A New Photoactive Crystalline Highly Porous Titanium(IV) Dicarboxylate

Nanoscale covalent organic frameworks: from controlled synthesis to cancer therapy

Covalent organic frameworks (COFs), as a new type of crystalline porous materials, mainly consist of light-weight elements (H, B, C, N and O) linked by dynamic covalent bonds to form periodical structures of two or three dimensions. As an attribute of their low density, large surface area, and excellent adjustable pore size, COFs show great potential in many fields including energy storage and separation, catalysis, sensing, and biomedicine. However, compared with metal organic frameworks (MOFs), the relatively large size and irregular morphology of COFs affect their biocompatibility and bioavailability in vivo, thus impeding their further biomedical applications. This Review focuses on the controlled design strategies of nanoscale COFs (NCOFs), unique properties of NCOFs for biomedical applications, and recent progress in NCOFs for cancer therapy. In addition, current challenges for the biomedical use of NCOFs and perspectives for further improvements are presented.

Enhancing Photocatalytic Hydrogen Production via the Construction of Robust Multivariate Ti-MOF/COF Composite

Titanium metal-organic frameworks (Ti-MOFs), as an appealing type of artificial photocatalysts, have shown great potentials in the field of solar energy conversion due to their well-studied photo-redox activity similar to TiO 2 and good optical responsiveness of linkers serving as the antenna to absorb visible-light. Although enormous efforts have been dedicated to developing Ti-MOFs with high photocatalytic activity, their solar energy conversion performances are still poor. Herein, a covalent-integrated strategy has been implemented to construct a series of multivariate Ti-MOF/COF hybrid materials, PdTCPP⸦PCN-415(NH 2 )/TpPa (composites 1, 2, and 3), featuring excellent visible-light utilization, suitable band gap, and high surface area for photocatalytic H 2 production. Notably, the resulting composites demonstrated remarkably enhanced visible-light-driven photocatalytic H 2 evolution performance, especially for the composite 2 with the maximum H 2 evolution rate of 13.98 mmol g -1 h -1 (turn-over frequency (TOF) = 227 h -1 ), which is much higher than the prototypical counterparts, PdTCPP⸦PCN-415(NH 2 ) (0.21 mmol g -1 h -1 ) and TpPa (6.51 mmol g -1 h -1 ). Our work thereby suggests a new approach to develop highly efficient photocatalysts for photocatalytic H 2 evolution reaction and beyond.

Efficient Computation of Nonadiabatic Coupling Coefficients for Modeling Charge Carrier Recombination in Extended Systems: The Case of Metal-Organic Frameworks

Modeling excited state charge carrier dynamics and recombination in extended systems, such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and other hybrid organic-inorganic materials, by surface-hopping approaches is a challenging task due to the high computational cost. In this work, the steps of the simulations and the bottlenecks for such systems are analyzed. In particular, the bottlenecks related to computation of the nonadiabatic coupling coefficients (NACs) are considered. A simple, inexpensive, and portable scheme for computing scalar NACs employing a grid representation of the wave functions is presented and implemented in a Python code. It is tested for the simulation of the electron-hole nonradiative recombination in the MIL-125-NH₂ model system. The proposed approach allows for an on-the-fly estimation of the NACs alongside the simulation of the molecular dynamics trajectory and enables a straightforward interface between the Python libraries for nonadiabatic molecular dynamics and the majority of the existing quantum chemical codes.

Mechanochemistry of Group 4 Element-Based Metal-Organic Frameworks

Mechanochemical synthesis is emerging as an environmentally friendly yet efficient approach to preparing metal-organic frameworks (MOFs). Herein, we report our systematic investigation on the mechanochemical syntheses of Group 4 element-based MOFs. The developed mechanochemistry allows us to synthesize a family of Hf₄O₄(OH)₄(OOC)₁₂-based MOFs. Integrating [Zr₆O₄(OH)₄(OAc)₁₂]₂ and [Hf₆O₄(OH)₄(OAc)₁₂]₂ under the mechanochemical conditions leads to a unique family of cluster-precise multimetallic MOFs that cannot be accessed by the conventional solvothermal synthesis. Extensive efforts have not yielded an effective pathway for preparing Ti^IV-derived MOFs, tentatively because of the relatively low Ti-O bond dissociation energy.

