Synthesis, Structure, Assembly, and Modulation of the CO2 Adsorption Properties of a Zinc-Adeninate Macrocycle

Three-Dimensional Hydrogen-Bonded Porous Metal-Organic Framework for Natural Gas Separation with High Selectivity

A 3D hydrogen-bonded metal-organic framework, [Cu(apc)2]n (TJU-Dan-5, Hapc = 2-aminopyrimidine-5-carboxylic acid), was synthesized via a solvothermal reaction. The activated TJU-Dan-5 with permanent porosity exhibits a moderate uptake of 1.52 wt% of hydrogen gas at 77 K. The appropriate BET surface areas and decoration of the internal polar pore surfaces with groups that form extensive hydrogen bonds offer a more favorable environment for selective C2H6 adsorption, with a predicted selectivity for C2H6/CH4 of around 101 in C2H6/CH4 (5:95, v/v) mixtures at 273 K under 100 kPa. The molecular model calculation demonstrates a C-H···π interaction and a van der Waals host-guest interaction of C2H6 with the pore walls. This work provides a strategy for the construction of 3D hydrogen-bonded MOFs, which may have great potential in the purification of natural gas.

Trajectory in biological metal-organic frameworks: Biosensing and sustainable strategies-perspectives and challenges

The ligand attribute of biomolecules to form coordination bonds with metal ions led to the discovery of a novel class of materials called biomolecule-associated metal-organic frameworks (Bio-MOFs). These biomolecules coordinate in multiple ways and provide versatile applications. Far-spread bio-ligands include nucleobases, amino acids, peptides, cyclodextrins, saccharides, porphyrins/metalloporphyrin, proteins, etc. Low-toxicity, self-assembly, stability, designable and selectable porous size, the existence of rigid and flexible forms, bio-compatibility, and synergistic interactions between metal ions have led Bio-MOFs to be commercialized in industries such as sensors, food, pharma, and eco-sensing. The rapid growth and commercialization are stunted by absolute bio-compatibility issues, bulk morphology that makes it rigid to alter shape/porosity, longer reaction times, and inadequate research. This review elucidates the structural vitality, biocompatibility issues, and vital sensing applications, including challenges for incorporating bio-ligands into MOF. Critical innovations in Bio-MOFs' applicative spectrum, including sustainable food packaging, biosensing, insulin and phosphoprotein detection, gas sensing, CO2 capture, pesticide carriers, toxicant adsorptions, etc., have been elucidated. Emphasis is placed on biosensing and biomedical applications with biomimetic catalysis and sensitive sensor designing.

Dynamic Hydrogen-Bonded Zinc Adeninate Framework (ZAF) for Immobilization of Catalytic DNA

Effective immobilization and delivery of genetic materials is at the forefront of biological and medical research directed toward tackling scientific challenges such as gene therapy and cancer treatment. Herein we present a biologically inspired hydrogen-bonded zinc adeninate framework (ZAF) consisting of zinc adeninate macrocycles that self-assemble into a 3D framework through adenine-adenine interactions. ZAF can efficiently immobilize DNAzyme with full protection against enzyme degradation and physiological conditions until it is successfully delivered into the nucleus. As compared to zeolitic imidazolate frameworks (ZIFs), ZAFs are twofold more biocompatible with a significant loading efficiency of 96 %. Overall, our design paves the way for expanding functional hydrogen-bonding-based systems as potential platforms for the loading and delivery of biologics.

Ferrocene-Functionalized Crystalline Biomimetic Catalysts for Efficient CO2 Photoreduction

Photoreducing carbon dioxide (CO2) into highly valued chemicals or energy products has been recognized as one of the most promising proposals to degrade atmospheric CO2 concentration and achieve carbon neutrality. Adenine with a photosensitive amino group and aromatic nitrogen atom can strongly interact with CO2 and has been authenticated for its catalytic activity for the CO2 photoreduction reaction (CO2RR). Herein, two adenine-constructed crystalline biomimetic photocatalysts (Co2-AW and Co2-AF) were designed and synthesized to achieve CO2RR. Between them, Co2-AF displayed higher photocatalytic activity (225.8 μmol g-1 h-1) for CO2-to-HCOOH conversion than that of Co2-AW. It was found that the superior charge transfer capacity of the functional ferrocene group in Co2-AF is the primary reason to facilitate the photocatalytic performance efficiently. Additionally, this work also demonstrated the great potential of the ferrocene group as an electron donor and mediator in improving the photocatalytic activity of crystalline coordination catalysts.

