Metallotetrapyrazinoporphyrazine-based conductive covalent-organic frameworks for the ultrasensitive detection and rapid differentiation of analytes

Abstract

The present disclosure pertains to a composition that includes a covalent-organic framework. The covalent-organic framework includes: (1) a plurality of first atoms; (2) a plurality of second atoms; and (3) a plurality of tetrapyrazinoporphyrazine -based ligands, where each of the tetrapyrazinoporphyrazine-based ligands is coordinated with a first atom and a second atom. The present disclosure also pertains to methods of detecting analytes in a sample by (1) associating the sample with the composition that is in the form of a sensor; (2) detecting a change in a property of the sensor; and (3) correlating the change in the property to the presence of the analyte.

Description

PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003TITLEMETALLOTETRAPYRAZINOPORPHYRAZINE-BASED CONDUCTIVE COVALENT- ORGANIC FRAMEWORKS FOR THE ULTRASENSITIVE DETECTION AND RAPID DIFFERENTIATION OF ANALYTESSTATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0001] This invention was made with government support under R35GM138318, awarded by the National Institutes of Health, and 1945218, awarded by the National Science Foundation. The government has certain rights in the invention.CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 681,605, filed on August 9, 2024. The entirety of the aforementioned application is incorporated herein by reference.BACKGROUND

[0003] Current methods and systems for detecting analytes from samples have numerous limitations. The embodiments of the present disclosure aim to address the aforementioned limitations.SUMMARY

[0004] In some embodiments, the present disclosure pertains to a composition that includes a covalent- organic framework. In some embodiments, the covalent-organic framework includes: (1) a plurality of first atoms; (2) a plurality of second atoms; and (3) a plurality of tetrapyrazinoporphyrazine-based ligands, where each of the tetrapyrazinoporphyrazine-based ligands is coordinated with a first atom and a second atom.

[0005] In some embodiments, the compositions of the present disclosure may be components of an electrode. In some embodiments, the covalent-organic frameworks of the present disclosure are a component of a sensor.

[0006] Additional embodiments of the present disclosure pertain to methods of detecting analytes in a sample. In some embodiments, such methods include: (1) associating the sample with a composition of the present disclosure, where the composition is in the form of a sensor; and (2) detecting the presence of the analyte from the sample. The detection generally includes: (a) detecting a change in a property of the sensor, and (b) correlating the change in the property to the presence of the analyte.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003BRIEF DESCRIPTION OF DRAWINGS

[0007] FIG. 1 illustrates a method of detecting analytes from a sample in accordance with various embodiments of the present disclosure.

[0008] FIGS. 2A-2D illustrate a synthetic scheme for the synthesis of metallo- tetrapyrazinoporphyrazine (MTPz)-Cu-metal organic frameworks (MOFs), where M = Co, Ni, or Cu (FIG. 2A); experimental powder X-ray diffraction (PXRD) diffraction patterns of the three MTPz- Cu-Metal-Organic Frameworks (MOFs) compared to the simulated eclipsed AA stacking and the staggered ABAB stacking (FIG. 2B); and scanning electron microscopy (SEM) images (FIG. 2C) and transmission electron microscopy (TEM) images (FIG. 2D) of CoTPz-Cu-MOF, NiTPz-Cu- MOF, and CuTPz-Cu-MOF, respectively.

[0009] FIGS. 3A-3L illustrate average sensing responses of CoTPz-Cu-MOF, NiTPz-Cu-MOF, and CuTPz-Cu-MOF towaids H2S (FIGS. 3A-FIG. 3C), NH3(FIGS. 3D-FIG. 3F), SO2(FIGS. 3G-FIG. 31), and NO (FIGS. 3J-FIG. 3L) at the different concentrations (40, 20, 10, 5, and 1 ppm). The shaded region indicates the time of exposure to each gaseous analyte.

[0010] FIGS. 4A-4D illustrate bar graphs showing the normalized response values of CoTPz-, NiTPz- , and CuTPz-Cu-MOFs at 10 minutes of exposure towards H2S (FIG. 4A), NH3 (FIG. 4B), SO2(FIG. 4C), and NO (FIG. 4D).

[0011] FIGS. 5A-5D illustrate diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) difference spectra recorded at 10 minutes of exposure for CoTPz-, NiTPz-, and CuTPz-Cu-MOFs towards 1000 ppm of H2S (FIG. 5A), 1% of NH3 (FIG. 5B), 1% of SO2(FIG. 5C), and 1% of NO (FIG. 5D) in N2.

