Molecular Sieving of C-2-C-3 Alkene from Alkyne with Tuned Threshold Pressure in Robust Layered Metal-Organic Frameworks

摘要

C-2-C-3 alkyne/alkene separation is of great importance; however, designing materials for an efficient molecular sieving of alkenes from alkynes remains challenging. Now, two hydrolytically stable layered MOFs, [Cu(dps)(2)(GeF6)] (GeFSIX-dps-Cu, dps=4,4 '-dipyridylsulfide) and [Zn(dps)(2)(GeF6)] (GeFSIX-dps-Zn), can achieve almost complete exclusion of both C3H6 and C2H4 from their alkyne analogues. GeFSIX-dps-Cu displays a notable advanced threshold pressure for alkynes adsorption and thus substantial uptakes at lower pressures, providing record C3H4/C3H6 uptake ratios and capacity-enhanced C2H2/C2H4 sieving for a wide composition range. Metal substitution (Zn to Cu) affords fine tuning of linker rotation and layer stacking, creating slightly expanded pore aperture and interlayer space coupled with multiple hydrogen-bonding sites, allowing easier entrance of alkyne while excluding alkene. Breakthrough experiments confirmed tunable sieving by these MOFs for C3H4/C3H6 and C2H2/C2H4 mixtures.