Zinc-Based Metal-Organic Frameworks in Drug Delivery, Cell Imaging, and Sensing

The design and structural frameworks for targeted drug delivery of medicinal compounds and improved cell imaging have been developed with several advantages. However, metal-organic frameworks (MOFs) are supplemented tremendously for medical uses with efficient efficacy. These MOFs are considered as an absolutely new class of porous materials, extensively used in drug delivery systems, cell imaging, and detecting the analytes, especially for cancer biomarkers, due to their excellent biocompatibility, easy functionalization, high storage capacity, and excellent biodegradability. While Zn-metal centers in MOFs have been found by enhanced efficient detection and improved drug delivery, these Zn-based MOFs have appeared to be safe as elucidated by different cytotoxicity assays for targeted drug delivery. On the other hand, the MOF-based heterogeneous catalyst is durable and can regenerate multiple times without losing activity. Therefore, as functional carriers for drug delivery, cell imaging, and chemosensory, MOFs' chemical composition and flexible porous structure allowed engineering to improve their medical formulation and functionality. This review summarizes the methodology for fabricating ultrasensitive and selective Zn-MOF-based sensors, as well as their application in early cancer diagnosis and therapy. This review also offers a systematic approach to understanding the development of MOFs as efficient drug carriers and provides new insights on their applications and limitations in utility with possible solutions.

Assembly of {Co14} nanoclusters from adenine-modified Co4-thiacalix[4]arene units

An adenine-modified Co₄-thiacalix[4]arene unit can serve as a second building unit for fabrication of three Co₁₄ clusters with different structures.

Recent Advances in the Chemistry of Metal Carbamates

Following a related review dating back to 2003, the present review discusses in detail the various synthetic, structural and reactivity aspects of metal species containing one or more carbamato ligands, representing a large family of compounds across all the periodic table. A preliminary overview is provided on the reactivity of carbon dioxide with amines, and emphasis is given to recent findings concerning applications in various fields.

Spacer-Assisted Amine-Coiled Carbon Nanotubes for CO2 Capture

Architecture of a DNA-wrapped carbon nanotube (CNT) inspires rational design of a polymer-wrapped CNT effective for CO₂ capture. Polyethyleneimine (PEI) selected as a spiral wrapper of CNT is modified by insertion of spacer molecules loaded with amino groups such as siloxanes and purine to enhance the CO₂ capture performance. A porous adsorbent made by packing these functional nanowires (e.g., PEI-purine-CNT) reveals CO₂ uptake as large as 3.875 mmol/g. Adsorbent materials from this biomolecule-inspired design drop the adsorption heat to 29.00 kJ/mol if secondary and tertiary amines are adopted, besides the primary one, a value that is one-third of the absorption heat of an industrially deployed, liquid absorbent of CO₂. The corresponding adsorption and desorption kinetics agree with an Avrami model, indicating that both processes involve multiple sorption pathways. Furthermore, PEI-purine-CNT maintains its adsorption capacity after 50 adsorption-desorption cycles, implying a great potential for carbon capture from smokestacks and air in a stable and cyclic manner.

A zinc(ii) metal–organic framework with high affinity for CO2 based on triazole and tetrazolyl benzene carboxylic acid

A new metal–organic framework {[Zn₂(Htzba)₂(dmtrz)]·(CH₃)₂NH}_n (1) has already been solvothermally synthesized that exhibits a high CO₂ uptake capacity.

Supermacrocyclic Assemblies by Hydrogen-Bond Codes of C7-Phenol Pyrazolo and Pyrrolo Derivatives of Adenine

Hydrogen bond (HB) mediated base pair motifs are versatile scaffolds of diverse supramolecular constructs. Here, we report that two new four- and six-membered supermacrocyclic assemblies with intriguing geometries could self-assemble from two new adenine derivatives, APN (1) and APC (2). The conversion of a conventional HB acceptor, N8 of 1, to a non-conventional HB donor, C8-H of 2, had a pronounced impact on the overall intricate HB network and self-assembly patterns, epitomizing the subtleties in design and exploitation of such base-pair motifs as promising tectons for building supramolecular architectures.

Hybrid materials based on transition metal–BTC–benzimidazole: solvent assisted crystallographic and structural switching

Five transition metal–BTC–BIm based coordination polymers with hierarchical structures were synthesized under hydro/solvothermal condition. Crystal structure analysis of the compounds showed that 1 forms a 1D chain, 2 and 3 have 2D layers, while 4 and 5 have three-dimensional architectures.

An Adeninate-Based Metal–Organic Framework for Antitumour Drug Delivery and Anti-Osteogenic Sarcoma Activity Evolution

Targeted anticancer drug delivery systems (DDSs) have been considered as one of the most important approaches for reducing the side effects and enhancing the therapy effect in cancer treatment. This work presents a targeted anticancer DDS on the basis of a newly synthesised adeninate-based metal–organic framework (MOF) [Zn2(ad)2(AMDB)(H2O)](DMF)3 (1) with biomolecular adenine (HAd), zinc(ii) ions, and 4,4′-(aminomethylene)dibenzoic acid (H2AMDB) as the molecular building blocks. The structural analysis via X-ray diffraction technology shows MOF 1 is a channel-type three-dimensional network composed of rod-like Zn–Ad chains. Due to its large inner free spaces and uncoordinated N donor sites functionalised pore surroundings, the antitumour molecule 5-fluorouracil (5-Fu) could be loaded into the pores of 1a (activated 1) though an adsorption process, which shows a moderate high storage capacity of 32 wt-%. At the same time, the pH-dependent delivery of 5-Fu could be achieved in phosphate-buffered saline (PBS) solution. With a lower pH value, the drug release will be enhanced. Furthermore, the invitro antitumour activity of the drug/1a composite has been probed via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on two human osteogenic sarcoma cells (MG63 and U2OS).

