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Post-Synthetic Mannich Chemistry on Metal-Organic Frameworks: System-Specific Reactivity and Functionality-Triggered Dissolution.

ABSTRACT: The Mannich reaction of the zirconium MOF [Zr6 O4 (OH)4 (bdc-NH2 )6 ] (UiO-66-NH2 , bdc-NH2 =2-amino-1,4-benzenedicarboxylate) with paraformaldehyde and pyrazole, imidazole or 2-mercaptoimidazole led to post-synthetic modification (PSM) through C-N bond formation. The reaction with imidazole (Him) goes to completion whereas those with pyrazole (Hpyz) and 2-mercaptoimidazole (HimSH) give up to 41 and 36?% conversion, respectively. The BET surface areas for the Mannich products are reduced from that of UiO-66-NH2 , but the compounds show enhanced selectivity for adsorption of CO2 over N2 at 273?K. The thiol-containing MOFs adsorb mercury(II) ions from aqueous solution, removing up to 99?%. The Mannich reaction with pyrazole succeeds on [Zn4 O(bdc-NH2 )3 ] (IRMOF-3), but a similar reaction on [Zn2 (bdc-NH2 )2 (dabco)] (dabco=1,4-diazabicyclo[2.2.2]octane) gave [Zn3 (bdc-NH2 )1.32 (bdc-NHCH2 pyz)1.68 (dabco)]?2?C7 H8 5, whereas the reaction with imidazole gave the expected PSM product. Compound?5 forms via a dissolution-recrystallisation process that is triggered by the "free" pyrazolate nitrogen atom competing with dabco for coordination to the zinc(II) centre. In contrast, the "free" nitrogen atom on the imidazolate is too far away to compete in this way. Mannich reactions on [In(OH)(bdc-NH2 )] (MIL-68(In)-NH2 ) stop after the first step, and the product was identified as [In(OH)(bdc-NH2 )0.41 (bdc-NHCH2 OCH3 )0.30 (bdc-N=CH2 )0.29 ], with addition of the heterocycle prevented by steric interactions.

SUBMITTER: Amer Hamzah H

PROVIDER: S-EPMC6099314 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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Post-Synthetic Mannich Chemistry on Metal-Organic Frameworks: System-Specific Reactivity and Functionality-Triggered Dissolution.

Amer Hamzah Harina H Gee William J WJ Raithby Paul R PR Teat Simon J SJ Mahon Mary F MF Burrows Andrew D AD

Chemistry (Weinheim an der Bergstrasse, Germany) 20180626 43

The Mannich reaction of the zirconium MOF [Zr6 O4 (OH)4 (bdc-NH2 )6 ] (UiO-66-NH2 , bdc-NH2 =2-amino-1,4-benzenedicarboxylate) with paraformaldehyde and pyrazole, imidazole or 2-mercaptoimidazole led to post-synthetic modification (PSM) through C-N bond formation. The reaction with imidazole (Him) goes to completion whereas those with pyrazole (Hpyz) and 2-mercaptoimidazole (HimSH) give up to 41 and 36 % conversion, res ...[more]

PMID: 29808942

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Project description:Metal-organic frameworks are a class of porous crystalline materials based on the ordered connection of metal centers or metal clusters by organic linkers with comprehensive functionalities. The interest in these materials is rapidly moving towards their application in industry and real life. In this context, cheap and sustainable synthetic strategies of MOFs with tailored structures and functions are nowadays a topic widely studied from different points of view. In this review, fluorinated MOFs (F-MOFs) and their applications are investigated. The principal aim is to provide an overview of the structural features and the main application of MOFs containing fluorine atoms both as anionic units or as coordinating elements of more complex inorganic units and, therefore, directly linked to the structural metals or as part of fluorinated linkers used in the synthesis of MOFs. Herein we present a review of F-MOFs reported in the recent literature compared to benchmark compounds published over the last 10 years. The compounds are discussed in terms of their structure and properties according to the aforementioned classification, with an insight into the different chemical nature of the bonds. The application fields of F-MOFs, especially in sustainability related issues, such as harmful gas sorption and separation, will also be discussed. F-MOFs are compounds containing fluorine atoms in their framework and they can be based on: (a) fluorinated metallic or semi-metallic anionic clusters or: (b) fluorinated organic linkers or (c) eventually containing both the building blocks. The nature of a covalent C-F bond in terms of length, charge separation and dipole moment sensibly differs from that of a partly ionic M-F (M = metal) one so that the two classes of materials (points a and b) have different properties and they find various application fields. The study shows how the insertion of polar M-F and C-F bonds in the MOF structure may confer several advantages in terms of interaction with gaseous molecules and the compounds can find application in gas sorption and separation. In addition, hydrophobicity tends to increase compared to non-fluorinated analogues, resulting in an overall improvement in moisture stability.

Dataset Information

Post-Synthetic Mannich Chemistry on Metal-Organic Frameworks: System-Specific Reactivity and Functionality-Triggered Dissolution.

Publications

Post-Synthetic Mannich Chemistry on Metal-Organic Frameworks: System-Specific Reactivity and Functionality-Triggered Dissolution.

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