Boosting Catalytic Performance of Metal–Organic Framework by Increasing the Defects via a Facile and Green Approach

Abstract

The control of defects in crystalline materials has long been of significance since the defects are correlated with the performances of the materials. Yet such control remains a challenge for metal-organic frameworks (MOFs), which are usually well-crystallized under hydro-/solvothermal conditions. In this contribution, we demonstrate for the first time how to increase the defects of MOF via a facile and green approach as exemplified in the context of solvent-free synthesis of UiO-66(Zr). Such increase of defects leads to drastic enhancement of catalysis performance when compared to UiO-66(Zr) prepared from conventional hydro-/solvothermal synthesis. Our work therefore not only opens a new door for boosting the catalytic activities of MOFs but also contributes a new approach to control the defects in crystalline materials for various applications.

Creation of Active Sites in MOF‐808(Zr) by a Facile Route for Oxidative Desulfurization of Model Diesel Oil

“…For examples, under the same reaction condition, the conversion of DBT in model oil will be less than 10 % if UiO‐66(Zr), MIL‐101(Cr) or MIL‐100(Fe) is used as ODS catalyst. Obviously, UiO‐66‐defect with more defect sites displays enhanced catalytic activity compared with UiO‐66(Zr) (Figure ) and the conversion of DBT is about 20 % after a reaction time of 20 min . These results indicate that the defect sites in MOF‐808(Zr)‐H should be created by the treatment in hot ethanol and MOF‐808(Zr)‐H is a good ODS catalyst.…”

“…The defects in structure are helpful for the formation of M‐OH/‐OH 2 sites. It is known from the structural composition that the calculated amount of M‐OH/‐OH 2 is 2.4 mmol g −1 in UiO‐66(Zr) (Zr 6 O 4 (OH) 4 (BDC) 6 ), 2.6 mmol g −1 in MIL‐125(Ti) (Ti 8 O 8 (OH) 4 (BDC) 6 ) and 11.6 mmol g −1 in MOF‐808(Zr) (Zr 6 O 4 (OH) 4 (BTC) 2 (HCOO) 6 ), respectively. However, the real amount of defect sites in the structure strongly depended on the synthetic method.…”

“…As for the structure of MOF‐808(Zr), the coordination of the secondary building units (SBUs) is completed with six formate ligands, which accounts for the charge balance . This means that two coordination vacancies on each Zr 6 node would be left and form defect sites if one formate ligand is removed (Figure S1), which could be active sites for catalytic reactions . However, current methods need to take complicated procedures and long time (several days) to reach the goal .…”

Cancer‐Cell Imaging Using Copper‐Doped Zeolite Imidazole Framework‐8 Nanocrystals Exhibiting Oxidative Catalytic Activity

“…The pore volumei ncreaseda fter Cu doping, presumably as ar esult of the generation of crystal defects and the subsequent destruction of micropores by replacement of Zn with Cu. [29] The crystal defects mayb ec aused by the difference in the coordination geometry of these two metal ions;Z ni st etrahedral and Cu is trigonal-pyramidal. [30] However,t he pore size changed little (Dd = 1.6 %), which suggestst hat the main frameworks of ZIF-8 were not considerably deformed.…”

“…The pore volume and pore size of ZIF‐8 and Cu/ZIF‐8 were determined from the isotherm and are summarized in Table . The pore volume increased after Cu doping, presumably as a result of the generation of crystal defects and the subsequent destruction of micropores by replacement of Zn with Cu . The crystal defects may be caused by the difference in the coordination geometry of these two metal ions; Zn is tetrahedral and Cu is trigonal‐pyramidal .…”