Post-synthesis Functionalization Research Articles

Facile fabrication of UiO-66-NH2 modified with dodecyl and polyethyleneimine by post-synthesis functionalization strategy and simultaneous adsorption removal of anionic and cationic dyes

To achieve simultaneous adsorption removal of anionic and cationic dyes, UiO-66-NH2@Dodecyl functionalized with dodecyl (long-chain alkane) and UiO-66-NH2@PEI modified by polyethyleneimine (PEI) (containing multiple amino groups) were facilely fabricated by post-synthesis functionalization strategy, and characterized systematically. UiO-66-NH2@Dodecyl and UiO-66-NH2@PEI both showed higher adsorption capacities for Congo red (458.2 and 583.4 mg/g) and methylene blue (218.0 and 286.3 mg/g). Adsorption kinetic and isotherm curves could be simulated best by pseudo-second-order kinetic model and Langmuir isotherm model, respectively. Under coexistence of inorganic salts and alkalinity, it was beneficial to improve adsorption capacities. Adsorption capacity of UiO-66-NH2@PEI with multiple amino groups was higher than UiO-66-NH2@Dodecyl at the same experimental conditions, indicating that hydrogen bonding had greater influence on adsorption efficiency. And UiO-66-NH2@Dodecyl and UiO-66-NH2@PEI had better stability. Hydrogen bonding, π-π conjugation, electrostatic interaction and van der Waals force were main adsorption driving forces. The results could provide theoretical and technical help for simultaneous adsorption removal of anionic and cationic dyes.

Progress on application of covalent organic frameworks for advanced lithium metal batteries

Since Li metal batteries (LMBs) theoretically possess high energy density, they are the most concerned rechargeable batteries at present. Whereas, poor safety and short cycling lives of the LMBs originate from various problems of LMBs components including cathode/anode materials, electrolytes, and separators have impeded their practical application. Covalent organic frameworks (COFs), which feature diverse structures, flexible frameworks, and versatile functions, have been extensively investigated as potential alternatives for above mentioned key components of LMBs. With the rational design and pre-/postsynthesis functionalization, COFs can be precisely customized for targeted functionalities, which can tackle the issues of LMBs. The current status of the application of COFs in LMBs, which covers working principles and strategies for improving electrochemical performance, will be discussed in this review. What's more, the challenges and potential directions for further developments of COFs in LMBs are presented in the final section.

The post-synthesis modification (PSM) of MOFs for catalysis.

While there are myriad ways to construct metal-organic framework (MOF) based catalysts, the introduction of catalytic functionality via covalent post-synthesis functionalization (PSM) offers multiple advantages: (i) a wide range of different catalyst types are generated from a handful of well-known parent MOFs, (ii) MOF catalyst properties can be systematically tuned while changing few variables, and (iii) catalytically active functional groups that would otherwise interfere with MOF assembly can be introduced facilely. This last advantage is particularly crucial for our quest to generate MOF active sites that are decorated with multiple functional groups capable of cooperative activity, analogous to enzyme active sites.

Surface-Modified MXenes: Simulation to Potential Applications

MXenes are promising two-dimensional materials with good electrical conductivity, layered structure, biocompatibility, hydrophilicity, chemical inertness, and high surface area. Since the discovery of MXenes, they have been used for multiple applications, including energy storage, sensors, electronics, and optical devices. Theoretically, various MXenes are predicted by multiple studies, but few have been synthesized experimentally. The synthesized MXenes can possess various terminating groups that provide a great avenue to modify the surface of MXenes to fine-tune their chemical and physical properties. Notably, the terminating group of MXenes can be adjusted using diverse modification strategies, including covalent and noncovalent approaches. To advance future applications, it is necessary to have a deeper understanding of both theoretical and experimental approaches of MXenes. Although there have been some reviews on MXenes, less attention has been paid to the essential principle involved in surface modification using covalent and noncovalent chemistry and the controllable design of various MXenes compositions based on the theoretical calculations. This review focuses on a detailed understanding of the synthesis process of MXenes, as well as theoretical and experimental approaches toward the determination of their physical and chemical properties. In effect, both synthetic methods and postsynthesis functionalization will be complemented by density functional theory calculations. Furthermore, various functionalization strategies of MXenes have been discussed. Finally, we have provided an overview of current trends of modified MXenes in energy storage devices, electrocatalysts, and sensors applications with a brief comparison of the current state-of-the-art methods. This review will help researchers understand the feasibility of MXenes at the fundamental level for potential use in large-scale practical applications.

