Photochemical CO₂ Splitting by Metal-to-Metal Charge-Transfer Excitation in Mesoporous ZrCu(I)-MCM-41 Silicate Sieve

Abstract

Binuclear redox sites consisting of a Zr oxo-bridged to a Cu(I) center have been obtained on the pore surface of MCM-41 silicate sieve by a stepwise grafting procedure, along with isolated metal centers. The bimetallic site features a Zr(IV)-O-Cu(I) to Zr(III)-O-Cu(II) metal-to-metal charge-transfer (MMCT) absorption extending from the UV region to about 500 nm. The Zr-O-Cu linkage is revealed by a Cu(I)-O infrared stretch mode at 643 cm-1. Irradiation of the MMCT chromophore of ZrCu(I)-MCM-41 loaded with 1 atm of CO2 gas at room temperature resulted in growth of CO (2150 cm-1) and H2O (1600 cm-1). Photolysis experiments using 13CO2 and C18O2 demonstrate that carbon monoxide and the oxygen atom of the water product originate from CO2. This indicates splitting of the CO2 by the excited MMCT moiety to CO and a surface OH radical, followed by trapping of the products at Cu(I) centers (OH is reduced to H2O). This is the first observation of CO2 photoreduction at a binuclear MMCT site at the gas-solid interface.

Functioning devices for solar to fuel conversion

“…Two other major routes suggest themselves, for storing the collected photonic energy in the form of chemicals: -H 2 production by water splitting [11][12][13][14][15][16] -CO 2 reduction, combined with water oxidation (to O 2 ), yielding liquids such as alcohols or even hydrocarbons. This process is commonly referred to as artificial photosynthesis [17][18][19][20][21][22][23].…”

Visible-Light Photoredox Catalysis: Selective Reduction of Carbon Dioxide to Carbon Monoxide by a Nickel N-Heterocyclic Carbene–Isoquinoline Complex

“…12,13 However, examples of selective light-driven CO 2 conversion to reduced carbon products in heterogeneous systems are limited mainly to these wide-band gap, UV-absorbing materials that do not exhibit selectivity towards a single carbon product, 24-27 aside from select transitionmetal doped silicates. [28][29][30] The use of semiconductors with molecular electrocatalysts has also been investigated for photoelectrochemical CO 2 conversion, 31-33 and recent work in improved inorganic materials for electrocatalytic CO 2 reduction continues to emerge, 34-40 but limited photocatalytic applications have been reported.…”

“…12,13 However, examples of selective light-driven CO 2 conversion to reduced carbon products in heterogeneous systems are limited mainly to these wide-band gap, UV-absorbing materials that do not exhibit selectivity towards a single carbon product, 24-27 aside from select transitionmetal doped silicates. [28][29][30] The use of semiconductors with molecular electrocatalysts has also been investigated for photoelectrochemical CO 2 conversion, 31-33 and recent work in improved inorganic materials for electrocatalytic CO 2 reduction continues to emerge, 34-40 but limited photocatalytic applications have been reported.Homogeneous molecular systems offer an alternative strategy for solar CO 2 fixation that allows for modular tuning of their performances via synthetic chemistry. However, most CO 2 reduction efforts in this context have focused on electrocatalysts, including those based on cobalt and nickel polyamine macrocycles, 41-47 second-and third-row transition metal polypyridines, 48-58 metal porphyrins 59-62 and phthalocyanines, 63-65 metal phosphines 3,66-69 and thiolates, 70 metal clusters, 71 pyridine and amine derivatives, [72][73][74][75] and N-heterocyclic carbene-pyridine platforms.…”

Highly efficient photochemical HCOOH production from CO2 and water using an inorganic system

“…Carbon monoxide (CO) [1][2][3][4] and formic acid (HCOOH) 5 have been successfully produced from CO 2 by light illumination. Research interest has recently extended to certain types of hybrid materials, [6][7][8][9] and reactor systems have been been reconsidered in connection with the shape of cataysts. [10][11][12] In the intensive challenges until now, it may be one of the milestones that high selectvity for conversion from CO 2 to methanol was shown using gallium phosphide (GaP) accompanied by homogeneous pyridinium catalyst.…”