Pore-structure control in bimetallic coordination networks for natural gas purification with record C2H6/CH4 selectivity†

Abstract

Developing effective adsorbents with high adsorption capacity and selectivity for separating methane (CH₄) from natural gas mixtures containing ethane (C₂H₆) and propane (C₃H₈) remains a significant challenge. Previous studies on CH₄/C₂H₆/C₃H₈ separation have primarily focused on enhancing C₃H₈/CH₄ selectivity, often neglecting the crucial role of C₂H₆/CH₄ selectivity, thereby limiting CH₄ productivity. Here, we present a strategy to modulate pore size and chemistry in two bimetallic coordination networks, CuIn(ina)₄ and CuIn(3-ain)₄, to enhance the separation of CH₄/C₂H₆/C₃H₈ mixtures. Remarkably, CuIn(3-ain)₄ exhibits a record C₂H₆/CH₄ selectivity and a benchmark low-pressure C₂H₆ adsorption capacity, achieving a CH₄ productivity of 7.92 mmol g⁻¹ with a purity exceeding 99.9999%, surpassing most known porous materials. Theoretical simulations reveal how selective adsorption can be finely tuned by adjusting pore size and geometry. Moreover, breakthrough experiments with ternary mixtures, along with regeneration and cycling tests, underscore the exceptional potential of CuIn(3-ain)₄ as a highly efficient adsorbent for natural gas separation.