Novel tin

Researchers from Tokyo Tech have developed a tin-based metal–organic framework (MOF) that can photocatalytically reduce carbon dioxide (CO2) into formate under visible light. The tin-based MOF exhibited a high apparent quantum yield of 9.8% and carried out extremely selective photoreduction without needing an additional photosensitizer. This could prove extremely useful, as currently, most metal complexes for reducing CO2 to useful chemicals utilize expensive, rare and precious metals.

A paper on the work is published in Angewandte Chemie, International Edition.

The ongoing demand for carbon-rich fuels to drive the economy keeps adding more carbon dioxide (CO2) to the atmosphere. While efforts are being made to reduce CO2 emissions, that alone cannot counter the adverse effects of the gas already present in the atmosphere. So, scientists are developing innovative ways to use existing atmospheric CO2 by transforming it into useful chemicals such as formic acid (HCOOH) and methanol. A popular method for carrying out such conversions is to use visible light for driving the photoreduction of CO2 via photocatalysts.

A team of researchers led by Prof. Kazuhiko Maeda of Tokyo Institute of Technology has developed a tin-based metal–organic framework (MOF) that can enable selective photoreduction of CO2. They reported a novel tin (Sn)-based MOF called KGF-10, with the formula [SnII2(H3ttc)2.MeOH]n (H3ttc: trithiocyanuric acid and MeOH: methanol). It successfully reduced CO2 into HCOOH in the presence of visible light.

Most high-performance CO2 reduction photocatalysts driven by visible light rely on rare, precious metals as principal components. Furthermore, integrating the functions of light absorption and catalysis into a single molecular unit made up of abundant metals has remained a long-standing challenge. Hence, Sn was the ideal candidate as it can overcome both challenges.

MOFs, which bring the best of both metals and organic materials, are being explored as the more sustainable alternative to conventional rare-earth metal-based photocatalysts. While MOFs composed of zirconium, iron, and lead have been widely explored, not much is known about Sn-based MOFs.

For synthesizing the Sn-based MOF KGF-10, the researchers used H3ttc, MeOH, and tin chloride as the starting materials and chose 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole as the electron donor and the hydrogen source. The prepared KGF-10 was then subjected to several analysis techniques. They revealed that the material showed moderate CO2 adsorption ability, had a bandgap of 2.5 eV, and absorbed visible light wavelengths.

Once aware of the physical and chemical properties of the new material, scientists used it for catalyzing the reduction of CO2 in the presence of visible light. They found that KGF-10 successfully reduced CO2 into formate (HCOO-) with 99% selectivity without needing any additional photosensitizer or catalyst.

It also exhibited a record-high apparent quantum yield—the ratio of the number of electrons involved in the reaction to the total number of incident photons—of 9.8% at 400 nm. Furthermore, structural analysis carried out during the reactions revealed that KGF-10 underwent structural changes while facilitating photocatalytic reduction.

This study presented for the first time a tin-based high-performance, precious-metal free, and single-component photocatalyst for visible-light-driven reduction of CO2 to formate. The excellent properties of KGF-10 demonstrated by the team could open new avenues for its application as a photocatalyst in reactions such as solar energy-driven CO2 reduction.

Resources

Yoshinobu Kamakura, Chomponoot Suppaso, Issei Yamamoto, Ryusuke Mizuochi, Yusuke Asai, Teruki Motohashi, Daisuke Tanaka, and Kazuhiko Maeda1 (2023) "Tin(II)-Based Metal–Organic Frameworks Enabling Efficient, Selective Reduction of CO2 to Formate under Visible Light" Angewandte Chemie, International Edition doi: 10.1002/anie.202305923

Posted on 05 June 2023 in Carbon Capture and Conversion (CCC), Fuels, Market Background, Materials | Permalink | Comments (2)