Crosslinking two-dimensional metalloporphyrin (Me-TCPP) nanosheet with poly(ethylene) glycol semi-interpenetrating polymer network for ultrahigh CO2/N2 separation selectivity via "rubber-band" straightening effect.

To efficient separate carbon dioxide from power plant flue gas, three two-dimensional (2D) metalloporphyrin (Me-TCPP) nanosheets, Zn-TCPP, Cu-TCPP, and Ni-TCPP are crosslinked with poly(ethylene) glycol (PEO) semi-interpenetrating polymer via "rubber-band" straightening effect. Dispersion-corrected periodic density functional (DFT-D2) calculation reveals that the lowest N 4 -Metalδ+···Oδ− distance (2.81 Å) and the highest binding energy (19.9 kJ mol−1) are obtained between CO 2 molecule and metalloporphyrin center (Zn–N 4), as well as the lowest O 4 -Metalδ+···Oδ− distance (4.68 Å) and the highest binding energy (18.8 kJ mol−1) on metal cluster (Zn–O 4). The 2D Zn-TCPP nanosheet with the strongest affinity toward CO 2 molecule generates Zn2+-CO 2 complex to remarkably boost CO 2 solubility in mixed matrix membrane (MMMs). Thus, 2.5 wt% Zn-TCPP nanosheet incorporated PEO-based MMMs dramatically promotes CO 2 permeability to 198 Barrers and ultrahigh CO 2 /N 2 selectivity to 81. A novel "rubber-band" straightening effect is found and verified, which is induced by abundant interfacial coordination bonds between metal ions in nanosheets and ester groups (O–C O) in PEO polymer chains, the strong Me–O–C O interaction sites hold polymer chains and lead to their regular rearrangement. Owing to the abundant PEG groups in PEGMEA macromolecule chains, incorporating 1 wt% Zn-TCPP nanosheet into crosslinked XLPEGDAcoPEGMEA polymer achieves the highest CO 2 permeability of 398 Barrers. Graphical abstract of fabrication process of crosslinked PEO-based (MMMs doped with 2D Ni-TCPP, Cu-TCPP, and Zn-TCPP nanosheets. [Display omitted] • Three 2D metalloporphyrin (Me-TCPP) nanosheets, Zn-TCPP, Cu-TCPP, and Ni-TCPP are crosslinked with PEO semi-interpenetrating polymer. • A novel "rubber-band" straightening effect is verified, induced by interfacial coordination bonds between metal ions and ester groups. • DFT calculation reveal effect between Me-TCPP nanosheet and CO 2 via N 4 –Me⋯F and O 4 –Me⋯F interaction. • 2.5 wt% Zn-TCPP nanosheet incorporated PEO-based MMMs dramatically achieve ultrahigh CO 2 /N 2 selectivity of 81. [ABSTRACT FROM AUTHOR]