A DFT study on the selective adsorption of CO from water-gas shift reaction tail gas by 3d transition metal porphyrins

Abstract

This study employs density functional theory (DFT) to systematically investigate the selective adsorption mechanisms and desorption conditions of carbon monoxide (CO) from water-gas shift reaction (WGSR) tail gas using 3d transition metal porphyrins (MP, M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn). The aim is to provide a theoretical basis for designing high-performance CO capture materials for WGSR tail gas treatment. The results indicate that ScP, TiP, and VP exhibit strong CO adsorption capacity and high selectivity within the WGSR environment; however, they face challenges in desorption. In contrast, FeP and CoP exhibit moderate CO adsorption performance, and within the temperature range of 300–800 K, up to 99% of CO can be desorbed. Electronic structure analysis reveals that σ-donation and π-backdonation dominate the variation in adsorption energy in the ScP-CO, TiP-CO, and VP-CO systems. For the FeP-CO and CoP-CO systems, despite their relatively strong σ-donation and π-backdonation interactions, the extremely short adsorption distance leads to a sharp increase in mutual polarization, resulting in comparatively weaker interactions with CO. Among the 3d transition metal porphyrins, ScP, TiP, VP, FeP, and CoP show potential as promising materials for purifying WGSR tail gas.