Group 4 Metal-Based Metal—Organic Frameworks for Chemical Sensors

Metal-organic frameworks (MOFs) have attracted great attention for their applications in chemical sensors mainly due to their high porosity resulting in high density of spatially accessible active sites, which can interact with the aimed analyte. Among various MOFs, frameworks constructed from group 4 metal-based (e.g., zirconium, titanium, hafnium, and cerium) MOFs, have become especially of interest for the sensors requiring the operations in aqueous media owing to their remarkable chemical stability in water. Research efforts have been made to utilize these group 4 metal-based MOFs in chemosensors such as luminescent sensors, colorimetric sensors, electrochemical sensors, and resistive sensors for a range of analytes since 2013. Though several studies in this subfield have been published especially over the past 3–5 years, some challenges and concerns are still there and sometimes they might be overlooked. In this review, we aim to highlight the recent progress in the use of group 4 metal-based MOFs in chemical sensors, and focus on the challenges, potential concerns, and opportunities in future studies regarding the developments of such chemically robust MOFs for sensing applications.

Interrogating Light-initiated Dynamics in Metal-Organic Frameworks with Time-resolved Spectroscopy

Time-resolved spectroscopy is an essential part of both fundamental and applied chemical research. Such techniques access light-initiated dynamics on time scales ranging from femtosecond to microsecond. Many techniques falling under this description have been applied to gain significant insight into metal-organic frameworks (MOFs), a diverse class of porous coordination polymers. MOFs are highly tunable, both compositionally and structurally, and unique challenges are encountered in applying time-resolved spectroscopy to interrogate their light-initiated properties. These properties involve various excited state mechanisms such as crystallographically defined energy transfer, charge transfer, and localization within the framework, photoconductivity, and structural dynamics. The field of time-resolved MOF spectroscopic studies is quite nascent; each original report cited in this review was published within the past decade. As such, this review is a timely and comprehensive summary of the most significant contributions in this emerging field, with focuses on the overarching spectroscopic concepts applied and on identifying key challenges and future outlooks moving forward.

Boron containing metal-organic framework for highly selective photocatalytic production of H2O2 by promoting two-electron O2 reduction

A zirconium-based metal-organic framework containing boron (UiO-66-B) is prepared, which displays efficient photocatalytic H₂O₂ production. The H₂O₂ evolution rate is about 1002 μmol g^-1 h^-1, much higher than that of most known photocatalysts. Pristine UiO-66 displays a much lower activity (314 μmol g^-1 h^-1) under the same conditions, suggesting the significant role of boron. Both theoretical calculations and the combined experimental results verify the above conclusion, and the role of boron is ascribed to the following aspects: (1) enhanced O₂ adsorption, (2) highly selective proton-coupled two-electron transfer, (3) faster carrier separation and surface charge transfer, and (4) faster generation but slower decomposition rates of H₂O₂. This work highlights key factors in the two-electron O₂ reduction reaction (ORR), presents a deeper understanding of the role of boron in enhancing H₂O₂ production, and provides a new strategy for designing photocatalysts with excellent H₂O₂ evolution efficiency.

Amino-functionalized Ti-metal-organic framework decorated BiOI sphere for simultaneous elimination of Cr(VI) and tetracycline

A subtle flower-like MIL-125-NH₂@BiOI was fabricated by a facile solvothermal method for simultaneously eliminating Cr(VI)/tetracycline mixed pollutants under visible light. The strong interaction between amino in MIL-125-NH₂ and Bi³⁺ of BiOI promotes the formation of this unique inlaid structure and enables the favorable contact between MIL-125-NH₂ and BiOI, thus accelerating the transfer of charge carriers. Remarkably, MIL-125-NH₂@BiOI displays a superior activity compared with that of two monomers for the photocatalytic reduction of Cr(VI) and degradation of tetracycline. More significantly, the photocatalytic efficiency can be further boosted in the coexistence of Cr(VI) and tetracycline, which is 1.8 and 1.6 times that of single Cr(VI) and tetracycline, respectively. The synergistic effect between Cr(VI) reduction and tetracycline oxidative degradation can further facilitate the separation of photo-induced electrons and holes, resulting in the improved efficiencies in the Cr(VI)/tetracycline coexistent environment. This work sheds light on that MOF-based photocatalysts possess huge potential for practical environmental remediation.

Two Isostructural Titanium Metal-Organic Frameworks for Light Hydrocarbon Separation

Presented here is the light hydrocarbon separation of titanium metal-organic frameworks (Ti-MOFs). Compared with the cyclic Ti-oxo cluster (Ti₈O₈(CO₂)₁₆, Ti₈Ph), porous structures of FIR-125 and FIR-126 (FIR = Fujian Institute Research) can effectively improve the adsorption amounts of light hydrocarbons. The introduction of different functional groups and Ti-oxo clusters with small window sizes enables them to exhibit the highly selective separation of C₂ and C₃ hydrocarbons versus methane in an ambient atmosphere. The results show that Ti-MOFs are potential porous adsorbents for the separation of light hydrocarbons.

