Adsorption Of Small Molecules Research Articles

DFT study on adsorption of small gas molecules on Pt-capped armchair and zigzag single-walled carbon nanotubes

The adsorption of small gas molecules (CO, O2 and N2) on Pt-capped armchair and zigzag single-walled carbon nanotubes (SWCNT) has been investigated by density functional theory (DFT) method to determine the potential for gas sensor detection. Results indicated that O2 and N2 molecules with lower adsorption energies (1.66 eV and 1.00 eV) exhibited weak chemical adsorption on SWCNT(4,4)-Pt. However, CO demonstrates strong chemical adsorption with a high adsorption energy of 2.23 eV on SWCNT(4,4)-Pt. The adsorption energy of CO on SWCNT(7,0)-Pt shows the chemical adsorption between CO and SWCNT(7,0)-Pt. In addition, these findings also implied Pt-capped SWCNT could act as small gas molecule sensors to detect CO toxic gas at room temperature. In this system, CO is the electron donor and SWCNT-Pt is the electron receptor. The interaction of Pt and carbon nanotube backbone delocalized π electrons could not only increases the conductivity of SWCNT-Pt, but also enhances the conductivity of SWCNT-Pt-CO. The HOMO-LUMO gap (Δε) of Pt-capped SWCNT(7,0) reduced from 0.43 eV to 0.39 eV after CO adsorption, and the Δε value of Pt-capped SWCNT(4,4) decreased by 0.08 eV. The electrical conductivity of Pt-capped armchair and zigzag SWCNT has increased after the adsorption of CO molecule. The results may be helpful for designing a promising Pt-capped SWCNT-based CO sensors.

Small-Molecule Adsorption Energy Predictions for High-Throughput Screening of Electrocatalysts.

Predicting adsorption energies of small molecules (e.g., OH, OOH, CO) on electrocatalysts involved in electrochemical reactions aids in accelerating the design and screening of electrocatalysts. Avoiding computationally expensive electronic structure calculations increases the speed of such predictions. Geometric and electronic descriptors have been reported to characterize the environment around surface active sites and predict adsorption energies. However, these descriptors cannot be used to predict adsorption energies of small molecules on various substrates, e.g., metal-oxide and nonmetal electrocatalysts. We compare the performance of these descriptors in predicting adsorption energies of small molecules on various electrocatalysts with adsorption energies calculated from density functional theory. We show that two recently developed machine learning algorithms, Crystal Graph Convolutional Neural Network (CGCNN) and Atomistic Line Graph Neural Network (ALIGNN), outperform the reported descriptors based on geometric (coordination number of the active site and its nearest neighbors) and electronic (the bond-energy-integrated orbitalwise coordination number, the electronegativity, and the number of valence electrons of the active site) properties in predicting the adsorption energies. Our results suggest that ALIGNN is almost always more accurate than CGCNN in adsorption energy predictions. The improvement ranges from 0.02 to 1.0 eV in the mean absolute errors (MAEs). We also compare the performance of CGCNN and ALIGNN algorithms in predicting the overpotentials of the oxygen evolution reaction occurring on various electrocatalysts with MAEs of 0.06 and 0.05 V, respectively.

Computational study on the adsorption of small molecules to surface-supported Ni-porphyrins

With their flexible oxidation and spin states, surface-supported metalloporphyrins are attractive building blocks for tuneable, periodic spin interfaces. A technique to manipulate the spin in such systems is based on the adsorption of external gas ligands to the chelated metal center. In the search for promising interfaces, computational studies allow for a convenient scan through potential ligand candidates. In this contribution, we perform density functional theory calculations to investigate the coordination of six exemplary gases (CH4, H2O, NH3, CO, NO and NO2) to nickel tetraphenylporphyrin interfaces. Analyzing the formed complexes, we distinguish four major interaction mechanisms between metal center and ligand: non-interacting, weak field d-splitting, competing surface trans-effect and redox reaction. We find that a surface-mediated redox reaction between a strong π-acceptor (e.g.: NO2) and an unusually reduced metal (e.g.: Ni d9) has the strongest potential to induce spin changes at ambient conditions. Furthermore, we demonstrate how commonly chosen theoretical approximations may influence the interpretation of DFT calculations for metalloporphyrins and their complexes. By highlighting the limitations and possibilities of theoretical approaches, we hope to contribute to a better understanding and more selective harnessing of the special properties of surface-supported metalloporphyrins.

