Co-adsorption enhancement of formaldehyde/carbon dioxide over modified hexagonal boron nitride for whole-surface capture purification

Abstract

Simultaneous capture of formaldehyde (HCHO) and carbon dioxide (CO₂) in indoor air is promising of achieving indoor-air purification. Of all potential adsorbents, hexagonal boron nitride (h-BN) is one of the most suitable species owing to facile formation of attraction points. Therefore, in this study, performances of HCHO and CO₂ being adsorbed over pure/modified h-BN are systematically investigated via density functional theory (DFT) calculations. Minutely speaking, direct interaction between HCHO and CO₂, single-point adsorption enhancement of HCHO over modified h-BN, co-adsorption reinforcement of HCHO/CO₂ as well as relevant thermodynamic characteristics are major research contents. According to calculation results, there is relatively strong attraction between HCHO and CO₂ owing to hydrogen bonds, which is in favor of co-adsorption of HCHO/CO₂. As to single-adsorption of HCHO, C-doped h-BN shows better adsorption features than P-doped h-BN and C/P-doped h-BN is slightly weakened in adsorption ability due to surficial deformation caused by P atoms. For co-adsorption of HCHO/CO₂, CO₂ is the protagonist via formation of quasi-carbonate with the help of delocalized π-orbital electrons. Regarding effects of temperatures on adsorption strengths, they depend on interelectronic interactions among dopant atoms and finally derives from dispersion of π bonds across adsorbents. Overall, this study provides detailed mechanisms for co-capture of HCHO/CO₂ to accomplish indoor-air purification.

Keywords: Carbon dioxide; Co-adsorption enhancement; DFT; Formaldehyde; Indoor air purification.