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1.
Defect engineering in metal-organic frameworks is commonly performed by using thermal or chemical treatments. Herein we report that oxygen plasma treatment generates structural defects on MIL-125(Ti)-NH 2, leading to an increase in its photocatalytic activity. Characterization data indicate that plasma-treated materials retain most of their initial crystallinity, while exhibiting somewhat lower surface area and pore volume. XPS and FT-IR spectroscopy reveal that oxygen plasma induces MIL-125(Ti)-NH 2 partial terephthalate decarboxylation and an increase in the Ti-OH population. Thermogravimetric analyses confirm the generation of structural defects by oxygen plasma and allowed an estimation of the resulting experimental formula of the treated MIL-125(Ti)-NH 2 solids. SEM analyses show that oxygen plasma treatment of MIL-125(Ti)-NH 2 gradually decreases its particle size. Importantly, diffuse reflectance UV/Vis spectroscopy and valence band measurements demonstrate that oxygen plasma treatment alters the MIL-125(Ti)-NH 2 band gap and, more significantly, the alignment of highest occupied and lowest unoccupied crystal orbitals. An optimal oxygen plasma treatment to achieve the highest efficiency in water splitting with or without methanol as sacrificial electron donor under UV/Vis or simulated sunlight was determined. The optimized plasma-treated MIL-125(Ti)-NH 2 photocatalyst acts as a truly heterogeneous photocatalyst and retains most of its initial photoactivity and crystallinity upon reuse. 相似文献
2.
The binary Ag 3PO 4/MIL-125-NH 2 (AMN-X) composites were synthesized through ion exchange-solution method, and the ternary Ag/Ag 3PO 4/MIL-125-NH 2 (AAMN-X) Z-scheme heterojunctions were prepared via the photo chemical reduction deposition strategy. The photocatalytic hexavalent chromium (Cr(VI)) sequestration over AMN-X and AAMN-X were investigated under visible light. AAMN-120 accomplished superior reduction performance due to that Ag nanoparticles (NPs) act as electrons transfer bridge to enhance the separation efficiency of photogenerated e −-h + pairs, in which the reaction rates ( k value) were 2.77 and 124.2 fold higher than those of individual MIL-125-NH 2 and Ag 3PO 4, respectively. The influences of different pH values, small organic acids and coexisting ions on the photocatalytic performance of AAMN-120 were also investigated. In addition, the AAMN-120 heterojunction expressed great reusability and stability in cycling experiments. The mechanism of photocatalytic Cr(VI) was investigated and verified through photoluminescence (PL), electrochemistry, electron spin resonance (ESR), active species capture, and Pt element deposition experiments. 相似文献
3.
Metal–organic framework (MOF) NH 2‐Uio‐66(Zr) exhibits photocatalytic activity for CO 2 reduction in the presence of triethanolamine as sacrificial agent under visible‐light irradiation. Photoinduced electron transfer from the excited 2‐aminoterephthalate (ATA) to Zr oxo clusters in NH 2‐Uio‐66(Zr) was for the first time revealed by photoluminescence studies. Generation of Zr III and its involvement in photocatalytic CO 2 reduction was confirmed by ESR analysis. Moreover, NH 2‐Uio‐66(Zr) with mixed ATA and 2,5‐diaminoterephthalate (DTA) ligands was prepared and shown to exhibit higher performance for photocatalytic CO 2 reduction due to its enhanced light adsorption and increased adsorption of CO 2. This study provides a better understanding of photocatalytic CO 2 reduction over MOF‐based photocatalysts and also demonstrates the great potential of using MOFs as highly stable, molecularly tunable, and recyclable photocatalysts in CO 2 reduction. 相似文献
4.