Understanding polymer-porous solid interactions based on small gas molecule adsorption behavior

Understanding the interactions between molten polymers and inorganic porous solids is critical for the heterogeneous catalytic conversion of waste polymers into useful chemicals and the fabrication of nanocomposites and nanostructured polymers. Developing experimental and theoretical approaches to quantify and understand polymer-surface interactions would be extremely useful for the design of new catalysts and composites. Here, we demonstrate that the interfacial energy between molten polystyrene (PS) or polyethylene (PE) and various inorganic surfaces prepared via atomic layer deposition (ALD) such as SiO2, TiO2, WO3, and CaCO3 are correlated with the adsorption of small molecules that bear structural similarity to the repeat unit of the two polymers. The interfacial energy inferred from the dynamics of polymer infiltration into ALD-modified porous solids is compared with the heats of adsorption of small molecules on mesoporous silica (SBA-15) modified with ALD. Both our experimental and computational results suggest a strong correlation between the polymer-solid interfacial energy and the adsorption strengths of their respective small molecules on the same surface. These results highlight that even though there are no specific modes of interaction between the polymers and the inorganic surfaces, their interaction energies vary significantly and are dominated by differences in the enthalpic interactions between each repeat unit and the solid surface. Besides providing a novel method for measuring the polymer-solid interaction, this work bridges the gap between the behavior of macromolecules on solid surfaces and the adsorption properties of small gas molecules. This understanding will have important implications for designing new catalysts for polymer upcycling and composite membranes for gas and potentially polymer separation.

Fabrication of granular MOF@γ-Al2O3 composites as promising dual-function adsorbents for the efficient capture of iodine and dyes

As reported herein, we have designed an effective way to achieve in-situ loading of metal-organic frameworks (MOFs) into the pores of activated γ-Al2O3 particles to prepare low-cost, easy-to-obtain and high-yield granular MOFs composites (GMCs). MOF-5, ZIF-8, Ni-BTC, and Co-BTC have been selected to prepare GMCs via in-situ synthesis methods, thereby leading to the GMCs MOF-5-X@γ-Al2O3, ZIF-8-X@γ-Al2O3, Ni-BTC-X@γ-Al2O3, and Co-BTC-X@γ-Al2O3 (X = NO3 or OAc), respectively. The physical and chemical properties of the as-prepared MOF@γ-Al2O3 GMCs were characterized in detail. The results show that MOF-5-X@γ-Al2O3 and ZIF-8-X@γ-Al2O3 exhibit selective adsorption behavior for anionic dye. The adsorption capacities of MOF-5-X@γ-Al2O3 are 1388.01 mg g−1 (for CR and X = NO3), 1431.25 mg g−1 (for CR and X = OAc), 406.50 mg g−1 (for MO and X = NO3), and 234.16 mg g−1 (for MO and X = OAc), respectively, while the adsorption capacities of ZIF-8-X@γ-Al2O3 are 1426.85 mg g−1 (for CR and X = NO3), 1543.91 mg g−1 (for CR and X = OAc), 477.03 mg g−1 (for MO and X = NO3), and 451.02 mg g−1 (for MO and X = OAc), respectively. Moreover, ZIF-8-X@γ-Al2O3 has high adsorption performance for iodine molecules in solution, and the adsorption capacity reaches 630.63 mg g−1 for ZIF-8-NO3@γ-Al2O3 and 583.92 mg g−1 for ZIF-8-OAc@γ-Al2O3, respectively. This method is universal and can be used as an effective approach to prepare GMCs. In addition, the materials prepared by this method can be widely used in the adsorption of small molecules.

Adsorption of a photoresponsive surfactant at the water–quartz interface: The role of UV irradiation and cucurbit[7]uril

It is a challenge to develop a method of controlling the adsorption of small molecules at different interfaces. Here, we report the photocontrolled adsorption of a surfactant containing an azobenzene group (AZO) at the aqueous solution–quartz interface. The adsorption of the surfactant decreases at the interface and the corresponding adsorption layer becomes more rigid after UV irradiation. In addition, the adsorption of the surfactant at the interface is also decreased by addition of cucurbit[7]uril (Q[7]) due to the host–guest interaction between Q[7] and the surfactant. Adsorption of surfactant is stronger at the aqueous solution–quartz interface than at the aqueous solution–air one. The aqueous solution–quartz interfacial tension (γsl) of the surfactant is decreased by using UV irradiation or Q[7]. The adsorption mechanisms of the surfactant were investigated. Our study provides the methods to control the adsorption of the small molecules at the aqueous solution–solid interface.

