Ruthenium Complexes Immobilized on an Azolium Based Metal Organic Framework for Highly Efficient Conversion of CO2 into Formic Acid

Microenvironment Modulation of Single-Atom Ru in ZrSBA-15 for CO2 Hydrogenation to Formic Acid

The chemical microenvironment modulation of active sites holds promise for facilitating their catalytic performance. Herein, single-atom Ru anchored by ZrSBA-15 modified with diverse organic amine groups has been fabricated and enabled CO2 hydrogenation to produce formic acid (FA) under mild conditions. However, the reaction cannot be achieved without the modification of organic amines. The functional groups as the microenvironment around Ru active sites effectively regulated the activity, in which Ru encapsulated in ZrSBA-15 bearing -NH2 groups exhibited the highest activity, with turnover number (TON) and turnover frequency (TOF) values of 505 and 64 h-1, respectively. Both characterization and experimental results validated that the functional group manipulated the adsorption capacity of the reactant, the electronic state of Ru and hydrophilicity/hydrophobicity of the materials, and thus the catalytic performance.

Boosting CO2 Hydrogenation to Formate over Edge-Sulfur Vacancies of Molybdenum Disulfide

Synthesis of formate from hydrogenation of carbon dioxide (CO2 ) is an atom-economic reaction but is confronted with challenges in developing high-performance non-precious metal catalysts for application of the process. Herein, we report a highly durable edge-rich molybdenum disulfide (MoS2 ) catalyst for CO2 hydrogenation to formate at 200 °C, which delivers a high selectivity of over 99 % with a superior turnover frequency of 780.7 h-1 surpassing those of previously reported non-precious metal catalysts. Multiple experimental characterization techniques combined with theoretical calculations reveal that sulfur vacancies at MoS2 edges are the active sites and the selective production of formate is enabled via a completely new water-mediated hydrogenation mechanism, in which surface OH* and H* species in dynamic equilibrium with water serve as moderate hydrogenating agents for CO2 with residual O* reduced by hydrogen. This study provides a new route for developing low-cost high-performance catalysts for CO2 hydrogenation to formate.

A novel test device and quantitative colorimetric method for the detection of human chorionic gonadotropin (hCG) based on Au@Zn-salen MOF for POCT applications

The human chorionic gonadotropin (hCG) hormone is a biomarker that can predict tumors and early pregnancy; however, it is challenging to develop sensitive qualitative-quantitative procedures that are also effective, inventive, and unique. In this study, we used a novel easy in situ reaction of an organic nano-linker with Zn(NO₃)₂·6H₂O and HAuCl₄·3H₂O to produce a gold-zinc-salen metal-organic framework composite known as Au-Zn-Sln-MOF. A wide variety of micro-analytical instruments and spectroscopic techniques were used in order to characterize the newly synthesized Au-Zn-Sln-MOF composite. Disclosure is provided for a novel swab test instrument and a straightforward colorimetric approach for detecting hCG hormone based on an Au-Zn-Sln-MOF composite. Both of these methods are easy. In order to validate a natural enzyme-free immunoassay, an Au-Zn-Sln-MOF composite was utilized in the role of an enzyme; a woman can use this gadget to determine whether or not she is pregnant in the early stages of the pregnancy or whether or not her hCG levels are excessively high, which is a symptom that she may have a tumor. This cotton swab test device is compatible with testing of various biological fluids, such as serum, plasma, or urine, and it can be easily transferred to the market to commercialize it as a costless kit, which will be 20-30% cheaper than what is available on the market. Additionally, it can be used easily at home and for near-patient testing (applications of point-of-care testing (POCT)).

Confinement Effects in Well-Defined Metal-Organic Frameworks (MOFs) for Selective CO2 Hydrogenation: A Review

Decarbonization has become an urgent affair to restrain global warming. CO₂ hydrogenation coupled with H₂ derived from water electrolysis is considered a promising route to mitigate the negative impact of carbon emission and also promote the application of hydrogen. It is of great significance to develop catalysts with excellent performance and large-scale implementation. In the past decades, metal-organic frameworks (MOFs) have been widely involved in the rational design of catalysts for CO₂ hydrogenation due to their high surface areas, tunable porosities, well-ordered pore structures, and diversities in metals and functional groups. Confinement effects in MOFs or MOF-derived materials have been reported to promote the stability of CO₂ hydrogenation catalysts, such as molecular complexes of immobilization effect, active sites in size effect, stabilization in the encapsulation effect, and electron transfer and interfacial catalysis in the synergistic effect. This review attempts to summarize the progress of MOF-based CO₂ hydrogenation catalysts up to now, and demonstrate the synthetic strategies, unique features, and enhancement mechanisms compared with traditionally supported catalysts. Great emphasis will be placed on various confinement effects in CO₂ hydrogenation. The challenges and opportunities in precise design, synthesis, and applications of MOF-confined catalysis for CO₂ hydrogenation are also summarized.

