Metal Emissions Research Articles

Emissions of multiple metals from vehicular brake linings wear in China, 1980–2020

Metals emitted from brake linings wear have adverse effects on air quality and human health due to their toxicity and reactivity. However, complexities of factors affecting brake like conditions of vehicles and roads hinder the accurate quantification. Here, we established a comprehensive emission inventory for multi-metals from brake linings wear in China during 1980–2020, based on metals contents in well-representative samples, the wear of brake linings before replacement, vehicle populations, fleet composition, and vehicle-kilometers travelled (VKT). We show that with the boom of vehicle population, the total emissions of studied metals have surged from 3.7 × 106 g in 1980 to 4.9 × 1010 g in 2020, which mainly concentrated in coastal and eastern urban areas while grown significantly in the central and western urban areas in recent years. Therein, Ca, Fe, Mg, Al, Cu, and Ba were the top six metals emitted, together responsible for >94 % of the mass total. Jointly determined by brake linings especially metals contents thereof, VKTs, and vehicle populations, heavy-duty trucks, light-duty passenger vehicles, and heavy-duty passenger vehicles were the top three contributors in metals emissions, together accounting about 90 % of the total. Moreover, more precise description on real-world metals emissions from brake linings wear are still urgently needed, considering the increasingly significant role it has been playing on worsening air quality and public health.

Synthesis of Polyvinyl Alcohol/Coal Fly Ash Hybrid Nano-Fiber Membranes for Adsorption of Heavy Metals in Diesel Fuel.

Some studies have shown that the heavy metal emissions (HMEs) emitted from diesel engines can seriously threaten human health. HMEs are mainly related to the content of heavy metal ions in diesel fuel. Therefore, in order to reduce HMEs from diesel engines, a nano-fiber membrane filtration technology for diesel fuel was investigated. Herein, coal fly ash (CFA) from coal-fired power plants combined with polyvinyl alcohol (PVA) was successfully fabricated into nano-fibrous membranes using green electrospinning technology. In order to evaluate the adsorption properties, various hybrid membranes with different mixing ratios (PVA/CFA = 10/0, 10/1, 10/3, 10/5, and 10/7 by weight) were fabricated. The results show that eight metal ions with different concentrations are found in the diesel fuel, including Pb, Cu, Zn, Al, Fe, Cr, Ba, and Ni. All PVA/FA membranes have different adsorption capacities for metal ions, following the order: Cu > Fe > Pb > Al > Zn > Cr > Ba > Ni. In addition, the adsorption capacity of CFA3 (PVA/CFA = 10/3) is the largest. The super lipophilicity of the PVA/FA membranes also provide more adsorption sites for the contact of HMs with the membranes. The above research results provide guidance for development of ultra-fine filters in the future.

High-resolution risk mapping of heavy metals in soil with an integrated static-dynamic interaction model: A case study in an industrial agglomeration area in China

Heavy metal pollution of soils in industrial agglomeration areas is an increasing concern worldwide. In this study, we traced the sources of heavy metal emissions using a positive matrix factorization (PMF) model. Accordingly, we proposed a novel static-dynamic risk interaction model incorporating multiple risk-related factors to quantify the spatial interaction of emission sources and the probability of accumulation of heavy metals on a large scale. This model was further classified using the Jenks optimization technique to predict the spatial distribution of high-risk hotspots. Our results determined four primary emission sources of heavy metals: industrial (35.01 %), natural (28.61 %), agricultural (26.07 %), and traffic (10.31 %) sources. Five levels were classified by the integrated risk coefficient (IRC), namely, from extremely high to extremely low risk. The extremely high- and high-risk hotspots constituting 41.52 % of the total area of the Zhenhai District, with IRC values ranging from 0.221 to 0.413, were mainly generated by multiple sources linked to PMF-based factors. This quantitative evaluation framework can generate a high-resolution spatially distributed pollution risk map at the grid scale (1 km), which can provide a relatively precise basis for policymaking for point-to-point soil pollution management.

