Researchers develop new strategy for visible-light-induced CO2 conversion

A team of researchers, led by Prof. Tian Jia from the Shanghai Institute of Organic Chemistry of the Chinese Academy of Sciences, has made a significant breakthrough in the field of carbon dioxide (CO2) conversion. Their work, published in Nature Catalysis on May 18, details a novel strategy for selectively converting CO2 using visible light, inspired by the key elements and assembly structures found in natural photosynthetic purple bacterial chromatophores.

Photosynthesis serves as the primary energy and organic matter source for nearly all living organisms. Within nature, photosynthetic organelles utilize solar radiation to generate energy-rich compounds from water and atmospheric CO2 through intricate supramolecular assemblies.

While artificial photocatalytic cycles have demonstrated higher intrinsic efficiencies, their low selectivity and stability in water for multi-electron CO2 reduction have hindered practical applications. Thus, the development of water-compatible artificial photocatalytic systems that mimic the natural photosynthetic apparatus and enable selective and efficient solar fuel production has remained a significant challenge.

In their study, the researchers employed a supramolecular assembly approach to construct an artificial photosynthetic chromatophore nanomicelle system based on the structure of natural photosynthetic purple bacteria. This system was utilized for the selective catalytic conversion of CO2 in water under visible light irradiation, demonstrating excellent stability and efficiency.

The team’s work presents a promising solution for energy conversion and storage through “zero-carbon cycle” pathways, offering an effective means to address the energy crisis and reduce carbon emissions.

The amphiphilic tri-block porphyrin-based supramolecules formed spherical nanomicelles that displayed remarkable stability in aqueous environments, thanks to intermolecular hydrogen bonding. These nanomicelles acted as chromatophores, exhibiting a pronounced light-harvesting antenna effect and exceptional resistance to photobleaching.

Furthermore, the surface of the nanomicelles featured electronegative ring-like porphyrin arrays with a diameter of approximately 4.2 nm, comprising around 12 porphyrin molecules based on calculations.

To achieve efficient electron injection, an electropositive carbon monoxide catalyst was selected due to the electrostatic force that brought it closer to the ring-like porphyrin array. Under visible light irradiation, the artificial photocatalytic system achieved highly efficient and selective conversion of CO2 to methane.

Additionally, the researchers proposed a two-stage mechanism, considering carbon monoxide as an intermediate species, which was further substantiated through isotope labeling experiments, steady-state and transient absorption spectra, and density functional theory calculations.

Source: Chinese Academy of Sciences

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