Open coordination sites (OCSs) in metal−organic frameworks (MOFs) often function as key factors in the potential applications of MOFs, such as gas separation, gas sorption, and catalysis. For these applications, the activation process to remove the solvent molecules coordinated at the OCSs is an essential step that must be performed prior to use of the MOFs. To date, the thermal method performed by applying heat and vacuum has been the only method for such activation. In this report, we demonstrate that methylene chloride (MC) itself can perform the activation role: this process can serve as an alternative “chemical route” for the activation that does not require applying heat. To the best of our knowledge, no previous study has demonstrated this function of MC, although MC has been popularly used in the pretreatment step prior to the thermal activation process. On the basis of a Raman study, we propose a plausible mechanism for the chemical activation, in which the function of MC is possibly due to its coordination with the Cu2+ center and subsequent spontaneous decoordination. Using HKUST-1 film, we further demonstrate that this chemical activation route is highly suitable for activating large-area MOF films. ⓒ 2016 DGIST
Table Of Contents
1. INTRODUCTION 1 -- 1.1 Metal-Organic Frameworks (MOFs) 1 -- 1.2 Analyzation for Structural frame of HKUST-1 2 -- 1.3 Open Coordination Sites (OCSs) 3 -- 1.4 Present Strategies for Activation of Open Coordination Sites (OCSs) 5 -- 1.5 Motivation and Purpose 6 -- 2. EXPERIMENTAL DETAILS 8 -- 2.1 Material and methods 8 -- 2.1.1 Materials 8 -- 2.1.2 Synthesis of HKUST-1 9 -- 2.1.3 Synthesis of Cu-MOF-2 9 -- 2.1.4 Synthesis of HKUST-1film on patterned copper plate 10 -- 2.1.5 Thermal activation (TA) of HKUST-1 and Cu-MOF-2 11 -- 2.1.6 Chemical activation (CA) of HKUST-1 and Cu-MOF-2 11 -- 2.1.7 Exchange of coordinated molecules in HKUST-1 12 -- 2.1.8 Sample preparation for the Raman and UV-vis absorption analysis 12 -- 2.1.9 Sample preparation for the 1H-NMR measurements 13 -- 2.1.10 Sample preparation for measurement of moisture sorption 13 -- 2.2 Instrumentation 13 -- 3. RESULTS AND DISCUSSION 15 -- 1.1 Optical Color Change between Pristine HKUST-1 and Treated HKUST-1 15 -- 1.2 Structural Stability and Molecules Dissociation of Thermally Treated HKUST-1 16 -- 1.3 Structural stability and Surface Areas of Treated HKUST-1 17 -- 1.4 1H-NMR, Raman, and BET Results for Room Temperature Evacuation of HKUST-1 20 -- 1.5 The Surest Evidence of Molecules Dissociation for MC treated HKUST-1 21 -- 1.6 Raman Spectra and Water sorption Experiments of HKUST-1 23 -- 1.7 Raman Spectra of Activated HKUST-1 after Exposure to Ambient Atmosphere 28 -- 1.8 Theoretical Studies for Raman Shift of Cu-Cu vibration in HKUST-1 29 -- 1.9 1H-NMR, Raman and BET Result for Room Temperature Evacuation of HKUST-1 32 -- 1.10 Application to Cu-MOF-2 with Chemical Activation 33 -- 1.11 Structural Stability of Treated Cu-MOF-2 36 -- 1.12 Application to Large size MOF Films with Chemical Activation 36 -- 4. CONCLUSION 38 -- 5. REFERENCE 39