Light-Induced Binding and Reduction of CO ₂ over Transient Open Ce(III) Sites in a Metal–Organic Framework

Metal–organic framework (MOF) materials share some common features with metalloenzymes including site-isolated metal centers that template dynamic substrate activation within a functionalized cavity or pocket. We report the light-induced reversible binding of CO 2 in a cerium-based MOF, Ce-UiO-66-NH 2, incorporating an amino functionalized linker, which enables photoreduction of CO 2 to CO in H 2 O without using sacrificial agents. A production rate for CO of 126 μmol·g –1 ·h –1 with 100% selectivity is observed, outperforming its non-amine analogue (Ce-UiO-66) and benchmark catalysts reported to date. In situ infrared, X-ray absorption, electron paramagnetic resonance and transient absorption spectroscopy reveal that photoexcitation induces a ligand-to-metal charge transfer to generate transient open Ce(III) sites that bind CO 2 in a μ-(η 1 -O)(η 1 -C) binding mode. This binding is reversible and activates CO 2 for subsequent photoreduction to CO. This work will promote the design of photocatalysts capable of synthesizing fuels from CO 2 .