Ultramicroporous Lonsdaleite Topology MOF with High Propane Uptake and Propane/Methane Selectivity for Propane Capture from Simulated Natural Gas.

Propane (C 3 H 8 ) is a widely used fuel gas. Metal-organic framework (MOF) physisorbents that are C 3 H 8 selective offer the potential to significantly reduce the energy footprint for capturing C 3 H 8 from natural gas, where C 3 H 8 is typically present as a minor component. Here we report the C 3 H 8 recovery performance of a previously unreported lonsdaleite, lon , topology MOF, a chiral metal-organic material, [Ni( S -IEDC)(bipy)(SCN)] n , CMOM-7 . CMOM-7 was prepared from three low-cost precursors: Ni(SCN) 2 , S -indoline-2-carboxylic acid ( S -IDECH), and 4,4'-bipyridine (bipy), and its structure was determined by single crystal X-ray crystallography. Pure gas adsorption isotherms revealed that CMOM-7 exhibited high C 3 H 8 uptake (2.71 mmol g -1 ) at 0.05 bar, an indication of a higher affinity for C 3 H 8 than both C 2 H 6 and CH 4 . Dynamic column breakthrough experiments afforded high purity C 3 H 8 capture from a gas mixture comprising C 3 H 8 /C 2 H 6 /CH 4 (v/v/v = 5/10/85). Despite the dilute C 3 H 8 stream, CMOM-7 registered a high dynamic uptake of C 3 H 8 and a breakthrough time difference between C 3 H 8 and C 2 H 6 of 79.5 min g -1 , superior to those of previous MOF physisorbents studied under the same flow rate. Analysis of crystallographic data and Grand Canonical Monte Carlo simulations provides insight into the two C 3 H 8 binding sites in CMOM-7 , both of which are driven by C-H···π and hydrogen bonding interactions.