Surfactant-assisted synthesis of titanium nanoMOFs for thin film fabrication

We use dodecanoic acid as a modulator to yield titanium MOF nanoparticles with good control of size and colloid stability and minimum impact to the properties of the framework to enable direct fabrication of crystalline, porous thin films.

The Importance of Highly Connected Building Units in Reticular Chemistry: Thoughtful Design of Metal-Organic Frameworks

The prediction of crystal structures assembled in three dimensions has been considered for a long time, simultaneously as a chemical wasteland and a certain growth point of the chemistry of the future. Less than 30 years after Roald Hoffmann's statement, we can categorically affirm that the elevation of reticular chemistry and the introduction of metal-organic frameworks (MOFs) significantly tackled this tridimensional assembly issue. MOFs result from the assembly of organic polytopic organic ligands bridging metal nodes, clusters, chains, or layers together into mostly three-periodic open frameworks. They can exhibit extremely high porosity and offer great potential as revolutionary catalysts, drug carrier systems, sensors, smart materials, and, of course, separation agents. Overall, the progressive development of reticular chemistry has been a game changer in materials chemistry during the last 25 years.Such diverse properties often result not only from the selected organic and inorganic molecular building blocks (MBBs) but also from their distribution within the framework. Indeed, the size and shape of the porous system, as well as the location of active sites influence the overall properties. Therefore, in the continuity of achieving the crystallization of three-periodic structures, chemists and crystal engineers faced the next challenge, as summarized by John Maddox: "it remains in general impossible to predict the structure of even the simplest crystallographic solids from knowledge of their chemical composition". This is where rational design takes place.In this Account, we detail three specific approaches developed by our group to facilitate the design and assembly of finely tuned MOFs. All are based on careful geometrical consideration and a deep study and understanding of the existing nets and topologies. We recognized that highly connected nets, if possible, edge-transitive, are ideal blueprints because their number is limited in contrast to nets with lower connectivity. Therefore, we embarked on taking advantage of existing highly connected MBBs, or, in parallel, promoting their formation to meet our requirements. This is achieved by utilizing externally decorated metal-organic polyhedra as supermolecular building blocks (SBBs), serving as a net-coding building unit, comprising the requisite connectivity and directional information coding for the chosen nets. The SBB approach allowed the synthesis of several families of SBB-based MOFs, including fcu, rht, and gea-MOFs, that are detailed here.The second strategy is directly inherited from the success of the SBB approach. In seeking highly connected building units, our group naturally expanded its research focus to nets that can be deconstructed into layers, pillared in various ways. In the supermolecular building layer (SBL) approach, the layers have an almost infinite connectivity, and the framework backbone is fixed in two dimensions while the third is free for pillar expansion and functionalization. The cases of trigonal pillaring leading to rtl, eea, and apo MOFs as well as the quadrangular pillaring leading to a family of tbo-MOFs are discussed here, along with recent cases of highly connected pillars in pek and aea-MOFs.Finally, our experience with highly coordinated MBBs led us to develop a novel way to use them as secondary building units of lower connectivity and unlock the possibility of assembling a novel class of zeolite-like MOFs (ZMOFs). The case of the Zr-sod-ZMOFs designed through a cantellation strategy is described as a future leading direction of MOF design.

Charge State of Au25(SG)18 Nanoclusters Induced by Interaction with a Metal Organic Framework Support and Its Effect on Catalytic Performance

We investigated the charge transfer between Au₂₅(SG)₁₈ nanoclusters and metal-organic framework (MOF) supports including Mil-101-Cr, Mil-125-Ti, and ZIF-8 by an X-ray photoemission technique and discussed the influence of resulted charge states of supported Au₂₅(SG)₁₈ nanoclusters on the 4-nitrophenol reduction reaction. Charge transfer from Au₂₅(SG)₁₈ to Mil-101-Cr induces positive charge Au^δ+ (0 < δ < 1) while charge transfer from ZIF-8 to Au₂₅(SG)₁₈ generates negative charge Au^δ- due to different metal-support interactions. Au₂₅(SG)₁₈ on Mil-125 shows metallic Au⁰, similar to unsupported Au₂₅(SG)₁₈, due to negligible charge transfer. The resulted charge state of Au^δ- inhibits the formation of adsorbed hydride (H^-) species because of electrostatic repulsion, while Au^δ+ impairs the reductive ability of adsorbed hydride (H^-) species due to strong affinity between them. In comparison, metallic Au⁰ in Au₂₅(SG)₁₈/Mil-125 and unsupported Au₂₅(SG)₁₈ presents the optimum catalytic activity. The current work provides guidelines to design effective metal nanoclusters in heterogeneous catalysis through metal-support interaction exerted by metal-oxo/nitric clusters within MOFs.

