金属有机骨架UiO-66在催化领域的应用

金属有机骨架（MOFs）经过二十多年的快速发展,已经合成了成千上万种,然而MOFs材料普遍具有较低的稳定性,在一定程度上限制了MOFs的发展。UiO-66的合成是MOFs材料稳定性的一个突破,其在催化领域的发展尤为迅速。本文首先介绍了理想及实际状态下UiO-66的结构特征,并说明了配体缺失导致的节点空位处的元素组成。然后综述了利用UiO-66特殊的结构特征或将其功能化用于催化反应的研究,包括节点空位、功能化节点空位、负载金属纳米颗粒、功能化配体等。最后,考虑到可以综合利用UiO-66的特殊结构,对UiO-66在未来多功能催化剂的设计合成领域所能发挥的作用进行展望。     

UiO-66的制备、功能化及膜分离研究进展

UiO-66是一种具有优异物理化学稳定性的金属有机骨架（MOFs）材料,近年来引起了研究者们的强烈关注。本文详细介绍了UiO-66的结构,重点探讨了溶剂热法过程中的一系列影响因素,包括使用不同的金属前体,改变合成温度、溶剂、各组分配比以及模板剂等,制备各种性能的UiO-66。针对溶剂热法合成效率较低的问题,介绍了微波合成法、微流控、连续流和无溶剂法等其它UiO-66的制备方法。为了扩大UiO-66的应用范围,对其有机配体进行功能化改性或与其他材料复合改性,具体介绍了改性后UiO-66在气体吸附、水处理、催化、电化学和化学传感等方面的应用。最后综述了利用UiO-66具有多孔特性构建分离膜方面的研究进展,具体阐述了纯UiO-66膜和UiO-66复合膜在气体分离和水处理方面的应用。     

缺陷UiO-66对水中塑化剂的吸附

金属有机骨架材料（metal-organic frameworks,MOFs）是一种具有骨架结构的新型多孔材料。本研究合成了金属有机框架化合物UiO-66和有缺陷的UiO-66（UiO-66-1）,并研究了其作为吸附剂吸附塑化剂邻苯二甲酸二甲酯（DMP）的性能及其吸附动力学,最后通过拟合吸附等温线和吸附动力学模型拟合了吸附剂的最大吸附量和最快吸附时间。实验结果表明,UiO-66-1对DMP有更好的吸附性能,在5~10min内快速达到吸附平衡,pH在3~10吸附率仍可保持稳定;分析测试结果表明,引入缺陷的UiO-66-1的比表面积比UiO-66大,达到了1438m²/g,孔容为0.58cm³/g,晶体的尺寸也明显增大,吸附量增大了近一倍,最大吸附量可达到404mg/g,且循环利用率高;通过吸附等温线模型和吸附动力学模型的拟合研究表明,UiO-66-1的吸附过程比较符合Langmuir模型和拟二级动力学模型。     

Assembling Ag/UiO-66-NH2 Composites for Photocatalytic Dye Degradation

The water pollution currently constitutes a severe threat to our living life, and MOF (metal–organic framework)-based photocatalysts offer an efficient route to clean various water pollutants in an eco-friendly manner. Integration of metal nanoparticles (MNPs) with photoactive MOFs has proven an effective way to further boost the photocatalytic performance. In this work, Ag/UiO-66-NH₂ composites (UiO?=?University of Oslo) have been facilely assembled in two steps involving first wet impregnation of AgNO₃ into UiO-66-NH₂ followed by chemical reduction with NaBH₄. Benefited from the built-in heterostructure that can promote both the electron–hole separation, and the absorption of the visible-light, Ag/UiO-66-NH₂ composites exhibited an enhanced photocatalytic performance than the pristine UiO-66-NH₂ towards photodegradation of RhB (Rhodamine B) dye under the irradiation of UV–Visible light. About 96% of RhB can be degraded by Ag/UiO-66-NH₂ in a period of 40 min. Besides, Ag/UiO-66-NH₂ demonstrated a good recycling stability which showed an only slight drop in the dye photodegradation efficiency after three consecutive runs. The current work suggests that Ag/UiO-66-NH₂ composites have a great potential in practical application toward water remediation.