Direct Synthesis of Aliphatic Polyesters with Pendant Hydroxyl Groups from Bio-Renewable Monomers: A Reactive Precursor for Functionalized Biomaterials.

Introducing desired functionalities into biomaterials is an effective way to obtain functionalized biomaterials. A versatile platform with the possibility of postsynthesis functionalization is highly desired but challenging in biomedical engineering. In this work, linear aliphatic polyesters with pendant hydroxyl (PEOH) groups were directly synthesized using renewable malic acid/tartaric acid as raw materials under mild conditions through the polyesterification reaction promoted by 1,1,3,3-tetramethylguanidine (TMG). The hydroxyl groups on PEOH provide an active stepping stone for the fabrication of demanded functionalized polyesters. We demonstrated the possibility of the PEOH as a reactive precursor for functional group transformation, coupling of bioactive molecules, and formation of crosslinking networks. Moreover, a theranostic nanoplatform (mPEG-b-(P7-asp&TPV)-b-mPEG NPs) was synthesized using PEOH as a reactive stepping stone by the programmable combination of the above functionalization methods. Overall, these hydroxyl-containing polyesters have great potential in biological applications.

Conquering the Synthesis and Functionalization of Bicyclo[1.1.1]pentanes.

Bicyclo[1.1.1]pentanes (BCPs) have become established as attractive bioisosteres for para-substituted benzene rings in drug design. Conferring various beneficial properties compared with their aromatic "parents," BCPs featuring a wide array of bridgehead substituents can now be accessed by an equivalent variety of methods. In this perspective, we discuss the evolution of this field and focus on the most enabling and general methods for BCPs synthesis, considering both scope and limitation. Recent breakthroughs on the synthesis of bridge-substituted BCPs are described, as well as methodologies for postsynthesis functionalization. We further explore new challenges and directions for the field, such as the emergence of other rigid small ring hydrocarbons and heterocycles possessing unique substituent exit vectors.

One-step laser ablation synthesis of magnetic nanoparticles with carbon coating for tribological applications

Among different materials able to reduce wear and friction in tribological couplings, there are lubricant nanofluids obtained by dispersing suitable nanoparticles into a host fluid. Carbon-based nanomaterials are known to be effective additives, but their efficiency can be further improved by combination with magnetic compounds. Unfortunately, the preparation of such bifunctional materials often require complex syntheses or need post-synthesis functionalization processes, thus increasing costs and reducing reliability. Herein, a simple and cost-effective one-step synthesis method, based on laser ablation in solution, is used to produce magnetic responsive nanoparticles surrounded by a carbon matrix to be exploited as lubricating additives. The lubricating colloidal solutions are thus easily obtained without the use of surfactants nor multi-step processes, which can contaminate the final product or increase production costs. They exhibit a very good stability and reduce the wear coefficient of almost 50% in presence of an applied magnetic field in respect to the base fluid alone. The importance of the presence of the carbon matrix surrounding the magnetic core to develop a positive tribological behaviour has been proved.

Thiol-epoxy 'click' chemistry: a focus on molecular attributes in the context of polymer chemistry.

