Abstract
Postsynthetic modification of metal-organic framework is a general and practical approach to access MOF-based catalysts bearing multiple active sites. The isoreticular metal–organic framework-3 (IRMOF-3) was modified with lactic acid through condensation reaction of the carboxyl group of lactic acid and amino group present in IRMOF-3 frameworks. Au3+ was subsequently anchored onto the metal–organic framework IRMOF-3 using postsynthetic modification. The synthezized IRMOF-3-LA-Au (LA = lactic acid) was characterized by powder X-ray diffraction, N2 adsorption-desorption, infrared spectroscopy, liquid-state nuclear magnetic resonance, thermogravimetric analysis, H2-temperature programmed reduction, transmission electro microscopy, and inductively coupled plasma–optical emission spectrometry. IRMOF-3-LA-Au acted as an efficient heterogeneous catalyst in the synthesis of propargylamines by three-component coupling reaction of aldehyde, alkyne, and amine. Moreover, the catalyst is applicable to various substituted substrates, including aromatic and aliphatic aldehydes, alkyl- and aryl-substituted terminal alkynes, and alicyclic amines. In addition, the catalyst can be easily separated from the mixture and can be reused for four consecutive cycles.
Highlights
MOFs can be customized by postsynthetic modification with different functional groups[38,39,40,41,42]
The present study investigated the ability of lactic acid to modify isoreticular metal–organic framework-3 (IRMOF-3) and generate a new functionalized MOF IRMOF-3-LA in a parallel approximation
IRMOF-3 was synthesized via a solvothermal method at 100 °C for 24 h by using 2-aminoterephthalic acid, Zn(NO3)2·6H2O, and N,N′dimethylformamide (DMF)
Summary
MOFs can be customized by postsynthetic modification with different functional groups[38,39,40,41,42]. UMCM1-AMFesal is catalytically active in Mukaiyama–aldol reaction over multiple catalytic cycles without showing loss of activity or crystallinity[33]. Candu et al.[43] prepared a highly active and enantioselective MOF through postsynthetic modification of [Cu2(mand)2(hmt)] (mand = mandelic acid, hmt = hexamethylenetetramine) with chiral and dimeric Cr3+ salen complexes. We designed and synthesized a new Au3+–containing catalyst, IRMOF-3-LA-Au, through postsynthetic modification of IRMOF-3 with lactic acid and gold. IRMOF-3-LA-Au was found to be active and selective for catalyzing A3 coupling reaction of aldehyde, alkyne, and amine in 1,4-dioxane. They display better catalytic activity than the catalyst containing Au° nanoparticles. The catalyst is compatible with various substituted substrates and could be reused for at least four reaction cycles
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