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The CO 2 capture and separation performance is enhanced by the improved structural polarity and additional adsorption sites created by anchoring alkali metal Li/Na/K. And the increase shows a positive correlation with AM concentration. Specially, UPC-6Li presents the best CO 2 capture capacity of 221.64 cm3 cm−3, along with the CO 2 over N 2 /CH 4 selectivity of 308/206, among UPC-AMs. [Display omitted] • CO 2 capture and separation performance were evaluated in 2D-COFs anchored by different concentration alkali metal (Li, Na, and K). • UPC-6Li exhibited the best CO 2 capture capacity of 221.64 cm3 cm−3 and CO 2 over N 2 /CH 4 selectivity of 308/206. • Improved structural polarity and additional metal adsorption sites are the main reasons for optimized performance. The development of advanced adsorbents with high CO 2 capture and separation performances is essential for decreasing atmospheric CO 2 concentration. Herein, grand canonical Monte Carlo and density functional theory were employed to investigate the adsorption and separation properties of CO 2 , N 2 , and CH 4 in 2D covalent organic framework (COFs) anchored by alkali metal (AMs) Li, Na, and K (UPC-nAMs, n = 3 or 6) at 298 K and 0–1.0 bar. The anchoring of AMs formed favorable adsorption sites, endowing UPC-nAMs with better CO 2 capture and separation performances. This effect was more evident with an increase in Li/Na/K concentration. The CO 2 adsorption capacity of UPC-6Li/Na/K was ∼ 221.64, 188.28, and 140.50 cm3 cm−3. The smaller atomic size of Li occupied less adsorption space, resulting in the highest CO 2 capture capacity of 221.64 cm3 cm−3 with selectivity of 308/206 over N 2 /CH 4 in UPC-6Li at 298 K and 1.0 bar. Structural stability, pore characteristics, isothermal adsorption heat, van der Waals and Coulomb interactions, gas distribution density, adsorption configuration, and gas radial distribution function were analyzed to identify the intrinsic mechanism of anchoring Li/Na/K to improve CO 2 capture and separation performances. [ABSTRACT FROM AUTHOR]

• The octopus tentacle-like composite coagulant was prepared. • This special structure can improve performance of the coagulant. • Destabilizing O/W emulsified oil droplets. • The treated sewage meets the reinjection standard. The complexity of oily sewage from oilfields has risen with the advancement of polymer flooding technology, thereby increasing the treatment challenge. In this study, a composite coagulant, PVPAM-PPFS, was proposed, inspired by octopus tentacles, with PVP as the backbone. FTIR, 1H NMR and Rg radius of gyration were used to characterize the functional groups and conformation of PVPAM-PPFS in aqueous environments. The composite coagulant exhibits facile dispersion in water. Upon hydrolysis of PVPAM-PPFS, numerous molecular chains resembling octopus tentacles are formed and confirmed through Atomic Force Microscopy (AFM). When applied to oily sewage in oilfields, PVPAM-PPFS demonstrates enhanced interaction with emulsified oil layers, capturing colloidal particles in water and thereby facilitating efficient separation of oil, water, and flocs. Lastly, the mechanism of PVPAM-PPFS was analyzed through a combination of coagulation experiments and detection of floc morphology. PVPAM-PPFS will better interact with colloidal particles in water through increased charge neutralization, bridging adsorption, and sweeping capabilities. Significantly, an enhanced crude oil recovery rate is observed from the recovered oil droplets following the disruption of the emulsion layer. [ABSTRACT FROM AUTHOR]