MNPs@MOF catalysts
obtained by encapsulating metal nanoparticles
(NPs) into metal–organic frameworks (MOFs) show fascinating
performance in heterogeneous catalysis. The improvement of catalytic
activity and reusability of MNPs@MOF catalysts has been a great challenge
for a long time. Herein, we demonstrate well-designed Pd/MOFs, featuring
hollow double-shell structure and magnetic property, exhibiting high
reusability, efficient catalytic activity, and size selectivity for
hydrogenation reaction. The as-synthesized Pd/MOF, denoted as Void nFe3O4@Pd/ZIF-8@ZIF-8, possesses diverse
functional structural features. The hollow cavity can improve mass
transfer; superparamagnetic Fe3O4 NPs embedded
in the inner MOF shell can enhance the separation and recyclability;
Pd NPs are highly dispersed in the matrix of the inner MOF shell,
and the outer MOF shell acts as a protector to prevent the leaching
of Pd NPs and a sieve to achieve size selectivity. As a proof of concept,
the Void nFe3O4@Pd/ZIF-8@ZIF-8
catalyst exhibited excellent performance for the hydrogenation of
styrene at room temperature. The activity only reduced 10% after 20
cycles for the higher conversions (>90%), and the lower conversion
only decreased 3.6% (from 32.5 to 28.9% conversion) after twenty consecutive
cycles, indicating the good and intrinsic reusability of the catalyst.
The proposed structure in this work provides a strategy to effectively
improve the reusability of MNPs@MOF catalysts, which would increase
their practical applications.
A new metal−organic framework was prepared based on a mixed ligand system of the designed nitrogen-rich 3,6bis(2-methylimidazole)pyrimidine (b2mpm) and benzophenone 4,4′-dicarboxylic acid (H 2 bpndc). The prepared material shows a three-dimensional 2-fold interpenetrated pcu framework and features rectangular channels decorated with nitrogen sites. Thanks to the abundant hydrogen bonding and π−π stacking interactions, the titled material can rapidly adsorb Congo red (CR) and presents ultrahigh adsorption capacity (2348 mg g −1 ). Moreover, this material has an adsorptive selectivity toward CR and can be regenerated by simply washing it with ethanol. The adsorption kinetic and isotherm of the titled material were also determined, indicating that the adsorption kinetic conforms to the pseudo-second-order model and the adsorption isotherm obeys the Langmuir model. Additionally, the titled material exhibits the suitable adsorption ability toward CO 2 (15.2 cm 3 g −1 under 1 atm at 298 K). These results demonstrate that the titled material would be an effective and easily regenerated adsorbent for CR removal from wastewater.
A well-designed magnetic rodlike MOF-based nanocomposite confining highly dispersed Pt single atoms and clusters (denoted as Fe 3 O 4 -NR@ ZIF-8/Pt) is fabricated and plays dual functional roles in high-efficient nanocatalysis and magnetically actuated stirring. Results of the catalytic experiments for dye degradation, hydrogen production of NaBH 4 , and hydrogenation of olefins show that Fe 3 O 4 -NR@ZIF-8/Pt exhibits enhanced catalytic performance in the absence of external stirring, compared with those of traditional catalytic systems, which need external stirring. Of special note, this proposed structure provides a facile and effective methodology to improve the catalytic performance of MOF-based composites without traditional external stirring and offers an outlook toward extending more application fields of MOFs and other porous materials.
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