Tuning the selectivity of light hydrocarbons in natural gas in a family of isoreticular MOFsElectronic supplementary information (ESI) available: Preparation and physical characterization data. Crystallographic refinement details. Additional Fig. S1-S12 and Table S1. CCDC 1530549 and 1530550. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7ta01179b

Purification of methane from other light hydrocarbons in natural gas is a topic of intense research due to its fundamental importance in the utilization of natural gas fields. Porous materials have emerged as excellent alternative platforms to conventional cryogenic methodologies to perform this task in a cost- and energy-efficient manner. Here we report a new family of isoreticular chiral MOFs, prepared from oxamidato ligands derived from natural amino acids l -alanine, l -valine and l -leucine, where, by increasing the length of the alkyl residue of the amino acid, the charge density of the MOF's channels can be tuned ( 1 > 2 > 3 ), decreasing the adsorption preference towards methane over light hydrocarbons thus improving this purification process. The validity of our rational design strategy has been proved by a combination of single-component adsorption isotherms, adsorption kinetics of CH 4 , C 2 H 6 , C 3 H 8 and n -C 4 H 10 , and breakthrough experiments of binary CH 4 /C 2 H 6 and CH 4 /C 3 H 8 mixtures. The kinetic adsorption selectivity of methane versus other light hydrocarbons, present in natural gas, is tuned in a rationally synthesized family of isoreticular MOFs.