Base-catalyzed ring-opening reaction of epoxides with the thiol nucleophiles is useful in the preparation and post-polymerization modification of synthetic polymers. Due to its many beneficial characteristics, this process is referred to as the thiol-epoxy 'click' reaction. In this article, our aim is to discuss the fundamental attributes of this process by tracing our own steps in the field. We initially address the aspects of efficiency, regio-selectivity, stoichiometry, and reaction conditions with the help of linear, hyperbranched, graft, dendritic, and cross-linked poly(β-hydroxy thioether)s. A special emphasis is placed on hydrogel synthesis and photopolymerization on surfaces. Subsequently, quenching of the alkoxide anion is considered which is a critical step in the formation of the β-hydroxy thioether linkage upon completion of reaction. The amenability of further reaction on the hydroxy and thioether groups through esterification and sulfur alkylation is then discussed. Initially, post-gelation/fabrication modification of sulfide linkages is considered to obtain cationic sulfonium hydrogels and zwitterionic photopatterned networks with antibacterial and antibiofouling properties, respectively. A post-synthesis functionalization strategy is then described to access same centered and segregated main-chain poly(β-hydroxy sulfonium)s as potent antibacterial materials. In side-chain polysulfides, the sequential post-synthesis modifications involving poly(glycidyl methacrylate) scaffolds can lead to the formation of amphiphilic homopolymers. The application of such materials is discussed in the arena of siRNA delivery. Finally, concerns relating to the formation of disulfide defects and open research goals such as study of the orthogonality of the reaction are addressed.

Pepper-Mediated Green Synthesis of Selenium and Tellurium Nanoparticles with Antibacterial and Anticancer Potential.

The production of nanoparticles for biomedical applications (namely with antimicrobial and anticancer properties) has been significantly hampered using traditional physicochemical approaches, which often produce nanostructures with poor biocompatibility properties requiring post-synthesis functionalization to implement features that such biomedical applications require. As an alternative, green nanotechnology and the synthesis of environmentally friendly nanomaterials have been gaining attention over the last few decades, using living organisms or biomolecules derived from them, as the main raw materials to produce cost-effective, environmentally friendly, and ready-to-be-used nanomaterials. In this article and building upon previous knowledge, we have designed and implemented the synthesis of selenium and tellurium nanoparticles using extracts from fresh jalapeño and habanero peppers. After characterization, in this study, the nanoparticles were tested for both their antimicrobial and anticancer features against isolates of antibiotic-resistant bacterial strains and skin cancer cell lines, respectively. The nanosystems produced nanoparticles via a fast, eco-friendly, and cost-effective method showing different antimicrobial profiles between elements. While selenium nanoparticles lacked an antimicrobial effect at the concentrations tested, those made of tellurium produced a significant antibacterial effect even at the lowest concentration tested. These effects were correlated when the nanoparticles were tested for their cytocompatibility and anticancer properties. While selenium nanoparticles were biocompatible and had a dose-dependent anticancer effect, tellurium-based nanoparticles lacked such biocompatibility while exerting a powerful anti-cancer effect. Further, this study demonstrated a suitable mechanism of action for killing bacteria and cancer cells involving reactive oxygen species (ROS) generation. In summary, this study introduces a new green nanomedicine synthesis approach to create novel selenium and tellurium nanoparticles with attractive properties for numerous biomedical applications.

Optimization of particle rinsing process in linker-free post-synthesis functionalization for sensitive encoded hydrogel microparticle-based immunoassay

Graphically encoded hydrogel microparticles has garnered attention as effective multiplex immunoassay platform owing to their large multiplex capacity and high sensitivity. In particular, the newly developed capture antibody functionalization technique for hydrogel microparticle-based immunoassay called linker-free post-synthesis functionalization (PSF) enables enhanced detection performance based on direct and homogeneous antibody conjugation. After the linker-free PSF process, multiple particle rinsing steps are required to prevent unfavorable side reactions during the target capture step between unbound capture antibodies and target molecules, which can degrade the detection performance. This study investigates the importance of extent of dilution during particle rinsing after the linker-free PSF process on the sensitivity of encoded hydrogel microparticle-based immunoassay. First, the impact of dilution level in particle rinsing on signal intensity after immunoassay was characterized for four types of preeclampsia-related protein biomarkers. Consequently, the optimal dilution factor for particle rinsing was determined, and significantly enhanced sensitivity based on the optimized particle rinsing was realized. In addition, the robust specificity and spike recovery of the optimized rinsing process during the multiplex detection were validated.

