Facile Post-synthetic Modification Research Articles

Unique Method for Facile Postsynthetic Modification of Nonisocyanate Polyurethanes.

Nonisocyanate polyurethanes (NIPUs) are broadly investigated as a potential replacement for conventional polyurethanes (PUs) to eliminate the use of toxic isocyanates and reduce occupational hazards. One of the most popular approaches to NIPU synthesis is the polyaddition of cyclic bis(carbonate)s and diamines to form poly(hydroxyurethane)s (PHUs). However, such PHUs are highly hydrophilic due to the presence of two hydroxyl groups per repeat unit, and the resulting moisture absorption significantly degrades their thermomechanical performance and physical stability upon exposure to humidity, thus limiting their utility. Here, we introduce a simple and scalable approach for the modification of PHUs to increase hydrophobicity and adjust their properties. The proposed reaction between aldehydes and appropriately spaced hydroxyl groups in the polymer backbone resulted in high degrees of modification (up to 84%) and up to 3-fold reductions in water uptake at 85% RH. Furthermore, the use of aromatic aldehydes in particular enabled the retention of mechanical properties over a wide range of humidity levels, resulting in performance comparable to conventional PUs. Finally, we note that this approach is not limited to reducing moisture sensitivity alone and provides ample opportunities for imparting a broad range of novel properties to PHUs through an appropriate selection of functional aldehydes.

Ratiometric detection of Cu2+ in water and drinks using Tb(III)-functionalized UiO-66-type metal-organic frameworks.

As an important trace element in the human body, the concentration of Cu2+ has an important impact on the environment and human health, and its quantitative determination is of great significance in the fields of environmental protection and food safety. Here, a ratiometric fluorescent probe based on Tb(III)-functionalized UiO-66-type MOFs has been synthesized via a facile post-synthetic modification method by employing mixed linkers containing terephthalic acid and 2,6-pyridinedicarboxylic acid for Cu2+ detection. The blue fluorescence intensity at 440 nm from the ligands of MOFs does not change much with increasing Cu2+ concentrations and can be used as a reference signal, while the green fluorescence of Tb3+ can be rapidly and selectively quenched, causing fluorescence intensity at 547 nm to decrease. The probe can be used as a ratiometric sensor for Cu2+ detection with a good linear response and low detection limit. The use of the probe for the determination of Cu2+ in real water samples and drinks shows good practicality. This method for Cu2+ detection is simple, specific and visualized to meet the needs of environmental monitoring and food analysis and provides a new strategy for the construction of new copper ion fluorescent sensors to analyze complex samples.

MIL-53-based homochiral metal-organic framework as a stationary phase for open-tubular capillary electrochromatography

Homochiral metal-organic frameworks (MOFs) have attracted considerable attention in many fields of research, such as chiral catalysis and chiral chromatography. However, only few homochiral MOFs can be effectively used in capillary electrochromatography (CEC) and their performances are far from adequate. In this study, we successfully synthesized achiral nanocrystalline MIL-53. A facile post-synthetic modification strategy was then implemented to functionalize the product, yielding a homochiral MOF: l-His-NH-MIL-53. This MOF was then employed as a chiral coating in open-tubular CEC mode (OT-CEC), and, as such, it exhibited high enantioselectivities for several racemic drugs. The homochiral MOF and the fabricated capillary coating were systematically characterized using transmission electron microscopy, scanning electron microscopy (with energy-dispersive X-ray spectrometry), Fourier-transform infrared spectroscopy, X-ray diffractometry, thermogravimetric analysis, circular dichroism spectroscopy, Brunauer-Emmett-Teller surface area measurements, and X-ray photoelectron spectroscopy. This study is expected to provide a new strategy for the design and establishment of MOF-based chiral OT-CEC systems.

Reversible Diels-Alder and Michael Addition Reactions Enable the Facile Postsynthetic Modification of Metal-Organic Frameworks.