     

Efficient and selective adsorption of nitroaromatic explosives by Zr-MOF

Herein, the Zr-MOF UiO-66-NH₂ was synthesized in a facile method. When the as-synthesized UiO-66-NH₂ is served as an adsorbent for 2,4,6-trinitrophenol (PA), styphnic acid (TNR), 2,4-dinitrophenol (2,4-DNP), 2,4,6-trinitrotoluene (TNT), and 2,4-dinitrotoluene (2,4-DNT) in water, the absorption capacities are 0.0225, 0.024, 0.0296, 0.0005, and 0.002 g/g, respectively. This suggests that UiO-66-NH₂ is an excellent adsorbent for PA, TNR, and 2,4-DNP and is promising material for the removal of PA, TNR, and 2,4-DNP from wastewater. The excellent adsorption performance is attributed to the hydrogen-bond interactions between UiO-66-NH₂ and these explosives.     

锆基金属有机骨架UiO-66的合成及在化学防护领域中的研究进展

UiO-66除了具备其他MOFs材料的比表面积大、孔隙率高及孔道易调、易功能化等特点外，与大多数MOFs 材料不同，还具有优异的化学稳定性、机械稳定性、热稳定性和抗水性能，使其在吸附及催化领域具有巨大的应用前景。本文详细介绍了UiO-66的合成方法最新研究进展，包括溶剂热法、机械研磨法、微波辅助法、持续流法及干胶转化法，同时指出干胶转化法产品收率高，纯化、活化过程简单且不产生有机废液，是UiO-66合成及未来工业化生产的发展方向。同时综述了改性UiO-66材料近年来在有毒工业化学品吸附及化学战剂催化降解领域中的研究进展，展望了静电纺纳米纤维负载UiO-66在化学防护领域应用的发展趋势。     

功能化Zr-MOF强化混合基质膜CO2分离

混合基质膜（MMMs）在气体分离领域具有良好的应用前景,金属有机框架（MOFs）由于具有高孔隙率和有机连接基团,常被用作填料制备MMMs。但由于MOFs与聚合物的界面相容性问题,MMMs的气体分离性能提升受到限制。本文合成了功能化的Zr-MOF（UiO-66-AC）,并利用其与聚醚共聚酰胺（Pebax）共同制备了混合基质膜。填料中引入的羰基和羧基等基团提供了MOFs与聚合物基质之间较强的界面相互作用。与纯Pebax膜相比,UiO-66-AC/Pebax MMMs的气体渗透性能得到了显著提高。当填料质量分数为6%时,膜的CO₂渗透系数为102.4 Barrer,CO₂/N₂和CO₂/CH₄选择性分别为90.6和26.0,CO₂/N₂分离性能突破了Robeson上限(2008),表明该混合基质膜在CO₂的分离应用上具有潜力。     

Encapsulation and controlled release of fragrances from functionalized porous metal–organic frameworks

In the fragrance and perfume industry, the encapsulation and controlled release of fragrance is important to appeal to consumers and promote the quality of products. Here, we demonstrate that porous metal–organic frameworks (MOFs) can effectively encapsulate and release fragrant molecules in a controlled manner. The incorporation of functional groups into MOFs can improve the adsorption and release behavior of fragrant molecules. We find that polar ester-type fragrances exhibit higher adsorption on polar hydroxyl-functionalized MOF [UiO-66-(OH)₂] than on nonpolar MOF (UiO-66), while nonpolar terpenoid-type fragrances show no adsorption difference between these two MOFs. The release profiles show that UiO-66-(OH)₂ can prolong the release of polar fragrances compared with nonpolar fragrances. Both the experimental results and computer molecular modeling demonstrate that the hydroxyl groups in UiO-66-(OH)₂ can form strong hydrogen binding with different ester fragrances. The releasing kinetics indicates that pore diffusion is the rate-limiting step of fragrance release from MOFs. © 2018 American Institute of Chemical Engineers AIChE J, 65: 491–499, 2019     