ZnO nanorods-grafted durable antibacterial and hydrophobic cotton fabrics by a new grafting protocol

• Synthesis and functionalization of ZnO nanorods by hydrothermal technique. • Functionalized ZnO nanorods were grafted on cotton by new synthetic protocol. • A durable antimicrobial and hydrophobic cotton surface was obtained. This work reports a new method for the preparation of durable antibacterial and hydrophobic nanotextile by covalent grafting of zinc oxide nanorods (ZnO NRs) on cotton. The method involves synthesis and post-synthesis functionalization of the ZnO NRs with amino (–NH 2 ) groups followed by their grafting with hydroxyl groups on the cotton by reliable and effective condensation protocol. The ZnO NRs grafted cotton fabric exhibited excellent antibacterial efficacy against E-coli bacteria and showed a static water contact angle (WCA) of 121°. The covalent grafting of nanomaterials with antibacterial and hydrophobic properties on various textile substrates guarantees durability of the resulting nanotextile. Threfore, this report is a significant advancement towards the development of durable antibacterial as well as hydrophobic nanotextiles.

Post-synthesis functionalization of ZIF-90 with sulfonate groups for high proton conduction.

Introducing sulfonic acid groups into MOF materials is one of the effective approaches to enhance proton conduction. Here, we attempted to prepare a new post-modified ZIF-90-based material by addition reaction of the aldehyde group with bisulfite to obtain partially functionalized ZIF-90-SO3Na(2.3). ZIF-90-SO3Na(2.3) exhibits a high proton conductivity of 2.26 × 10-2 S cm-1 at 98% RH and 100 °C.

An Active Surface Preservation Strategy for the Rational Development of Carbon Dots as pH-Responsive Fluorescent Nanosensors

Here we report the rational development of a carbon dot (CDs)-based fluorescent pH nanosensor by employing an active surface preservation strategy. More specifically, citric acid, urea and fluorescein were subjected to a one-pot hydrothermal treatment, which preserved fluorescein-like structures on the surface of the CDs. The obtained CDs showed pH-sensitive green emission, which can be used to determine pH variations from 3.7 to 12.1 by fluorescence enhancement. Moreover, the obtained nanoparticles showed excellent selectivity toward pH, fluorescence reversibility in different pH values, photostability, while being compatible with human cell lines (even at high concentrations). Furthermore, their performance as pH sensors was comparable with reference pH determination procedures. Thus, an active surface preservation strategy was successfully employed to develop fluorescence pH nanosensors in a rational manner and without post-synthesis functionalization strategies, which show potential for future use in pH determination.

Enhancing toxic gas uptake performance of Zr-based MOF through uncoordinated carboxylate and copper insertion; ammonia adsorption

This study reports the development of a new type of Zr-based MOF by inserting copper and carboxylate into HCl modulated UiO-67 (UiO-67-vac) which gained higher surface area/vacant than UiO-67. Copper was inserted into MOF containing uncoordinated carboxylate group, to create open metal site in the form of −COOCu which called UiO-67-ox-Cu. PXRD, FTIR, BET, SEM, EDS, UV-Vis and XPS were used to characterize the obtained MOFs. As expected, UiO-67-ox-Cu exhibits the highest ammonia capacity (178.3 mg/g) among UiO-67 (104 mg/g) and UiO-67-vac (121 mg/g) at 298 K and 1 bar pressure. In fact, the significant increase in ammonia uptake of UiO-67-ox-Cu is related to the modified binding affinity of −COOCu groups with ammonia. Moreover, UiO-67-vac with the highest surface area showed the hydrogen adsorption capacity of 18.75 mg/g at 77 K, which is comparable or even superior to the previously reported value. Interestingly, adsorption capacities were retained with slight changes around five cycles and three regeneration temperatures, 25, 60 and 120 °C under vacuum pressure which were proved by PXRD after ammonia adsorption/desorption. The good results obtained in the current work clearly show the role of postsynthesis functionalization approach for creation of new metal/active sites into MOFs.

