A 2-Fold Interpenetrated Nitrogen-Rich Metal-Organic Framework for Rapid and Selective Adsorption of Congo Red.

A new metal-organic framework was prepared based on a mixed ligand system of the designed nitrogen-rich 3,6-bis(2-methylimidazole)pyrimidine (b2mpm) and benzophenone 4,4'-dicarboxylic acid (H2bpndc). 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 CO2 (15.2 cm3 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.

Fabrication of Magnetic Pd/MOF Hollow Nanospheres with Double-Shell Structure: Toward Highly Efficient and Recyclable Nanocatalysts for Hydrogenation Reaction.

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.