Major and trace element emission rates in hydrothermal plumes in a tropical environment. The case of La Soufrière de Guadeloupe volcano

Hydrothermal or low-temperature volcanic emissions, most commonly occurring in fumarolic environments, dominate the global volcanic landscape. This work presents physicochemical characterization of the aerosols contained in steam- and H2S-rich plumes discharged from La Soufrière volcano, in conjunction with the first report on their heavy metal degassing emission rates. Our results indicate that the plume is enriched in certain lithophile (K, Ti, Si, Al, Mn, and Mg) and siderophile (Fe) elements, related to hydrothermal rock leaching, and chalcophile (Sb, As, Zn, Pb, and Tl) elements, which are usually degassed from the magma source. Heavy metal emission rates were found to be below 15 g/d, which are modest compared to available worldwide data. Nevertheless, Cr and Sb emission rates were very similar to those of Lascar volcano (Chile), which instead has produced magmatic eruptions in recent times. We propose that the depth of the magma chamber and the input of meteoric waters play an important role in scavenging heavy metals in the hydrothermal system of magmatic-hydrothermal volcanoes. Notwithstanding low heavy metal emission rates, La Soufrière can be regarded as an important pollution source in the Lesser Antilles volcanic arc.

Risk Assessment and Source Apportionment of Metals on Atmospheric Particulate Matter in a Suburban Background Area of Gran Canaria (Spain).

Concentration levels of 11 heavy metals were analyzed in PM10 and PM2.5 samples from a suburban area frequently affected by Saharan dust in which is located a school. The heavy metals risk assessment was carried out by the 2011 U.S. Environmental Protection Agency method, estimating the chronic and carcinogenic hazard levels both in adults and children. The highest level of chronic hazard was reached for Cr, with values of approximately 8 (PM10, adulthood), 2 (PM10, childhood) and 1.5 (PM2.5, adult age), significantly exceeding the limit value (equal to 1). Regarding the carcinogenic risk level, it was also high for Cr, with values between 10-3 and 10-1 for both study populations and particle size. For the rest of the studied metals, no health risk levels of concern were obtained. The positive matrix factorization method was used for the estimation of heavy metal emission sources apportionment. Non-exhaust vehicle emissions were the main source of Cr emissions under PM2.5, while industrial processes were the main source for PM10. Mineral dust and marine aerosol were common emission sources for both particles sizes-with different contributions. Vehicle emissions, construction and agricultural activities were the main emission sources for PM10, and fossil fuel combustion, road dust re-suspension and ammonium sulfate were for PM2.5. The results obtained in this study support the need to continue applying mitigation measures in suburban areas which are affected by nearby anthropogenic emissions, causing the consequent emission of materials hazardous to human health.

Internal exposure risk based on urinary metabolites of PAHs of occupation and non-occupation populations around a non-ferrous metal smelting plant

The emission of various metals from non-ferrous metal smelting activities is well known. However, relative investigations on potential occupational exposure of organic pollutants are still limited. Herein, total of 619 human urine samples were collected from workers engaged in smelting activities and residents living near and/or far from the smelting sites, and ten mono-hydroxylated metabolites of polycyclic aromatic hydrocarbons (OH-PAHs) in human urine were determined. The median levels of Σ10OH-PAHs in smelting workers (25.6 ng/mL) were significantly higher (p < 0.01) than that of surrounding residents (9.00 ng/mL) and rural residents as the control (8.17 ng/mL), indicating an increase in occupational PAH exposure in non-ferrous metal smelting activities. The composition profiles of OH-PAH congeners were similar in three groups, in which naphthalene metabolites accounted for 76–82% of the total. The effects of smoking, drinking, gender, BMI, and occupational categories on urinary OH-PAHs were considered. The partial correlation analysis showed an insignificant effect of non-ferrous metal smelting activities on PAH exposure for surrounding residents. In the health risk assessments, almost all smelting workers had cancer risks exceeded the acceptable level of 10−6. This study provides a reference to occupational PAH exposure and reinforce the necessary of health monitoring among smelting workers.

Alkaline gases emission estimation and paraconsistent logic techniques application to label bagasse combustion conditions

When some renewable energy sources are used, such as biomass solid waste, it is necessary to measure and control pollutant emissions. Since raw sugarcane comes from a wide variety of supply sources, it is necessary to monitor the behavior of the biomass residues during the burning process to control flame stability, emissions, and combustion efficiency. The variation in the combustion temperature of biomass affects the combustion efficiency and also the emission of alkaline metals, such as potassium (K) and sodium (Na), which can cause corrosion in boilers. The objective of the present work is to estimate the content of alkali gases in the flames during the burning of solid biomass residues, specifically sugarcane bagasse in this case. The flame emission spectroscopy (FES) spectrometry technique is used and flame emission spectra is captured during the combustion of bagasse in a pilot furnace. The flame temperature is calculated using the two-color method together with the inverse Levenberg-Marquard method. Models and correlations from literature are used to obtain a database of emission content of sodium and potassium. Using paraconsistent logic techniques, a predictor algorithm is implemented and bagasse samples were labeled to identify similar physical combustion conditions. The results of the emission of sodium and potassium estimated for groups labeled using the algorithm of paraconsistent logic are compared and show good agreement between them. A good and reasonable agreement was found in the estimation of the emission content of potassium and sodium.

