Adsorption and Photochemical Properties of a Molecular CO₂ Reduction Catalyst in Hierarchical Mesoporous ZSM-5: An In Situ FTIR Study

Abstract

As part of our recent effort to attach well-defined molecular photocatalysts to solid-state surfaces, this present study investigates adsorption and photochemical properties of a tricarbonyl rhenium(I) compound, Re(bpy)(CO)3Cl (bpy = 2,2'-bipyridine), in hierarchical mesoporous ZSM-5. The molecular Re(I) catalyst, a Ru(bpy)3(2+) photosensitizer, and an amine-based electron donor were coadsorbed in the mesopores of the hierarchical ZSM-5 through simple liquid-phase adsorption. The functionalized ZSM-5 was then characterized with infrared and UV-visible spectroscopies and was tested in CO2 reduction photocatalysis at the gas-surface interface. In the mesoporous ZSM-5, CO2 molecules were adsorbed on the amine electron-donor molecules as bicarbonate, which would release CO2 upon light irradiation to react with the Re(I) catalyst. The formation of important reaction intermediates, particularly a Re-carboxylato species, was revealed with in situ Fourier transform infrared spectroscopy in combination with isotopic labeling. The experimental results indicate that hierarchical mesoporous zeolites are promising host materials for molecular photocatalysts and that zeolite mesopores are potential "reaction vessels" for CO2 reduction photocatalysis at the gas-solid interface.

Organometallic Iridium(III) Complex Sensitized Ternary Hybrid Photocatalyst for CO2 to CO Conversion

“…The primary reason fort he long-term durability of the ternary hybrid observedwould be fast consumption of the long-lived reduced speciesb yt he TiO 2 mediator,w hich otherwise facilitates photodegradation of IrPC À ,b ecause there is generally ad ecomposition pathway,s uch as ad isproportionb etween reactive free reduced species. [39,43,55] This interpretation is in line with our previousr eports that ah ighly durable and efficient photocatalysis is achieved only by TiO 2 immobilization of af ragile organic PS, which allows efficient charge separation and injection during photolysis. [39] Irradiation at al ongerw avelength (l > 500 nm, instead of l > 435 nm) slightly increased the TON to 407 during 150 h; this implies that the lower energy irradiation prevents photobleaching.…”

“…[18] The early leveling-off tendency is thought to be derived from loss of the originalc omponentsb ecause of unwanted interactions between various long-lived reactive speciesa nd intermediates, which lead to as-yet not fully defined deformation (i.e.,CO 2 -coordinated Re complexes and one-electron reduced species (OERS)). [52][53][54][55] Notably,p hotocatalysis of the IrP-immobilized ternary system ( piq IrP/TiO 2 /ReP) is highert han that of either the homo-geneous mixed system ( piq IrPE + RePE) or the binary system ( piq IrPE + TiO 2 /ReP) with free IrPE as the PS (Figure 8). The performances of both the binary and ternary system were similar to each other in the early stage, but the binary system tended to level off after 25 hb ecause of the relatively low stability of the homogeneous IrPE molecules during photolysis.…”

Zeolite–TiO 2 hybrid composites for pollutant degradation in gas phase

“…They concluded that zeolite structures exhibit relevant physicochemical properties over other adsorbents such as activated carbon. Zeolites Y and ZSM-5 are some of the most commonly ordered structures used for photocatalytic studies, including the removal of nitrogen oxides [10,11], isomerisation or cyclization reactions [12,13], disinfection [14], CO 2 photoreduction [15] or the photocatalytic degradation of organic molecules [16]. Anpo et al [17] studied hydrophilic and hydrophobic zeolite Y for the elimination of toluene and benzene http://dx.doi.org/10.1016/j.apcatb.2014.…”

Visible‐Light‐Responsive Carbon Dioxide Reduction System: Rhenium Complex Intercalated into a Zirconium Phosphate Layered Matrix

“…Based on previous results and the present work, a possible mechanism for photocatalytic CO 2 reduction in our system is proposed in Scheme . After absorption of light by the Re complex, a one‐electron reduced species 1 , which is formed through an MLCT mechanism, is reductively quenched by TEOA to form species 2 .…”

“…FTIR spectra of [Re(bpy)(CO) 3 Cl], α‐ZrP, and Re/ZrP with different loadings are shown in Figure . The characteristic bands of the CO group in the Re complex appear in the region of =1800–2100 cm −1 , assigned to the vibration of the CO ligands in a perturbed C 3ν environment . These stretches are absent in the spectrum of the dry solid α‐ZrP.…”