Unlocking Catalytic Activity of Co (II)‐MOFs Through Nitrogen‐Rich Sites and Tunable Acid‐Base Functionalities beyond Porosity

ABSTRACT

A combination of highly functional N,N′‐bis(pyridine‐4‐yl)pyridine‐2,6‐dicarboxamide ( L1 ) and 2,6‐naphthalenedicarboxylic acid (H ₂ L ₂ ) with Co(II) ions yields a two‐dimensional three‐fold interpenetrated staircase Metal‐organic framework (MOF), CoMOF‐1 . Although the interpenetration reduces porosity, as confirmed by surface analysis, CoMOF‐1 features bifunctional catalytic sites, i.e., acidic (16.320 mmol g ⁻¹ ) from H ₂ L2 and nitrogen‐rich basic sites (1.983 mmol g ⁻¹ ) from L1 quantified by temperature‐programmed desorption (TPD). The structural traits of CoMOF‐1 were compared with CoMOF‐2 , a three‐component 3D framework, constructed from Co(II) ions, the imine‐based ((1E,1'E)‐N,N'‐(1,4‐phenylene)bis(1‐(pyridin‐4‐yl)methanimine) ( L3 ) and 1,1′‐biphenyl‐4,4′‐dicarboxylic acid (H ₂ L4 ) ligand. Despite their relatively low porosity, both CoMOF‐1 and CoMOF‐2 were employed for cycloaddition of CO ₂ , converting challenging substrates such as styrene oxide to cyclic carbonates in high yields (∼98%) and with high turnover numbers. CoMOF‐1 and CoMOF‐2 also exhibit excellent stability and recyclability over six catalytic cycles. These findings highlight that nitrogen donor functionalities are essential for promoting CO ₂ cycloaddition and can compensate for limited porosity, offering a robust design strategy for efficient CO ₂ conversion using MOF‐based catalysts.