Observations of alkaline emissions NaI, KI and LiI during first minutes after DART probe impact on Dimorphos

We report on the results of the analysis of spectral observations of the asteroid Didymos at the time of impact of the DART mission probe, obtained a few minutes before, directly at the moment, and within a few minutes after the spacecraft hit the surface of the Dimorphos. We found evidence of alkali metal emissions that appeared at the moment and continued for several minutes after the impact. The observation evidence of the appearance of Na, Li and K atoms as a result of the impact of the DART probe on the Dimorphos in a relative amount close to the abundance of these elements in the Solar System are reliably established. We conclude that the main contribution to alkaline emissions is atoms bound to the dust cloud ejected during the impact. This dust cloud is a steady source of alkaline metal atoms. We did not detect the presence of alkaline mater not bound to the dust cloud and moved independently.

Products distribution and heavy metals migration during catalytic pyrolysis of refinery oily sludge

The reclamation disposal of oily sludge, which is a hazardous waste from the extraction, transportation, storage, and refining of crude oil, is a paramount challenge for environmental protection and resource recycle. Herein, a catalytic pyrolysis approach with the participation of CaO was adopted for oil resource recovery. The results show that the optimal pyrolysis temperature for recovering oil was 500 °C, in which the pyrolysis oil yield was 44.37%. CaO could act as a catalyst during the pyrolysis process, thus promoting the formation of light components in the pyrolysis oil. The light components in pyrolysis oil increased from 5.08% to 16.67% with the participation of CaO. Meanwhile, the addition of CaO immobilized As, Cr, Pb and Zn into the pyrolysis slag, thus decreasing their migration into pyrolysis oil and gas. The migration of Ni displayed a different trend, and part of Ni entered into the pyrolysis oil and gas. The BCR continuous extraction experiments display that the highly biological-activity heavy metals (i.e., F1, F2 and F3 form) was transformed to a more stable state (i.e., F4 form). These results demonstrate that the catalytic pyrolysis approach with the participation of CaO not only improve the yield and quality of pyrolysis oil, but also reduce the emission and mobility of heavy metals.

Intermolecular arrangement facilitated broadband blue emission in group-12 metal (Zn, Cd) hybrid halides and their applications

Various fluorescent organic materials are widely known for their potential applications in light-emitting diodes, organic lasers, anti-counterfeiting and bio-imaging. However, poor emission efficiency and stability issues limit their usability. Here we report the syntheses, crystal and electronic structures, and optical characterizations of two new hybrid organic-inorganic group 12 halides, (P-xd)ZnCl4 and (P-xd)CdCl4 (where (P-xd) = p-xylylenediammonium). Single crystals of both compounds can be conveniently synthesized by solution chemistry methods from their low-cost, low toxicity and easily available precursors. (P-xd)ZnCl4 possesses a crystal structure featuring alternating layers of organic cations and completely separated anionic [ZnCl4]2- tetrahedral units of zero-dimensional (0D) connectivity. In contrast, (P-xd)CdCl4 adopts similar layering of organic cations sandwiched between perovskite sheets of two-dimensional (2D) connectivity, which are formed by corner-sharing anionic [CdCl6]4- octahedral units. The structural, optical, and electronic studies suggest that the incorporation of organic and inorganic structural units into a hybrid structure improves its blue emission efficiency with nearly 23 times and 4 times higher photoluminescence quantum yield (PLQY) values in (P-xd)ZnCl4 and (P-xd)CdCl4, respectively, as compared to the organic precursor. Notably, PLQY of 23% for (P-xd)ZnCl4 is the highest reported to date for Zn-based hybrid organic-inorganic metal halides, where emission originates from the organic component. Both (P-xd)ZnCl4 and (P-xd)CdCl4 demonstrate considerably improved air-, thermal- and photostability, which suggest their suitability for potential practical applications such as fingerprint detection and solid-state lighting.