Fabrication of Homochiral Metal-Organic Frameworks in TiO2 Nanochannels for In Situ Identification of 3,4-Dihydroxyphenylalanine Enantiomers

Enantioselective identification of chiral molecules is important for biomedical and pharmaceutical research. However, owing to identical molecular formulas and chemical properties of enantiomers, signal transduction and amplification are still the two major challenges in chiral sensing. In this study, we developed an enantioselective membrane by integrating homochiral metal-organic frameworks (MOFs) with nanochannels for the sensitive identification and quantification of chiral compounds. The membrane was designed using a TiO₂ nanochannel membrane (TiNM) as the metal ion precursor of MOFs (using MIL-125(Ti)) and incorporating l-glutamine (l-Glu) into the framework of MIL-125(Ti). Using 3,4-dihydroxyphenylalanine (DOPA) as the model analyte, the as-prepared homochiral l-Glu/MIL-125(Ti)/TiNM exhibits a remarkable chiral recognition to d-DOPA than l-DOPA. More importantly, benefiting from the highly enlarged surface area and confinement effect provided by the MOFs-in-nanochannel architecture, the discrimination for chiral recognition is largely amplified through the chelation interaction of Fenton-like activity of Fe³⁺ onto DOPA. Using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) as the substrate, the positively charged ABTS^•+ product via Fenton-like reaction induces significant ionic transport changes in nanochannels, which in turn provides information about chiral recognition. This innovative signal amplification strategy on homochiral nanochannels might pave a new way for sensitive monitoring and chiral recognition.

MOF-derived Co2+-doped TiO2 nanoparticles as photoanodes for dye-sensitized solar cells

Facile synthesis and application of nano-sized semiconductor metal oxides for optoelectronic devices have always affected fabrication challenges since it involves multi-step synthesis processes. In this regard, semiconductor oxides derived directly from metal-organic frameworks (MOFs) routes have gained a great deal of scientific interest owing to their high specific surface area, regular and tunable pore structures. Exploring the application potential of these MOF-derived semiconductor oxides systems for clean energy conversion and storage devices is currently a hot topic of research. In this study, titanium-based MIL-125(Ti) MOFs were used as a precursor to synthesize cobalt-doped TiO2-based dye-sensitized solar cells (DSSCs) for the first time. The thermal decomposition of the MOF precursor under an air atmosphere at 400 °C resulted in mesoporous anatase-type TiO2 nanoparticles (NPs) of uniform morphology, large surface area with narrow pore distribution. The Co2+ doping in TiO2 leads to enhanced light absorption in the visible region. When used as photoanode in DSSCs, a good power conversion efficiency (PCE) of 6.86% with good photocurrent density (Jsc) of 13.96 mA cm-2 was obtained with the lowest recombination resistance and the longest electron lifetime, which is better than the performance of the pristine TiO2-based photoanode.

Tunable Band Gaps in MUV-10(M): A Family of Photoredox-Active MOFs with Earth-Abundant Open Metal Sites

Titanium-based metal-organic frameworks (Ti-MOFs) have attracted intense research attention because they can store charges in the form of Ti³⁺ and they serve as photosensitizers to cocatalysts through heterogeneous photoredox reactions at the MOF-liquid interface. Both the charge storage and charge transfer depend on the redox potentials of the MOF and the molecular substrate, but the factors controlling these energetic aspects are not well understood. Additionally, photocatalysis involving Ti-MOFs relies on cocatalysts rather than the intrinsic Ti reactivity, in part because Ti-MOFs with open metal sites are rare. Here, we report that the class of Ti-MOFs known as MUV-10 can be synthetically modified to include a range of redox-inactive ions with flexible coordination environments that control the energies of the photoactive orbitals. Lewis acidic cations installed in the MOF cluster (Cd²⁺, Sr²⁺, and Ba²⁺) or introduced to the pores (H⁺, Li⁺, Na⁺, K⁺) tune the electronic structure and band gaps of the MOFs. Through the use of optical redox indicators, we report the first direct measurement of the Fermi levels (redox potentials) of photoexcited MOFs in situ. Taken together, these results explain the ability of Ti-MOFs to store charges and provide design principles for achieving heterogeneous photoredox chemistry with electrostatic control.