M‐doped NH 2‐MIL‐125(Ti) (M=Pt and Au) were prepared by using the wetness impregnation method followed by a treatment with H 2 flow. The resultant samples were characterized by powder X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), X‐ray absorption fine structure (XAFS) analyses, N 2‐sorption BET surface area, and UV/Vis diffuse reflectance spectroscopy (DRS). The photocatalytic reaction carried out in saturated CO 2 with triethanolamine (TEOA) as sacrificial agent under visible‐light irradiations showed that the noble metal‐doping on NH 2‐MIL‐125(Ti) promoted the photocatalytic hydrogen evolution. Unlike that over pure NH 2‐MIL‐125(Ti), in which only formate was produced, both hydrogen and formate were formed over Pt‐ and Au‐loaded NH 2‐MIL‐125(Ti). However, Pt and Au have different effects on the photocatalytic performance for formate production. Compared with pure NH 2‐MIL‐125(Ti), Pt/NH 2‐MIL‐125(Ti) showed an enhanced activity for photocatalytic formate formation, whereas Au has a negative effect on this reaction. To elucidate the origin of the different photocatalytic performance, electron spin resonance (ESR) analyses and density functional theory (DFT) calculations were carried out over M/NH 2‐MIL‐125(Ti).The photocatalytic mechanisms over M/NH 2‐MIL‐125(Ti) (M=Pt and Au) were proposed. For the first time, the hydrogen spillover from the noble metal Pt to the framework of NH 2‐MIL‐125(Ti) and its promoting effect on the photocatalytic CO 2 reduction is revealed. The elucidation of the mechanism on the photocatalysis over M/NH 2‐MIL‐125(Ti) can provide some guidance in the development of new photocatalysts based on MOF materials. This study also demonstrates the potential of using noble metal‐doped MOFs in photocatalytic reactions involving hydrogen as a reactant, like hydrogenation reactions. 相似文献
5.
Let your light shine: The photocatalytic reduction of carbon dioxide to the formate anion under visible light irradiation is for the first time realized over a photoactive Ti-containing metal-organic framework, NH(2) -MIL-125(Ti), which is fabricated by a facile substitution of ligands in the UV-responsive MIL-125(Ti) material (see scheme; TEOA=triethanolamine). 相似文献
6.
Solid-state photovoltaic cells based on robust metal-organic frameworks (MOFs), MIL-125(Ti), MIL-125(Ti)-NH 2, UiO-67, Ru(bpy) 2-UiO-67, (bpy 2,2‘-bipyridine) as active components and spiro-MeOTAD (MeOTAD 2,2‘,7,7‘-tetrakis[N,N-di(p-methoxyphenyl)amino]-9,9′-spirobifluorene) as hole transporting layer have been prepared., The photovoltaic response of this material increases in the presence of bathochromic −NH 2 groups on the linker or Ru (II) polypyridyl complexes light harvester. These results show that the strategies typically employed in photocatalysis to enhance the photocatalytic activity of MOFs can also be applied in the field of photovoltaic devices. 相似文献
7.
采用实验与分子模拟结合的方法研究298 K下CO_2在氨基改性得到的MIL-101(Cr)-NH_2和MIL-101(Cr)-ED(ED:乙二胺)上的吸附性能。比较MIL-101(Cr)、MIL-101(Cr)-NH_2和MIL-101(Cr)-ED的吸附等温线与吸附热的结果,表明采用直接合成改性法得到的MIL-101(Cr)-NH_2比采用合成后再改性得到的MIL-101(Cr)-ED有更高的CO_2吸附容量。进一步比较密度分布图和径向密度分布曲线,分析CO_2在氨基改性MIL-101(Cr)中的吸附位,表明在低压下CO_2首先吸附在MIL-101(Cr)微孔的超级四面体中,随着吸附压力的增大逐渐填充到更大的孔中。氨基的存在增加了CO_2的吸附位点,使MIL-101(Cr)-NH_2具有较高CO_2吸附容量;同时MIL-101(Cr)-ED中的ED分子的存在增加了CO_2的吸附位点,使MIL-101(Cr)-ED也具有较高CO_2吸附容量;但是MIL-101(Cr)-ED中的ED分子占据了MIL-101(Cr)中Cr的吸附位点,使Cr对CO_2的吸附强度减弱,同时可吸附位点少于MIL-101(Cr)-NH_2,导致其对CO_2的吸附容量少于MIL-101(Cr)-NH_2。 相似文献
8.