Metal line emission from galaxy haloes at z ≈ 1

ABSTRACT We present a study of the metal-enriched halo gas, traced using Mg ii and [O ii] emission lines, in two large, blind galaxy surveys – the MUSE (Multi Unit Spectroscopic Explorer) Analysis of Gas around Galaxies (MAGG) and the MUSE Ultra Deep Field (MUDF). By stacking a sample of ≈600 galaxies (stellar masses $M_*$ ≈ 106–12 $\rm M_\odot$), we characterize for the first time the average metal line emission from a general population of galaxy haloes at 0.7 ≤ z ≤ 1.5. The Mg ii and [O ii] line emission extends farther out than the stellar continuum emission, on average out to ≈25 and ≈45 kpc, respectively, at a surface brightness (SB) level of 10−20 $\rm erg\, s^{-1}\, cm^{-2}\, arcsec^{-2}$. The radial profile of the Mg ii SB is shallower than that of the [O ii], suggesting that the resonant Mg ii emission is affected by dust and radiative transfer effects. The [O ii] to Mg ii SB ratio is ≈3 over ≈20–40 kpc, also indicating a significant in situ origin of the extended metal emission. The average SB profiles are intrinsically brighter by a factor of ≈2–3 and more radially extended by a factor of ≈1.3 at 1.0 &amp;lt; z ≤ 1.5 than at 0.7 ≤ z ≤ 1.0. The average extent of the metal emission also increases independently with increasing stellar mass and in overdense group environments. When considering individual detections, we find extended [O ii] emission up to ≈50 kpc around ≈30–40 per cent of the group galaxies, and extended (≈30–40 kpc) Mg ii emission around two z ≈ 1 quasars in groups, which could arise from outflows or environmental processes.

Spatial Distribution of Heavy Metal Contamination in Road Dust Samples from an Urban Environment in Samsun, Türkiye.

Road dust is an environmental pollution indicator created by human activities for urban land use. This study aimed to determine the spatial distribution pattern and degree of trace metals in road dust samples collected from 5 different areas in Samsun city center. The trace metals of Mn, Co, Cd, Cr, Cu, Ni, Pb, and Zn are the most examined contaminants in road dust because their hot-spot areas were mainly associated with high traffic density. Factors governing potential contamination index range values of Co, Cr, and Ni were 0.34-0.62, 0.23-0.78, and 0.24-0.48 as the lowest contamination. However, potential contamination index values of Cu, Pb, and Zn in the main road site were 1.80, 2.32, and 2.84 suggesting that relatively high values were uncontaminated to moderately. Pollution assessment methods were applied to toxic metals and revealed that Samsun city had been affected as uncontaminated to moderately contaminated by anthropogenic emission of heavy metals.

Heavy metal removal from coal fly ash for low carbon footprint cement

Development of cementitious materials with low carbon footprint is critical for greenhouse gas mitigation. Coal fly ash (CFA) is an attractive diluent additive in cement due to its widespread availability and ultralow cost, but the heavy metals in CFA could leach out over time. Traditional acid washing processes for heavy metal removal suffer from high chemical consumption and high-volume wastewater streams. Here, we report a rapid and water-free process based on flash Joule heating (FJH) for heavy metals removal from CFA. The FJH process ramps the temperature to ~3000 °C within one second by an electric pulse, enabling the evaporative removal of heavy metals with efficiencies of 70–90% for arsenic, cadmium, cobalt, nickel, and lead. The purified CFA is partially substituted in Portland cement, showing enhanced strength and less heavy metal leakage under acid leaching. Techno-economic analysis shows that the process is energy-efficient with the cost of ~$21 ton−1 in electrical energy. Life cycle analysis reveals the reuse of CFA in cement reduces greenhouse gas emissions by ~30% and heavy metal emissions by ~41%, while the energy consumption is balanced, when compared to landfilling. The FJH strategy also works for decontamination of other industrial wastes such as bauxite residue.

Emission Characteristics and Control of Heavy Metals in Secondary Copper Smelting Process

Secondary copper smelting is an important source of heavy metal emission. Flue gas samples were collected from different stages in secondary copper smelters to study the emission characteristics and control of particulate matters (PM) and heavy metals such as Cd, Cr, As, Pb, Sn, and Sb. The mass concentrations of heavy metals in flue gas and fly ash were determined using inductively coupled plasma-mass spectrometry. The emission factors of heavy metals were estimated. The results showed that the mass concentrations of heavy metals and PM in the flue gas were high in the cooling stage. After passing through a series of air pollution control devices, such as a bag filter and adsorption tower, the heavy metals and PM were simultaneously removed with a removal efficiency of 80%-99%. The concentration order of heavy metals in the stack gas from different anode furnace stages followed feeding-fusion>oxidation≈deoxidization. In general, the mass concentrations of heavy metals and PM in the stack gas could meet the industry emission standards. The average emission factors of As, Pb, Cr, Sn, Sb, and Cd were 2.6×103, 2.4×103, 2.7×103, 5.6×102, 34.1, and 9.8 mg·t-1, respectively. This could provide data support for estimating the annual emission amounts of heavy metals from the secondary copper industry and establishing the emission inventories. The fly ash contained high concentrations of Cu and Zn, which can be recycled as raw materials for recycling the valuable metals.

