A bifunctional Zr-MOF catalyst containing palladium nanoclusters (NCs) has been developed. The formation of Pd NCs was confirmed by transmission electron microscopy (TEM) and extended X-ray absorption fine structure (EXAFS). Combining the oxidation activity of Pd NCs and the acetalization activity of the Lewis acid sites in UiO-66-NH 2 , this catalyst (Pd@UiO-66-NH 2) exhibits excellent catalytic activity and selectivity in a one-pot tandem oxidation-acetalization reaction. This catalyst shows 99.9% selectivity to benzaldehyde ethylene acetal in the tandem reaction of benzyl alcohol and ethylene glycol at 99.9% conversion of benzyl alcohol. We also examined various substituted benzyl alcohols and found that alcohols with electron-donating groups showed better conversion and selectivity compared to those with electron-withdrawing groups. We further proved that there was no leaching of active catalytic species during the reaction and the catalyst can be recycled at least five times without significant deactivation.
The facile pyrolysis of a bipyridyl metal-organic framework, MOF-253, produces N-doped porous carbons (Cz-MOF-253), which exhibit excellent catalytic activity in the Knoevenagel condensation reaction and outperform other nitrogen-containing MOF-derived carbons. More importantly, by virtue of their high Lewis basicity and porous nature, Cz-MOF-253-supported Pd nanoparticles (Pd/Cz-MOF-253-800) show excellent performance in a one-pot sequential Knoevenagel condensation-hydrogenation reaction.
Alcohols have been demonstrated to be efficient reducing agents for AGET-ATRP for the first time. Well-controlled polymerizations have been successfully achieved with the typical characteristics of "living"/controlled radical polymerization.
We report palladium(ii)-functionalized MOF-253 (MOF-253-Pd(OAc)2) as a recyclable catalyst to form all-carbon quaternary centers via conjugate additions of arylboronic acids to β,β-disubstituted enones in aqueous media.
An interfacial etchinga pproach was developed for the synthesis of monodispersea nd ultrasmall thiolated palladium nanoclusters( Pd NCs) using Zr-UiO-66-NH 2 metal-organic frameworks (MOFs) as sacrificial templates.T he Pd NCs were originally synthesized inside the cavities of the MOFs (Pd@UiO-66-NH 2 ). The Pd NCs released from the MOFs have as trikingly small size with narrow distribution (1.1 AE 0.1 nm), amounting to ac lusters ize of ca. 40 Pd atoms. The 1 HNMR spectrum indicates that thiol is the only capping agent for these Pd NCs. We derived the composition of the thiolated Pd NCs using thermogravimetric analysis( TGA) and inductively coupled plasma mass spectrometry (ICP-MS) analysis. Moreover, the Pd NCs size can be tuned by using MOF templates with different cavity sizes. The thiolated Pd NCs are catalytically active in am odel Suzuki-Miyaura coupling reaction.[a] X.
Covalent organic frameworks (COFs) have emerged as auspicious porous adsorbents for radioiodine capture. However, their conventional solvothermal synthesis demands multiday synthetic times and anaerobic conditions, largely hampering their practical use. To tackle these challenges, we present a facile microwave-assisted synthesis of 2D imine-linked COFs, Mw-TFB-BD-X, (X = −CH 3 and −OCH 3 ) under air within just 1 h. The resultant COFs possessed higher crystallinity, better yields, and more uniform morphology than their solvothermal counterparts. Remarkably, Mw-TFB-BD-CH 3 and Mw-TFB-BD-OCH 3 exhibited exceptional iodine adsorption capacities of 7.83 g g −1 and 7.05 g g −1 , respectively, placing them among the bestperforming COF adsorbents for static iodine vapor capture. Moreover, Mw-TFB-BD-CH 3 and Mw-TFB-BD-OCH 3 can be reused 5 times with no apparent loss in the adsorption capacity. The exceptionally high iodine adsorption capacities and excellent reusability of COFs were mainly attributed to their uniform spherical morphology and enhanced chemical stability due to the in-built electron-donating groups, despite their low surface areas. This work establishes a benchmark for developing advanced iodine adsorbents that combine fast kinetics, high capacity, excellent reusability, and facile rapid synthesis, a set of appealing features that remain challenging to merge in COF adsorbents so far.
The
development of chiral covalent organic frameworks (COFs) by
postsynthetic modification is challenging due to the common occurrences
of racemization and crystallinity decrement under harsh modification
conditions. Herein, we employ an effective site-selective synthetic
strategy for the fabrication of an amine-functionalized hydrazone-linked
COF, NH2-Th-Tz COF, by the Schiff-base condensation between
aminoterephthalohydrazide (NH2-Th) and 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde
(Tz). The resulting NH2-Th-Tz COF with free amine groups
on the pore walls provides an appealing platform to install desired
chiral moieties through postsynthetic modification. Three chiral moieties
including tartaric acid, camphor-10-sulfonyl chloride, and diacetyl-tartaric
anhydride were postsynthetically integrated into NH2-Th-Tz
COF by reacting amine groups with acid, acyl chloride, and anhydride,
giving rise to a series of chiral COFs with distinctive chiral pore
surfaces. Moreover, the crystallinity, porosity, and chirality of
chiral COFs were retained after modification. Remarkably, the chiral
COFs exhibited an exceptional enantioselective adsorption capability
toward tyrosine with a maximum enantiomeric excess (ee) value of up
to 25.20%. Molecular docking simulations along with experimental results
underscored the pivotal role of hydrogen bonds between chiral COFs
and tyrosine in enantioselective adsorption. This work highlights
the potential of site-selective synthesis as an effective tool for
the preparation of highly crystalline and robust amine-decorated COFs,
which offer an auspicious platform for the facile synthesis of tailor-made
chiral COFs for enantioselective adsorption and beyond.
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