Metal-organic framework-stabilized organic anion radicals that electrocatalytically convert CO2 into multi-carbon products.

Abstract

The electrochemical reduction of CO2 to multi-carbon (C2+) products remains a major challenge due to the high activation barrier associated with C-C bond formation and the limited availability of selective electrocatalytic platforms. Herein, we demonstrate that Metal-Organic Frameworks (MOFs) can stabilize electrochemically generated organic anion radicals that drive heterogeneous CO2 conversion through single-electron transfer pathways. Specifically, benzonitrile-functionalized UiO-66 (UiO-66-CN) was employed as a porous scaffold that spatially isolates redox-active organic sites, enabling the heterogeneous electrochemical formation of benzonitrile anion radicals. These MOF-tethered radicals activate CO2 to form CO2 -˙ intermediates, which subsequently undergo C-C coupling to yield a C2 product, oxalate, with faradaic efficiencies reaching 85%. Operando scanning electrochemical microscopy (SECM) directly detected CO2 -˙ during catalysis, while operando infrared reflection absorption spectroscopy measurements revealed catalyst-CO2 interactions consistent with an inner-sphere electron-transfer mechanism. Beyond oxalate formation, the generated CO2 -˙ species were harnessed for electrocatalytic styrene carboxylation, affording phenylsuccinic acid and 3-phenylpropanoic acid with total faradaic efficiencies exceeding 50%. These findings establish MOF-stabilized organic anion radicals as a versatile metal-free heterogeneous catalytic platform for promoting selective CO2 activation and complex carbon-carbon bond-forming reactions, to generate value-added multi-carbon products.

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