Condensability sieving porous coordination polymer membranes for preferential permeation of C1–C4 alkanes over H2

Abstract

Refinery gas contains abundant H₂ and a small amount of C₁–C₄ hydrocarbons. Here, we propose a condensability sieving strategy to realize preferential permeation of hydrocarbons over H₂ by developing halogen-induced porous coordination polymer (PCP) mixed matrix membranes (MMMs) that display condensability sieving gas transport. The 4-Cl-PCP, 5-Cl-PCP and 5-Br-PCP are synthesized by using Zr⁴⁺ and X-isophthalic acid (where X ​= ​4-Cl or 5-Cl or 5-Br) exhibit increased gas adsorption capacity with the increase in carbon number of the feed gas, but with almost no H₂ adsorption. MMMs containing the PCPs with different charge distributions enhance condensability sieving selectivity and inhibit diffusion selectivity. The permeances of the MMMs originated from condensability sieving are consistent with the polarizability-dependent adsorption of the PCP. The selectivity of the obtained MMMs for n-C₄H₁₀/H₂, C₃H₈/H₂, C₂H₆/H₂, and CH₄/H₂ achieve ∼40, ∼15, ∼5, and ∼2, respectively, exhibiting promising applications in refinery gas purification owing to their lower energy consumption compared with H₂-preferential permeation membranes.