Experimental and Theoretical Study on the Interchange between Zr and Ti within the MIL-125-NH2 Metal Cluster

This study aims to investigate the effect of replacing Ti with Zr in the SBU of MIL-125-NH₂ . We were able to replace Ti with Zr in the mixed metal synthesis of MIL-125-NH₂ , for the first time. After experimentally confirming the consistency in their framework structure and comparing their morphology, we related the femtosecond light dynamics with photocatalytic CO₂ visible light conversion yield of the different variants in order to establish the composition-function relation in MIL-125 vis a vis CO₂ reduction. Introducing Zr to the system was found to cause structure defects due to missing linkers. The lifetime of the charge carriers for the mixed metal samples were shorter than that of the MIL-125-NH₂ . The study of CO₂ photocatalytic reduction under visible light indicated that the NH₂ group enhances the photocatalytic activity while the Zr incorporation inside the MIL framework introduces no significant improvements. In addition, the material systems were modelled and simulated through DFT calculations which concluded that the decrease of the photocatalytic activity is not related to the system electronic structure, insinuating that defects are the culprit.

Fabricating a wettable microwells array onto a nitrogen plasma-treated ITO substrate: high-throughput fluorimetric platform for selective sensing of ammonia in blood using polymer-stabilized NH2-MIL-125

A high-throughput and selective fluorimetric platform has been constructed for the analysis of ammonia in blood by using a polymer-stabilized metal-organic framework (MOF) of porous NH2-MIL-125, which was coated onto a wettable microwells array constructed on an indium tin oxide (ITO) substrate. It was found that the nitrogen plasma treatment for the ITO substrate could create a super-hydrophilic interface that combined with the hydrophobic pattern yielded a wettable microwells array, enabling the condensation-based enrichment of targets from the sample droplets. Moreover, the NH2-MIL-125 MOF encapsulated using polymers could be firmly coated onto the microwells to act as fluorescent probes for sensing NH3 with enhanced responses. In addition, the use of the polymer polyvinyl pyrrolidone could protect and stabilize the crystals of NH2-MIL-125 probe in aqueous media, revealing the improved hydrophilicity and significantly depressed signal background. The as-developed fluorimetric platform, containing a MOF-coated microwells array, can enable the detection of ammonia in blood, with concentrations ranging linearly from 0.10 to 300 μM. More importantly, this plasma treatment-based fabrication route may hold promise for designing different wettable microwells arrays for the high-throughput detection of multiple targets in the fields of biomedical analysis and environmental monitoring.

Stable Crystalline Organic-Inorganic Hybrid Indium Phosphate with Dye Removal and Ractopamine Detection Applications

A highly stable framework of an organic-inorganic hybrid indium phosphate (NTOU-7) was synthesized under hydro(solvo)thermal conditions and structurally characterized by single-crystal X-ray diffraction and solid-state NMR spectroscopy. This is the first example of a post-transition-metal phosphate incorporating tetradentate organic molecules. The In atoms in the inorganic layers are coordinated by imidazole rings of the 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene linkers to generate a new solid-state material. NTOU-7 showed high chemical stability and displayed excellent performance for both dye removal and ractopamine (RAC) detection, which are interesting environmental and biosensing applications. The sensitivity and ultralow limit of detection were 607.9 μA·μM·cm^-2 and 2.74 × 10^-10 mol·L^-1 (0.08 ppb), which meet the requirements stated by the Codex Alimentarius Commission (10 ppb RAC residue in beef and pork). The detection performance was confirmed by sensing spiked-in RAC in real pork samples. We also reported the synthesis, characterization, structural stability, dye removal, and sensing properties of NTOU-7.