Functionalization of metal-organic frameworks (MOFs) is critical in exploring their structural and chemical diversity for numerous potential applications. Herein, we report multiple approaches for the tandem postsynthetic modification (PSM) of various MOFs derived from Zr(IV), Al(III), and Zn(II). Our current work is based on our efforts to develop a wide range of MOF platforms with a dynamic functional nature that can be chemically switched via thermally triggered reversible Diels-Alder (DA) and hetero-Diels-Alder (HDA) ligations. Furan-tagged MOFs (furan-UiO-66-Zr) were conjugated with maleimide groups bearing dienophiles to prepare MOFs with a chemically switchable nature. As HDA pairs, phosphoryl dithioester-based moieties and cyclopentadiene (Cp)-grafted MOF (Cp-MIL-53-Al) were utilized to demonstrate the cleavage and rebonding of the linkages as a function of temperature. In addition to these strategies, the Michael addition reaction was also applied for the tandem PSM of IRMOF-3-Zn. Maleimide groups were postsynthetically introduced in the MOF lattice, which were further ligated with cysteine-based biomolecules via the thiol-maleimide Michael addition reaction. On the basis of the versatility of the herein presented chemistry, we expect that these approaches will help in designing a variety of sophisticated functional MOF materials addressing diverse applications.

CO2 cycloaddition over ionic liquid immobilized hybrid zeolitic imidazolate frameworks: Effect of Lewis acid/base sites

Ionic liquid (IL) immobilized zeolitic imidazolate framework (ZIF) catalysts (IL-ZIF-8) were prepared through grafting IL on a dual-ligand ZIF by a facile post-synthetic modification. The coordinately unsaturated Zn as Lewis acid sites and bromide ions as Lewis base sites were confirmed in the resulted IL-ZIF. The density of Lewis acid/base sites was tuned easily by content of mixed linkers in the framework and/or the IL loadings. The coexistence of Lewis acid/base sites remarkably improved the activity for cycloaddition of CO2 with propylene oxide, compared with parent ZIFs and IL. In the absence of any co-catalyst and solvent, the prepared IL-ZIF-8(0.3) obtained a high yield of 97% with good stability and reusability. Besides, a Lewis acid/base synergistic catalytic mechanism was proposed. The synergetic interaction of Lewis acid sites and Lewis base sites significantly reduces energy barrier of propylene oxide ring-opening to 11.5 kcal mol−1 and thus promotes the CO2 cycloaddition reaction.

8-Hydroxyquinoline and Eu3+ Incorporated Metal–Organic Framework Nanosystems with Tunable Emissions for White Light and Anticounterfeiting Applications

Metal–organic frameworks (MOFs) are a platform with multiple luminescent centers resulting from the multifaceted nature of their structure. Herein, via a facile postsynthetic modification method ap...

An easy and low-cost method of embedding chiral molecules in metal–organic frameworks for enantioseparation

A facile method, post-synthetic exchange of modulators (PSEm), has been demonstrated here to prepare chiral metal-organic frameworks for enantioseparation. Based on this method, three chiral porous Zr-based metal-organic frameworks have been prepared through exchanging the coordinated modulators on metal clusters of MOFs with commercially available chiral carboxylic acid molecules. In addition, the obtained materials show enantioselectivity toward three different enantiomers, which presents a proof of concept for the design of MOF materials for enantioseparation by an easy and low-cost method.

Sulfite modification of platinum nanoparticles modulates electrocatalytic formic acid oxidation activity

A facile post-synthetic modification of commercial Pt catalysts by sulfite leads to significantly enhanced formic acid oxidation activity.

A facile post-synthetic modification of ordered mesoporous carbon to get efficient catalysts for the formation of acetins

Highly active and stable solid acid catalysts based on ordered mesoporous carbons were synthesized via hard template method and further functionalization with sulfonic (SO3H) groups. Two post-synthetic modification strategies were applied. In the first one, the pristine carbon was modified with concentrated sulfuric acid. The second approach included the reaction of carbon with aryl diazonium cation generated in situ from sulfanilic acid. The morphology, structure, composition, and surface functionalities of the resulting carbons were determined by scanning and transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, N2 adsorption-desorption measurement, elemental analysis, potentiometric titration, X-ray photoelectron spectroscopy and FT-IR method. The obtained samples were further tested in acetylation of glycerol with acetic acid under various conditions, and were found to efficiently produce acetins, valuable fuel additives. An excellent catalytic activity was shown especially by the SO3H-bearing mesoporous carbon prepared by a facile method with the use of 4-benzenediazonium sulfonate under ambient conditions. Furthermore, very good recycling properties of this catalyst was demonstrated by four consecutive runs. It is supposed that acidic catalytic activity of the synthesized materials can be further extended to other acid-catalyzed reactions.

