Harmonizing Between Chemical Functionality and Surface Area of Porous Organic Polymeric Nanotraps for Tuning Carbon Dioxide Capture

Abstract

The energy sector has demonstrated significant enthusiasm for investigating post-combustion CO₂ capture, storage, and separation. However, the practical application of current porous adsorbents is impeded by challenges related to cost competitiveness, stability, and scalability. Intregation of heteroatoms in the porous organic polymers (POPs) dispense it more susceptible for CO₂ adsorption to attenuate green house gases. In this regard, two hydroxy rich hypercrosslinked POPs, namely Ph/Tt-POP have been developed by one-pot condensation polymerization using a facile synthetic strategy. The high surface areas of both the Ph/Tt-POP (1057 and 893 m²g⁻¹, respectively), and the heteroatom functionality in the POP framework instigated us to explore our material for CO₂ adsorption study. The CO₂ uptake capacities in Ph/Tt-POP are found to be 2.45 and 2.2 mmol g⁻¹, at 273 K respectively. Further, in-situ static ¹³C NMR experiment shows that CO₂ molecules in Tt-POP appear to be less mobile than those in Ph-POP which probably due to the presence of triazine functional groups along with high abundant −OH groups in the Tt-POP framework. An in-depth study of the CO₂ adsorption mechanism by density functional theory (DFT) calculations also shows that CO₂ adsorption at the cages formed by two benzyl rings represents the most stable interaction and CO₂ molecule is more favorably adsorbed on the Ph-POP with the more negative interaction energies values compared to that of Tt-POP. Further, Non-covalent interaction (NCI) plot reveals that CO₂ molecules adsorb more on the Ph-POP than Tt-POP, which can be explain by hydrogen bond formation in case of Tt-POP repeating units turning aside CO₂ molecule to interact with the Ph component. Overall, our present study reflects the comprising effects of surface area of the solid adsorbents as well as their functionality can be beneficial for developing efficient hypercrosslinked porous polymers as solid CO₂ adsorbent.