Mechanism for the Dynamic Adsorption of CO₂ and CH₄ in a Flexible Linear Chain Coordination Polymer as Determined from In Situ Infrared Spectroscopy

Abstract

Adsorption-desorption cycles for CO 2 and CH 4 on the one-dimensional coordination polymer, catenabis(dibenzoylmethanato)-(4,4′-bipyridyl)nickel(II), "Ni-DBM-BPY", showed pronounced step-shape isotherms, where minimal gas adsorption was detected below a threshold pressure and rapid gas uptake was observed above this threshold. Desorption isotherms from the saturated state displayed significant hysteresis from the adsorption isotherm path. Such behavior is rare in one-dimensional coordination polymers that lack a robust framework with permanent porosity. This step-shape adsorption behavior for CO 2 was shown by in situ FT-IR measurements to be the result of a structural phase transition in the Ni-DBM-BPY host which arises from a change in conformation of the DBM ligands. After the structural transition, the adsorption spectrum of the adsorbed CO 2 changed significantly due to an enhanced CO 2 interaction with the host. A similar mechanism can be inferred for CH 4 from the isotherm shape, but the host structural phase transitions could not be observed directly with CH 4 uptake, since the threshold conditions were outside the temperature and pressure limits of the instrument. These reported results highlight the importance of in situ FT-IR measurements for determining gas adsorption mechanisms in flexible porous coordination polymers.

Tailoring Metal–Organic Frameworks for CO2 Capture: The Amino Effect

“…] gas ( 12 CO 2 ) [45] 667.3 1388.3 2349.3 gas ( 13 CO 2 ) [52] 649 1334 2283 silicalite [45,53] < 1 662 2341 PS [13] 657.2 2334.9 UiO-66 [22] 0.72 2340 UiO-66-NH 2 [22] 0.72 2337 UiO-66-NO 2 [22,54] 0.72 685, 669, 659, 649 2339 UiO-66-Br [22,54] 0.72 684, 669, 662, 657, 649 2338 MIL-53(Cr) [55,56] 11 669, 662, 650 2335 MIL-53(Al) [55] 661, 649 MIL-53(Al)-NH 2 [20] 200 669, 667, 661, 655, 649 2334 IRMOF-3 [14,20] 669, 667, 653 HKUST-1 2333 CPO-27-Mg [39] 2353 Ni-DBM-BPy [57] 2000 661, 645 2333 1288 www.chemsuschem.org cates that, upon interaction, the CO 2 bending mode is always followed by the splitting of the degenerate bending mode into two separate components. For the amines, a large variety of species have been considered in this study, which were selected by choosing those already reported in the literature and by proposing some new functionalities.…”

Crystallography of Representative MOFs Based on Pillared Cyanonickelate (PICNIC) Architecture

“…In recent years, National Energy and Technology Laboratory (NETL) has been one of the leading laboratories in the area of science and engineering research of novel Ni(CN) 4 -based flexible MOFs [56,[61][62][63][64][65]. The precursors of these flexible MOFs are typically a cyanometallate complex that acts as a ligand and a transition metal complex with available coordination sites.…”

“…These compounds undergo cooperative spin transitions at high temperatures, and the host-guest interactions inside the pores have considerable effects on the spin crossover properties of these materials. Agusti et al [60] In recent years, National Energy and Technology Laboratory (NETL) has been one of the leading laboratories in the area of science and engineering research of novel Ni(CN)4-based flexible MOFs [56,[61][62][63][64][65]. The precursors of these flexible MOFs are typically a cyanometallate complex that acts as a ligand and a transition metal complex with available coordination sites.…”

Flexible metal-organic framework compounds: In situ studies for selective CO2 capture

“…[78] The catenabis(dibenzoylmethanate)-(4,4-bipyridyl)nickel(II) polymer (NiDBMBpy) compound was prepared by reaction of anhydrous bis(dibenzoylmethanato)nickel(II) (Ni(DBM) 2 ) with 4,4-bipyridine in dry tetrahydrofuran (THF) as previously described. [79] The ‡ Certain commercial materials and equipment are identified in this paper only to specify adequately the experimental procedure. In no case does such identification imply recommendation by NIST nor does it imply that the material or equipment identified is necessarily the best available for this purpose.…”

“…Thus, study of the contrasting structure transition mechanisms in NiBpene and NiDBM-Bpy can provide insights into how the nature of the structure transitions influences material performance. In this connection, and building on the previous structure characterizations [78,79] , an initial assessment of the crystal structure transitions…”