Photo-Responsive Carbon Capture over Metalloporphyrin-C60 Metal-Organic Frameworks via Charge-Transfer.

Abstract

Great efforts have been devoted to the study of photo-responsive adsorption, but its current methodology largely depends on the well-defined photochromic units and their photo-driven molecular deformation. Here, a methodology to fabricate nondeforming photo-responsive sorbents is successfully exploited. With C₆₀-fullerene doping in metalloporphyrin metal-organic frameworks (PCN-M, M = Fe, Co, or Ni) and intensively interacting with the metalloporphyrin sites, effective charge-transfer can be achieved over the metalloporphyrin-C₆₀ architectures once excited by the light at 350 to 780 nm. The electron density distribution and the resultant adsorption activity are thus changed by excited states, which are also stable enough to meet the timescale of microscopic adsorption equilibrium. The charge-transfer over Co(II)-porphyrin-C₆₀ is proved to be more efficient than the Fe(II)- and Ni(II)-porphyrin-C₆₀ sites, as well as than all the metalloporphyrin sites, so the CO₂ adsorption capacity (CAC; at 0 °C and 1 bar) over the C₆₀-doped PCN-Co can be largely improved from 2.05 mmol g^-1 in the darkness to 2.69 mmol g^-1 with light, increased by 31%, in contrast to photo-irresponsive CAC over all C₆₀-undoped PCN-M sorbents and only the photo-loss CAC over C₆₀.