Engineering of covalent organic framework (COF) via mono-doping and co-doping for the detection of CO2 gas pollutant

Abstract

The increasing accumulation of carbon dioxide (CO₂) in the atmosphere as a result of human activities such as burning of fossil fuel and deforestation, pose a significant threat to human well-being, biodiversity, and ecosystems. As a potential greenhouse gas, contributing to global warming and climate change, the need for its environmental remediation via capturing through COF-based materials arose herein. In this work, the detection of CO₂ gas on newly modified covalent organic framework (COF) surface was investigated using density functional theory (DFT). All computational calculations were performed using the DFT/ωB97XD/6–311 + +g(d,p)/def2svp/LANL2DZ computational method. Various analyses were conducted to inquire into the electronic properties, nature of inter- and intra-molecular interactions, adsorption phenomena, and sensor properties. Upon adsorption, the studied systems showcased a non-covalent form of interaction in most cases as observed in AIM analysis. Red colors observed at the center of all the B₃O₃ and benzene rings of the COF surface encompassing the doped metal and heteroatoms, identified steric repulsive forces, suggesting spatial constraints and repulsion among neighboring atoms. The green colors observed over the CO₂ gas molecule and the benzene ring with the doped atoms identified the presence of van der Waals force of attraction. Additionally, the doping and co-doping effects of the COF surface significantly dropped the energy gap for all the newly modelled surfaces, thereby increasing reactivity of the modified surfaces. The present of dopant atoms significantly increased the dipole moment, which is as a result of enhanced charge separation in the doped atoms, resulting in higher intensity of charge separation. The adsorption phenomenal is best describe as physisorption, owing to the positive adsorption energies obtained for all systems. Least adsorption energy of 0.327, 0.490, and 0.327 eV are in CO₂@S-Ni-COF, CO₂-COF, and CO₂@Ni-COF systems, implying that the CO₂ gas pollutants would be strongly sensed on S-Ni-COF, COF, and Ni-COF adsorbents. Hence, the S-Ni-COF and Ni-COF adsorbent materials has potential use in the development of efficient CO₂ gas sensors and capture materials, promoting environmental remediation and the mitigation of climate change.