Nano-Metal Organic Framework for Enhanced Mechanical, Flame Retardant and Ultraviolet-Blue Light Shielding Properties of Transparent Cellulose-Based Bioplastics

From the perspective of sustainable development and practical applications, there has been a great need for the design of multifunctional transparent cellulose-based composite films. We herein propose a novel concept of improving the mechanical, fire-resistant and ultraviolet (UV)-blue light shielding properties of cellulose-based composite bioplastic films though in situ embedding nano-metal organic framework (MIL-125(Ti)-NH₂) into regenerated cellulose gel. Regenerated cellulose hydrogel (CH) with a porous structure acts as a nanoreactor and stabilizer to facilitate the growth and anchorage of MIL-125(Ti)-NH₂ nanoparticles (MNPs). Subsequently, hot-pressing induces the formation of transparent MIL-125(Ti)-NH₂@cellulose bioplastics (MNP@CBPs). As expected, the MNP@CBPs exhibit exceptional UV-blue light shielding capability, while retaining satisfactory optical transmittance. Meanwhile, with the incorporation of MNPs, the mechanical strength of MNP@CBPs is increased by 6.5~25.9%. In addition, MNPs enhance the flame retardant effect of the MNP@CBPs. The limited oxygen index (LOI) of the MNP@CBPs increased from 21.95 to 27.01%. The hot-pressing process improves the resistance of the MNP@CBPs to the penetration of water/non-aqueous liquids. This simple strategy would direct sustainable multifunctional MNP@CBPs toward diversified applications: food containers or packaging materials that can reduce or eliminate food spoilage, screen protectors for blocking harmful light, and promising candidates for protective plastic products, among others.

Advances in chlorin-based photodynamic therapy with nanoparticle delivery system for cancer treatment

Introduction: The treatment of tumors is one of the most difficult problems in the medical field at present. Patients often use a comprehensive therapy that combines surgery, radiotherapy, and chemotherapy. Photodynamic therapy (PDT) has prominent potential for eradicating various cancers. Chlorin-based photosensitizers (PSs), as one of the most utilized photosensitizers, have many advantages over conventional photosensitizers; however, a successful chlorin-based PDT needs multi-functional nano-carriers for selective photosensitizer delivery. The number of researches about nanoparticles designed for improved chlorin-based PSs is increasing in the current era. In this article, we give a brief review focused on the recent research progress in design of chlorin-based nanoparticles for the treatment of malignant tumors with photodynamic therapy.Areas covered: This review focuses on the current nanoparticle platforms for PDT, and describes different strategies to achieve controllable PDT by chlorin-nano-delivery systems. The challenges and prospects of PDT in clinical applications are also discussed.Expert opinions: The requirement for PDT to eradicate cancers has increased exponentially in recent years. The major clinically used photosensitizers are hydrophobic. The main obstacles in effective delivery of PSs are associated with this intrinsic nature. The design of nano-delivery systems to load PSs is pivotal for PSs' widespread use.

Observable removal of pharmaceutical residues by highly porous photoactive cellulose acetate@MIL-MOF film

Pharmaceutical products are used tremendously worldwide and subsequently released into wastewater even at very low concentration caused serious environmental problem due to their high activity. Therefore, the present work focuses on remarkable removal of paracetamol as one from the most used pharmaceutical intermediates, by using porous film based on cellulose acetate@metal organic framework (CA@Ti-MIL-NH₂). The film was designed to achieve extreme removal of paracetamol by action of both of adsorption and degradation. Metal organic frame work was directly synthesized and inserted within the pre-prepared porous CA film to obtain porous CA@Ti-MIL-NH₂ film. The synthesized films were applied in adsorption and photo-degradation of paracetamol separately and together. Due to the photocatalytic activity of Ti-MIL-NH_2, the photo-degradation of paracetamol in visible-light was much effective and considerably high degradation of paracetamol was observed (k₁ = 760.0 m^-1) comparing to the adsorption (k₁ = 160.0 m^-1). The overall removal of paracetamol was significantly enlarged from 82.7 mg/g for CA film to 519.1 mg/g for porous CA@Ti-MIL-NH₂ film. The used film exhibited quite good reusability and the removal of paracetamol was lowered from 96% to 85% after 5 regeneration cycles. Results of total organic carbon confirmed that paracetamol was fully degraded to CO₂ and water.

Assembly of a Titanium-Oxo Cluster and a Bismuth Iodide Cluster, a Single-Source Precursor of a p-n-Type Photocatalyst