Nickel–cobalt oxides decorated Chitosan electrocatalyst for ethylene glycol oxidation

A composite of NiCo2O4 modified electrocatalyst is prepared to enhance the ethylene glycol electrooxidation. Chitosan matrix is used to improve the activity and adsorption ability of the surface to enhance ethylene glycol conversion. A Comparative study is investigated between pristine NiCo2O4 and Chitosan-modified spinel oxide to evaluate the synergistic effect between spinel oxide and chitosan. The composite is studied in an alkaline solution using electrochemistry techniques. The electrochemical activity towards ethylene glycol electrooxidation is studied as a function of anodic oxidation current density. Thus, the oxidation current values for NiCo2O4 and NiCo2O4@Chitosan in 1.0 M EG and 1.0 M KOH are 36 and 42 mA cm−2, respectively. The long-term stability of the electrode is measured by constant potential chronoamperometry. Kinetic parameters like diffusion coefficient, Tafel slope, surface coverage, and transfer coefficient are calculated. The density-functional theory estimates the adsorption of small molecules like ethylene glycol, urea, and carbon monoxide. The adsorption energy is studied on the top site of Ni and Co atoms of NiCo2O4. Forcite model is used to study the interaction between spinel oxide and chitosan. The energy calculation assumes that chitosan is adsorbed on the spinel oxide surface and enhances chitosan's ability for the adsorption of small molecules.

Adsorption of small gas molecules onto the two-dimensional Janus SnSSe monolayer

First-principles electronic structure calculations under density functional theory (DFT), carbon monoxide (CO), nitrogen monoxide (NO), nitrogen dioxide (NO2), ammonia (NH3), and oxygen gas (O2) has been studied to explain the small gas detection capabilities onto the two-dimensional (2D) Janus SnSSe monolayer considering for each different sites. By including van der Waals (vdW) interactions between gas molecules and SnSSe, we have found that NO, NO2 and NH3 from these proposed molecules could be strongly adsorbed on the SnSSe monolayer with large adsorption energies. The charge transfer variation of electronic structures and the partial density of states are discussed. Thus, our results for the potential applications of the SnSSe monolayer in gas sensing provide a theoretical basis as well as an important explanation for the experimental findings.

Dispersion interactions with analytes at the center of graphene nanoflakes turn into electrostatic at the edge

Adsorption of small gaseous molecules on the center and edges of polycyclic aromatic hydrocarbons is studied through density functional theory calculations. The choice of selected functional for the study is based on a benchmarking, where 37 functionals are evaluated at low cost basis set against high level DFT SAPT calculations for adsorption of water molecule on coronene and hexabenzocoronene. After benchmarking, the detailed analysis is performed for the adsorption of H2S, H2O, NH3, CH3OH, HCN, H2O2 and NH2NH2 on coronene at its center and edges. The coronene is chosen to better elucidate the edge effect on the adsorption of analytes. All of the studied analytes are physiosorbed on coronene with adsorption energies ranging from 1 to 6 kcal mol−1. These complexes are stabilized by X-H---π interactions between analytes and coronene surface. The SAPT0 analysis reveals that the X-H---π interactions at the center (non-edge) position of coronene are dominated by dispersion interaction whereas the similar interactions at the edges are dominated by electrostatic interactions. The change from dispersion to electrostatic on edges is attributed to polarization of the systems by C–H polarity differences. The complexes having lone pair---π interactions have unexpectedly repulsive electrostatic interactions in H2S@GNF and NH3@GNF complexes. Electronic properties reveal that coronene surface is highly selective for hydrazine whereas adsorption of other analytes does not bring any significant changes in the electronic structure of coronene. The high selectivity of coronene for NH2NH2 is also evident from the redistribution of densities in frontier molecular orbitals. For NH2NH2@GNF complexes, the HOMOs are present on hydrazine whereas LUMOs are present in coronene. For other analytes, HOMOs and LUMOs are present merely on graphene nanoflake. This high sensitivity of coronene for hydrazine is due to better overlap of frontier molecular orbitals of analyte with coronene.

Photo-Enhanced Chemo-Transistor Platform for Ultrasensitive Assay of Small Molecules.

