Highly porous MOF integrated with coordination polymer glass membrane for efficient CO2/N2 separation

Abstract

The MOF crystal-glass composites (CGC) membrane, comprising a MOF crystal and MOF glass matrix, represents a novel self-supported membrane that has been effectively applied in gas separation. Nevertheless, the typical MOF glass matrix requires a higher operating temperature (>400 °C), which constrains its combination with a multitude of MOF crystals characterized by high porosity and low decomposition. In this work, Zn–P-dmbIm (coordination polymer) was chosen as the glass matrix, and MIL-101 crystal with high porosity were integrated at an operating temperature of 190 °C. Furthermore, the intrinsic low porosity of a_gZn-P-dmbIm can be enhanced by the incorporation of higher porosity MIL-101, which possessed a high specific surface area (from ∼1.7 m²/g to 401 m²/g) and porosity (from ∼0.0014 cm³/g/nm to 0.5605 cm³/g/nm) of the CGC. The intimate combination of MIL-101 and a_gZn-P-dmbIm by in-situ melting to reduce the interfacial defects, which also provides a robust foundation for effective CO₂/N₂ separation. In CO₂/N₂ (50/50, v/v) mixed gas conditions, the MIL-101/a_gZn-P-dmbIm membrane demonstrated a impressively high CO₂ permeability of 18670 barrer and CO₂/N₂ selectivity of 61, exceeding the CO₂/N₂ upper bound. The variable pressure (1–12 bar) and long-term stability (120 h) of the CGC membrane exhibited enhancing separation stability. Hence, the self-supported MIL-101/a_gZn-P-dmbIm membrane demonstrated effective CO₂/N₂ separation performance, which had the potential to significantly extend the scope of applications for MOF crystal-glass matrices.