Photoreduction of Carbon Dioxide to Methanol over Copper Based Zeolitic Imidazolate Framework-8: A New Generation Photocatalyst

Abstract

The efficient reduction of CO2 into valuable products such as methanol, over metal-organic frameworks (MOFs) based catalyst, has received much attention. The photocatalytic reduction is considered the most economical method due to the utilization of solar energy. In this study, Copper (II)/Zeolitic Imidazolate Framework-8 (Cu/ZIF-8) catalysts were synthesized via a hydrothermal method for photocatalytic reduction of CO2 to methanol. The synthesized catalysts were characterized by X-ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM) coupled with Energy Dispersive X-ray (EDX), Ultraviolet-visible (UV-vis) spectroscopy, and X-Ray Diffraction (XRD). The host ZIF-8, treated with 2 mmol copper prepared in 2M ammonium hydroxide solution showed the highest photocatalytic activity. The crystal structures of ZIF-8 and 2Cu/ZIF-8N2 catalysts were observed as cubic and orthorhombic, respectively and the XPS analysis confirmed the deposition of Cu (II) ions over ZIF-8 surface among all the prepared catalysts. The orthorhombic structure, nano-sized crystals, morphology and Cu loading of the 2Cu/ZIF-8N2 catalyst were the core factors to influence the photocatalytic activity. The yield of Methanol was found to be 35.82 µmol/L·g after 6 h of irradiations on 2Cu/ZIF-8N2 catalyst in the wavelength range between 530–580 nm. The copper-based ZIF-8 catalyst has proven as an alternative approach for the economical photocatalytic reduction of CO2 to CH3OH.

A Review on Removal of Carbon Dioxide (CO2) using Zeolitic Imidazolate Frameworks: Adsorption and Conversion via Catalysis

“…For example, ZIF-8 has bandgap of 4.3 eV [74] . Thus, it shows zero rate of photocatalytic reduction of CO2 [323][324][325] . The common applications of ZIF for photo-reduction are co-catalysts or support (Table 5) [326,327] .…”

“…Au@PtAg/ZIF-8 [329] , Ag@ZIF-8@g-C3N4 [330] , CdS/ZIF-8 [331] , CdS@ZIF-67 [332] , CdSe@ZIF-8 [333] , ZnO/ZIF-8 [325,334] , ZnO@Pt/ZIF-8 [335] , ZnO/Au@ZIF-8 [336] , Au@ZIF-67 [337] , TiO2/ZIF-8 [338,339] , TiO2/Co-ZIF-90 [340] , Cu/ZIF-8 [323] , Zn2GeO4/ZIF-8 [324] , and WO3/CsPbBr3/ZIF-67 [341] (Table 5). ZIFs materials were also used as precursor for the synthesis of metal oxide embedded into carbon such as ZIF-67/MIL-125-derived Co3O4/TiO2 (Figure 17) [342][215] .…”

Photocatalytic Reduction of CO2 to Methanol Using a Copper-Zirconia Imidazolate Framework

“…Catalytic activity and optimization study of catalysts were tested in an optical fiber photocatalytic reactor. The detailed set up of the photocatalytic study has been reported in previous work [43]. The schematic representation of photocatalytic reduction is shown in Figure A2.…”

Recent Innovation of Metal-Organic Frameworks for Carbon Dioxide Photocatalytic Reduction

“…The incorporation of metal ions into the MOFs will increase the photocatalytic performance of CO 2 reduction to respective products, rendered from the enhanced photogenerated charge carrier and separation with apt minimum decay; thus, carefully engineered Cu-based MOFs are effective in long-lived electron generation and substrate reduction. Goyal et al provided an orthorhombic structured NP of MOF from Copper (II)/Zeolitic Imidazolate Framework-8 (2Cu/ZIF-8N2) photocatalyst in ammonium hydroxide concentration via hydrothermal process used for CO 2 conversion to methanol; the as-synthesized MOF had a bandgap of 1.75 eV, VB (0.72 V vs. NHE), and CB (−1.02 V vs. NHE @ pH = 7), implying lower VB than that of ZIF-8 (2.41 V vs. NHE), meaning the oxidation reaction took place in ZIF-8 [220]. On the other hand, the more negative-value CB of synthesized MOF to the CO 2 to MeOH potential (−0.38 V) affirmed this MOF's reduction potential with apropos metal loading.…”