Current trends in structural development and modification strategies for metal-organic frameworks (MOFs) towards photocatalytic H2 production: A review

Photocatalytic H₂ generation using semiconductor photocatalysts is considered as a cost-effective and eco-friendly technology for solar to energy conversion; however, the present photocatalysts have been recognized to depict low efficiency. Currently, porous coordination polymers known as metal-organic frameworks (MOFs) constituting flexible and modifiable porous structure and having excess active sites are considered to be appropriate for photocatalytic H₂ production. This review highlights current progress in structural development of MOF materials along with modification strategies for enhanced photoactivity. Initially, the review discusses the photocatalytic H₂ production mechanism with the concepts of thermodynamics and mass transfer with particular focus on MOFs. Elaboration of the structural categories of MOFs into Type I, Type II, Type III and classification of MOFs for H₂ generation into transition metal based, post-transition metal based, noble-metal based and hetero-metal based has been systematically discussed. The review also critically deliberate various modification approaches of band engineering, improvement of charge separation, efficient irradiation utilization and overall efficiency of MOFs including metal modification, heterojunction formation, Z-scheme formation, by introducing electron mediator, and dye based composites. Also, the MOF synthesized derivatives for photocatalytic H₂ generation are elaborated. Finally, future perspectives of MOFs for H₂ generation and approaches for efficiency improvement have been suggested.     

纳米MOFs及其衍生物在超级电容器中的研究进展

金属有机框架（MOFs）材料因其大的比表面积、可调控的孔道结构和丰富的活性位点引起了国内外学者们的广泛关注。近年来MOFs基材料广泛应用于能量储存与转化领域,但大多数MOFs基材料的低稳定性和低导电性等缺陷限制了其实际应用。通过对MOFs基材料进行改性,如采用共轭度高的有机配体以增加MOFs材料的稳定性,或MOFs衍生物以提高其氧化还原活性位点和导电性,从而达到提高MOFs基电极材料的电化学性能。主要介绍了原始MOFs及其衍生材料如碳材料、金属氧化物、金属硫化物、金属氢氧化物和金属磷化物等在超级电容器电极材料中的最新研究进展。研究表明,多金属MOFs材料或多金属MOFs衍生物有利于提高电极材料的电化学性能,而导电MOFs材料或MOFs衍生物中的碳材料有利于提高电极材料的导电性。最后对MOFs基电极材料在电化学储能领域中的研究做出了展望,指出MOFs基材料的形貌、组分和导电性是未来研究的发展方向。     

MOFs复合材料催化降解水中有机污染物的应用研究进展

金属有机框架材料（MOFs）具有比表面积较高、孔径尺寸可调、结构可设计和可以功能化的特点，近年来受到广泛关注，尤其是基于MOFs的复合材料在催化降解水中有机污染物的作用越来越突出，这是近年来MOFs的一个重要研究方向。本文综述了MOFs复合材料在催化降解水中有机污染物领域的研究情况；介绍了MOFs及其特性；说明了MOFs复合材料的负载方式；总结了MOFs复合材料在催化降解水中有机污染物方面的应用。同时，阐述了MOFs复合材料催化降解水中有机污染物的机理及其存在的问题。最后，提出未来MOFs复合材料在催化降解水中有机污染物的研究方向是合成形貌多样、结晶性能好的新型高稳定性材料以及开发新的MOFs及其复合材料的制备方法。     

Glyphosate Adsorption from Water Using Hierarchically Porous Metal–Organic Frameworks

The selective removal of one ligand in mixed-ligand MOFs upon thermolysis provides a powerful strategy to introduce additional mesopores without affecting the overall MOF structure. By varying the initial ligand ratio, MOFs of the MIL-125-Ti family with two distinct hierarchical pore architectures are synthesized, resembling either large cavities or branching fractures. The performance of the resulting hierarchically porous MOFs is evaluated toward the adsorptive removal of glyphosate (N-(phosphonomethyl)glycine) from water, and the adsorption kinetics and mechanism are examined. Due to their strong affinity for phosphoric groups, the numerous Ti–OH groups resulting from the selective ligand removal act as natural anchor points for effective glyphosate uptake. The relationships between contact duration, glyphosate concentration, and adsorbent dosage are investigated, and the impact of these parameters on the effectiveness of glyphosate removal from contaminated water samples is examined. The introduction of additional mesopores has increased the adsorption capacities by nearly 3 times with record values exceeding 440.9 mg g⁻¹, which ranks these MOFs among the best-reported adsorbents.     

