Graphene quantum dots incorporated UiO-66-NH2 as a promising photocatalyst for degradation of long-chain oleic acid

[Display omitted] •Precoating of ZnO on AISI steel mesh facilitate the homogenous loading of MOF by self assembling.•The deposited mesh shows better performance for continuous water treatment.•Incorporation of GQD has amazing effect on inhibition of e/h recombination. Graphene quantum dot (GQD) incorporated UiO-66-NH2 MOF was deposited on a steel foam for photocatalytic degradation of a long-chain oleic-acid. To have a better adhesion and homogenous distribution of MOF particles, the surface of steel foam was precoated by a thin film of ZnO. The formation of heterojunctions, crystallinity, morphology, particle size, proper separation of excitons, and elemental contents were examined by FTIR, XRD, Raman spectroscopy, SEM, TEM, BET, PL and contact angle tests. Interestingly, the photoluminescence study revealed that the heterojunctions completely extinct the UiO-66-NH2 characteristic peaks at 450 and 670 nm via the electron/hole recombination inhibition. The experiments showed that the increased density of photogenerated electron/hole pairs resulted in a very fast degradation of organic structure of the oleic acid to small chain and less-hydrophobic species. In addition, the AISI steel/ZnO/UiO-66-NH2/GQDs showed completely hydrophilic characteristic at ~ 3 h irradiation, while the intrinsic AISI steel/ZnO sample was needed to a continuous irradiation for 7 h to decrease the water contact angle from ~ 76° to ~ 45°. The results were repeated for three times and showed only 10% decrease in the photocatalytic performance. The improved photocatalytic performance was mainly assigned to the charge transfer between UiO-66-NH2 and the GQD which could inhibit the photogenerated electron/hole recombination.