锆基金属有机骨架材料用于氨吸附性能的研究

近年来,金属有机骨架材料（MOF）在气体吸附和储存领域得到了迅速发展,但由于结构的不稳定性,其在强腐蚀性气体氨（NH₃）的吸附方面并不令人满意。考虑到NH₃是唯一的无碳排放的氢能源载体,开发高效的储氨技术来载氢是有效的降低二氧化碳排放的手段。利用MOF材料具有的高比表面积和结构多样的特性,在NH₃的吸附和储存方面具有广阔的应用前景。而NH₃具有孤对电子,会攻击金属与配体之间形成的配位键,使MOF材料的结构遭到破坏。锆基金属有机骨架材料是公认结构稳定性较好的MOF材料,但其是否能胜任干燥NH₃及含水条件下的稳定性仍未深入考察,由此需探究该系列材料在NH₃吸附领域的适用性。在此,通过实验和计算模拟研究锆基系列的金属有机骨架UiO-66、NU-1000、MOF-801和 MOF-808的结构特征、稳定性和NH₃吸附性能。结果表明,UiO-66、NU-1000和MOF-808在纯NH₃环境下的稳定性较好,并且显示出高吸附量且可循环的氨吸附性能（13.04、6.38、9.65 mmol/g）。受限于水和氨对结构的协同破坏作用,NU-1000和MOF-801的结构均不能维持,而UiO-66和MOF-808的结构非常稳定,无论在干燥NH₃环境及含水NH₃环境下均能胜任而应用于NH₃吸附和储存。     

Metal-organic framework UiO-66 membranes

Metal-organic frameworks (MOFs) have emerged as a class of promising membrane materials. UiO-66 is a prototypical and stable MOF material with a number of analogues. In this article, we review five approaches for fabricating UiO-66 polycrystalline membranes including in situ synthesis, secondary synthesis, biphase synthesis, gas-phase deposition and electrochemical deposition, as well as their applications in gas separation, pervaporation, nanofiltration and ion separation. On this basis, we propose possible methods for scalable synthesis of UiO-66 membranes and their potential separation applications in the future.     

Moisture stability of ethane-selective Ni(II), Fe(III), Zr(IV)-based metal–organic frameworks

Metal–organic frameworks (MOFs) combined with selective adsorption capacity of ethane over ethylene and good moisture stability are highly urged by adsorption industrial community. Here, the moisture stability mechanism of Zr-bptc, UiO-66, PCN-245, and Ni(bdc)(ted)_0.5 were investigated by moisture stability experiments, and computational simulation of metal node-linker breaking energy caused by water. Results show that the moisture stability follows the order of Zr-bptc > UiO-66 > PCN-245 > Ni(bdc)(ted)_0.5. The different moisture stability for these MOFs is likely attributed to the bond strength between metal center and ligands, the coordination number of metal center, the hydrophobicity of framework, as well as the degree of interpenetrated framework. Additionally, comparing with ethylene-selective MOFs, ethane-selective MOFs have fewer coordinatively unsaturated metal sites. Breakthrough experiments indicated that Zr-bptc is the promising material for ethane/ethylene separation.     

Engineering the direct Z-scheme systems over lattice intergrown of MOF-on-MOF for selective CO2 photoreduction to CO

The direct Z-scheme provides a potential strategy for highly efficient CO₂ photoreduction, whereas the heterointerface contact resistance is significantly limited the interfacial electron transfer kinetic. Herein, we build the directional charge-transfer channels in a direct Z-scheme system over metal–organic frameworks (MOFs), that is, the lattice-guided MOF-on-MOF hybrids, to facilitate CO₂ photoreduction. The heteroepitaxial lattice growth along the c-axis of MIL-88B(Fe) via the high-activity (001) facet over the stable (111) facet of UiO-66-NH₂. Theoretical calculations and experimental results provide direct evidence that engineering direct Z-scheme of these MOFs hybrids can induce the electrons migration from UiO-66-NH₂ to the holes of MIL-88B(Fe) by directional charge-transfer channels owing to their lattice match. This can dramatically boost photocatalytic CO₂-to-CO selectivity up to nearly 100%, with a rate of 2.26 μmol g⁻¹ h⁻¹. This work demonstrates that the efficiently selective CO₂ photoreduction processes can be achieved by engineering Z-scheme via lattice intergrown of MOF hybrids strategy.     

