, due at least in part to the kinetic restrictions imposed by the structural difference between linear CO2 and bent CO2 •-. An alternative and more favorable pathway is to reduce CO2 though proton-assisted multiple-electron transfer. The development of catalysts, redox mediators, or both that efficiently drive these reactions remains an important and active area of research. We divide these reactions into two class types. In Type I photocatalysis, a molecular light absorber and a transition metal catalyst work in concert. We also consider a special case of Type 1 photocatalysis, where a saturated hydrocarbon links the catalyst and the light absorber in a supramolecular compound. In Type II photocatalysis, the light absorber and the catalyst are the same molecule. In these reactions, transition-metal coordination compounds often serve as catalysts because they can absorb a significant portion of the solar spectrum and can promote activation of small molecules. This Account discusses four classes of transition-metal catalysts: (A) metal tetraaza-macrocyclic compounds; (B) supramolecular complexes; (C) metalloporphyrins and related metallomacrocycles; (D) Re(CO)3(bpy) Xbased compounds where bpy ) =2,′-bipyridine. Carbon monoxide and formate are the primary CO2 reduction products, and we also propose bicarbonate/carbonate production. For comprehensiveness, we briefly discuss hydrogen formation, a common side reaction that occurs concurrently with CO 2 reduction, though the details of that process are beyond the scope of this Account. It is our hope that drawing attention both to current mechanistic hypotheses and to the areas that are poorly understood will stimulate research that could one day provide an efficient solution to this global problem.",
author = "Morris, {Amanda J.} and Meyer, {Gerald J.} and Etsuko Fujita",
year = "2009",
month = "12",
day = "21",
doi = "10.1021/ar9001679",
language = "English",
volume = "42",
pages = "1983--1994",
journal = "Accounts of Chemical Research",
issn = "0001-4842",
publisher = "American Chemical Society",
number = "12",

}

TY - JOUR

T1 - Molecular approaches to the photocatalytic reduction of carbon dioxide for solar fuels

AU - Morris, Amanda J.

AU - Meyer, Gerald J.

AU - Fujita, Etsuko

PY - 2009/12/21

Y1 - 2009/12/21

N2 - the scientific community now agrees that the rise in atmospheric CO 2, the most abundant green house gas, comes from anthropogenic sources such as the burning of fossil fuels. This atmospheric rise in CO 2 results in global climate change. Therefore methods for photochemically transforming CO2 into a source of fuel could offer an attractive way to decrease atmospheric concentrations. One way to accomplish this conversion is through the light-driven reduction of carbon dioxide to methane (CH4(g)) or methanol (CH3OH (l)) with electrons and protons derived from water. Existing infrastructure already supports the delivery of natural gas and liquid fuels, which makes these possible CO2 reduction products particularly appealing. This Account focuses on molecular approaches to photochemical CO 2 reduction in homogeneous solution. The reduction of CO2 by one electron to form CO2 •- is highly unfavorable, having a formal reduction potential of -2.14 V vs SCE. Rapid reduction requires an overpotential of up to 0.6 V, due at least in part to the kinetic restrictions imposed by the structural difference between linear CO2 and bent CO2 •-. An alternative and more favorable pathway is to reduce CO2 though proton-assisted multiple-electron transfer. The development of catalysts, redox mediators, or both that efficiently drive these reactions remains an important and active area of research. We divide these reactions into two class types. In Type I photocatalysis, a molecular light absorber and a transition metal catalyst work in concert. We also consider a special case of Type 1 photocatalysis, where a saturated hydrocarbon links the catalyst and the light absorber in a supramolecular compound. In Type II photocatalysis, the light absorber and the catalyst are the same molecule. In these reactions, transition-metal coordination compounds often serve as catalysts because they can absorb a significant portion of the solar spectrum and can promote activation of small molecules. This Account discusses four classes of transition-metal catalysts: (A) metal tetraaza-macrocyclic compounds; (B) supramolecular complexes; (C) metalloporphyrins and related metallomacrocycles; (D) Re(CO)3(bpy) Xbased compounds where bpy ) =2,′-bipyridine. Carbon monoxide and formate are the primary CO2 reduction products, and we also propose bicarbonate/carbonate production. For comprehensiveness, we briefly discuss hydrogen formation, a common side reaction that occurs concurrently with CO 2 reduction, though the details of that process are beyond the scope of this Account. It is our hope that drawing attention both to current mechanistic hypotheses and to the areas that are poorly understood will stimulate research that could one day provide an efficient solution to this global problem.

AB - the scientific community now agrees that the rise in atmospheric CO 2, the most abundant green house gas, comes from anthropogenic sources such as the burning of fossil fuels. This atmospheric rise in CO 2 results in global climate change. Therefore methods for photochemically transforming CO2 into a source of fuel could offer an attractive way to decrease atmospheric concentrations. One way to accomplish this conversion is through the light-driven reduction of carbon dioxide to methane (CH4(g)) or methanol (CH3OH (l)) with electrons and protons derived from water. Existing infrastructure already supports the delivery of natural gas and liquid fuels, which makes these possible CO2 reduction products particularly appealing. This Account focuses on molecular approaches to photochemical CO 2 reduction in homogeneous solution. The reduction of CO2 by one electron to form CO2 •- is highly unfavorable, having a formal reduction potential of -2.14 V vs SCE. Rapid reduction requires an overpotential of up to 0.6 V, due at least in part to the kinetic restrictions imposed by the structural difference between linear CO2 and bent CO2 •-. An alternative and more favorable pathway is to reduce CO2 though proton-assisted multiple-electron transfer. The development of catalysts, redox mediators, or both that efficiently drive these reactions remains an important and active area of research. We divide these reactions into two class types. In Type I photocatalysis, a molecular light absorber and a transition metal catalyst work in concert. We also consider a special case of Type 1 photocatalysis, where a saturated hydrocarbon links the catalyst and the light absorber in a supramolecular compound. In Type II photocatalysis, the light absorber and the catalyst are the same molecule. In these reactions, transition-metal coordination compounds often serve as catalysts because they can absorb a significant portion of the solar spectrum and can promote activation of small molecules. This Account discusses four classes of transition-metal catalysts: (A) metal tetraaza-macrocyclic compounds; (B) supramolecular complexes; (C) metalloporphyrins and related metallomacrocycles; (D) Re(CO)3(bpy) Xbased compounds where bpy ) =2,′-bipyridine. Carbon monoxide and formate are the primary CO2 reduction products, and we also propose bicarbonate/carbonate production. For comprehensiveness, we briefly discuss hydrogen formation, a common side reaction that occurs concurrently with CO 2 reduction, though the details of that process are beyond the scope of this Account. It is our hope that drawing attention both to current mechanistic hypotheses and to the areas that are poorly understood will stimulate research that could one day provide an efficient solution to this global problem.

UR - http://www.scopus.com/inward/record.url?scp=72949117212&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=72949117212&partnerID=8YFLogxK

U2 - 10.1021/ar9001679

DO - 10.1021/ar9001679

M3 - Article

C2 - 19928829

AN - SCOPUS:72949117212

VL - 42

SP - 1983

EP - 1994

JO - Accounts of Chemical Research

JF - Accounts of Chemical Research

SN - 0001-4842

IS - 12

ER -