Pulse EPR Study of Gas Adsorption in Cu2+-Doped Metal–Organic Framework [Zn2(1,4-bdc)2(dabco)]

Probing Local Structural Changes at Cu2+ in a Flexible Mixed-Metal Metal-Organic Framework by in Situ Electron Paramagnetic Resonance during CO2 Ad- and Desorption

“…They are typical for a square planar coordination , and thus reflect the lack of any axial ligand at the Cu 2+ site. The adsorption of an axial ligand like methanol at this site increases the g-value to g zz = 2.381 ± 0.002 and decreases the hfi value to A zz 63 Cu = 474 ± 12 MHz reflecting the change to a square pyramidal coordination of the Cu 2+ ion. ,, In the case of the Cu-doped, as-synthesized Zn 1.9 Cu 0.1 (bdc) 2 dabco material, EPR-derived parameters g zz = 2.349 ± 0.001 and A zz 63 Cu = 426 ± 6 MHz have been reported for the mixed-metal paddlewheel unit. , Again, due to the axial coordination of the dabco ligand the EPR-derived parameters of the framework Cu 2+ ion are typical for a square pyramidal coordination , and are similar to the values reported for species A I and A II in the present contribution (Table ). We therefore tentatively assign those Cu 2+ species to ions of mixed-metal paddlewheel units, where they replace one Zn 2+ ion in the framework as illustrated in Figure a.…”

“…Our analysis is based on the calculation of the second moment contributing to the EPR line shape for a periodic arrangement of spins, which solely interact by dipole-dipole interactions. Here we neglect inhomogeneous line broadening effects due to unresolved 1 H and 14 N ligand hfi which are reported to be smaller than approximately 5 MHz and g-strain effects. We note that X- and Q-band spectra of a sample kept under ambient conditions provide comparable line widths in the g zz direction (SI Figure S8).…”

“…Therefore, we suggest that a paramagnetically doped derivative of this MOF is an ideal model system for a first time investigation using our newly developed in situ EPR setup. Recently, the formation of paramagnetic Zn 2+ -Cu 2+ paddlewheels in the parent Zn 1– x Cu x (bdc) 2 dabco MOF material was verified by cw EPR and pulsed EPR . Therefore, in the present study we have chosen Cu 2+ “dopants” acting as a high-resolution EPR active probe species for the characterization of small local structural changes upon CO 2 adsorption when the np → lp phase transition takes place, giving more detailed insights into the phase transition process of the Zn 1.9 Cu 0.1 (BME-bdc) 2 dabco material.…”

Large breathing effect induced by water sorption in a remarkably stable nonporous cyanide-bridged coordination polymer

“…This can be done directly in the case of paramagnetic guests [61][62][63][64][65] or indirectly by analysing the g-factor shift of paramagnetic metal centers as in some Cu II -based porous materials. 54,[66][67][68] Noteworthy, EPR spectroscopy is commonly applied to study the state of the paramagnetic active sites doped into the mesoporous hosts such as zeolites in various catalytic processes. [69][70][71][72] In the case of 1Mn, presented herein, the state of the Mn II sites was successfully monitored in the real time by employing in situ EPR spectroscopy during the adsorption/desorption of water molecules.…”

Large Breathing Effect Induced by Water Sorption in the Exceptionally Stable Nonporous Non-MOF Crystalline Material

“…This can be done directly in the case of paramagnetic guests [61][62][63][64][65] or indirectly by analyzing the g-factor shift of paramagnetic metal centers as in some Cu II -based porous materials. 58,[66][67][68] Noteworthy, EPR spectroscopy is commonly applied to study the state of the paramagnetic active sites doped into the mesoporous hosts such as zeolites in various catalytic processes. [69][70][71][72] In the case of 1Mn, presented herein, the state of the Mn II sites was successfully monitored in the real time by employing in situ EPR spectroscopy during the sorption/desorption of water molecules.…”