Enamine Approach for Versatile and Reversible Functionalization on Cellulose Related Porous Sponges

A readily modifiable cellulose sponge was prepared from cellulose acetoacetate (CAA). Facile postsynthetic modification with primary amino-containing modifiers such as octadecyl amine (ODA), cysteine (CYS), and l-glutamic acid (GLU) could be achieved demonstrating the ease of anchoring a broad selection of functional groups to the surface of the sponges. This postsynthetic modification process was systematically characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, which confirmed the formation of the enamine bonds. Besides, the microstructures and mechanical properties of the sponges were well preserved throughout the postsynthetic modification process. The enamine bonds, as one of the dynamic covalent bonds, were easily formed under mild and neutral conditions and broken under exposure to a low pH stimulus. The enamine bonds were used to modify the CAA sponges, which can achieve the versatility and recycling of cellulose porous materials. Therefore, the resulting...

Immobilization of thiol-functionalized ionic liquids onto the surface of MIL-101(Cr) frameworks by S[sbnd]Cr coordination bond for biodiesel production

A novel functionalized MOF heterogeneous catalyst (MIL-101(Cr) @MBIAILs), 2-Mercaptobenzimidazole ILs with electron-rich SH groups immobilized onto the surface of the well-defined MIL-101(Cr) frameworks, was constructed and fabricated by the SCr coordination bond on the basis of the facile post-synthetic modification strategy. The heterogeneous catalyst was measured by XRD, FTIR, SEM, TEM, TGA, EA and N2 adsorption–desorption, and the catalytic behavior of the catalyst was assessed by the esterification about oleic acid and methanol as a model reaction. The results showed that MBIAILs have been successfully immobilized onto the surface of MIL-101(Cr) frameworks by SCr coordinate bonds. More importantly, the conversion of oleic acid just decreased from 91.0% to 82.1% when the catalyst had been reused six times. This exhibited the prepared catalyst had superior catalytic behavior and excellent reusability.

A Facile Post-Synthetic Modification Method To Improve Hydrothermal Stability and CO2 Selectivity of CuBTC Metal–Organic Framework

Practical applications require hydrothermally stable metal–organic frameworks (MOFs). Achieving stable MOFs in the presence of water or humidity is challenging, especially for MOFs with open metals sites (OMSs) due to the high affinity of water molecules toward OMSs. A straightforward solution to tackling this problem is to protect OMSs in the porous structure of MOFs. A facile post-synthetic modification (PSM) method for the synthesis of molecular glycine-doped CuBTC MOF (BTC = benzene-1,3,5-tricarboxylic acid) was developed in this study. Developed materials, i.e., Gly-CuBTC MOFs, were characterized using various characterization techniques and evaluated using single-component gas (CO2 and N2) adsorption and dynamic water vapor adsorption experiments. The economical dopant of molecular glycine with amine and a carboxyl group was found to be able to saturate OMSs in the parent CuBTC MOF, leading to improved hydrothermal stability and CO2:N2 selectivity. It was also found that the adsorption capacity, CO2...

Increasing the Therapeutic Index of PDT with Hypothermia for Glioma Treatment

s / Photodiagnosis and Photodynamic Therapy 12 (2015) 325–375 369 key challenge. We demonstrate a rational design and synthesis of covalently linked Pc nanospheres to address the issue. Covalently linked Pc nanospheres with a hollow interior were synthesized and fully characterized by elemental analysis. MTT assay was performed on KB cells to assess their in vitro dark and phototoxicity (660nm laser, 500mW cm-2 for 2.5 mins). We compared singlet oxygen generation ability of ZnPcmonomers and nanospheres. The phototoxicity of nanospheres was also compared with ZnPc tetrasulfonate on KB cells. Cell viability was 78% for phthalocyanine tetrasulfonate at 10 M against 14% for the same concentration of ZnPc nanosphere. The result is consistent with the higher SOG efficiency of the nanospheres compared with a monomer. The ZnPc nanospheres had better SOG efficiency and in vitro phototoxicity than monomeric Pc molecules, suggesting their higher potential in PDT. Easy synthesis coupledwith facile post-syntheticmodification may allow Pc nanospheres to be a versatile platform for a diverse range of medical and non-medical applications. http://dx.doi.org/10.1016/j.pdpdt.2015.07.198 Singlet oxygen explicit dosimetry for PDT