UiO-66复合材料用于典型有机污染物吸附和光催化氧化的研究进展

UiO-66系列金属有机骨架（MOFs）材料因具有较高的比表面积、丰富的孔结构、优异的结构稳定性和类半导体特性而广泛应用于污染物的吸附和催化领域。文中指出：液相有机污染物主要通过物理吸附、静电、氢键、π-π相互作用被UiO-66基材料吸附去除,同时由于电性等性质差异,UiO-66基材料可从性质差异显著的多种有机污染物中选择性吸附污染物,而气相有机污染物主要通过氢键或UiO-66基材料孔道被吸附去除,同时环境中的水汽对污染物的吸附去除具有显著影响;针对光催化,由于载流子的快速复合,纯UiO-66基材料具有较低的光催化活性,通过与半导体材料复合可显著提高材料载流子分离速率,同时活性位点高度均匀分散在UiO-66基材料表面,利于光的激发及污染物与活性位点的充分接触,进而显著提高材料的光催化活性。与此同时,本文也提出了UiO-66基材料在有机污染物吸附和去除中的不足之处。最后展望了UiO-66基材料的发展前景。     

锆基MOFs的合成和表征及催化制备生物柴油

采用不同有机配体（对苯二甲酸，2-硝基对苯二甲酸、2-氨基对苯二甲酸、2-羟基对苯二甲酸），利用剂热合成法合成锆基MOFs结构UiO-66及其衍生物，添加不同的调节剂（甲酸、乙酸、苯甲酸和盐酸）调节锆基MOFs结构。采用XRD、SEM和FT-IR等对锆基MOFs材料进行表征，研究不同的调节剂和添加量对锆基MOFs形貌特征和结构性质的影响。研究发现调节剂的不同对锆基MOFs结构形成产生不同影响，盐酸和乙酸混合调节剂能显著提高UiO-66的结晶度，当n(调节剂)∶n(ZrCl4)=30∶1时，苯甲酸调节剂可以获得尺寸为500 nm结构规整的UiO-66八面体晶体，甲酸调节剂将UiO-66的比表面积由1173.3 m2/g提高到1973.8 m2/g。选择3种锆基MOFs作为酯化反应催化剂，UiO-66-NH2催化活性较好，其游离脂肪酸转化率为50.7%，用KOH催化酯化油反应得到的生物柴油产率为51.6%，脂肪酸甲酯含量达99%以上。     

Fabrication of in-situ polymerized UiO-66/PVDF supramolecular membranes with high anti-fouling performance

The composite membrane with the advantages of high separation efficiency and wide application, has been widely concerned in the field of water purification and molecular separation. However, the common composite membrane cannot achieve continuity, or the grafting process is complex, which significantly hinders its further development. In this work, the in-situ polymerization of UiO-66/PVDF supramolecular flat membranes as the continuous and high-performance composite membrane can be easily synthesized using the supramolecular force, (such as, hydrogen bond, etc.). These supramolecular membranes exhibit good hydrophilic (61°) and anti-fouling performance for bovine serum albumin (BSA) solution with rejection rate 97.79% than the original membrane. Moreover, this membrane can achieve more MOF doping based on maintaining the membrane performance, which undoubtedly greatly improves its hydrophilicity and mechanical properties. In addition, we also characterized the porous microstructure of the UiO-66/PVDF supramolecular membrane to analyze the influence of different doping amounts on the membrane structure. This supramolecular membrane has the advantages of simple synthesis, good hydrophilicity and water separation performance, which provides a more convenient and effective way for the preparation of MOFs/polymer flat membrane, and also provides a new method and new idea for expanding the application of MOFs/polymer ultrafiltration membrane in water treatment.     

氯代UiO-66吸附染色纸废水中罗丹明B和刚果红

为了进一步提高金属-有机骨架材料（metal-organic frameworks, MOFs）的吸附性能,本文将有机配体对苯二甲酸替换为2-氯对苯二甲酸,合成了金属-有机骨架化合物UiO-66的衍生物——氯代UiO-66（UiO-66-Cl）。以UiO-66、木质活性炭（AC）和蔗渣作为参照,研究了UiO-66-Cl对染色纸废水中罗丹明B（Rh-B）和刚果红（CR）的吸附性能和对染料废水pH的适应性,优化其吸附工艺条件,基于等温吸附模型（Langmuir和Freundlich）拟合其最大吸附量,最终对该吸附剂的回收、解吸附和再利用性能进行评价。研究结果表明：UiO-66-Cl对两种染料（Rh-B和CR）的吸附性能和对染料溶液pH的适应性均显著高于UiO-66、AC和蔗渣;其对Rh-B和CR的吸附过程符合Freundlich等温吸附模型,属于非均质多位点的多层吸附;在10~1000mg/L的初始染料浓度范围内,该吸附剂对Rh-B和CR的最大吸附容量分别为94.28mg/g和151.84mg/g;与HCl（0.1mol/L）、NaOH（0.1mol/L）和95%（体积分数）乙醇溶液相比,乙醇-HCl溶液（0.1mol/L HCl与95%乙醇溶液的体积比为0.5∶99.5）是UiO-66-Cl的良好再生溶剂体系,染料初始浓度为50mg/L时,再生UiO-66-Cl对Rh-B和CR的移除率均接近90%。由此可见,UiO-66-Cl可作为一种稳定、高效且易再生的吸附剂应用于去除染色纸废水中的Rh-B和CR。     

