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

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.