Iridium Photosensitizers Immobilized on Metal–Organic Layers Lead to Enhanced Enantioselectivity in Ni/Ir Dual Photocatalysis

The Ir/Ni dual-catalytic system plays a crucial role in asymmetric photocatalysis for synthesizing enantioenriched compounds. However, challenges such as the high cost and limited sustainability of Ir complexes hinder its broader application. In this study, we designed three metal-organic layers (MOLs) and immobilized functionalized Ir photosensitizers (Ir-PSs) on their surfaces via coordination exchange or click chemistry, yielding six MOL-PSs hybrids. Chiral Ni complexes also adhere to the MOL surface through coordination bonds. These dual catalysts exhibited enantioselectivity (up to 99% ee) superior to that of Ir-PF₆ in the asymmetric acylation of saturated N-heterocycles at α-C(sp³)─H bonds. The enhanced enantioselectivity of the MOL-PSs over Ir-PF₆ likely arises from steric change of chiral Ni complexes coordinating with hydroxyl or amine groups on the MOLs, which also form ion pairs with Ir-PSs. This strategy demonstrates broad applicability across diverse chiral ligands and substrates, underscoring the potential of using MOLs in asymmetric photocatalysis to enhance both enantioselectivity and catalyst reusability.