Electron‐Rich Nanorelay Enhances Ligand‐to‐Metal Charge Transfer in Lanthanide Metal–Organic Frameworks during Photocatalytic CO 2 Conversion

Abstract Lanthanide metal–organic frameworks (Ln‐MOFs) exhibit potential yet limitations for photocatalytic CO 2 conversion. Their “potential” stems from their CO 2 adsorption capability, attributed to the ligand‐field effects and specialized pore microenvironments; the “limitation” is due to the inertness of ligand‐to‐metal charge transfer (LMCT) originating from the 4 f electron shielding effect, high ionization energies, and low electron affinities. Introducing electron‐rich active components, acting as nanorelays, into Ln‐MOF pores offers a viable strategy to overcome these drawbacks, though the underlying mechanisms remain to be elucidated. Herein, the mechanistic pathway underlying efficient photocatalytic CO 2 conversion in the B 12 H 12 @Tb‐based MOF composite is elucidated, wherein the electron‐rich closo ‐[B 12 H 12 ] 2− serves as the counteranion and functions within the pores as an electron nanorelay. The crystalline structure of this composite is revealed by single‐crystal X‐ray diffraction data. In situ and transient techniques, together with theoretical calculation, uncovered the serial mechanism, including how closo ‐[B 12 H 12 ] 2− nanorelay facilitates a radical‐assisted electron transfer and subsequently improves LMCT within Ln‐MOF, as well as how Tb 3+ serves as the catalytic active center for the intermediate process pathways of CO 2 molecules. These mechanistic studies not only unveil the “black box” of MOF‐based composite photocatalyst, but also provide solutions for the development of efficient artificial photosynthesis catalysts.