Multielectron transportation of polyoxometalate-grafted metalloporphyrin coordination frameworks for selective...

Photocatalytic CO₂ reduction into energy carriers is of utmost importance due to the rising concentrations of CO₂ and the depleting energy resource. However, the highly selective generation of desirable hydrocarbon fuel, such as methane (CH₄), from CO₂ remains extremely challenging. Herein, we present two stable polyoxometalate-grafted metalloporphyrin coordination frameworks (POMCFs), which are constructed with reductive Zn-ϵ-Keggin clusters and photosensitive tetrakis(4-carboxylphenyl)porphyrin (H₂TCPP) linkers, exhibiting high selectivity (>96%) for CH₄ formation in a photocatalytic CO₂-reduction system. To our knowledge, the high CH₄ selectivity of POMCFs has surpassed all of the reported coordination-framework-based heterogeneous photocatalysts for CO₂-to-CH₄ conversion. Significantly, the introduction of a Zn-ϵ-keggin cluster with strong reducing ability is the important origin for POMCFs to obtain high photocatalytic selectivity for CH₄ formation, considering that eight Mo^V atoms can theoretically donate eight electrons to fulfill the multielectron reduction process of CO₂-to-CH₄ transformation.