Photochemical Atmospheric CO2 Capture and Accumulation in Hydrolyzed Zirconium–Indole Systems

Gregory G. Arzoumanidis; Michail S. Paraskevas

doi:10.53941/photocatalysis.2026.100008

Abstract

Hydrolyzed 2-phenylindole (PI)–ZrCl₄ systems exhibit progressive atmospheric CO₂ capture and molecular evolution under ambient light, air, and moisture, providing insight into the evolution of self-organizing zirconium coordination networks. MALDI-TOF, FTIR, and NMR analyses reveal the progressive formation of coordinated CO₂ adducts together with carbonate-, bicarbonate-, and formate-containing zirconium species, demonstrating continuous evolution of oxygenated carbon environments during prolonged exposure. Time-dependent incorporation of secondary and tertiary CO₂ units into zirconium-bound intermediates, accompanied by the emergence of oxygenated PI oligomer series and multinuclear zirconium assemblies, indicates progressive molecular evolution in which precursor and descendant species coexist, allowing sequential CO₂ incorporation and network growth to be followed. The results further suggest that ligand oligomerization contributes to carbon retention and stabilization within the evolving zirconium matrix rather than serving solely as a deactivation pathway. In contrast to hydrolyzed titanium systems, which support formaldehyde-mediated carbon growth and carbon-chain propagation, the zirconium ensembles remain dominated by CO₂ capture, carbonate stabilization, and oxygenated carbon accumulation. This behavior defines a distinct functional boundary between photocatalytic carbon capture and reactive artificial photosynthesis. The hydrolyzed PI–ZrCl₄ ensembles therefore represent a dynamic photochemical platform in which hydrolysis, CO₂ coordination, carbonate formation, oligomer evolution proceed cooperatively under ambient conditions. These findings establish hydrolyzed zirconium–indole systems as a dynamically evolving atmospheric CO₂ capture platform whose behavior complements previously reported titanium systems. Moreover, combining the complementary properties of titanium and zirconium may provide a route toward integrating efficient atmospheric CO₂ capture with subsequent photochemical carbon-conversion pathways.

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