GraftFast Surface Engineering to Improve MOF Nanoparticles Furtiveness

Controlling the outer surface of nanometric metal–organic frameworks (nanoMOFs) and further understanding the in vivo effect of the coated material are crucial for the convenient biomedical applications of MOFs. However, in most studies, the surface modification protocol is often associated with significant toxicity and/or lack of selectivity. As an alternative, how the highly selective and general grafting GraftFast method leads, through a green and simple process, to the successful attachment of multifunctional biopolymers (polyethylene glycol (PEG) and hyaluronic acid) on the external surface of nanoMOFs is reported. In particular, effectively PEGylated iron trimesate MIL‐100(Fe) nanoparticles (NPs) exhibit suitable grafting stability and superior chemical and colloidal stability in different biofluids, while conserving full porosity and allowing the adsorption of bioactive molecules (cosmetic and antitumor agents). Furthermore, the nature of the MOF–PEG interaction is deeply investigated using high‐resolution soft X‐ray spectroscopy. Finally, a cell penetration study using the radio‐labeled antitumor agent gemcitabine monophosphate (³H‐GMP)‐loaded MIL‐100(Fe)@PEG NPs shows reduced macrophage phagocytosis, confirming a significant in vitro PEG furtiveness.     

The Influence of Carbon Nitride Nanosheets Doping on the Crystalline Formation of MIL‐88B(Fe) and the Photocatalytic Activities

In this research, bulk graphitic carbon nitride (g‐C₃N₄) is exfoliated and transferred to the carbon nitride nanosheets (CNNSs), which are then coupled with MIL‐88B(Fe) to form the hybrid. From the results of the powder X‐ray diffraction, scanning electronic microscopy and thermogravimetric analysis, it is found that the doping of CNNSs on the surface of MIL‐88(Fe) could maintain the basic structure of MIL‐88B(Fe), and the smaller dimension of CNNSs might influence the crystallization process of metal‐organic frameworks (MOFs) compared to bulk g‐C₃N₄. Besides, the effects of the CNNSs incorporation on photocatalysis are also investigated. Through the photoluminescence spectra, electrochemical measurements, and photocatalytic experiments, the hybrid containing 6% CNNSs is certified to possess the highest catalytic activity to degrade methylene blue and reduce Cr(VI) under visible light. The improvement of the photocatalytic performance can be attributed to the matched energy level which favors the formation of the heterojunctions. Besides, it promotes the charge migration such that the contact between MOFs and CNNSs is more intimate, which can be inferred from the electronic microscopy images. Finally, a possible photocatalytic mechanism is put forward by the relative calculation and the employment of the scavengers to trap the active species.     

Hydrogen storage: The major technological barrier to the development of hydrogen fuel cell cars

In this paper, we review the current technology for the storage of hydrogen on board a fuel cell-propelled vehicle. Having outlined the technical specifications necessary to match the performance of hydrocarbon. fue1, we first outline the inherent difficulties with gas pressure and liquid hydrogen storage. We then outline the history of transition metal hydride storage, leading to the development of metal hydride batteries. A viable system, however, must involve lighter elements and be vacuum-tight. The first new system to get serious consideration is titanium-activated sodium alanate, followed by the lithium amide and borohydride systems that potentially overcome several of the disadvantages of alanates. Borohydrides can alternatively produce hydrogen by reaction with water in the presence of a catalyst but the product would have to be recycled via a chemical plant. Finally various possible ways of making magnesium hydride decompose and reform more readily are discussed. The alternative to lighter hydrides is the development of physisorption of molecular hydrogen on high surface area materials such as carbons, metal oxide frameworks, zeolites. Here the problem is that the surface binding energy is too low to work at anything above liquid nitrogen temperature. Recent investigations of the interaction mechanism are discussed which show that systems with stronger interactions will inevitably require a surface interaction that increases the molecular hydrogen-hydrogen distance.     

MOFs 材料金属位点设计及沼气纯化应用研究

改变MOFs材料的中心金属能影响其气体的亲和性和双组份气体的吸附选择性（如比表面积,孔道结构,内部电场等）,本文合成并表征了M－DABCO系列（M＝Ni, Co, Cu, Zn） MOFs材料。并应用理想吸附溶液理论（Ideal Adsorbed Solution Theory,简称IAST）量化模拟了环境条件下双组分混合气体（组分比CO2：CH4＝40％：60％）的吸附选择性。 Ni－DABCO材料具有良好的CO2吸附性能和在环境条件下对CO2／CH4混合气体的吸附选择性。本文通过实验、表征及计算等来讨论中心金属对M－DABCO系列吸附位点的影响。