Strategic design of a bifunctional Ag(i)-grafted NHC-MOF for efficient chemical fixation of CO2 from a dilute gas under ambient conditions

Facile grafting of catalytically active Ag(i) into CO2-philic NHC-MOF for simultaneous capture and conversion of CO2 from dilute gas to value-added α-alkylidene cyclic carbonate and oxazolidinones under mild conditions is demonstrated.

A Ni-MOF based luminescent sensor for selective and rapid sensing of Fe(ii) and Fe(iii) ions

In this work, a bis(N,N-trimellitoyl)-4,4′-oxydianiline linker was synthesized and characterized by spectroscopic techniques. The molecular structure and luminescence intensity of the Ni-MOF treated with different metal ions were investigated.

CO2 hydrogenation over functional nanoporous polymers and metal-organic frameworks

CO₂ is one of the major environmental pollutants and its mitigation is attracting huge attention over the years due to continuous increase in this greenhouse gas emission in the atmosphere. Being environmentally hazardous and plentiful presence in nature, CO₂ utilization as C1 resource into fuels and feedstock is very demanding from the green chemistry perspectives. To accomplish this CO₂ utilization issue, functional organic materials like porous organic polymers (POPs), covalent organic frameworks (COFs) as well as organic-inorganic hybrid materials like metal-organic frameworks (MOFs), having characteristics of large surface area, high thermal stability and tunability in the porous nanostructures play significant role in designing the suitable catalyst for the CO₂ hydrogenation reactions. Although CO₂ hydrogenation is a widely studied and emerging area of research, till date review exclusively focused on designing POPs, COFs and MOFs bearing reactive functional groups is very limited. A thorough literature review on this matter will enrich our knowledge over the CO₂ hydrogenation processes and the catalytic sites responsible for carrying out these chemical transformations. We emphasize recent state-of-the art developments in POPs/COFs/MOFs having unique functionalities and topologies in stabilizing metallic NPs and molecular complexes for the CO₂ reduction reactions. The major differences between MOFs and porous organics are critically summarized in the outlook section with the aim of the future benefit in mitigating CO₂ emission from ambient air.

N-heterocyclic carbene-functionalized metal-organic frameworks for the chemical fixation of CO2

N-heterocyclic carbenes (NHCs) are a class of molecules with a lone pair of carbene electrons and thus, they have the ability to activate CO2 to form imidazolium carboxylates. The incorporation of activated, metal-free NHC moieties into metal-organic frameworks (MOFs) without the decomposition of metal-carboxylate coordination motifs is highly desired owing to the high CO2 affinity and versatile chemical functionalities in MOFs. Herein, we have summarized the recent in situ generation approaches to form metal-free NHC-functionalized MOFs, which are a unique class of CO2-conversion catalysts with high catalytic activity, selectivity and stability, superior to those of homogenous and other heterogeneous NHC analogues. The NHC-functionalized MOFs for catalytic CO2 reduction include reactions such as the hydroboration of CO2, hydrosilylation of CO2, N-methylation using CO2 and hydrogenation of CO2 to formic acid. Overall, the synthetic strategy of metal-free NHC-functionalized MOFs, the unique catalytic pathways of NHC-functionalized MOFs, and potentially new research directions of NHC-functionalized MOFs are discussed, which will guide researchers to attempt to design new NHC-MOFs and extend their catalytic applications in the chemical fixation of CO2.

A Facile Method for Preparing UiO-66 Encapsulated Ru Catalyst and its Application in Plasma-Assisted CO2 Methanation

With increasing applications of metal-organic frameworks (MOFs) in the field of gas separation and catalysis, the preparation and performance research of encapsulating metal nanoparticles (NPs) into MOFs (M@MOF) have attracted extensive attention recently. Herein, an Ru@UiO-66 catalyst is prepared by a one-step method. Ru NPs are encapsulated in situ in the UiO-66 skeleton structure during the synthesis of UiO-66 metal-organic framework via a solvothermal method, and its catalytic activity for CO₂ methanation with the synergy of cold plasma is studied. The crystallinity and structural integrity of UiO-66 is maintained after encapsulating Ru NPs according to the X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). As illustrated by X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), and mapping analysis, the Ru species of the hydration ruthenium trichloride precursor are reduced to metallic Ru NPs without additional reducing processes during the synthesis of Ru@UiO-66, and the Ru NPs are uniformly distributed inside the Ru@UiO-66. Thermogravimetric analysis (TGA) and N₂ sorption analysis show that the specific surface area and thermal stability of Ru@UiO-66 decrease slightly compared with that of UiO-66 and was ascribed to the encapsulation of Ru NPs in the UiO-66 skeleton. The results of plasma-assisted catalytic CO₂ methanation indicate that Ru@UiO-66 exhibits excellent catalytic activity. CO₂ conversion and CH₄ selectivity over Ru@UiO-66 reached 72.2% and 95.4% under 13.0 W of discharge power and a 30 mL·min^-1 gas flow rate ( V H 2 : V C O 2 = 4 : 1 ), respectively. Both values are significantly higher than pure UiO-66 with plasma and Ru/Al₂O₃ with plasma. The enhanced performance of Ru@UiO-66 is attributed to its unique framework structure and excellent dispersion of Ru NPs.