Polyethyleneimine-Modified UiO-66-NH(Zr) Metal-Organic Frameworks: Preparation and Enhanced CO Selective Adsorption.

UiO-66-NH, a zirconium-based functional metal-organic framework (MOF), was postsynthetically modified via Schiff base reaction between aldehyde groups in glutaraldehyde and amino groups in UiO-66-NH and CO-preabsorbed polyethyleneimine (PEI). The resulting PEI-modified MOFs, abbreviated as PEI@UiO, were characterized with H NMR, Fourier transform infrared, powder X-ray diffraction, Brunauer-Emmett-Teller, scanning electron microscopy, and thermogravimetric analysis and evaluated as CO adsorbents. In comparison with pristine UiO-66-NH, the PEI@UiO adsorbents have reduced specific surface area (7-150 m/g) but maintained the same crystal structure. Particularly, the PEI96@UiO adsorbent exhibited significantly improved CO/N adsorption selectivity (48 vs 25) and higher CO adsorption capacity (3.2 vs 2.7 mmol/g). The adsorbent also displayed moderate desorption energy (68 kJ/mol CO), superior moisture endurance, and recyclability, which are very desirable for practical applications.