The Interaction of Guest Molecules with Co‐MOF‐74: A Vis/NIR and Raman Approach

Abstract

Co-MOF-74 rod like crystals with a length of several hundred micrometers are synthesized by a solvothermal procedure and their interaction with different gases is evaluated for selective gas sensing. We show strongly anisotropic absorption behavior of the Co-MOF-74 crystals when illuminated with polarized light. The interactions of guests (CO , propane, propene, Ar, MeOH, H O) with Co-MOF-74, is studied by various spectroscopic techniques. Vis/NIR shows peak shifts of Co-MOF-74 depending on the interaction with the guest. In the visible and the NIR the maximum absorbance is shifted selectively corresponding to the intensity of the Co -guest interaction. Even propene and propane could be distinguished at room temperature by their different interactions with Co-MOF-74. Raman spectroscopy was used to detect a modified vibrational behavior of Co-MOF-74 upon gas adsorption. We show that the adsorption of H O leads to a characteristic shift of the peak maxima in the Raman spectra.

Humidity-Mediated Anisotropic Proton Conductivity through the 1D Channels of Co-MOF-74

“…Figure 2a shows the SEM image of an exemplary Co-MOF-74 crystal with a representative length of 550 µm and a width around 100 µm. The Raman spectrum ( Figure 2b) is in good accordance with previously published MOF-74 Raman data [28]. The peak at 572 cm −1 corresponds to the benzene ring vibration (ring deformation mode), the peak at 818 cm −1 can be assigned to the C-H bending in the benzene ring, the peak at 1281 cm −1 correlates with the C=O stretching, and the O-C-O stretching of the carboxylate group of the organic linker is situated at 1417 cm −1 [33].…”

Host–Guest Interactions in Metal–Organic Frameworks Doped with Acceptor Molecules as Revealed by Resonance Raman Spectroscopy

“…TCNQ has four intense Raman modes at 1207, 1455, 1602, and 2227 cm –1 , which can be assigned to C–H bending (in-plane-deformation), exocyclic C=C stretching, ring C=C stretching, and C≡N stretching modes, 42 respectively. The two most intense bands of Mn-MOF-74 located at 1275 and 1404 cm –1 can be assigned to the C–O stretching 29 , 36 , 43 and O–C–O symmetric stretching 29 , 36 , 43 − 45 modes of the linker (2,5-dihydroxyterephthalic acid), respectively. In addition, three bands are discerned at 1499, 1556, and 1613 cm –1 .…”

“…In addition, three bands are discerned at 1499, 1556, and 1613 cm –1 . The band at 1499 cm –1 belongs to the O–C–O asymmetric stretching mode of the carboxylate group, 36 , 43 , 45 and the bands at 1556 and 1613 cm –1 belong to the benzene ring-stretching vibrations of the linker. 43 , 45 All these modes of TCNQ and Mn-MOF-74 are invisible or largely shifted in the spectra of TCNQ-doped Mn-MOF-74.…”

Highly dispersed ultrafine Ni particles embedded into MOF-74 arrays by partial carbonization for highly efficient hydrogen evolution

“…S4 (ESI †). 45 The peak at 576 cm À1 corresponds to the Ni-O stretching mode (n(Ni-O)) of Ni-MOF-74, and the peaks at 1416 and 1554 cm À1 correspond to the symmetric and asymmetric stretching modes of the carboxylate groups (n as,s (COO À )), respectively. The peak at 820 cm À1 is assigned to the C-H bending of the benzene ring, and the peak at 1489 cm À1 corresponds to the stretching modes of the phenolate groups (n(C-O)).…”