Post‐Nickelation of a Crystalline Trinuclear Copper Organic Framework for Synergistic Photocatalytic Carbon Dioxide Conversion

Abstract Rational regulation of electronic structures and functionalities of framework materials still remains challenging. Herein, reaction of 4,4′,4′′‐nitrilo‐tribenzhydrazide with tris(μ 2 ‐4‐carboxaldehyde‐pyrazolato‐N,N′)‐tricopper (Cu 3 Py 3 ) generates the crystalline copper organic framework USTB‐11(Cu). Post‐modification with divalent nickel ions affords the heterometallic framework USTB‐11(Cu,Ni). Powder X‐ray diffraction and theoretical simulations reveal their two‐dimensional hexagonal structure geometry. A series of advanced spectroscopic techniques disclose the mixed Cu I /Cu II state nature of Cu 3 Py 3 in USTB‐11(Cu,Ni) with a uniform bistable Cu 3 4+ (Cu I 2 Cu II ) : Cu 3 5+ (Cu I Cu II 2 ) (ca. 1 : 3) oxidation state, resulting in a significantly improved formation efficiency of the charge‐separation state. This endows the Ni sites with enhanced activity and USTB‐11(Cu,Ni) with outstanding photocatalytic CO 2 to CO performance with a conversion rate of 22 130 μmol g −1 h −1 and selectivity of 98 %.