A new coordination polymer-based photocatalyst for CO2 reduction exhibits unprecedented performance, giving Tokyo Tech scientists hope in the fight against global warming. Made from abundant elements and requiring no complex post-synthesis processing or modification, this promising photocatalyst could pave the way for a new class of photocatalysts to efficiently convert CO2 into useful chemicals.
Carbon dioxide (CO2) released into the atmosphere during the combustion of fossil fuels is one of the main causes of global warming. One way to deal with this growing threat is to develop CO2 reduction technologies, which convert CO2 into useful chemicals, such as CO and formic acid (HCOOH). In particular, photocatalytic CO2 abatement systems use visible or ultraviolet light to conduct CO2 reduction, much like how plants use sunlight to perform photosynthesis. In recent years, scientists have reported many sophisticated photocatalysts based on metal-organic frameworks and coordination polymers (PCs). Unfortunately, most of them either require complex post-synthesis processing and modifications, or are made from precious metals.
In a recent study published in ACS catalysis, a Japanese research team has found a way to overcome these challenges. Led by specially appointed Assistant Professor Yoshinobu Kamakura and Professor Kazuhiko Maeda of the Tokyo Institute of Technology (Tokyo Tech), the team developed a new type of photocatalyst for CO2 reduction based on a CP containing lead-sulfur (Pb-S) bonds. Known as KGF-9, the new CP consists of an infinity (-Pb-S-) not structure with properties unlike any other known photocatalyst.
For example, KGF-9 has no pores or voids, which means it has a low surface area. Despite this, however, it achieved spectacular photoreduction performance. Under visible light irradiation at 400 nm, KGF-9 demonstrated an apparent quantum yield (yield of product per photon absorbed) of 2.6% and a selectivity of more than 99% in the reduction of CO2 format (HCOO−). “These values are the highest ever reported for single-component, precious metal-free photocatalyst CO reduction.2 at HCOO−“, emphasizes Professor Maeda. “Our work could shed light on the potential of non-porous PCs as building units for photocatalytic CO2 conversion systems.
In addition to its remarkable performance, KGF-9 is easier to synthesize and use than other photocatalysts. Since the active sites of Pb (where CO2 reduction occurs) are already “installed” on its surface, KGF-9 does not require the presence of a cocatalyst, such as metal nanoparticles or metal complexes. Moreover, it does not require any other post-synthesis modification to operate at room temperature and under visible light illumination.
The Tokyo Tech team is already exploring new strategies to increase the surface area of KGF-9 and further improve its performance. As the first photocatalyst with Pb(II) as the active center, there is a good chance that KGF-9 will pave the way for more economically feasible CO2 reduction. In this regard, the research team concludes: “We believe that our study provides an unprecedented opportunity to develop a new class of low-cost photocatalysts for CO2 reduction consisting of abundant earth elements.”
Hopefully further research in this area will give us an edge in the fight against climate change.
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