Improving ammonia uptake performance of zirconium-based metal-organic frameworks through open metal site insertion strategy

• The Zr-based MOF, UiO-67-bpy, inserted by transition metals was developed for gas uptake. • Ni, Co, Mn, Fe and Cu were inserted into MOF to create OMS. • PSF-Mn could achieve a maximum NH 3 adsorption capacity of 245.90 mg/g at 298 K. • OPS-Co showed a maximum H 2 adsorption capacity 20.78 mg/g at 1 bar and 77 K. • The MOFs with inserted OMS can achieve a higher gas uptake capacity than pristine MOFs. This study reports the development of a new type of MOFs by inserting transition metals into the bipyridine dicarboxylate ligand-containing Zr-based MOF, UiO-67-bpy, through one-pot synthesis (OPS) and post-synthesis functionalization (PSF) methods. Transition metals including Ni, Co, Mn, Fe and Cu were inserted into MOF to create open metal site (OMS). PXRD, FTIR, BET, SEM, EDS, UV-Vis and ICP were used to characterize the obtained MOFs. The ammonia and hydrogen uptake capacity of all samples was evaluated by static measurements. Among all samples, the Mn-containing UiO-67-bpy modified by PSF method, PSF-Mn, could achieve a maximum ammonia adsorption capacity of 245.90 mg/g at 298 K (Langmuir model). Among the samples processed by OPS, the MOF containing Mn, namely OPS-Mn, has a maximum adsorption capacity of 224.50 mg/g, showing the highest capacity. Moreover, Co-containing UiO-67-bpy modified by OPS method, OPS-Co, showed the hydrogen adsorption capacity of 20.78 mg/g at 77 K, which is comparable or even superior to the previously reported value. According to the values of isosteric enthalpy of adsorption, H 2 adsorption behaviors of the UiO-67-bpy-M were strongly dependent on the metal species, so that the isosteric heats of H 2 adsorption for these MOFs were in the range 0.672–1.002 kJ mol −1 , where OPS-Co gained the highest (1.002 kJ/mol). The good results obtained in the current work clearly show that the combination of PSF and OPS techniques is a promising approach to inserting OMS into MOFs. Although the surface area of the MOF is reduced, compared to the original MOF with a higher surface area, the use of MOFs with inserted OMS can achieve a higher gas uptake capacity.

Porphyrinic zirconium metal-organic frameworks: Synthesis and applications for adsorption/catalysis

Zr-based porphyrinic MOFs, which have isolated porphyrin units imbedded in MOFs’ rigid structure, exhibit excellent textural properties and high stability. Among the porphyrin ligands, tetrakis(4-carboxyphenyl)-porphyrin (TCPP) is broadly employed, and so far, seven Zr-based porphyrinic MOFs of MOF-525, MOF-545 (also named PCN-222), PCN-221, PCN-223, PCN-224, PCN-225, and NU-902 have been synthesized using TCCP. The built-in TCPP ligand with various functionality and coordinatively unsaturated Zr clusters can be subjected to diverse pre- and post-synthesis functionalization or guest encapsulation. Aided by the excellent hydrothermal/chemical stability and high porosity, these Zr-based porphyrinic MOFs are gaining attention for applications in adsorption, sensors, heterogeneous catalysis for chemical conversions, photocatalysis, electrocatalysis, and others. This paper reviews the current status of research and development on the synthesis, characterization, functionalization, and adsorption/catalysis applications of Zr-based porphyrinic MOFs.

Current advances in bio-fabricated quantum dots emphasising the study of mechanisms to diversify their catalytic and biomedical applications.

Quantum dots (QDs), owing to their single atom-like electronic structure due to quantum confinement, are often referred to as artificial atoms. This unique physical property results in the diverse functions exhibited by QDs. A wide array of applications have been achieved by the surface functionalization of QDs, resulting in exceptional optical, antimicrobial, catalytic, cytotoxic and enzyme inhibition properties. Ordinarily, traditionally prepared QDs are subjected to post synthesis functionalization via a variety of methods, such as ligand exchange or covalent and non-covalent conjugation. Nevertheless, solvent toxicity, combined with the high temperature and pressure conditions during the preparation of QDs and the low product yield due to multiple steps in the functionalization, limit their overall use. This has driven scientists to investigate the development of greener, environmental friendly and cost-effective methods that can circumvent the complexity and strenuousness associated with traditional processes of bio-functionalization. In this review, a detailed analysis of the methods to bio-prepare pre-functionalized QDs, with elucidated mechanisms, and their application in the areas of catalysis and biomedical applications has been conducted. The environmental and health and safety aspects of the bio-derived QDs have been briefly discussed to unveil the future of nano-commercialization.