[0012] FIGS. 6A-6F illustrate preparation of NiTPz-Cu-MOF, NiTPz-Zn-MOF and JLTPz-Cu-MOF, where the product shows the simulated top and side view of eclipsed stacking MOFs (FIG. 6A); experimental and simulated PXRD patterns for NiTPz-Cu-MOF, NiTPz-Zn-MOF and H2TPz-Cu- MOF (FIG. 6B); simulated top and side view of staggered stacking MOF (FIG. 6C); and SEM (top) and TEM (bottom) images for (FIG. 6D) NiTPz-Cu-MOF, (FIG. 6E) NiTPz-Zn-MOF, and (FIG. 6F) H2TPZ-CU-MOF.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0013] FIGS. 7A-7F illustrate mean normalized response (-AG / Go) of NiTPz-Cu-MOF devices (n = 3) to six gaseous analytes at 1 ppm over 5 min (FIG. 7A; inset: magnified view excluding NO), and NO concentrations from 10 to 1000 ppb (FIG. 7B); saturated -AG / Go of NiTPz-Cu-MOF, NiTPz-Zn- MOF, and FLTPz-Cu-MOF to 1 ppm NO in dry N2 (FIG. 7C); -AG / Go of NiTPz-Cu-MOF to 1 ppm NO over five exposure-recovery cycles (FIG. 7D), and 1 ppm NO under different relative humidity levels after 5 min exposure (FIG. 7E); and time-dependent current (green) and average maximum % change per cycle (red bars) of NiTPz-Cu-MOF devices during exposure-recovery cycles in 98% RH nitrogen (FIG. 7F).

[0014] FIGS. 8A-8E illustrate comparison of the PXRD spectra (FIG. 8A), electron paramagnetic resonance (EPR) spectra (FIG. 8B), Cu 2p X-ray photoelectron spectroscopy (XPS) spectra (FIG. 8C), N Is XPS spectra (FIG. 8D), and O ls XPS spectra of the pristine NiTPz-Cu-MOF and NiTPz- Cu-MOF after 2-hour exposure to 1 ppm of NO (FIG. 8E).

[0015] FIGS. 9A-9C illustrate DRIFTS difference spectra of NiTPz-Cu-MOF after continuous exposure to 100 ppm of NO for 15 min, and 1 % NO for 10 min, (FIG. 9A); FT-IR spectrum of NiTPz- Cu-MOF, magnified DRIFTS difference spectra of the aromatic and metal-ligand regions, 500-1300 cm’1, (FIG. 9B); and DRIFTS difference spectra of NiTPz-Cu-MOF, NiTPz-Zn-MOF, NiTPz-(OH)8and FkTPz-Cu-MOF after continuous exposure to 1% NO (balance N2) for 10 min (FIG. 9C).

[0016] FIG. 10 illustrates periodic ribbon model of NiTPz-Cu-MOF, showing Cu(I) edge sites coordinated by EDA that bind NO in a square pyramidal configuration with the Cu-N distance labelled. The simulated NO vibrational frequency of 1685 cm’1is in close agreement with the experimental DRIFTS spectrum.

[0017] FIGS. 11A-12E illustrate a structure and synthetic scheme of CoTPz-Cu-MOF synthesis (FIG. 11A) and PXRD diffraction pattern of CoTPz-Cu-MOF compared to simulated patterns (FIG. 11B); SEM (FIG. 11C) and TEM (FIG. 11D) images of CoTPz-Cu-MOF; and gray value profile of lattice planes from TEM (FIG. HE).PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0018] FIGS. 12A-12F illustrate sensing responses of CoTPz-Cu-MOF at 2, 5, 10, 20, and 40 ppm of SO2 in dry nitrogen (FIG. 12A) and dry air (FIG. 12B); a bar graph comparing reversibility of responses towards different concentrations of SO2 in nitrogen and air atmospheres (FIG. 12C); sensing response vs concentration of SO2 at 2 and 5 min of exposure in dry nitrogen (FIG. 12D) and dry air (FIG. 12E); and initial rate of response (RoR) computed as the slope of the first minute of exposure vs concentration of SO2 in dry N2 and air atmospheres (FIG. 12F).

