Trace SO₂ capture within the engineered pore space using a highly stable SnF₆^2--pillared MOF

Developing reliable solid sorbents for efficient capture and removal of trace sulfur dioxide (SO₂) under ambient conditions is critical for industrial desulfurization operations, but poses a great challenge. Herein, we focus on SNFSIX-Cu-TPA, a highly stable fluorinated MOF that utilizes SnF₆^2- as pillars, for effectively capturing SO₂ at extremely low pressures. The exceptional affinity of SNFSIX-Cu-TPA towards SO₂ over CO₂ and N₂ was demonstrated through single-component isotherms and corroborated by computational simulations. At 298 K and 0.002 bar, this material displays a remarkable gas uptake of 2.22 mmol g^-1. Among various anion fluorinated MOFs, SNFSIX-Cu-TPA shows the highest SO₂/MF₆^2- of 1.39 mmol mmol^-1 and exhibits a low Q_st of 58.81 kJ mol^-1. Additionally, SNFSIX-Cu-TPA displays excellent potential for SO₂/CO₂ separation, as evidenced by its ideal adsorbed solution theory (IAST) selectivity of 148 at a molar fraction of SO₂ of 0.01. Dynamic breakthrough curves were obtained to reveal the effective removal of trace SO₂ from simulated flue gas (SO₂/CO₂/N₂; v/v/v 0.2/10/89.8) with a high dynamic capacity of up to 1.52 mmol g^-1. Furthermore, in situ TGA demonstrated the efficient and reversible capture of 500 ppm SO₂ over 20 adsorption-desorption tests. This durable material presents a rare combination of exceptional SO₂ capturing performance, good adsorption selectivity, and mild regeneration, thus making it a good candidate for a realistic desulfurization process.