采用实验与分子模拟结合的方法研究298 K下CO 2在氨基改性得到的MIL-101(Cr)-NH 2和MIL-101(Cr)-ED(ED:乙二胺)上的吸附性能。比较MIL-101(Cr)、MIL-101(Cr)-NH 2和MIL-101(Cr)-ED的吸附等温线与吸附热的结果,表明采用直接合成改性法得到的MIL-101(Cr)-NH 2比采用合成后再改性得到的MIL-101(Cr)-ED有更高的CO 2吸附容量。进一步比较密度分布图和径向密度分布曲线,分析CO 2在氨基改性MIL-101(Cr)中的吸附位,表明在低压下CO 2首先吸附在MIL-101(Cr)微孔的超级四面体中,随着吸附压力的增大逐渐填充到更大的孔中。氨基的存在增加了CO 2的吸附位点,使MIL-101(Cr)-NH 2具有较高CO 2吸附容量;同时MIL-101(Cr)-ED中的ED分子的存在增加了CO 2的吸附位点,使MIL-101(Cr)-ED也具有较高CO 2吸附容量;但是MIL-101(Cr)-ED中的ED分子占据了MIL-101(Cr)中Cr的吸附位点,使Cr对CO 2的吸附强度减弱,同时可吸附位点少于MIL-101(Cr)-NH 2,导致其对CO 2的吸附容量少于MIL-101(Cr)-NH 2。 相似文献
9.
Bi2WO6/UiO-66-NH2 photocatalysts were fabricated through solvothermal method using acetic acid as template. The photocatalytic performance of as-fabricated composites was highly improved under simulated visible light due to the addition of UiO-66-NH2. The structural and chemical properties of the composites were characterized through FTIR, XRD, XPS, SEM, BET, UV–vis DRS and PL. After 90 min of visible light irradiation, the RhB at an initial concentration of 10 mg·L?1 in the solution was degraded by 99.4% due to the addition of 10 mg of the composite. There was no significant decrease in the photocatalytic activity even after four rounds of cycles. The free radical capture experiments indicate that the photogenerated holes (h+) were the main active sites. The possible photocatalytic degradation mechanism was proposed as the specific surface area of the composite was enlarged due to the uniform distribution of UiO-66-NH2 on the surface of Bi2WO6. The electron–hole pairs recombination rate was decreased due to the photogenerated electrons (e?) on the CB of Bi2WO6 which can be rapidly transferred to the CB of UiO-66-NH2 and the photogenerated holes of UiO-66-NH2 transferred to the VB of Bi2WO6. Meanwhile, the RhB was directly oxidized to H2O and CO2 by h+ to achieve the purification effect. 相似文献
10.
采用简单的溶剂热法制备金属有机框架化合物MIL-125(Ti)和NH_2-MIL-125(Ti)材料,并通过X射线衍射仪、扫描电子显微镜、傅氏转换红外线光谱分析仪和比表面积测试仪对所得样品进行表征。将2种材料修饰构建为石英晶体微天平传感器,测试其在11%~97%RH相对湿度范围内的湿度感测性能。实验结果表明,基于MIL-125(Ti)和NH_2-MIL-125(Ti)构建的传感器对湿度具有灵敏度高、重复性好、响应/恢复快等特点。相对于没有氨基修饰的MIL-125(Ti),NH_2-MIL-125(Ti)材料修饰的传感器对湿度表现出更高的响应性能。在环境湿度约52%时,NH_2-MIL-125(Ti)传感器对11%RH湿度响应值比MIL-125(Ti)湿度传感器的大57 Hz,说明氨基功能化对MIL-125(Ti)的湿敏性能有显著的增强作用。此外,通过Materials Studio模拟计算获得了水分子与MIL-125(Ti)及NH_2-MIL-125(Ti)作用的吸附焓,也证明氨基功能化对MIL-125(Ti)的湿度敏感性能具有增强作用。 相似文献
11.
太阳能是一种清洁的可再生能源,其中,可见光占太阳能总能量的45%。发展可见光响应的光催化剂是光催化领域重要的研究内容之一。NH 2-MIL-125(Ti)是一种有代表性的金属有机骨架可见光催化剂,但其存在可见光利用效率不高、光生电子-空穴对复合快等缺点。近年来,研究者们通过对NH 2-MIL-125(Ti)的晶面、结构和组成进行调控和修饰,提高其可见光催化活性。本文对近年来报道的关于提高NH 2-MIL-125(Ti)可见光催化活性的方法进行了综述,并对NH 2-MIL-125(Ti)基可见光催化剂的发展方向提出了建议,以期为NH 2-MIL-125(Ti)在光催化反应中进一步应用研究提供参考。 相似文献
12.