Compared with traditional assay techniques, field-effect transistors (FETs) have advantages such as fast response, high sensitivity, being label-free, and point-of-care detection, while lacking generality to detect a wide range of small molecules since most of them are electrically neutral with a weak doping effect. Here, we demonstrate a photo-enhanced chemo-transistor platform based on a synergistic photo-chemical gating effect in order to overcome the aforementioned limitation. Under light irradiation, accumulated photoelectrons generated from covalent organic frameworks offer a photo-gating modulation, amplifying the response to small molecule adsorption including methylglyoxal, p-nitroaniline, nitrobenzene, aniline, and glyoxal when measuring the photocurrent. We perform testing in buffer, artificial urine, sweat, saliva, and diabetic mouse serum. The limit of detection is down to 10-19 M methylglyoxal, about 5 orders of magnitude lower than existing assay technologies. This work develops a photo-enhanced FET platform to detect small molecules or other neutral species with enhanced sensitivity for applications in fields such as biochemical research, health monitoring, and disease diagnosis.

Weakened crystalline SnNb2O6 for enhanced performance in photocatalytic H2 production and CO2 reduction.

Low crystalline photocatalysts with the unsaturated active site, such as oxygen vacancy (Ov), is reported to exhibit enhanced adsorption and activation of oxygen-containing small molecules, such as H2O and CO2, thus boosting the activity in photocatalytic H2 evolution and CO2 reduction. However, numerous low-crystalline photocatalysts show unsatisfactory stability due to the easily repaired surface Ov. Herein, three SnNb2O6 with different crystallinity were prepared by hydrothermal approach with similar precursors. Compared with bulk SnNb2O6 and ultra-thin layered SnNb2O6, low-crystalline SnNb2O6 (SNA) exhibits optimal visible-light-driven evolution rates of H2 (86.04 μmolg-1h-1) and CO from CO2 (71.97 μmolg-1h-1), which is mainly ascribed to the fast separation of the photogenerated carriers and enhanced photoreduction power caused by the surface Ov. More importantly, the sharp decrease of photocatalytic activity of SNA after seven cycles is well restored by the hydrothermal treatment of recycled SNA, ascribed to the reactivated surface Ov with the recovered low-crystalline structure. These works thus offer a promising strategy for developing low-crystalline and amorphous photocatalysts with high activity and stability.

High-silica FAU zeolite through controllable framework modulation for VOCs adsorption under high humidity

Although FAU zeolites have been widely used as absorbents for volatile organic compounds (VOCs) removal, preparation of high-silica FAU zeolite to expand its application under high humidity is still a big challenge. Here, two high-silica FAU zeolites were successfully prepared through the controllable framework modulation strategy. By carefully matching the degrees of dealumination and Si-insertion, the zeolite (FAU-H) with an ultra-high SiO2/Al2O3 ratio of 957 was obtained. FAU-H exhibited similar high adsorption capacities of VOCs (e.g. m-xylene and toluene) under dry and humid conditions, more importantly, its adsorption capacity of m-xylene was 25% higher than the industrial high-silica FAU zeolite (HSZ-390HUA) from Tosoh Corporation. When the dealumination degree was mismatched with that of Si-insertion, imperfect FAU-M (SiO2/Al2O3 = 108) with the existence of some defect sites was obtained that becomes a good candidate for the adsorption removal of small VOCs molecules (e.g. isopropanol). The moderate interaction between VOCs and zeolite framework is proved a key factor for small molecules adsorption on basis of the DFT calculations. Moreover, the fitted kinetic models, desorption tests, and adsorption−desorption cycling tests proved the good regenerability of FAU-H and FAU-M. Therefore, the proposed high-silica FAU zeolites are promising adsorbents for VOCs removal.

The state of art in the prediction of efficiency and modeling of the processes of benzene removal from water environment

Adsorption of small molecules on nanomaterials emerged as an interesting research area in several fields. Nanomaterials can be used in the removal of hazardous pollutants or the collection of industrial reaction products from water. In this work, the adsorption of benzene (BEN) molecules on the carbon nitride (CN) and functionalized CN nanosheets is investigated using molecular dynamics (MD), well-tempered metadynamics simulation, and quantum mechanical calculations. The obtained results showed that the functionalization of CN with polyethylene glycol (PEG) increased the adsorption of BEN at low concentrations. While in high concentrations, PEG covers the CN surface and prevents the absorption of some benzene molecules. Free energy calculation confirmed that the benzene molecule does not face any significant energy barriers to adsorb on pristine CN. At the most stable state, the free energy value of the PEG-CN system is around −261 kJ/mol, which is about 20 kJ/mol more than the free energy of the CN system.

