Tokyo Tech News

Novel Tin-Based Metal–Organic Frameworks for Reducing Carbon Dioxide to Formate


Published: June 2, 2023

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.

Novel Tin(II)-Based Metal–Organic Framework for Reducing Carbon Dioxide to Formate Under Visible Light

The never-ending demand for carbon-rich fuels to drive the economy keeps adding more and 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 have come up with 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.

In a recent breakthrough published in Angewandte Chemie, International Edition on May 8, 2023, a team of researchers led by Prof. Kazuhiko Maeda of Tokyo Institute of Technology 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," explains Prof. Maeda.

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. Sn, known for its ability to act as both a catalyst and absorber during a photocatalytic reaction, could be a promising candidate for MOF-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 would open new avenues for its application as a photocatalyst in reactions such as solar energy-driven CO2 reduction. "The results of our study are a testimony to the fact that MOFs can be a platform for creating outstanding photocatalytic functions, usually unattainable with molecular metal complexes, using non-toxic, inexpensive, and Earth-abundant metals," concludes Prof. Maeda.


Authors :
Yoshinobu Kamakura,1 Chomponoot Suppaso,1 Issei Yamamoto,1 Ryusuke Mizuochi,1 Yusuke Asai,2 Teruki Motohashi,2 Daisuke Tanaka,3* and Kazuhiko Maeda1,4,*
Title :
Tin(II)-Based Metal–Organic Frameworks Enabling Efficient, Selective Reduction of CO2 to Formate under Visible Light
Journal :
Angewandte Chemie, International Edition
Affiliations :

1 Department of Chemistry, School of Science, Tokyo Institute of Technology

2 Department of Materials and Life Chemistry, Faculty of Engineering, Kanagawa University

3 Department of Chemistry, School of Science, Kwansei Gakuin University

4 Living Systems Materialogy (LiSM) Research Group, International Research Frontiers Initiative (IRFI), Tokyo Institute of Technology

* Corresponding authors' emails:,

School of Science

School of Science —Exploring the Truth and Creating Knowledge—
Information on School of Science inaugurated in April 2016

School of Science

Schools, Departments, and Institute for Liberal Artsouter

Further Information

Professor Kazuhiko Maeda

Department of Chemistry
School of Science
Tokyo Institute of Technology



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