制备了多种金属-有机骨架(MOF)材料,采用浸渍-化学还原法制备了非晶态Ru-B/MOF催化剂,考察了它们在苯部分加氢反应中的催化性能.催化性能评价结果表明,这些催化剂的初始反应速率(r0)顺序为Ru-B/MIL-53(Al)Ru-B/MIL-53(Al)-NH2Ru-B/UIO-66(Zr)Ru-B/UIO-66(Zr)-NH2Ru-B/MIL-53(Cr)Ru-B/MIL-101(Cr)Ru-B/MIL-100(Fe),环己烯初始选择性(S0)顺序为Ru-B/MIL-53(Al)≈Ru-B/MIL-53(Cr)Ru-B/UIO-66(Zr)-NH2Ru-B/MIL-101(Cr)Ru-B/MIL-53(Al)-NH2Ru-B/UIO-66(Zr)≈Ru-B/MIL-100(Fe).催化性能最好的Ru-B/MIL-53(Al)催化剂上的r0和S0分别为23 mmol·min-1·g-1和72%.采用多种手段,对催化性能差异最为显著的Ru-B/MIL-53(Al)和Ru-B/MIL-100(Fe)催化剂的物理化学性质进行了表征.发现MIL-53(Al)载体能够更好地分散Ru-B纳米粒子,粒子的平均尺寸为3.2 nm,而MIL-100(Fe)载体上Ru-B纳米粒子团聚严重,粒径达46.6 nm.更小的粒径不仅能够提供更多的活性位,而且也有利于环己烯选择性的提高.对Ru-B/MIL-53(Al)催化剂的反应条件进行了优化,在180°C和5 MPa的H2压力下,环己烯得率可达24%,展示了MOF材料用作苯部分加氢催化剂载体的良好前景. 相似文献
13.
Atomically precise metal nanoclusters (NCs) with unique optical properties and abundant catalytic sites are promising in photocatalysis. However, their light-induced instability and the difficulty of utilizing the photogenerated carriers for photocatalysis pose significant challenges. Here, MAg 24 (M=Ag, Pd, Pt, and Au) NCs doped with diverse single heteroatoms have been encapsulated in a metal–organic framework (MOF), UiO-66-NH 2, affording MAg 24@UiO-66-NH 2. Strikingly, compared with Ag 25@UiO-66-NH 2, the MAg 24@UiO-66-NH 2 doped with heteroatom exhibits much enhanced activity in photocatalytic hydrogen production, among which AuAg 24@UiO-66-NH 2 presents the best activity up to 3.6 mmol g −1 h −1, far superior to all other counterparts. Moreover, they display excellent photocatalytic recyclability and stability. X-ray photoelectron spectroscopy and ultrafast transient absorption spectroscopy demonstrate that MAg 24 NCs encapsulated into the MOF create a favorable charge transfer pathway, similar to a Z-scheme heterojunction, when exposed to visible light. This promotes charge separation, along with optimized Ag electronic state, which are responsible for the superior activity in photocatalytic hydrogen production. 相似文献
14.
Transition metal Fe, Co, Ni and Cu doped strontium titanate-rich SrTiO 3@TiO 2 (STO@T) materials were prepared by hydrothermal method. The prepared doped materials exhibit better photocatalytic CO 2 reduction to CH 4 ability under visible light conditions. Among them, Fe-doped and undoped SrTiO 3@TiO 2 under visible light conditions CO 2 reduction products only CO, while M-STO@T (M=Co, Ni, Cu) samples converted CO 2 to CH 4. The average methane yield of Ni-doped STO@T samples are as high as 73.85 μmol g −1 h −1. The production of methane is mainly due to the increase in the response of the doped samples to visible light. And the increase in the separation rate of photogenerated electrons and holes and the efficiency of electron transport caused by the generation of impurity levels. The impurity level caused by Ti 3+ plays an important role in the production of methane by CO 2 visible light reduction. Ni doping effectively improves the photocatalytic performance of STO@T and CO 2 reduction mechanism were explained. 相似文献
15.
通过分步沉积法制备了不同Zr/Ti 摩尔比的锶锆钛(SZT)复合氧化物催化剂, 以X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、紫外-可见(UV-Vis)漫反射光谱等表征手段考察不同Zr/Ti 摩尔比下SZT催化剂的结构形态, 以可见光下光催化降解亚甲基蓝为模型反应考察样品的光催化活性. 结果表明: Zr/Ti 摩尔比<1 时SZT催化剂发生Zr 4+与Ti 4+同质替换, 引起晶格缺陷, 光催化活性小幅提高; Zr/Ti 摩尔比≥1 时SZT催化剂产生SrZrO 3/Ti nO 2n-1 (n=4, 9)的新晶相, Ti nO 2n-1 (n=4, 9)的存在有利于光生电子-空穴的传导与分离, 可大幅提高催化剂光催化活性. 其中, SZT-5/5 表现出最高的光催化活性, 其一级反应速率常数达到0.2133 min -1, 是同等光照条件下纯SrTiO 3样品(0.0158 min -1)的13.5倍. 相似文献
16.