Post-Synthesis Modification of Photoluminescent and Electrochemiluminescent Au Nanoclusters with Dopamine.

Here, we report a post-synthesis functionalization of the shell of Au nanoclusters (NCs) synthesized using glutathione as a thiolate ligand. The as-synthesized Au NCs are subjected to the post-synthesis functionalization via amidic coupling of dopamine on the cluster shell to tailor photoluminescence (PL) and electrochemiluminescence (ECL) features of the Au NCs. Because the NCs’ PL at ca. 610 nm is primarily ascribed to the Au(I)-thiolate (SG) motifs on the cluster shell of the NCs, the post-synthesis functionalization of the cluster shell enhanced the PL intensity of the Au NCs via rigidification of the cluster shell. In contrast to the PL enhancement, the post-synthesis modification of the cluster shell does not enhance the near-infrared (NIR) ECL of the NCs because the NIR ECL at ca. 800 nm is ascribed to the Au(0)-SG motifs in the metallic core of the NCs.

Preparation and characterisation of amino-functionalized pore-expanded mesoporous silica for carbon dioxide capture

In this study, the preparation of some large-pore ordered mesoporous silicas using a proper surfactant with different swelling agents was carried out. The synthesis of conventional SBA-15 was modified to obtain pore-expanded materials, with pore diameters up to 10 nm. To use a micelle swelling agent with a moderate swelling ability, three swelling agents were selected: 1-phenyl-decane (Dec), butyl benzene (BB), and mesitylene (Mes). These syntheses aimed to achieve a pore diameter enlargement but at the same time to avoid the formation of heterogeneous and/or poorly defined nanostructure of silica. The CO2 adsorbents were obtained by post-synthesis functionalization treatments carried out by grafting with 3-aminopropyl triethoxysilane. The CO2 adsorption/desorption experiments showed that carbon dioxide sorption capacities depend on the textural characteristics and the temperature used for the adsorption process. Good CO2 adsorption capacities were obtained for all prepared adsorbents, especially for SSBA-15-Mes-sil and SSBA-15-BB-sil samples. At 50 °C, the SSBA-15-Mes-sil sample has an adsorption capacity of 3.58 mmol CO2/g SiO2, and an efficiency of amino groups of 0.99 mmol CO2/mmol NH2. The results of adsorption capacities are comparable or even superior with the ones reported in literature for mesoporous silica functionalized with different amines. After nine adsorption–desorption cycles, the performance of the SSBA-15-Mes-sil adsorbent is relatively stable, with a low decrease in the adsorption capacity (0.1 mmol/g of CO2, i.e., 2.8% of initial capacity). These studies show the potential of mesoporous silica for carbon dioxide capture.

Kinetics of the functionalization of mesoporous silica nanoparticles: Implications on surface group distributions, adsorption and catalysis

Abstract The post-synthesis functionalization (grafting) kinetics of mesoporous silica nanoparticles (MSN) with organo-trimethoxysilanes (R-TMS) is studied via solution 1H NMR spectroscopy. The process involves a rapid adsorption/desorption pre-equilibrium followed by reaction of R-TMS with surface silanols. Grafting rates are affected by the functional group in R-TMS. For example, the grafting rate of aminopropyl-trimethoxysilane (AP-TMS) is one order of magnitude higher than other R-TMS. High concentrations of AP-TMS result in substrate-inhibition kinetics, likely due to steric and mobility constraints for reactant alignment at high coverage. The higher rates of AP-TMS grafting indicate a catalytic effect of amine groups. This effect depends on the amine's basicity and can be used to control the grafting rates and degree of condensation of other R-TMS. Adjusting the rate of mercaptopropyl-trimethoxysilane (MP-TMS) grafting using amines gives MP-MSN materials of varying adsorptive and catalytic activities, illustrated by Pd scavenging experiments and use of Pd@MP-MSN as catalysts for a Suzuki-Miyaura cross-coupling reaction.