ABSTRACT
NU-1000, being a hydrothermally stable metal-organic framework (MOF), with structural robustness is viable for functionalization with various entities. A postsynthetic modification strategy called solvent-assisted ligand incorporation (SALI) is chosen for functionalizing NU-1000 with thiol moieties using 2-mercaptobenzoic acid. In accordance with soft acid-soft base interactions, the thiol groups on NU-1000, as a scaffold, can immobilize the gold nanoparticles without much aggregation. The catalytically active gold sites on thiolated NU-1000 are utilized for hydrogen evolution reaction (HER). The catalyst delivered an overpotential of 101 mV at a current density of 10 mAcm-2 in 0.5 M H2SO4. The faster charge transfer kinetics determined from the Tafel slope of 44 mV/dec enhances the HER activity. The sustainable performance of the catalyst for 36 h proves its utility as a potential catalyst to produce neat hydrogen.
ABSTRACT
In this study, composites of HKUST-1 MOF with nanocellulose, HKUST-1@NCs, have been prepared and explored for CO2 /N2 gas-separation and dye-sorption based applications. Our biopolymer-MOF composites are prepared via a copper ion pre-seeding method, in which, the HKUST-1 crystallites are grown inâ situ on the Cu-seeded and carboxylate anchored NC fibers for a better interfacial integration between the MOF and the polymer matrices. Static gas sorption studies show the capability of one of our HKUST-1@NC composites to reach â¼300 % enhancement in the CO2 /N2 sorption selectivity compared to the corresponding MOF alone - blank reference sample prepared at similar conditions. The same composite, C100, in the bulk powder form, shows a remarkable IAST sorption selectivity of 298 (CO2 /N2 ) at 298â K and 1â bar for the CO2 /N2 (15/85, v/v) gas mixture. The relative position of the C100, in the bound plot visualizations of the CO2 /N2 separation trade-off factors indicate a significant potential. The HKUST-1@NC composites have also been processed along with a polymeric cellulose acetate (CA) matrix as HKUST-1@NC@CA films to study them as free-standing mixed-matrix membranes. The CO2 /N2 sorption selectivity, at 298â K and 1â bar is 600 for one such membrane, C-120@CA, as bulk sample studied by the static gas sorption. The composite, C120, exhibits a good uptake with an enhancement of 11 % for alizarin and 70 % for Congo red in comparison to the uptakes of the corresponding blank reference HKUST-1 sample, B120.
ABSTRACT
A post-synthetic technique, Solvent Assisted Ligand Incorporation (SALI), was used for thiol functionalization in the zirconium-based metal-organic framework NU-1000. This thiol-functionalized MOF was employed as a support for the growth of silver nanoparticles (Ag NPs) through coordination of a Ag(I) complex with a node-anchored thiol-ligand, followed by the reduction of Ag(I) to Ag(0). X-ray photoelectron spectroscopy revealed that the ratio of Ag(0) to Ag(I) proportionally increased with the loading of silver ions. The HER activity increased with the enhancement of Ag(0) in the system and the best efficiency was observed for the composite with â¼95% Ag(0). This composite displayed an overpotential of 165 mV in an acidic medium at 10 mA cm-2 and a Tafel slope of 53 mA dec-1. The loading of silver beyond the optimum value led to the aggregation of the particles which affected the overpotential substantially. The catalyst demonstrated appreciable static stability for 24 h, which promotes the use of the material as an HER catalyst. Therefore, these results emphasized that Ag NPs embedded onto a thiol-functionalized MOF is a propitious material for developing a clean and renewable energy source.
ABSTRACT
UiO-66 has been tailored using defect engineering methodology to introduce thiol functionalities into the MOF skeletal structure. The thiolated UiO-66 serves as a scaffold to support the platinum nanoparticles with a size of â¼2 nm through a soft-soft interaction. This Pt@UiO-66-SH, utilized as an HER catalyst, exhibited an overpotential of 57 mV at a current density of 10 mA cm-2 in an acidic medium with a Tafel slope of 75 mV/dec and a high TOF value (389.37 s-1). This catalyst showed long-term durability for 30 h, specifying the potential of the material to produce neat hydrogen.
