Propane-selective design of zirconium-based MOFs for propylene purification

Separating propane from propylene is a significant challenge in petrochemical industry. Rational chemistry design of the propane-selective adsorbent has not been reported. This work demonstrates the first design of propane-selective adsorbents. Two strategies based on surface chemistry tuning, namely compositing 2D g-C3N4 and replacing ligand, have been proposed to yield the propane-selective g-C3N4@Zr-BPDC (BPDC = biphenyl-4,4′-dicarboxylate) and Zr-BPYDC (2,2′-bipyridine 5,5′-dicarboxylate). Whereas g-C3N4@Zr-BPDC has a high propane capacity of 8.79 mmol/g at room temperature and ambient pressure, Zr-BPYDC exhibits superior propane/propylene selectivity. The isosteric heat of propane and propylene adsorption on both adsorbents is lower than that of most reported adsorbents, indicating facile regeneration of the adsorbents. DFT calculations suggest the propane-selectivity comes from multiple CHδ+⋯Nδ− interactions between propane and nitrogen atoms of the adsorbents. Moreover, both adsorbents produce polymer-grade propylene through a one-step separation using a packed column, facilitating the energy-effective production of polymer grade propylene under ambient conditions.