Titanium oxides and bismuth halides or oxyhalides have been known to be excellent semiconductors with both excellent photocatalytic and photoelectric properties. The design of supersalts assembled by titanium-oxo clusters (TOCs) and bismuth iodide clusters is a hopeful strategy for exploring the chemistry and application of new titanium-oxo clusters. We report herein a series of unusual ionic TOCs with Ti₁₂ oxo cluster cations and bismuth iodide anions, [Ti₁₂O₁₅(OⁱPr)₁₇]₃[Bi₃I₁₂] (Bi₃), [Ti₁₂O₁₄(OⁱPr)₁₈][Bi₄I₁₄(THF)₂] (Bi₄), and [Ti₁₂O₁₄(OⁱPr)₁₈][Ti₁₁BiO₁₄(OⁱPr)₁₇][Bi₆I₂₂] (Bi₆). Single-crystal X-ray analysis revealed that the type and charge of the Ti₁₂ clusters varied with the charges of different bismuth iodide clusters. Taking advantage of the easy hydrolysis of the TOCs and BiI clusters in water, we used these supersalt crystals as single-source precursors to prepare a p-n-type BiOI-TiO photocatalyst. The heterojunction materials were carefully characterized by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, etc. The synergistic effect of the two components of BiOI and TiO on the photocatalytic degradation of RhB in water is demonstrated. This is a very convenient method for obtaining a p-n-type BiOI-TiO heterojuction photocatalyst by just placing the ground TOC crystals into water.

Reticular design and crystal structure determination of covalent organic frameworks

Reticular chemistry of covalent organic frameworks (COFs) deals with the linking of discrete organic molecular building units into extended structures adopting various topologies by strong covalent bonds. The past decade has witnessed a rapid development of COF chemistry in terms of both structural diversity and applications. From the structural perspective, irrespective of our subject of concern with regard to COFs, it is inevitable to take into account the structural aspects of COFs in all dimensions from 1D ribbons to 3D frameworks, for which understanding the concepts of reticular chemistry, based mainly on 'reticular design', will seemingly lead to unlimited ways of exploring the exquisiteness of this advanced class of porous, extended, and crystalline materials. A comprehensive discussion and understanding of reticular design, therefore, is of paramount importance so that everyone willing to research on COFs can interpret well and chemically correlate the geometrical structures of this subset of reticular materials and their practical applications. This article lies at the heart of using the conceptual basis of reticular chemistry for designing, modeling, and determination of novel infinite and crystalline structures. Especially, the structure determinations are described by means of chronological advances of discoveries and development of COFs whereby their crystal structures are elucidated by modeling through the topological approach, 3D electron diffraction, single-crystal X-ray diffraction, and powder X-ray diffraction techniques.

Mesoporous TiO2 from Metal-Organic Frameworks for Photoluminescence-Based Optical Sensing of Oxygen

Metal−organic frameworks (MOFs) are a class of porous coordination networks extraordinarily varied in physicochemical characteristics such as porosity, morphologies, and compositions. These peculiarities make MOFs widely exploited in a large array of applications, such as catalysis, chemicals and gas sensing, drug delivery, energy storage, and energy conversion. MOFs can also serve as nanostructured precursors of metal oxides with peculiar characteristics and controlled shapes. In this work, starting from MIL125-(Ti), a 1,4-benzenedicarboxylate (BDC)-based MOF with Ti as metallic center, mesoporous TiO2 powders containing both anatase and rutile crystalline phases were produced. A challenging utilization of these porous MOF-derived Ti-based oxides is the optically-based quantitative detection of molecular oxygen (O2) in gaseous and/or aqueous media. In this study, the photoluminescence (PL) intensity changes during O2 exposure of two MOF-derived mixed-phase TiO2 powders were probed by exploiting the opposite response of rutile and anatase in VIS-PL and NIR-PL wavelength intervals. This result highlights promising future possibilities for the realization of MOF-derived doubly-parametric TiO2-based optical sensors.

The Composites of PCL and Tetranuclear Titanium(IV)-oxo Complexes as Materials Exhibiting the Photocatalytic and the Antimicrobial Activity

Excessive misuse of antibiotics and antimicrobials has led to a spread of microorganisms resistant to most currently used agents. The resulting global threats has driven the search for new materials with optimal antimicrobial activity and their application in various areas of our lives. In our research, we focused on the formation of composite materials produced by the dispersion of titanium(IV)-oxo complexes (TOCs) in poly(ε-caprolactone) (PCL) matrix, which exhibit optimal antimicrobial activity. TOCs, of the general formula [Ti₄O₂(OⁱBu)₁₀(O₂CR’)₂] (R’ = PhNH₂ (1), C₁₃H₉ (2)) were synthesized as a result of the direct reaction of titanium(IV) isobutoxide and 4-aminobenzoic acid or 9-fluorenecarboxylic acid. The microcrystalline powders of (1) and (2), whose structures were confirmed by infrared (IR) and Raman spectroscopy, were dispersed in PCL matrixes. In this way, the composites PCL + nTOCs (n = 5 and 20 wt.%) were produced. The structure and physicochemical properties were determined on the basis of Raman microscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), electron paramagnetic resonance spectroscopy (EPR), and UV–Vis diffuse reflectance spectroscopy (DRS). The degree of TOCs distribution in the polymer matrix was monitored by scanning electron microscopy (SEM). The addition of TOCs micro grains into the PCL matrix only slightly changed the thermal and mechanical properties of the composite compared to the pure PCL. Among the investigated PCL + TOCs systems, promising antibacterial properties were confirmed for samples of PCL + n(2) (n = 5, 20 wt.%) composites, which simultaneously revealed the best photocatalytic activity in the visible range.