Facile synthesis of amine-functionalized UiO-66 by microwave method and application for methylene blue adsorption

The metal–organic frameworks UiO-66 with amine functional groups were synthesized by microwave irradiation, their structures and properties were characterized. The results show that NH₂-UiO-66 can be prepared quickly and well-crystallized by microwave-assisted method within 15 min. The amine-functionalized UiO-66 was octahedral crystals of well defined sizes (500–900 nm) and had a high specific surface area about 924.37 m² g^?1 and micropore range from 2.0 to 11 nm. The amine-functionalized UiO-66 was thermally stable up to 540 °C stability and exhibited a good combination of methylene blue adsorption. The maximum adsorption capacity reached up to 203.95 mg g^?1. The kinetics and equilibrium of the adsorption process were found to follow the pseudo-second-order kinetic and Langmuir adsorption model, respectively.     

MOFs基多孔液体的制备及其应用

多孔液体(Porous Liquids, PLs)是一种结合了多孔固体材料永久孔隙率和液体流动性的新型液体材料,在气体吸附和分离、催化等应用领域中展示出巨大的潜力。金属框架材料(MOFs)因其具有高的比表面积、热和化学稳定性、独特的结构以及制备简单的特点,使其有望成为构筑PLs多孔宿主的最佳候选材料之一。近些年来,基于MOFs(ZIF-8、ZIF-67、UiO-66等)基多孔液体相关研究被陆续报道。首先,介绍了多孔液体的分类;其次,总结了近些年来MOFs基多孔液体的制备以及应用;最后,对MOFs基多孔液体的制备存在的挑战与未来在气体吸附、催化等领域进行了展望与总结。     

Integrating of metal-organic framework UiO-66-NH2 and cellulose nanofibers mat for high-performance adsorption of dye rose bengal

UiO-66-NH₂ is an efficient material for removing pollutants from wastewater due to its high specific surface area, high porosity and water stability. However, recycling them from wastewater is difficult. In this study, the cellulose nanofibers mat deacetylated from cellulose acetate nanofibers were used to combine with UiO-66-NH₂ by the method of in-situ growth to remove the toxic dye, rose bengal. Compared to previous work, the prepared composite could not only provide ease of separation of UiO-66-NH₂ from the water after adsorption but also demonstrate better adsorption capacity (683 mg∙g^‒1 (T = 25 °C, pH = 3)) than that of the simple UiO-66-NH₂ (309.6 mg∙g^‒1 (T = 25 °C, pH = 3)). Through the analysis of adsorption kinetics and isotherms, the adsorption for rose bengal is mainly suitable for the pseudo-second-order kinetic model and Freundlich model. Furthermore, the relevant research revealed that the main adsorption mechanism of the composite was electrostatic interaction, hydrogen bonding and π–π interaction. Overall, the approach depicts an efficient model for integrating metal-organic frameworks on cellulose nanofibers to improve metal-organic framework recovery performance with potentially broad applications.     

高稳定铪金属-有机骨架材料的合成及二氧化碳捕获性能

采用高温高浓度的溶剂热方法,合成了具有高结晶度的一种金属-有机骨架（metal-organic framework,MOF）材料UiO-66（Hf）,并发现该材料在沸水、酸碱等苛刻条件下具有非常好的化学稳定性。为了提高其对气体的吸附分离性能,进一步采用具有不同官能团的有机配体--氨基对苯二甲酸（H₂BDC-NH₂）、硝基对苯二甲酸（H₂BDC-NO₂）、溴对苯二甲酸（H₂BDC-Br）,设计合成了孔道表面具有不同化学性质的三种新型铪MOF材料,且这些材料与UiO-66（Hf）具有相同的拓扑结构。同时,气体吸附实验结果表明,极性基团的引入,尤其是氨基的引入,能极大提高材料对CO₂/N₂以及CO₂/CH₄体系的分离性能。这为以后应用于化工体系分离的新型多孔材料合成提供了理论指导。