Efficient Photocatalysts for CO₂ Reduction

Abstract

Three types of photocatalytic systems for CO2 reduction, which were recently developed in our group, are reviewed. First, two-component systems containing different rhenium(I) complexes having different roles; i.e., redox photosensitizer and catalyst in the reaction solution are described. The mixed system of a ring-shaped rhenium(I) trinuclear complex and fac-[Re(bpy)(CO)3(MeCN)](+) is currently the most efficient photocatalytic system for CO2 reduction (ΦCO = 0.82 at λex = 436 nm). The second is a series of supramolecular photocatalysts, which have units with different functions in one molecule, i.e., redox photosensitizer, catalyst, and bridging ligand. The highest durability and speed of photocatalysis were achieved by using this system (ΦCO = 0.45, TONCO = 3029, and TOFCO = 35.7 min(-1)). The third is a novel type of artificial Z-Scheme photocatalyst for CO2 reduction, of which photocatalysis is revealed by stepwise excitation of both a semiconductor photocatalyst unit and the supramolecular photocatalyst unit. This system has both strong oxidation and reduction powers.

Electrocatalytic reduction of CO2 using the dinuclear rhenium(I) complex [ReCl(CO)3(μ-tptzH)Re(CO)3]

“…It is the major greenhouse gas and causes environmental pollution and warming [1,2]. The capture and reduction of CO 2 have attracted intensive research efforts as a potential source of renewable fuels and a useful method for decreasing the overall CO 2 emissions [3,4].…”

Molecular Catalysis of the Electrochemical and Photochemical Reduction of CO2 with Earth-Abundant Metal Complexes. Selective Production of CO vs HCOOH by Switching of the Metal Center

“…Following the pioneering work on Ni and Co macrocyclic complexes as potential catalysts for electrochemical CO 2 reduction, 5,6 various metal complexes have been used in this purpose, including mainly Re, Ru, Ir, Rh, Os, Pd, Mo, Cu, Co, Ni, Mn and Fe. 1,[7][8][9][10][11][12][13][14] The reduction products may be oxalate, CO or more rarely formic acid. Only rare example has been shown to catalyze CO 2 reduction with more than two electrons in electrochemical conditions (formaldehyde production).…”

“…9,23,24 Mechanistic insights have been gained recently too with Re, [28][29][30] Mn 31,32 and Ni 33-36 based catalysts through electrochemical and spectroscopic analysis, and quantum chemistry calculations. The reduction of carbon dioxide into formate has been more rarely observed using molecular catalysts, in electrochemical conditions with Fe, Ni, Co, Ru, Rh or Ir based catalysts [37][38][39][40][41][42][43][44][45][46][47][48][49] (see also tables 2 and 3 in reference 7) and in photochemical conditions 13,14,[50][51][52][53] with Re, Ru, Ir main-2 ly and very recently Mn complexes. 53 Mechanistic studies have accordingly been scarce.…”

A importância do estado excitado 3MLCT de compostos de Ru(II), Re(I) e Ir(III) no desenvolvimento de fotossensores, OLEDS e fotorredução de CO2

“…Buscando evitar o processo de difusão, usa-se a abordagem supramolecular para unir covalentemente um fotossensibilizador redox, como um composto polipiridínico de Ru(II), a um catalisador, como um composto de Re(I). 178,[225][226][227][228][229] Desta maneira, aproveita-se a intensa absorção de luz visível característica de um com as propriedades catalíticas do outro, Esquema 3. Esta abordagem deve levar em conta fatores como, por exemplo, o comprimento das cadeias carbônicas e insaturações das estruturas do ligante-ponte.…”