Functionalized UiO-66-NH2 Metal-Organic Framework for Selective CO2/CH4 and CO2/N2 Separation: Adsorption Isotherms, IAST Selectivity, and Fixed-Bed Breakthrough Performance

This study investigates amine-functionalized UiO-66-NH2 MOF for selective CO2/CH4 and CO2/N2 separation with adsorption isotherm characterization, IAST selectivity calculation, and fixed-bed breakthrough column testing within the context of chemical engineering and porous materials science, an area of growing scientific importance given its implications for natural gas sweetening, post-combustion CO2 capture adsorbent design, and water-stable MOF screening for industrial gas separation. Using solvothermal MOF synthesis, PXRD phase purity, N2-BET surface area, TGA stability, single-component isotherms (Micromeritics ASAP 2020), dual-site Langmuir fitting, IAST selectivity for 15:85 CO2/N2 and 50:50 CO2/CH4, and fixed-bed breakthrough column (10 cm x 1 cm) at 1 bar and 10 bar, we examine UiO-66-NH2 amine groups providing additional CO2 chemisorption sites via carbamate formation at low CO2 partial pressures, increasing Henry law constant and selectivity at sub-atmospheric pressures relevant to post-combustion capture; Zr6O4(OH)4 nodes providing exceptional water stability (zeolite-like stability vs. water-sensitive MOFs) in 3 synthesis batches of UiO-66-NH2 with 5 commercial MOF comparators (HKUST-1, MIL-53(Al), MIL-101(Cr), Zeolite 13X, activated carbon) for selectivity benchmarking; breakthrough: n=3 column experiments per gas mixture per pressure drawn from Lakeview Chemical Engineering Institute materials synthesis lab, Micromeritics ASAP 2020 gas sorption analyzer, custom-built fixed-bed breakthrough column with Agilent GC for effluent analysis. Results indicate that UiO-66-NH2 CO2 uptake 2.84 mmol/g at 0.15 bar (298 K), IAST selectivity CO2/N2 = 48.4 (vs. 24.2 UiO-66 unfunctionalized) and CO2/CH4 = 12.4; breakthrough column CO2 purity >99.4% at 5 min bed saturation; water stable to 95% RH for 7 days (p < 0.001), with CO2/N2 selectivity 48.4; CO2 uptake 2.84 mmol/g; 99.4% CO2 purity in breakthrough as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to chemical engineering and porous materials science and carry actionable implications for the design of programs and policies targeting natural gas sweetening, post-combustion CO2 capture adsorbent design, and water-stable MOF screening for industrial gas separation.