Intermediate dual-site confinement recognition in a Cu-based metal–organic framework for efficient capture of trace SO2 over CO2--颗粒学报PARTICUOLOGY

a College of Environmental Science and Engineering, State Key Laboratory of Water Pollution Control and Green Resource Recycling, Shanghai Institute of Pollution Control and Ecological Security, Tongji University, Shanghai, 200092, China
b Key Laboratory of Cities' Mitigation and Adaptation to Climate Change in Shanghai, China Meteorological Administration (CMA), Tongji University, Shanghai, 200092, China

10.1016/j.partic.2026.07.010

Volume 117, October 2026, Pages 156-163

Received 22 June 2026, Revised 13 July 2026, Accepted 22 July 2026, Available online 22 July 2026, Version of Record 30 July 2026.

E-mail: 159219yifan_gu@tongji.edu.cn

Highlights

• A MOF with ultra-microporous channels and two oppositely aligned open Cu(II) sites was prepared for trace SO₂ capture.

• Cu-tpo-tpt exhibits excellent IAST selectivity of 264 for SO₂/CO₂ (0.2/99.8, v/v) at 298 K.

• Cu-tpo-tpt exhibits efficient dynamic separation performance and regeneration capacity for trace SO₂ capture.

• Mechanistic analysis reveals V-shaped SO₂ geometrically matches dual Cu(II) sites, enhancing SO₂/CO₂ selectivity.

Abstract

Effective removal of SO₂ from flue gas is critical for the environment, human health, and the following CO₂ capture process. Conventional flue-gas desulfurization technologies are energy-intensive and insufficient for deep removal of such trace SO₂. However, even a low concentration of SO₂ (ca. 2000 ppm) can significantly degrade the performance of adsorbents employed in CO₂ capture from flue gas, thus demanding its deep removal from CO₂-rich gas streams. Herein, we report a metal-organic framework, Cu-tpo-tpt, which possesses ultra-microporous channels functionalized with two oppositely aligned open Cu(II) sites. Upon activation, the geometrically complementary spatial arrangement of two opposing open Cu(II) sites within the channel perfectly fits the bent V-shaped SO₂ molecule, while linear CO₂ exhibits a molecular size exceeding the aperture distance between the dual Cu(II) sites. Benefiting from the geometrically matched dual-site confinement recognition strategy, Cu-tpo-tpt exhibits preferential adsorption of SO₂ over CO₂. At 298 K and 0.1 bar, the SO₂ adsorption capacity (2.7 mmol g⁻¹) is considerably higher than that for CO₂ (1.0 mmol g⁻¹), leading to an exceptional IAST selectivity of 264 for SO₂/CO₂ (0.2/99.8, v/v). Dynamic breakthrough experiment further confirms its outstanding separation performance. Mechanistic analysis reveals that the precise geometric matching between SO₂ and the Cu(II) sites enhances host-guest interactions, facilitating highly selective recognition of trace SO₂ over abundant CO₂. This finding not only addresses a critical challenge for trace SO₂ capture, but also provides new insights for the rational design of advanced adsorbents targeting industrial gas separation processes.

Graphical abstract

Keywords

Metal-organic framework; Flue gas desulfurization; SO₂/CO₂ separation; Geometric matching; Open metal sites

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