Adsorption-based separation techniques are pivotal in the purification of C2H2, leveraging their eco-friendly and energy-efficient attributes. However, the reusability of adsorbents is highly restricted by the trade-off between adsorption capacity and adsorption enthalpy, which is required to be urgently addressed. Herein, we demonstrated that the implantation of distortable ligands with functional groups is efficient in solving the above issue. The functional groups provided binding sites for C2H2 adsorption, while the distortable ligands optimized the pore structures to reduce adsorption enthalpy, thus balancing the trade-off between adsorption capacity and enthalpy. A series of ultra-microporous MOFs was successfully constructed by employing different pyridine ligands. The adsorption capacity of SNNU-504 after optimization was effectively enhanced, while the adsorption enthalpy hardly increased due to the adjustable ligand torsion angle. Breakthrough experiments and GCMC simulations further verified the potential C2H2/CO2 separation applications.
The removal of trace carbon dioxide (CO 2 ) from acetylene (C 2 H 2 ) through adsorption poses a significant challenge due to their similar kinetic diameters and physical properties. Here, we report a novel solid amine adsorbent, polyethyleneimine-diethanolamine functionalized silica dioxide (termed P/D-SD), which exhibited a remarkable CO 2 adsorption capacity of 1.76 mmol/g at 298 K and 0.0004 bar. The IAST selectivity of the CO 2 /C 2 H 2 (1/99, v/v) mixture of P/D-SD was 7.98E + 05. The exceptional separation performance of P/D-SD is demonstrated through breakthrough experiments, producing ultra-high purity C 2 H 2 (greater than 99.9 %) from CO 2 /C 2 H 2 (1/99) mixtures. Its CO 2 adsorption performance remains largely unaffected under different humidity condition. Furthermore, P/D-SD exhibited excellent stability in the adsorption–desorption cycle and rapid CO 2 adsorption kinetics at different temperatures when compared with P-SD. The adsorption mechanism of P/D-SD with CO 2 was studied as a chemisorption process via in situ DRIFTS.
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