Multielectron transportation of polyoxometalate-grafted metalloporphyrin coordination frameworks for selective CO-to-CH photoconversion.

Photocatalytic CO reduction into energy carriers is of utmost importance due to the rising concentrations of CO and the depleting energy resource. However, the highly selective generation of desirable hydrocarbon fuel, such as methane (CH), from CO 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 (HTCPP) linkers, exhibiting high selectivity (>96%) for CH formation in a photocatalytic CO-reduction system. To our knowledge, the high CH selectivity of POMCFs has surpassed all of the reported coordination-framework-based heterogeneous photocatalysts for CO-to-CH 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 CH formation, considering that eight Mo atoms can theoretically donate eight electrons to fulfill the multielectron reduction process of CO-to-CH transformation.