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

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 %.