Reticular chemistry offers a targeted and streamlined approach to synthesizing metal-organic frameworks (MOFs) through the assembly of predesigned molecular units. In this study, we investigated inorganic node-directed reticular diversification of MOFs by employing a nitrogen-containing aromatic polycarboxylate ligand as a fixed 4-connected organic node. By systematically tuning inorganic secondary building units (SBUs), various topological structures were obtained: the previously reported flu topology (derived from 8-connected nodes), dmc topology (from mixed 3,4-connected nodes), and a new pts-topology MOF (ZJNU-409) built from Zn-based paddlewheel 4-connected nodes. ZJNU-409 possesses a three-dimensional framework containing one-dimensional channels and dual-site functionalization and shows excellent selective performance for C2H6, C3H8, C2H2, and CO2 over CH4. Ideal adsorbed solution theory (IAST) calculations yielded selectivities of 135 for C3H8/CH4, 26 for C2H6/CH4, 100 for C2H2/CH4, and 29 for CO2/CH4. Fixed-bed breakthrough experiments confirmed that C2H6, C3H8, C2H2, and CO2 had retention times longer than those of CH4, and grand canonical Monte Carlo (GCMC) calculations confirmed stronger interactions between the framework and these gases compared to CH4. These results collectively underscore the potential of ZJNU-409 for efficient methane purification applications.
Zhao et al. (Sun,) studied this question.