2. Experimental
2.1. Materials
All chemicals, zirconium tetrachloride (ZrCl4),N ,N -dimethylformamide (DMF, 99%), terephthalic acid
(C8H6O4, 99+%),
hydrochloric acid (HCl, 37%) and ethanol (EtOH, 96%) were supplied by
either Alfa Aesar, Acros organics or VWR and used as received.
Nano-sized graphite (Nano-19) was supplied by Asbury Graphite Mills
Ltd., USA.
2.2. Synthesis of materials
All UiO-66 and composite samples were synthesized following the
procedure reported elsewhere [11, 12], with slight modifications.
The experimental steps were as follows: Step 1: A 120 mL vial was loaded
with 4 mL of concentrated HCl, 0.5 g of ZrCl4 and 20 mL
of DMF. Then, the mixture was sonicated for 20 minutes until complete
dissolution; Step 2: 40 mL of DMF and 0.5 g of
C8H6O4 (ligand) were
added to the solution, sonicated for 20 minutes and then heated
overnight at 80°C; Step 3: The resulting product was filtered off,
washed with DMF (8 × 30 mL) and subsequently with EtOH (8 × 30 mL) to
remove the excess of unreacted organic linkers. The final product was
dried in a vacuum oven at 90°C for 24 h before being analyzed.
The composite materials were synthesized by following exactly the same
procedure as described above but 1, 2, and 6 % of nanographite (based
on the final mass of MOF) were added in the first step. The samples were
labeled as UiO-66 and UiO-66-nGr1, UiO-66-nGr2 and UiO-66-nGr6 for the
composites with increasing nanographite contents.
2.3. Analysis Methods