Capitalization of tires waste as derived fuel for sustainable cement production

The co-incineration of tires waste is inexpensive; the questions are referring to the influence over clinker quality and gaseous emissions. The use of tires waste as a waste-derived fuel imposes more researches to establish influence over process parameters, technological availability, costs, kiln design for processing different type of fuels, quality and homogeneity of alternative fuels, the caloric value, quality of clinker, gaseous emission, etc. The data was obtained at an industrial scale, during two periods when 11% tires waste replaces coal, with or without raw mill in function. The results were compared with the period when coal was the only fuel used. The principal objective of this paper is to establish the influence, at the industrial scale, of the use of tires waste on: the technological parameters of the clinker kiln as well as on its energy efficiency and stability; the effects of tires waste incineration on clinker process and properties of clinker, SO2, NOx and heavy metals emission. The experimental results presented in the paper demonstrated that the co-incineration of tires wastes in cement plants have the multiple benefits: save raw materials, reduced CO2 emission, thermo-energy recovery of waste with rich energy content, reduces waste disposal, etc.

Experimental investigation on the separated gasification chemical looping combustion performance of phytoremediation plant and retention of heavy metals

Phytoremediation technology has been one of the important ways to treat soil heavy metal contaminant. However, if the harvested phytoremediation plant cannot be properly disposed, the heavy metals in phytoremediation plant may pollute the environment again. Separated gasification chemical looping combustion (SG-CLC) of phytoremediation plant is investigated in a two-stage reactor to reduce the emission of heavy metals into gas. And this technology has the superiority of traditional chemical looping combustion (CLC). The first-stage reactor temperature, bed material and steam mass flow are changed to investigate their effects on the combustion performance, retention of heavy metals in bottom residue and characteristics of oxygen carrier. Five redox experiment cycles are carried out under each condition. Results show that increasing the temperature from 450℃ to 650 ℃, the carbon conversion increases from 44.4% to 66.7%, and the retention rates of Mn, Ni, Zn and Pb decrease from 44.16%, 69.82%, 73.42% and 49.46% to 18.86%, 13.56%, 38.42% and 6.18% respectively. Increasing steam mass flow and using CaO as bed material are also beneficial to enhance the carbon conversion. This also affects the microscopic morphology of oxygen carrier in second-stage reactor. There appears obvious granular morphology on the surface of used oxygen carrier at 650 °C or using CaO as bed material. Rising the flowrate of steam from 0.36 g/min to 0.60 g/min has divergent effects on retention of heavy metals as retention rates of Mn, Ni, Zn and Pb change from 24.87%, 10.42%, 57.32% and 25.06% to 22.32%, 17.70%, 50.97% and 21.38%.

Integrated assessment of land-to-river Cd fluxes and riverine Cd loads using SWAT-HM to guide management strategies

In 2011, China invested US$9.8 billion to combat the severe heavy metal pollution in the Xiang River basin (XRB), aiming to reduce 50% of the 2008 industrial metal emissions by 2015. However, river pollution mitigation requires a holistic accounting of both point and diffuse sources, yet the detailed land-to-river metal fluxes in the XRB remain unclear. Here, by combining emissions inventories with the SWAT-HM model, we quantified the land-to-river cadmium (Cd) fluxes and riverine Cd loads across the XRB from 2000 to 2015. The model was validated against long-term historical observations of monthly streamflow and sediment load and Cd concentrations at 42, 11, and 10 gauges, respectively. The analysis of the simulation results showed that the soil erosion flux dominated the Cd exports (23.56–80.14 Mg yr−1). The industrial point flux decreased by 85.5% from 20.84 Mg in 2000 to 3.02 Mg in 2015. Of all the Cd inputs, approximately 54.9% (37.40 Mg yr−1) was finally drained into Dongting Lake; the remaining 45.1% (30.79 Mg yr−1) was deposited within the XRB, increasing the Cd concentration in riverbed sediment. Furthermore, in XRB's 5-order river network, the Cd concentrations in small streams (1st order and 2nd order) showed larger variability due to their low dilution capacity and intense Cd inputs. Our findings highlight the need for multi-path transport modeling to guide future management strategies and better monitoring schemes to restore the small polluted streams.

