Charge transfer dependence on CO2 hydrogenation activity to methanol in Cu nanoparticles covered with metal–organic framework systems

We report the charge transfer dependence on CO2 hydrogenation activity to methanol in Cu nanoparticles covered with metal–organic framework systems.


Synthesis of UiO-66 and the analogues
Zr-UiO-66: In a typical synthesis, DMF was added to a mixture of the ZrCl 4 and acetic acid additive and sonicated to dissolve, forming a slightly cloudy colourless solution. Next, the terephthalic acid was added to the solution and again sonicated to dissolve. Finally, water was added, and the solution was placed into a glass pressure vessel, sealed, and heated in an oven at 120 °C for 24 hours. Following synthesis, the powdery white product was recovered by vacuum filtration and washed with DMF, ethanol, and acetone. To ensure complete exchange of pore solvent/impurities with water, the samples were soaked in acetone (3 x 20 mL) followed by ultra-high-purity water (3 x 20 mL) for one day each in a centrifuge tube and were recovered each time by centrifugation. Finally, the samples were dried in an oven at ~60°C for 24 hours.
Zr-UiO-66-NH 2 : DMF (60 ml) was added to a mixture of the ZrCl 4 (866.6 mg) and acetic acid (7.5 ml) additive and sonicated to dissolve, forming a slightly cloudy colourless solution. Next, the 2aminoterephthalic acid (690.6 mg) was added to the solution and again sonicated to dissolve. Finally, water (200 μL) was added, and the solution was placed into a glass pressure vessel, sealed, and heated in an oven at 120 °C for 24 hours. After the synthesis, the same washing process was performed as the Zr-UiO-66.
Zr-UiO-66-COOH: The carboxylic acid functionalized UiO-66 was synthesized using a reflux method in water modified from a paper. [1] 1,2,4-benzenetricarboxylic acid (3.5601 g) was added to 90 mL of water in a round bottomed flask and stirred. Separately, ZrCl 4 (2.3024 g) was dissolved in 10 mL of water.
The ZrCl 4 solution was then added to the carboxylic acid solution and the solution was set to reflux for 16 hours. After reflux, the solution was cooled, and the product was isolated by centrifugation, washed with deionized water twice, then added to 100 mL of water and set to reflux again for 16 hours. After this the sample was again cooled and isolated by centrifugation, then washed again with water twice.
Hf-UiO-66: In a typical synthesis, DMF (60 ml) was added to a mixture of the HfCl 4 (1.1 g) and acetic acid (4.0 ml) additive and sonicated to dissolve, forming a slightly cloudy colourless solution. Next, the terephthalic acid (570 mg) was added to the solution and again sonicated to dissolve. Finally, water (200 μL) was added, the solution was stirred, placed into a glass pressure vessel, sealed, and heated in Transmission electron microscopy (TEM) images: TEM images were captured using a Hitachi HT7700 instrument operated at 100 kV accelerating voltage.

High-resolution STEM images and STEM-EDX mapping images: High-resolution STEM images and
STEM-EELS mapping images were captured using a JEOL JEM-ARM200F STEM instrument operated at 200 kV accelerating voltage.

Powder X-ray diffraction (PXRD) measurements:
The structures of MOF and Cu/MOF hybrid catalysts were investigated by powder XRD analysis using a Bruker D8 Advance diffractometer (Cu K radiation).

Inductively coupled plasma-mass spectrometry (ICP-MS):
The weignt % of Cu included in hybrid catalysts was estimated using a Shimadzu ICPE-9000 instrument. Defect Estimation. The defect estimation was performed following previously reported method. [2] Thermogravimetric analysis was performed in alumina pans under air from 20 °C to 600 °C at a rate of   Figure S4. N 2 sorption isotherms of UiO-66 and the analogues.

Characterization of Cu on UiO-66
TEM image of the composites revealed that Cu nanoparticles are located on the surface of UiO-66 (Fig. S17a). The mean diameter of Cu nanoparticles was estimated to be 38.0  11.5 nm. The amounts of Cu included in the composite was determined to be 15.6 wt%. The PXRD pattern of the composite composed of the diffraction from both Cu and the corresponding UiO-66 (Fig. S17b). The Cu on UiO-66 showed typical type-I sorption behavior originating from the microporosity of the MOF, with a decrease in total uptake versus Cu free UiO-66 due to the presence of Cu nanoparticles (Fig. S17c). S13