New microwave-assisted synthesis method significantly enhances the performance of a previously reported coordination polymer photocatalyst.
Transforming carbon dioxide (CO₂) into valuable chemicals presents an exciting strategy for reducing CO₂ emissions and mitigating climate change. Designing photocatalysts that harness light energy to facilitate CO₂ conversion is a key objective in the field of functional materials science.
Though various types of photocatalysts exist, coordination polymers (CPs) are a particularly attractive option. These heterogeneous materials can integrate the functions of light absorption and CO2 reduction catalysts simultaneously. Moreover, CPs can be synthesized from earth-abundant metals and organic molecules, which makes them widely usable at an industrial level.
In August 2022, Professor Kazuhiko Maeda and colleagues from the Institute of Science Tokyo, Japan, reported a precious-metal-free CP called KGF-9 that served as a standalone photocatalyst for converting CO2 to formate. Although KGF-9 was highly selective, its photocatalytic activity was rather low, as evidenced by its low apparent quantum yield (AQY). Now, in a more recent study published in Advanced Functional Materials on November 13, 2024, Maeda and his team managed to greatly improve KGF-9’s performance through an alternative synthesis approach, highlighting its previously untapped potential.
A Microwave-Assisted Synthesis Breakthrough
The approach in question was a microwave-assisted solvothermal method, which involves heating a solution in a sealed vessel using microwaves. “Volumetric heating with microwaves can directly and uniformly heat the entire reaction mixture, causing molecular rotations that result in a drastic increase in the reaction rate,” notes Maeda. On top of speeding up the production of KGF-9 from two full days to as little as an hour, this synthesis route had other important effects.
After thorough testing of the samples produced, the researchers noted that the microwave-assisted method produced thin KGF-9 fibrils with a much greater specific surface area and crystallinity than the previous synthesis route. Subsequent photocatalytic experiments revealed that these improvements led to a massive boost in AQY for CO2-to-formate conversion. To put this into numbers, the AQY of the newly synthesized KGF-9 was 25%, which represents a near ten-fold increase compared to the 2.6% value previously reported. “This AQY represents a record-high value among reported heterogeneous photocatalysts for CO2-to-formate conversion and is even on par with the AQY reported for homogeneous photocatalysts,” remarks Maeda.
Understanding the Mechanisms Behind the Improvements
The research team then conducted mechanistic studies to understand the origin of the observed improvements in CO2-to-formate conversion. Through careful analysis, they concluded that producing well-crystallized KGF-9 with few surface defects was a decisive factor. Interestingly, by combining KGF-9 with a carbonaceous conductor, they found that this compound also proves suitable for the electrocatalytic reduction of CO2, which uses electricity in an aqueous medium instead of light to drive the conversion of CO2 to formate.
Taken together, the findings of this study paint a bright future for KGF-9 and similar photocatalysts, which could soon become key in our efforts toward sustainable societies. With any luck, these affordable and versatile materials will help us achieve carbon neutrality to prevent further damage to our ecosystems.
Reference: “Fibrous Pb(II)-Based Coordination Polymer Operable as a Photocatalyst and Electrocatalyst for High-Rate, Selective CO2-to-Formate Conversion” by Chomponoot Suppaso, Ryosuke Nakazato, Shoko Nakahata, Yoshinobu Kamakura, Fumitaka Ishiwari, Akinori Saeki, Daisuke Tanaka, Kazuhide Kamiya and Kazuhiko Maeda, 13 November 2024, Advanced Functional Materials.
DOI: 10.1002/adfm.202417223
The study was funded by the Japan Science and Technology Agency, the Japan Society for the Promotion of Science, and the Japan Association for Chemical Innovation.
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3 Comments
Does anyone with any scientific qualifications at all ever vet these hyped claims, or are you just scribes for the University’s Press Office?
This “breakthrough” is nowhere near practical. Photocatalysis needs to compete with plant growth or PV panels, and the rates at which these things work isn’t even close. There are numerous other practical issues that these hucksters have yet to even survey.
You need to get a much firmer grasp on the difference between “sci” and “tech.” This “sci” may be interesting, but it is nowhere near being “tech” as yet.
The magazines like this one are 99.9% hype.
I wonder what would the net gain be on a real life scale, since he’ll of a lot of energy would have to go into that “microwave assistance”.