Selective capture of trace sulfur gas by porous covalent-organic materials

• PAF-302 shows the highest excess uptake of H2S and SO2.
• COF-6 is an excellent material for the separation of sulfur gas.
• The modified DIH equation is suitable for the separation of trace sulfur gas mixtures.

We have systematically investigated adsorption and separation of the sulfur gas H2S and SO2 in covalent-organic materials (COMs) by using molecular simulation. Results indicate that among these materials studied, PAF-302 shows the highest excess uptake of H2S (51.94 mmol/g) and SO2 (50.69 mmol/g) due to its large pore volume and high BET surface area. Both maximum excess uptakes of H2S and SO2 follow the order of PAF-302>COF-102>COF-10>COF-5>COF-8>COF-6, which is entirely consistent with the orders of the pore volumes. For gas mixtures, the selectivity of these two-dimensional (2D) COM materials is obviously better than the three-dimensional (3D) COM materials, especially for COF-6 with smaller pore size. In short, PAF-302 is an excellent candidate for H2S and SO2 adsorption, while COF-6 is an excellent material for sulfur gas separation. In addition, we also find that the modified equation based on the difference of isosteric heats (i.e. DIH equation) can predict the selectivity of trace sulfur gas mixtures at zero pressure satisfactorily.

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