Controlling Cooperative CO2 Adsorption in Diamine-Appended Mg2(dobpdc) Metal-Organic Frameworks

In the transition to a clean-energy future, CO2 separations will play a critical role in mitigating current greenhouse gas emissions and facilitating conversion to cleaner-burning and renewable fuels. New materials with high selectivities for CO2 adsorption, large CO2 removal capacities, and low regeneration energies are needed to achieve these separations efficiently at scale. Here, we present a detailed investigation of nine diamine-appended variants of the metal-organic framework Mg2(dobpdc) (dobpdc4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) that feature step-shaped CO2 adsorption isotherms resulting from cooperative and reversible insertion of CO2 into metal-amine bonds to form ammonium carbamate chains. Small modifications to the diamine structure are found to shift the threshold pressure for cooperative CO2 adsorption by over 4 orders of magnitude at a given temperature, and the observed trends are rationalized on the basis of crystal structures of the isostructural zinc frameworks obtained from in situ single-crystal X-ray diffraction experiments. The structure-activity relationships derived from these results can be leveraged to tailor adsorbents to the conditions of a given CO2 separation process. The unparalleled versatility of these materials, coupled with their high CO2 capacities and low projected energy costs, highlights their potential as next-generation adsorbents for a wide array of CO2 separations.

Biomimetic supercontainers for size-selective electrochemical sensing of molecular ions

New ionophores are essential for advancing the art of selective ion sensing. Metal-organic supercontainers (MOSCs), a new family of biomimetic coordination capsules designed using sulfonylcalix[4]arenes as container precursors, are known for their tunable molecular recognition capabilities towards an array of guests. Herein, we demonstrate the use of MOSCs as a new class of size-selective ionophores dedicated to electrochemical sensing of molecular ions. Specifically, a MOSC molecule with its cavities matching the size of methylene blue (MB⁺), a versatile organic molecule used for bio-recognition, was incorporated into a polymeric mixed-matrix membrane and used as an ion-selective electrode. This MOSC-incorporated electrode showed a near-Nernstian potentiometric response to MB⁺ in the nano- to micro-molar range. The exceptional size-selectivity was also evident through contrast studies. To demonstrate the practical utility of our approach, a simulated wastewater experiment was conducted using water from the Fyris River (Sweden). It not only showed a near-Nernstian response to MB⁺ but also revealed a possible method for potentiometric titration of the redox indicator. Our study thus represents a new paradigm for the rational design of ionophores that can rapidly and precisely monitor molecular ions relevant to environmental, biomedical, and other related areas.

Crystal structure dependent in vitro antioxidant activity of biocompatible calcium gallate MOFs

Two novel 3-D coordination polymers, denoted MIL-155 and MIL-156 (MIL stands for Materials Institute Lavoisier), built up from calcium and the naturally occurring gallic acid (H₄gal), have been hydrothermally synthesized and their crystal structures were determined by single-crystal X-ray diffraction. These solids are based on different inorganic subunits: infinite chains of edge-sharing dimers of CaO₇ polyhedra linked through partially deprotonated gallate ligands (H₂gal^2-) for MIL-155 or [Ca₂(H₂O)(H₂gal)₂]·2H₂O, and ribbon-like inorganic subunits containing both eight-fold or six-fold coordinated Ca^II ions linked through fully deprotonated gallate ligands (gal^4-) for MIL-156 or [Ca₃K₂(H₂O)₂(gal)₂]·nH₂O (n∼ 5). Both solids contain small channels filled with water molecules, with, however no accessible porosity towards N₂ at 77 K. MIL-155 and MIL-156 were proven to be biocompatible, as evidenced by in vitro assays (viability and cell proliferation/death balance). While the high chemical stability of MIL-156 makes it almost bioinert, the progressive degradation of MIL-155 leads to an important protective antioxidant effect, associated with the release of the bioactive gallate ligand.

Insights into the pores of microwave-assisted metal–imidazolate frameworks showing enhanced gas sorption

Microwave assisted synthesized materials have an inherent ability to trap extra linkers, thereby reducing the pore sizes of CE- heating materials to ultra/micropores. These ultramicropores are responsible for high gas sorption.

Metal organic frameworks based on bioactive components

This review highlights the latest advances of Metal Organic Frameworks (MOFs) in the promising biomedical domain, from their synthesis to their biorelated activities.

Designing structurally tunable and functionally versatile synthetic supercontainers

A new family of flexible metal–organic supercontainers exhibit selective binding with cationic guests and tunable supramolecular catalytic activity.