Modification of Hydrophobic and Hydrophilic Features in Isostructural 3D Pillar-Layered Coordination Polymers for Adsorption Studies

A series of new microporous three-dimensional (3D) pillar-layered coordination polymers, including [Zn(pzt)(R-ipa)_0.5]_n (R = H (1-H), NH₂ (1-NH₂), and OH (1-OH)) and [Co(pzt)(ppa)_0.5]_n (2) (Hpzt = 5-(3-pyridyl)-1,3,4-oxadiazole-2-thiol, H₂R-ipa = 5-position-substituted isophthalic acid, and H₂ppa = 1,4-phenylenedipropionic acid), were synthesized using a solvothermal method. Single-crystal X-ray diffraction analysis revealed that 1-H, 1-NH₂, 1-OH, and 2 exhibit an isoreticular framework. Through the bridging-chelating modes of different pillar dicarboxylates (R-ipa^2– for 1 and ppa^2– for 2), each coordination layer with heteroatom (N-, O-, and S-)-functionalized pzt^– ligands is extended into a 3D framework with one-dimensional (1D) channels. The altered pore characteristics, influenced by different functional groups of pillar dicarboxylate linkers, present unique hydrophilic and hydrophobic features of microporous CPs. PXRD and TG analyses confirmed the high stability of the porous structures after activation at 100 °C. The water vapor uptake capacities can be tuned from 33.0 to 68.0 cm³ (STP)/g at 298 K (P_e = 2.5 kPa), while the methanol vapor adsorption capacities are configurable from 14.0 to 46.3 cm³ (STP)/g at 298 K (P_e = 12 kPa). Different adsorption isotherms were examined, each associated with a specific type of guest molecule and the hydrophilic or hydrophobic nature of the pore structure.

A series of hydrophilic and hydrophobic porous coordination polymers with heteroatomic ligands for water and methanol adsorption studies.