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Powered by sunlight as the only energy input, artificial photosynthesis has become an especially attractive approach to store solar energy in the form of renewable fuels and chemicals. Hybrid heterojunctions based on conjugated porous polymers (CPPs) coupled to TiO2 have shown promising optoelectronic properties, such as enhanced light absorption and improved photocharge generation and transport, which substantially enhanced the photocatalytic activity of the system. Despite the versatility of CPPs, their use in artificial photosynthesis is limited and relatively new, particularly for CO2 photoreduction and N2 photofixation to ammonia. Here, we explore the use of conjugated porous polymers (CPPs), based on BOPHY and BODIPY dyes, as part of organic–inorganic hybrid materials for artificial photosynthesis.
Here, we demonstrate that interface interactions in CPPs/TiO2 heterojunctions contribute to improve the multi-electron transfer reactions involved in the artificial photosynthesis process, leading to improved CO2 photoreduction rates, as well as enhanced H2 evolution and N2 fixation into NH3. Our study reveals that interface interactions in hybrid materials may introduce synergetic optical and electronic effects, modifying the electron transfer kinetics and driving the artificial photosynthesis process more efficiently. Indeed, the physical separation of charge carriers in CPPs/TiO2 heterojunctions results in 4-times higher CH4 productions, and 16-fold improvement of hydrogen evolution from water.
This work opens up possibilities for novel CPPs/ TiO2 heterojunctions that can be applied in the challenging artificial photosynthesis process. Importantly, this study takes us a step closer towards developing a green and sustainable ammonia synthesis approach, and progressing the CO2 recycling into renewable fuels and chemicals powered by sunlight.