Photoinduced Phase Transition of Ce-UiO-66 to Ce-BDC-OH

Abstract

External stimuli-responsive phase transition of metal−organic frameworks (MOFs) introduces intriguing functions for diverse applications under practical settings. Herein, we reported a phase transition from cubic Ce-UiO-66 to triclinic Ce-BDC-OH under light irradiation. Such a phase transition underwent a ligand-to-metal charge transfer process, which was unambiguously revealed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, electron paramagnetic resonance, etc. We proposed a phase transition mechanism through (1) the photoreduction of the metal core from Ce 4+ into Ce 3+ ; (2) the photogeneration of • OH and hydroxylation of BDC into BDC-OH; and (3) the carboxylate migration and lattice rearrangement for transitions. The phenomenon of the Ce 4+ -to-Ce 3+ reduction also enables a diamagnetism-to-paramagnetism transition, suggesting its potential as a photostimulus-responsive magnetic switch.

Concentration- and Self-Catalysis-Dominated Rapid Synthesis of Multifunctional UiO-66(Ce) for Dual-Mode Sensing of Tetracycline

“…In contrast with UiO-66­(Ce), the absorption peaks at 1243 and 962 cm –1 newly appeared on M-UiO-66­(Ce). They belonged to the ν­(C–OH) stretching vibration band and the σ­(O–H) bending vibration band, respectively, indicating that the −OH functional group formed on M-UiO-66­(Ce) . In addition, the peak at 1648 cm –1 assigned to the ν­(CO) stretching vibration band of N , N -dimethylformamide (DMF) was significantly weakened, possibly caused by desolvation of the DMF molecules remaining in the pore channel .…”

“…They belonged to the ν(C−OH) stretching vibration band and the σ(O−H) bending vibration band, respectively, indicating that the −OH functional group formed on M-UiO-66(Ce). 24 In addition, the peak at 1648 cm −1 assigned to the ν(C�O) stretching vibration band of N,Ndimethylformamide (DMF) was significantly weakened, possibly caused by desolvation of the DMF molecules remaining in the pore channel. 21 Due to this decrease of the remaining DMF in the pore channel of M-UiO-66(Ce), less weight loss of M-UiO-66(Ce) during 200−280 °C than that of UiO-66(Ce) can be observed (Figure S3).…”

“…The decreased grain size, specific surface area, and pore volume of M-UiO-66(Ce) might be attributed to the increased crystal defects or some collapse of the structure. 24,25 This difference between M-UiO-66(Ce) and UiO-66(Ce) was probably caused by the transformation from Ce 4+ to Ce 3+ during conversion from UiO-66(Ce) to M-UiO-66(Ce). 24 X-ray photoelectron spectroscopy (XPS) analysis (Figure S2) verified this transformation, and the Ce 3d highresolution XPS results showed a higher content of Ce 4+ /Ce 3+ in UiO-66(Ce) (1.74) than in M-UiO-66(Ce) (1.28) (Figure 2b).…”

Effect of Linker Structure and Functionalization on Secondary Gas Formation in Metal–Organic Frameworks

“…A popular organic linker used in MOFs is terephthalic acid (BDC), ,,,,, with various functionalized BDC derivatives used as linkers in UiO-66 and MOF-74 structures. ,,− Functionalization of BDC has allowed UiO-66 to be incorporated in a porous liquid and to allow for secondary reactions between the linker and molecules inside the MOF pores. For instance, UiO-66 with mixed BDC-NH 2 and BDC-NO 2 functionalized linkers increased extraction of environmental pollutants by 60% .…”

Elucidating phase transformation of Eu-based metal organic framework with intermediate isolation and theoretical calculations

“…It is ubiquitous in nature and useful in our daily life; commonly encountered examples include ice melting upon heating and supercritical fluid extraction. [1][2][3][4] One of the most frequently studied branches is crystal-to-crystal transition, which involves the phase transition of crystalline materials. [5][6][7][8][9] Metal-organic frameworks (MOFs), as a class of crystalline polymers composed of organic linkers and metal nodes, have captured the interest of researchers owing to their large specific surface area, rich functionality, tunable porosity and found applications in various areas, such as heterogeneous catalysis, [10][11][12][13][14][15] sensing, [16][17][18][19][20] gas separation, [21][22][23][24] and drug delivery.…”