Carbon dioxide adsorption capacity of porous carbon after polyamine impregnation under different pore structures and temperatures

Abstract

Composites of polyethyleneimine (PEI) and porous carbon (PC) are effective and reversible CO2 adsorbents. Within these composite materials, the morphologies of PEI in different pore structures significantly influence CO2 capture behaviors, yet little is known about the movement of PEI molecules in PC. In this work, the CO2 adsorption capacity of PEI loaded on PC with different pore structures was investigated. The result shows that the average pore size of 3.63 nm loaded PEI has the maximum CO2 adsorption capacity at 50 ℃. Based on it, we establish a model that the loading of PEI in different pore size PCs for the first time and explain the morphology of PEI in the pore channel. This model displayed the changes in PEI chains and PEI agglomerated cores at different temperatures and pore sizes. In particular, the uptake amount of CO2 in PEI is attributed to the number of amine sites accessible. The PEI agglomerated core formed in smaller pore sizes is smaller and is more susceptible to temperature, thus the PEI agglomerated core exposes more amine sites for CO2 adsorption with increasing temperature. As the PC pore size increases, the PEI agglomerate core also enlarges, leading to greater spatial resistance and therefore exposing fewer amine-based sites when the temperature increases. The investigation of PEI/PC structure–property correlations and adsorption properties provides unique insights that could inform the rational design of better adsorbents.