Improved Capture and Removal Efficiency of Gaseous Acetaldehyde by a Self-Powered Photocatalytic System with an External Electric Field

Using clean and sustainable stochastic energy from the environment to eliminate pollution caused by gaseous aldehydes would be an effective strategy to achieve the sustainable development of energy and preserve the environment. Here, a piston-based triboelectric nanogenerator (P-TENG) was used to enhance gaseous acetaldehyde absorption and photocatalytic degradation. An external electric field could be generated on a conductive substrate by the P-TENG, converting wind energy into electricity. This made it possible to efficiently degrade gaseous acetaldehyde in the photocatalytic system. Driven by a light breeze (3.0 m/s), the acetaldehyde removal rate of the system reached 63% within 30 min. The presence of an external electric field could generate more hydroxyl radicals (^•OH), superoxide radicals (^•O₂^-), and holes (h⁺), which has a positive effect on the photocatalytic degradation of acetaldehyde. The design and concept of this study not only realized the efficient conversion of renewable and sustainable random energy but also could be applied to the efficient removal of gaseous aldehydes, providing an effective way to create a cleaner environment.

Construction of C-C bonds via photoreductive coupling of ketones and aldehydes in the metal-organic-framework MFM-300(Cr)

Construction of C-C bonds via reductive coupling of aldehydes and ketones is hindered by the highly negative reduction potential of these carbonyl substrates, particularly ketones, and this renders the formation of ketyl radicals extremely endergonic. Here, we report the efficient activation of carbonyl compounds by the formation of specific host-guest interactions in a hydroxyl-decorated porous photocatalyst. MFM-300(Cr) exhibits a band gap of 1.75 eV and shows excellent catalytic activity and stability towards the photoreductive coupling of 30 different aldehydes and ketones to the corresponding 1,2-diols at room temperature. Synchrotron X-ray diffraction and electron paramagnetic resonance spectroscopy confirm the generation of ketyl radicals via confinement within MFM-300(Cr). This protocol removes simultaneously the need for a precious metal-based photocatalyst or for amine-based sacrificial agents for the photochemical synthesis.

A Showcase of Green Chemistry: Sustainable Synthetic Approach of Zirconium-Based MOF Materials

Zirconium-based metal-organic framework materials (Zr-MOFs) have more practical usage over most conventional benchmark porous materials and even many other MOFs due to the excellent structural stability, rich coordination forms, and various active sites. However, their mass-production and application are restricted by the high-cost raw materials, complex synthesis procedures, harsh reaction conditions, and unexpected environmental impact. Based on the principles of "Green Chemistry", considerable efforts have been done for breaking through the limitations, and significant progress has been made in the sustainable synthesis of Zr-MOFs over the past decade. In this review, the advancements of green raw materials and green synthesis methods in the synthesis of Zr-MOFs are reviewed, along with the corresponding drawbacks. The challenges and prospects are discussed and outlooked, expecting to provide guidance for the acceleration of the industrialization and commercialization of Zr-MOFs.

Size modulation of MIL-125 nanocrystals to promote the catalytic performance towards oxidative desulfurization

The Ti-based metal-organic framework (Ti-MOF) MIL-125 with tunable crystalline size in the range of ca. 50 nm to 1500 nm was synthesized by the coordination modulation method using trans-cinnamic acid (CA) as a modulator. The coordination modulation also induced hierarchical porosity and structure defects on the nanocrystals. A significant size-dependent catalytic activity towards the oxidative desulfurization (ODS) reaction was observed for these MIL-125 nanocrystals. In particular, the MIL-125 nanocrystals with a mean size of ca. 50 nm exhibit dramatically enhanced catalytic performance for the bulky sulfur compound 4,6-dimethyldibenzothiophene (4,6-DMDBT) compared to the microcrystals. It is demonstrated that the size modulation of MIL-125 is an effective approach to promote its performance for the catalysis of bulky molecules.