Polyethyleneimine-Modified UiO-66-NH2(Zr) Metal–Organic Frameworks: Preparation and Enhanced CO2 Selective Adsorption

UiO-66-NH 2 , 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 2 and CO 2 -preabsorbed polyethyleneimine (PEI). The resulting PEI-modified MOFs, abbreviated as PEI C @UiO, were characterized with 1 H NMR, Fourier transform infrared, powder X-ray diffraction, Brunauer-Emmett-Teller, scanning electron microscopy, and thermogravimetric analysis and evaluated as CO 2 adsorbents. In comparison with pristine UiO-66-NH 2 , the PEI C @UiO adsorbents have reduced specific surface area (7-150 m 2 /g) but maintained the same crystal structure. Particularly, the PEI C 96@UiO adsorbent exhibited significantly improved CO 2 /N 2 adsorption selectivity (48 vs 25) and higher CO 2 adsorption capacity (3.2 vs 2.7 mmol/g). The adsorbent also displayed moderate desorption energy (68 kJ/mol CO 2 ), superior moisture endurance, and recyclability, which are very desirable for practical applications.