Abstract:
Storage and separation of small (C1-C3) hydrocarbons are of great significance as these are alternative energy resources and also can be used as raw materials for many industrially important materials. Selective capture of greenhouse gas, CO2 from CH4 is important to improve the quality of natural gas. Among the available porous materials, MOFs with permanent porosity are the most suitable to serve these purposes. Herein, a two-fold entangled dynamic framework {[Zn-2(bdc)(2)(bpNDI)]4DMF}(n) with pore surface carved with polar functional groups and aromatic clouds is exploited for selective capture of CO2, C2, and C3 hydrocarbons at ambient condition. The framework shows stepwise CO2 and C2H2 uptake at 195K but type I profiles are observed at 298K. The IAST selectivity of CO2 over CH4 is the highest (598 at 298K) among the MOFs without open metal sites reported till date. It also shows high selectivity for C2H2, C2H4, C2H6, and C3H8 over CH4 at 298K. DFT calculations reveal that aromatic surface and the polar imide (RNC=O) functional groups are the primary adsorption sites for adsorption. Furthermore, breakthrough column experiments showed CO2/CH4 C2H6/CH4 and CO2/N-2 separation capability at ambient condition.
