A Data-Driven Approach to Molten Salt Synthesis of N-Rich Carbon Adsorbents for Selective CO₂ Capture.

Abstract

Applying a design of experiments methodology to the molten salt synthesis of nanoporous carbons enables inverse design and optimization of nitrogen (N)-rich carbon adsorbents with excellent CO₂ /N₂ selectivity and appreciable CO₂ capacity for carbon capture via swing adsorption from dilute gas mixtures such as natural gas combined cycle flue gas. This data-driven study reveals fundamental structure-function relationships between the synthesis conditions, physicochemical properties, and achievable selective adsorption performance of N-rich nanoporous carbons derived from molten salt synthesis for CO₂ capture. Taking advantage of size-sieving separation of CO₂ (3.30 Å) from N₂ (3.64 Å) within the turbostratic nanostructure of these N-rich carbons, while limiting deleterious N₂ adsorption in a weaker adsorption site that harms selectivity, enables a large CO₂ capacity (0.73 mmol g^-1 at 30.4 Torr and 30 °C) with noteworthy concurrent CO₂ /N₂ selectivity as predicted by the ideal adsorbed solution theory (S_IAST = 246) with an adsorbed phase purity of 91% from a simulated gas stream containing only 4% CO₂ . Optimized N-rich porous carbons, with good physicochemical stability, low cost, and moderate regeneration energy, can achieve performance for selective CO₂ adsorption that competes with other classes of advanced porous materials such as chemisorbing zeolites and functionalized metal-organic frameworks.