Singlet oxygen explicit dosimetry for PDT

s / Photodiagnosis and Photodynamic Therapy 12 (2015) 325–375 369 key challenge. We demonstrate a rational design and synthesis of covalently linked Pc nanospheres to address the issue. Covalently linked Pc nanospheres with a hollow interior were synthesized and fully characterized by elemental analysis. MTT assay was performed on KB cells to assess their in vitro dark and phototoxicity (660nm laser, 500mW cm-2 for 2.5 mins). We compared singlet oxygen generation ability of ZnPcmonomers and nanospheres. The phototoxicity of nanospheres was also compared with ZnPc tetrasulfonate on KB cells. Cell viability was 78% for phthalocyanine tetrasulfonate at 10 M against 14% for the same concentration of ZnPc nanosphere. The result is consistent with the higher SOG efficiency of the nanospheres compared with a monomer. The ZnPc nanospheres had better SOG efficiency and in vitro phototoxicity than monomeric Pc molecules, suggesting their higher potential in PDT. Easy synthesis coupledwith facile post-syntheticmodification may allow Pc nanospheres to be a versatile platform for a diverse range of medical and non-medical applications. http://dx.doi.org/10.1016/j.pdpdt.2015.07.198 Singlet oxygen explicit dosimetry for PDT

Self-assembled, covalently linked, hollow phthalocyanine nanospheres

A rational design and synthesis of covalently linked Pc nanospheres with a very thin shell and hollow interior, composed of approximately 12 000 Pc units on average, was demonstrated through thiol–ene “click” chemistry without using any templates or emulsifiers. The ZnPc nanospheres allow post-synthetic modification to improve their dispersibility in aqueous solution without altering the morphology of the nanospheres or the properties of ZnPc cores. More importantly, the ZnPc nanospheres showed higher singlet oxygen generation efficiency and in vitro phototoxicity than monomeric Pc molecules, suggesting that ZnPc nanospheres are potentially useful as a PS for PDT. We anticipate that the ZnPc nanospheres would allow other post-synthetic modifications such as the introduction of targeting ligands to deliver the nanospheres to specific target sites and perform a dual chemo- and photodynamic therapy by the encapsulation of therapeutic agents. The easy synthesis of a hollow spherical framework with a high Pc content, coupled with facile post-synthetic modification may allow Pc nanospheres to be a versatile platform for a diverse range of medical and non-medical applications.

Multi-functionalization of oligodeoxynucleotide: a facile post-synthetic modification technique for the preparation of oligodeoxynucleotides with two different functional molecules

Treatment of the support-bound novel multi-functionalizable oligodeoxyribonucleotides bearing both 5-cyanomethoxycarbonylmethyl- and 5-methoxycarbonylmethyl-uridine with tyramine followed by tris(2-aminoethyl)amine facilitated multi-functionalization of oligodeoxyribonucleotides having different amine molecules.

6-Thio-2′-deoxyinosine: Synthesis, incorporation, and evaluation as a postsynthetically modifiable base in oligonucleotides

The synthesis of 6-thio-2′-deoxyinosine (d S6I) in a form suitably protected for solid-phase oligonucleotide synthesis is reported. This thionucleic acid was incorporated in high yield into short oligodeoxynucleotides, and the thiocarbonyl group could be modified by S-alkylation with complete chemoselectivity. The quantitation of incorporation and facile post-synthetic modification was demonstrated by enzymatic digestion and HPLC analysis, and the effect of covalent alkylation was determined by ΔT m measurements of the corresponding duplex oligonucleotides with dC as the complementary base.