Unveiling the Role and Stabilization Mechanism of Cu + into Defective Ce-MOF Clusters during CO Oxidation.

Copper single-site catalysts supported on Zr-based metal-organic frameworks (MOFs) are well-known systems in which the nature of the active sites has been deeply investigated. Conversely, the redox chemistry of the Ce-counterparts is more limited, because of the often-unclear Cu ²⁺ /Cu ⁺ and Ce ⁴⁺ /Ce ³⁺ pairs behavior. Herein, we studied a novel Cu ²⁺ single-site catalyst supported on a defective Ce-MOF, Cu/UiO-67(Ce), as a catalyst for the CO oxidation reaction. Based on a combination of in situ DRIFT and operando XAS spectroscopies, we established that Cu ⁺ sites generated during catalysis play a pivotal role. Moreover, the oxygen vacancies associated with Ce ³⁺ sites and presented in the defective Cu/UiO-67(Ce) material are able to activate the O ₂ molecules, closing the catalytic cycle. The results presented in this work open a new route for the design of active and stable single-site catalysts supported on defective Ce-MOFs.