胺类分子在CO 2的捕获中可以起到选择性提升的作用,本文选择小尺寸的乙二胺分子对具有不饱和金属位点的轻金属铝基金属有机骨架(Al-MOFs)材料MIL-100Al进行改性,利用XRD、N 2吸附和FT-IR等对改性材料的结构进行表征,测试了不同浓度的乙二胺改性的MIL-100Al对CO 2和CH 4吸附性能。结果表明,与原始的MIL-100Al材料相比,改性后的材料对CO 2吸附量有明显提高,CH 4的吸附量却降低,从而进一步提高了材料的CO 2/CH 4吸附选择性,提升了吸附分离的效果。 相似文献
17.
胺类分子在CO_2的捕获中可以起到选择性提升的作用,本文选择小尺寸的乙二胺分子对具有不饱和金属位点的轻金属铝基金属有机骨架(Al-MOFs)材料MIL-100Al进行改性,利用XRD、N2吸附和FT-IR等对改性材料的结构进行表征,测试了不同浓度的乙二胺改性的MIL-100Al对CO_2和CH4吸附性能。结果表明,与原始的MIL-100Al材料相比,改性后的材料对CO_2吸附量有明显提高,CH4的吸附量却降低,从而进一步提高了材料的CO_2/CH4吸附选择性,提升了吸附分离的效果。 相似文献
18.
Highly-efficient photocatalytic conversion of CO 2 into valuable carbon-contained chemicals possesses a tremendous potential in solving the energy crisis and global warming problem. However, the inadequate separation of photogenerated electron-hole pairs and the unsatisfied capture of CO 2 stay the chief roadblocks. Herein, we designed a novel photocatalyst for CO 2 reduction by assembling three-dimensional graphene (3D GR) with a typical metal-organic framework material UIO-66-NH 2, aiming to construct a built-in electric field for charge separation as well as taking advantage of the typical 3D structure of GR for maximizing the exposed absorption site on the surface. The performance evaluation demonstrated that the photocatalytic activity has been improved for the composite materials compared with that of the pure UIO-66-NH 2. Further mechanism investigations proved that the enhanced photocatalytic performance is attributed to the synergy of enhanced CO 2 absorption and inhibited photogenerated charge recombination, which could be owing to the better distribution and exposure of absorption and reaction sites on composites, and the redistribution of photogenerated carriers between 3D GR and UIO-66-NH 2. This study provides a promising pathway to probe nanocomposites based on MOFs in environmental improvement and other relevant fields. 相似文献
19.
A new Pebax-based mixed matrix membrane with amide functionalized PCP filler shows promising CO 2/N 2 separation at ambient temperature. 相似文献
20.
Ammonia is one of the most essential chemicals in the modern society but its production still heavily relies on energy-consuming Haber-Bosch processes. The photocatalytic reduction of nitrogen with water for ammonia production has attracted much attention recently due to its synthesis under mild conditions at room temperature and atmospheric pressure using sunlight. Herein, we report a high-performance Au/MIL-100(Cr) photocatalyst, comprising MIL-100(Cr) and Au nanoparticles in photocatalytic nitrogen reduction to ammonia at ambient conditions under visible light irradiation. The optimized photocatalyst ( i.e., 0.10Au/MIL-100(Cr)) achieved the excellent ammonia production rate with 39.9 µg g cat?1 h ?1 compared with pure MIL-100(Cr) (2.73 µg g cat?1 h ?1), which was nearly 15 times that on pure MIL-100(Cr). The remarkable activity could be attributed to the adsorption-plasmonic synergistic effects in which the MIL-100(Cr) and Au are responsible to the strong trapping and adsorption of N 2 molecules and photo-induced plasmonic hot electrons activating and decomposing the N 2 molecules, respectively. This study might provide a new strategy for designing an efficient plasmonic photocatalyst to improve the photocatalytic performance of N 2 fixation under visible light irradiation. 相似文献
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