SCHEDULED MAINTENANCE
Elucidating the role of non-covalent interactions in unexpectedly high and selective CO2 uptake and catalytic conversion of porphyrin-based ionic organic polymers†
Abstract
Here, we present viologen-porphyrin based ionic covalent organic polymers (H2-ICOP and Zn-ICOP) with multiple CO2-philic sites. The specific surface areas of H2-ICOP and Zn-ICOP were found to be 9 m2 g−1 and 20 m2 g−1, respectively. CO2 uptake analyses reveal that H2-ICOP exhibits very high CO2 capture uptake (62.9 mg g−1), which is one of the highest values among previously reported ICOPs. The results indicate very efficient non-covalent interactions between H2-ICOP and CO2. The possible non-covalent interactions of hydrogen (OCO2⋯H–N), tetrel (CCO2⋯N, CCO2⋯Cl−), pnicogen (OCO2⋯N+), and spodium bonds (OCO2⋯Zn) between CO2 and H2-ICOP and Zn-ICOP are investigated via symmetry adapted perturbation theory (SAPT) analysis and electrostatic potential maps (MEP). The strength of non-covalent interactions in H2-ICOP and Zn-ICOP is decreasing in the following order ΔEC⋯N > ΔEC⋯Cl− > ΔEO⋯N+ and ΔEZn⋯O > ΔEC⋯Cl− > ΔEC⋯N > ΔEO⋯N+, respectively. The major CO2 uptake contribution comes from CCO2⋯N tetrel bonding (−22.02 kJ mol−1) interactions for H2-ICOP, whereas OCO2⋯Zn spodium bonding (−21.065 kJ mol−1) interactions for Zn-ICOP. H2-ICOP has more CO2-philic moieties with powerful non-covalent interactions compared to Zn-ICOP, which is in good agreement with the experimental results. Furthermore, the CO2 catalytic conversion performances of Zn-ICOP and H2-ICOP gave good yields of 83% and 54%, respectively. Surprisingly, Zn-ICOP, despite having significantly lower CO2 uptake capacity, displayed better catalytic activity than H2-ICOP, owing to a higher number of counter anions (Cl−) on its surface, which shows the crucial role of the counter anion (Cl−) in the mechanism of this catalytic reaction.
- This article is part of the themed collection: Hybrid Pores for CO2 Technologies
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