Facilitated Photocatalytic CO 2 Reduction in Aerobic Environment on a Copper-Porphyrin Metal-Organic Framework.

Herein, we fabricated a π-π stacking hybrid photocatalyst by combining two two-dimensional (2D) materials: g-C 3 N 4 and a Cu-porphyrin metal-organic framework (MOF). After an aerobic photocatalytic pretreatment, this hybrid catalyst exhibited an unprecedented ability to photocatalytically reduce CO 2 to CO and CH 4 under the typical level (20 %) of O 2 in the air. Intriguingly, the presence of O 2 did not suppress CO 2 reduction; instead, a fivefold increase compared with that in the absence of O 2 was observed. Structural analysis indicated that during aerobic pretreatment, the Cu node in the 2D-MOF moiety was hydroxylated by the hydroxyl generated from the reduction of O 2 . Then the formed hydroxylated Cu node maintained its structure during aerobic CO 2 reduction, whereas it underwent structural alteration and was reductively devitalized in the absence of O 2 . Theoretical calculations further demonstrated that CO 2 reduction, instead of O 2 reduction, occurred preferentially on the hydroxylated Cu node.