Carbon dioxide reduction mechanism via single‐atom nickel supported on graphitic carbon nitride

AbstractIn many photocatalytic reaction paths, the breaking of the first CO bond in a CO2 molecule is often the key step that becomes the rate‐controlled reaction step. In this paper, a graphitic carbon nitride (g‐C3N4) supported nickel single‐atom catalyst (Ni@g‐C3N4) was successfully constructed, and the mechanism of CO2 catalytic reduction was systematically studied based on density functional theory (DFT). The introduction of nickel promotes the adsorption of small molecules, especially for the CO2 activation. According to density of states (DOS) and frontier orbital analysis, the photogenerated carriers tend to jump from nitrogen atoms to carbon atoms, forming an electron transfer in real space, after g‐C3N4 is excited by light. With the appearance of nickel‐doped levels, the DOS of Ni@g‐C3N4 is no longer symmetric with respect to the spin up and down, especially around the original band gap of g‐C3N4. Single‐atom nickel has abundant frontier orbitals and high activity and is a favourable place for chemical reactions. The presence of surface hydrogen can promote the recovery of CO2, and the energy barrier of Ni@g‐C3N4 with hydrogen is only 15% of the clean g‐C3N4 surface. This paper provides a new idea for the development of efficient single‐atom catalysts for CO2 reduction.

Oriented adsorption and efficient sensing of NO2 on MoSe2 monolayer: a comparative study with WSe2 monolayer

Oriented adsorption is very rare on two-dimensional inorganic thin layers. Based on preliminary study, density functional theory (DFT) was used to explore the adsorption and sensing behavior of NO2 on MoSe2 perfect and defective monolayers including selenium vacancy (VSe), molybdenum vacancy (VMo), and antisite defect of selenium on molybdenum site (SeMo) by large-scale sampling. The adsorption energy can reach 0.29 eV with 0.182 e charge transfer on the perfect monolayer. The adsorption ability is improved largely on VSe, VMo, and SeMo monolayers (3.27, 0.93, and 1.20 eV) with considerable charge transfer (0.583, 0.152, and 0.139 e, respectively), demonstrating the potential of MoSe2 monolayers as NO2 sensing materials. Meanwhile, similar to WSe2 monolayer, oriented adsorption of NO2 is disclosed. NO2 molecule extends mainly along the Se–Mo–Se trough and the Se–Mo bond on all the four MoSe2 monolayers. Whereas, the oriented adsorption ability is weaker than the WSe2 monolayer, which can be confirmed by the relatively small proportion of oriented adsorption conformations. This kind of double oriented adsorption behavior (vertical adsorption and adsorption along specific direction of the two-dimensional material) was considered to be due to the good polarity match between molecule and monolayer. Molecular dipole moment and material bond population are believed to be two important parameters that determine the oriented adsorption capacity of molecular-material systems. The successive discovery of the unique oriented adsorption and the deepening of understanding provide chance for molecular design of oriented adsorption of inorganic small molecules on two-dimensional layered materials. The strong dissociation ability of the anionic vacancy monolayer to NO2 molecule indicates that MoSe2 monolayer has a very high adsorption, capture, and activation potential for nitrogen oxides. Comparative study proved that the Mo site activity was less than the W site activity on the perfect monolayer, and defects could help the Mo site activity overtake. These findings provide pivotal guidance for creating advanced surface regulated electronic systems, such as sensors.

Spectral properties of B40 enhanced by small molecule adsorption.

The luminescence characteristics of small molecule excited B40 have not been studied yet, and it may have a potential application value in quantum dot luminescence. Herein, the adsorption and fluorescence emission spectra of small molecules (pyridine, pyrazine and benzene) adsorbed on B40 are studied using first-principles. The results show that the absorption of pyridine and pyrazine on B40 can form stable chemisorption structures pyridine-B40 and pyrazine-B40, while benzene adsorption can form physisorption structure benzene-B40. Moreover, the adsorbed pyridine can enhance the intensity of emission spectra of B40. And the pyrazine adsorbed can obviously enhance the intensity of absorption and emission spectra of B40 and cause the spectra to redshift to the visible light range. And the adsorption of benzene has almost no enhancement effect on absorption and emission spectra of B40. In addition, the influence of different computational basis sets on spectra characteristics has also been discussed and the results show that the main peaks of absorption and emission spectra calculated by the diffuse function augmented basis sets are redshifted relatively. This finding provides a strategy for quantum dot luminescence and a theoretical reference for experimental research.

