The carbon dioxide (CO 2 ) released into the atmosphere during fossil fuel burning is a leading cause of global warming. One way to address this growing threat is to develop CO 2 reduction technologies, which convert CO 2 into useful chemicals, such as CO and formic acid (HCOOH). In particular, photocatalytic CO 2 reduction systems use visible or ultraviolet light to drive CO 2 reduction, much like how plants use sunlight to conduct photosynthesis. Over the past few years, scientists have reported many sophisticated photocatalysts based on metal-organic frameworks and coordination polymers (CPs). Unfortunately, most of them either require complex post-synthesis treatment and modifications or are made from precious metals.
In a recent study published in ACS Catalysis , a research team Japan found a way to overcome these challenges. Led by Specially Appointed Assistant Professor Yoshinobu Kamakura and Professor Kazuhiko Maeda from Tokyo Institute of Technology (Tokyo Tech), the team developed a new kind of photocatalyst for CO 2 reduction based on a CP containing lead–sulfur (Pb–S) bonds. Known as KGF-9, the novel CP consists of an infinite (–Pb–S–) n structure with properties unlike any other known photocatalyst.
For instance, KGF-9 has no pores or voids, meaning that it has a low surface area. Despite this, however, it achieved a spectacular photoreduction performance. Under visible-light irradiation at 400 nm, KGF-9 demonstrated an apparent quantum yield (product yield per photon absorbed) of 2.6% and a selectivity of over 99% in the reduction of CO 2 to formate (HCOO − ). “These values are the highest yet reported for a precious metal-free, single-component photocatalyst-driven reduction of CO 2 to HCOO − ,” highlights Prof. Maeda. “Our work could shed light on the potential of nonporous CPs as building units for photocatalytic CO 2 conversion systems.”
In addition to its remarkable performance, KGF-9 is easier to synthesize and use compared to other photocatalysts. Since the active Pb sites (where CO 2 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 requires no other post-synthesis modifications to operate at room temperature and under visible light illumination.
The team at Tokyo Tech is already exploring new strategies to increase the surface area of KGF-9 and boost its performance further. As the first photocatalyst with Pb(II) as an active center, there is a good chance that KGF-9 will pave the way to a more economically feasible CO 2 reduction. In this regard, the research team concludes: “We believe that our study provides an unprecedented opportunity for developing a new class of inexpensive photocatalysts for CO 2 reduction consisting of earth-abundant elements.”
Let us hope further research in this field will give us an edge in the fight against climate change.
ACS Catalysis
Experimental study
Not applicable
Selective CO2-to-Formate Conversion Driven by Visible Light over a Precious-Metal-Free Nonporous Coordination Polymer
5-Aug-2022