The creation of innovative porous materials for CO2 capture and separation is proving extremely relevant for environmental sustainability and global warming mitigation. In this study, modified Ce-UiO-66 MOFs were synthesized in 10 min using simultaneous microwave and ultrasound irradiation method. The porosity of the MOF was altered using the soft-templating approach. This strategy resulted in the construction of a hierarchically micro-mesoporous structure with an average mesopore size of 11.10 nm. The as-obtained MOFs, abbreviated as CUT, were characterized with SEM, XRD, FTIR, TGA, BET, and evaluated as CO2 adsorbents. The results displayed preserved crystal structure, higher thermal stability up to 570 °C. The heightened diffusion of CO2 molecules to the micropores promoted by mesopore channels, endued CUT with an over-all CO2 adsorption uptake of 2.53 mmol/g at 273 K at 1 bar outperforming equivalent Ce-UiO-66 MOFs. Notably, the CUT adsorbent showed improved CO2/N2 IAST selectivity (34.2 vs 24.6) and CO2 isosteric heat of adsorption (Qst = 30.15 vs 25 kJ/mol) in contrast to pristine UiO-66 (Zr).