Gate-Opening Gas Adsorption and Host–Guest Interacting Gas Trapping Behavior of Porous Coordination Polymers under Applied AC Electric Fields

Abstract

The gate-opening adsorption behavior of the one-dimensional chain compound [Ru2(4-Cl-2-OMePhCO2)4(phz)] (1; 4-Cl-2-OMePhCO2(-) = 4-chloro-o-anisate; phz = phenazine) for various gases (O2, NO, and CO2) was electronically monitored in situ by applying ac electric fields to pelletized samples attached to a cryostat, which was used to accurately control the temperature and gas pressure. The gate-opening and -closing transitions induced by gas adsorption/desorption, respectively, were accurately monitored by a sudden change in the real part of permittivity (ε'). The transition temperature (TGO) was also found to be dependent on the applied temperature and gas pressure according to the Clausius-Clapeyron equation. This behavior was also observed in the isostructural compound [Rh2(4-Cl-2-OMePhCO2)4(phz)] (2), which exhibited similar gate-opening adsorption properties, but was not detected in the nonporous gate-inactive compound [Ru2(o-OMePhCO2)4(phz)] (3). Furthermore, the imaginary part of permittivity (ε″) effectively captured the electronic perturbations of the samples induced by the introduced guest molecules. Only the introduction of NO resulted in the increase of the sample's electronic conductivity for 1 and 3, but not for 2. This behavior indicates that electronic host-guest interactions were present, albeit very weak, at the surface of sample 1 and 3, i.e., through grain boundaries of the sample, which resulted in perturbation of the conduction band of this material's framework. This technique involving the in situ application of ac electric fields is useful not only for rapidly monitoring gas sorption responses accompanied by gate-opening/-closing structural transitions but also potentially for the development of molecular framework materials as chemically driven electronic devices.

Magnetic Sponge with Neutral–Ionic Phase Transitions

“…This characteristic led us to prepare guest‐induced switching materials associated with the N–I phase transition, as reported for some porous coordination polymers (PCPs) in terms of spin states,23, 24, 25 electrical conductivity,26, 27 and magnetic ordering 28, 29, 30, 31, 32, 33, 34, 35…”

Gate-open-type Sorption in a Zigzag Paddlewheel Ru Dimer Chain Compound with a Phenylenediamine Linker Instructed by a Preliminary Structural Change of Desolvation

“…Nevertheless, the present gas-adsorption properties indicated the absence of an electronic interaction between the framework and gases, even for NO acting as an electron-acceptor. The donation ability of the [Ru 2 II,II ] units used is important for producing an electronic interaction between the framework and gases; 11 however, the charge transfer from [Ru 2 ] to L, i.e., MLCT may also be important in activating Lgas interactions, as was demonstrated in previous work. 11 In conclusion, the zigzag chain compound 1, induced from its solvated compound 1-DCE, adsorbed several gases via the modification of the chain itself and the packing characteristics.…”

“…The donation ability of the [Ru 2 II,II ] units used is important for producing an electronic interaction between the framework and gases; 11 however, the charge transfer from [Ru 2 ] to L, i.e., MLCT may also be important in activating Lgas interactions, as was demonstrated in previous work. 11 In conclusion, the zigzag chain compound 1, induced from its solvated compound 1-DCE, adsorbed several gases via the modification of the chain itself and the packing characteristics. The structural change preliminarily instructed by the crystal-tocrystal transition between 1-DCE and 1 is very important in inducing gate-opening structural changes with gases.…”

“…For all gases, the gating pressures increased with increasing sorption temperature, which obeyed the ClausiusClapeyron equation: 11,16,17 …”

“…This ¾¤T behavior indicates that each gas is rapidly adsorbed at the corresponding temperature at 100 kPa due to structural changes. 11 Note that 2 does not show such a decrease in ¾¤ even at 100 kPa of gas pressure ( Figure S8), because it is a non-gated adsorbent ( Figure S5).…”