Amorphous tetrazine–triazine-functionalized covalent organic framework for adsorption and removal of dyes

A new amorphous tetrazine–triazine-functionalized covalent organic framework (TzTPT-COF) was developed and employed as a porous adsorbent for the static and dynamic adsorption of small dye molecules, especially methylene blue (MB).

Revisiting Competitive Adsorption of Small Molecules in the Metal–Organic Framework Ni-MOF-74

To precisely evaluate the potential of metal-organic frameworks (MOFs) for gas separation and purification applications, it is crucial to understand how various molecules competitively adsorb inside MOFs. In this paper, we combine in situ infrared spectroscopy with ab initio calculations to investigate the mechanisms associated with coadsorption of several small molecules, including CO, NO, and CO2 inside the prototypical structure Ni-MOF-74. Surprisingly, we find that the displacement of CO bound inside Ni-MOF-74 (binding energy of 53 kJ/mol) is readily driven by CO2 exposure, even though CO2 has a noticeably weaker binding energy of only 41 kJ/mol; meanwhile, the significantly more strongly binding NO molecule (90 kJ/mol) is not able to easily displace bound CO inside Ni-MOF74. These results show that single-phase binding energies of a molecule inside the MOF cannot completely describe their interaction with the MOF in the presence of other guest molecules. We unveil many crucial factors, such as the kinetic barrier, partial pressure, secondary binding sites, and guest-host/lateral interactions that control the coadsorption process and, combined with the binding energy, are better descriptors of the behavior and adsorption of gas mixtures inside MOFs.

Reinforced Photogenerated Electrons in Few-Layer C3N5 for Enhanced Catalytic NO Oxidation and CO2 Reduction

Two-dimensional (2D) polymer carbon nitrides are cutting-edge environment-friendly photocatalysts relying on their extraordinary properties of cost-effectiveness, low toxicity, visible-light response, and chemical stability. Here, we report few-layer C3N5 with a thickness of around 1.2 nm as a case study, whose photogenerated carriers’ dynamics achieve a significant increase proven by the transient diffuse reflectance spectra. In addition, few-layer C3N5 changes to mainly exhibit the behavior of photogenerated electrons in comparison to bulk C3N5, whose lifetime extends 3.25-fold and is even 3.72-fold of that for g-C3N4. Density functional theory calculations further verify the superior adsorption and activation of small molecules of NO, O2, and CO2 over few-layer C3N5. The abovementioned unique intrinsic properties endow few-layer C3N5 with a significantly enhanced photocatalytic capability in air NO oxidation and CO2 reduction with respect to bulk C3N5 and traditional C3N4. This work may help in developing efficient 2D metal-free catalysts for photocatalytic applications.

Modular conductive MOF-gated field-effect biosensor for sensitive discrimination on the small molecular scale

Field-effect transistors (FETs) are a promising transducer for biosensors owing to their drastic signal amplification, showing a high sensitivity enough to detect ultra-low concentrations of small-molecular biomarkers in biofluids. However, the discrimination of small molecules from their structural analogues in biofluids using a FET is challenging; because of the 1) Debye screening in high-ionic-strength conditions, 2) few or no charges of the analytes, and 3) lack of target-specific receptors for small molecules. To overcome these limitations, we report a modular conductive MOF (c-MOF)-gated FET biosensor array that discriminates small-molecular neurotransmitters in biofluids. Adsorption and oxidation of analytes inside the pore of catalytic c-MOF films allow the sensitive detection of small molecules close to the clinically relevant concentration, regardless of the ionic strength of the media. The hierarchical screening ability of c-MOF attributed to their tunable pore size, surface charge, and host–guest interactions induces differentiated adsorption of small molecules. The cross-reaction intended by c-MOF design of our biosensor could provide discriminatory information of each neurotransmitter corresponding to the differences of one functional group in the molecule. Using our system, we also demonstrate discrimination capability under the interference of biologically relevant substances and artificial cerebrospinal fluid.