Porous Coordination Polymer Based on Bipyridinium Carboxylate Linkers with High and Reversible Ammonia Uptake

Abstract

The zwitterionic bipyridinium carboxylate ligand 1,1'-bis(4-carboxyphenyl)-4,4'-bipyridinium (pc1) in the presence of cadmium chloride affords novel porous coordination polymers (PCPs): [Cd4(pc1)3Cl6]·CdCl4·guest (1) crystallizing in the P3̅1c space group. In the structure, [Cd4Cl6(CO2)6] building units are linked together by six pc1 ligands, leading to a 3D high-symmetrical network exhibiting hexagonal channels along the c axis. The walls of this PCP consist of cationic electron-acceptor bipyridinium units. The PCP 1 reversibly adsorbs H2O and CH3OH up to about 0.1 g/g at saturation showing the adsorption isotherms characteristic of a moderately hydrophilic sorbent. Adsorption of ammonia (NH3) follows a different pattern, reaching an exceptional uptake of 0.39 g/g (22.3 mmol/g) after the first adsorption cycle. Although the crystalline structure of 1 collapses after the first adsorption, the solid can be regenerated and maintains the capacity of 0.29 g/g (17 mmol/g) in the following cycles. We found that the high NH3 uptake is due to a combination of pore filling taking place below 150 h·Pa and chemisorption occurring at higher pressures. The latter process was shown to involve two phenomena: (i) coordination of NH3 molecules to Cd(2+) cations as follows from (113)Cd NMR and (ii) strong donor-acceptor interactions between NH3 molecules and pc1 ligands.

Three birds, one stone – photo-/piezo-/chemochromism in one conjugated nanoporous ionic organic network

“…6c). Here, the NH 3 molecule is expected to act as the radical stabilizer, as reported in the literature19 and evidenced here by Raman, UV-Vis, ESR and XPS measurements in Fig. S26 and S29 (ESI†).…”

Responses of Defect-Rich Zr-Based Metal–Organic Frameworks toward NH3Adsorption

“…Sequential pore filling induced by different pore openings created by ligand defects leads to a two-step NH 3 adsorption isotherm in UiO-67. While responsive behaviors of MOFs to weakly interacting molecules such as hydrogen, carbon dioxide, and hydrocarbon have been widely explored, − ,− only a few reports focused on more polar coordinating gases such as water, alcohols, and NH 3 . ,,, In addition, although unusual adsorption behaviors for polar coordinating gases have been observed, ,,, in-depth study on sorption mechanisms and structural responses of MOFs is rarely explored at the molecular level. In this study, in situ high-resolution neutron and synchrotron X-ray powder diffractions (NPD and SXRD) combined with density functional theory (DFT) calculations were used to study the precise binding domains and the structural interactions of NH 3 with UiO-67 framework.…”

Adsorbents for Noxious Gas Sequestration: State of the Art

“…Membranes have also shown promising permeance and selectivity for CO 2 in flue gas mixtures. UiO-66CN@sPIM-1 [120] The same applies to their regenerability and reusability except for Polymer PCP-1 [142] which showed very low reusability potential due to the reduced number of pores during successive sorption cycles as a result of structural collapse.…”