Zn-MOFs Containing Pyridine and Bipyridine Carboxylate Organic Linkers and Open Zn2+ Sites

Two Zn-based metal-organic frameworks (Zn-MOFs) were solvothermally synthesized using two pyridine-based carboxylate linkers to generate unique pore topologies, as evidenced by single-crystal XRD analysis. These Zn-MOFs provided coordinatively unsaturated Zn2+ sites with square-pyramidal geometry, leading to an enhanced interaction with CO2, as demonstrated by sub-atmospheric pressure isotherms. The presence of open Zn2+ sites in these MOFs was validated by Raman spectroscopy under atmospheric CO2, revealing the presence of CO2 chemisorbed on surface sites. Additionally, in situ DRIFT spectra of chemisorbed acetic acid provided evidence for the formation of acetate-Zn2+ species after adsorption compared to IRMOF-1, which showed only physisorbed acetic acid species.