Atmospheric dry deposition fluxes of trace metals over the Eastern China Marginal Seas: Impact of emission controls

Atmospheric deposition is an important exogenous input of trace metals to Eastern China Marginal Seas (ECMS), which is strongly affected by human activities. With emission control practices implemented in China, it still remains unknown what changes have taken place in the atmospheric dry depositions of the trace metals over ECMS. This study aimed to estimate the atmospheric dry depositions of Zn, Pb, Cu, and Cd over ECMS via Weather Research and Forecasting Model-Community Multiscale Air Quality Modeling System (WRF-CMAQ) in the two winter periods of January 2012 and January 2019 as well as to explore the impacts of emission control on the depositions. The anthropogenic metal emissions from China, the Korean Peninsula, Japan, and marine ships were investigated in this study. In 2012, the dry deposition fluxes of Zn, Pb, Cu, and Cd over ECMS were in the ranges of 0.50–3.4 μg m−2 d−1, 0.22–1.9 μg m−2 d−1, 0.14–0.90 μg m−2 d−1, and 12–88 ng m−2 d−1, respectively. The deposition fluxes of the four metals over Bohai Sea (BS) and Yellow Sea (YS) were 2–3 times those over East China Sea (ECS). Outflow of polluted air masses from East Asia increased the metal depositions by 3– 5-fold relative to clear days. Compared with 2012, a 5–85 % reduction in the metal depositions over ECMS were estimated in 2019, largest reductions were found over YS and BS. Meteorological variation was able to decrease or increase the metal depositions. However, the emission control only caused a reduction in the entire study region. The metal inputs to the sea were significantly lower from the ship emissions than from the continental anthropogenic emissions, although the proportion of the ship emissions in the total metal depositions rose slightly from 2012 to 2019.

Up-conversion emission in transition metal and lanthanide co-doped systems: dimer sensitization revisited

Lanthanide (Ln) co-doped transition metal (TM) upconversion (UC) co-doped systems are being intensively investigated for their exciting applications in photonics, bioimaging, and luminescence thermometry. The presence of TM, such as Mo6 + /W6 +, Mn2 +, or Fe3 + determines significant changes in Ln UC emission, such as intensity enhancement, colour modulation, and even the alteration of the photon order. The current mechanism assumes a ground-state absorption/excited-state absorption (ESA/GSA) in TM-Yb dimer followed by direct energy transfer to Er/Tm excited states. We revisit this mechanism by addressing two issues that remain ignored: a dynamical approach to the investigation of the upconversion mechanism and the intrinsic chemical complexity of co-doped TM, Ln systems. To this aim, we employ a pulsed, excitation variable laser across a complete set of UC measurements, such as the emission and excitation spectra and emission decays and analyze multiple grains with transmission electron microscopy (TEM). In the Mo co-doped garnet, the results sustain the co-existence of Mo-free garnet and Mo oxide impurity. In this Mo oxide, the Er upconversion emission properties are fully explained by a relatively efficient sequential Yb to Er upconversion process, with no contribution from Yb-Mo dimer sensitization.

Multicomponent Anti-Kasha’s Rule Emission from Nanotubular Metal–Organic Frameworks for Selective Detection of Small Molecules

The peak photoluminescence (PL) of conventional fluorophores is independent of the excitation wavelength (called Kasha's rule), while the search of metal-organic framework materials with the so-called anti-Kasha's rule emission remains very limited. Herein, we report the observation of anti-Kasha's rule emission in a multicomponent PL three-dimensional nanotubular metal-organic framework (abbr. MOF-NT), [Zn(μ-L)(μ-bix)]n·0.33nH2O [H2L = biphenyl-3,5-dicarboxylic acid; bix = 1,4-bis(imidazole-1-ylmethyl)benzene]. The MOF-NT crystalline sample represents a notable example of strong excitation-dependent fluorescence from the ultraviolet to the visible spectral region. Moreover, by virtue of electronic flexibility and high PL efficiency, MOF-NT shows a discriminative PL response between isomeric nitroaromatic compounds. The work demonstrated the intrinsic anti-Kasha's rule emission in the crystalline-state MOF materials, providing new visions for the development of advanced solid-state emissive materials.