[0019] FIGS. 13A-13E illustrate sensing responses of CoTPz-Cu-MOF at 2, 5, 10, 20, and 40 ppm of SO2 in air at 98% RH (FIG. 13A) and linear concentration-dependent response at 98% RH in air at 1 and 10 minutes of exposure to SO2 (FIG. 13B); recyclability of response at 10 ppm SO2 for up to 5 times upon exposure for 10 min, followed by recovery for 60 min (FIG. 13C); and maximum values (FIG. 13D) and reversibility (FIG. 13E) of sensing responses towards 10 ppm of SO2 at different %RH in nitrogen and air atmospheres.

[0020] FIGS. 14A-14D illustrate DRIFTS spectra of CoTPz-Cu-MOF upon exposure to 400 ppm of SO2 in dry nitrogen and dry air atmospheres (FIG. 14A); Cu 2p (FIG. 14B), O ls (FIG. 14C), and S 2p (FIG. 14D) high-resolution XPS spectra of CoTPz-Cu-MOF before and after a three-hour exposure to 40 ppm of SO2 in dry N2, dry air, and 98% RH humid air.

[0021] FIGS. 15A-15E illustrate preparation of NiTPz-Co-MOF, the product shows the simulated top and side view of eclipsed stacking MOF (FIG. 15A); experimental and simulated PXRD patterns for NiTPz-Co-MOF (FIG. 15B); simulated top and side view of staggered stacking MOF (FIG. 15C); and SEM (FIG. 15D) and TEM (FIG. 15E) images for NiTPz-Co-MOF.

[0022] FIGS. 16A-16D illustrate Nyquist plots of NiTPz-Co-MOF at different temperatures under 98% RH (FIG. 16A); Arrhenius fitting of temperature-dependent proton conductivity of NiTPz-Co- MOF at 98% RH (FIG. 16B); and thermopower data of NiTPz-Co-MOF@dry (FIG. 16C) and NiTPz- CO-MOF@H2O (FIG. 16D).

[0023] FIGS. 17A-17D illustrate mean normalized response (-AG / Go) of NiTPz-Co-MOF (n = 3): response to four gaseous analytes at 40 ppm under different RH conditions in N2 over 5 minutes of exposure (FIG. 17A); response to 2-40 ppm SO2 (FIG. 17B); response after 1-5 minutes of exposure at varying SO2 concentrations (FIG. 17C); and response to 20 ppm SO2 over six exposure-recovery cycles in 98% RH N2(FIG. 17D).PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0024] FIGS. 18A-18E illustrate PXRD patterns (FIG. 18A), EPR spectra (FIG. 18B), S 2p XPS spectra (FIG. 18C), and N Is XPS spectra (FIG. 18D) of pristine NiTPz-Co-MOF and NiTPz-Co- MOF after exposure to 40 ppm SO2 in 98% RH N2; and DRIFTS difference spectra (FIG. 18E) of NiTPz-Co-MOF during continuous exposure to 1% SO2 in dry N2 for 10 minutes, followed by dry N2 purge for another 10 minutes.DETAILED DESCRIPTION

[0025] It is to be understood that both the foregoing general description and the following detailed description are illustrative and explanatory, and are not restrictive of the subject matter, as claimed. In this application, the use of the singular includes the plural, the word “a” or “an” means “at least one”, and the use of “or” means “and / or”, unless specifically stated otherwise. Furthermore, the use of the term “including”, as well as other forms, such as “includes” and “included”, is not limiting. Also, terms such as “element” or “component” encompass both elements or components comprising one unit and elements or components that include more than one unit unless specifically stated otherwise.

[0026] The section headings used herein are for organizational purposes and are not to be construed as limiting the subject matter described. All documents, or portions of documents, cited in this application, including, but not limited to, patents, patent applications, articles, books, and treatises, are hereby expressly incorporated herein by reference in their entirety for any purpose. In the event that one or more of the incorporated literature and similar materials defines a term in a manner that contradicts the definition of that term in this application, this application controls.

[0027] Analyte detection from various environments is critical in numerous industries. For instance, the detection of gaseous pollutants, such as hydrogen sulfide (H2S), ammonia (NH3), sulfur dioxide (SO2), and nitric oxide (NO), is critically important for ensuring environmental and industrial safety. These gases can be released into the environment at high concentrations anthropogenically from the combustion of fossil fuels for oil refinery, electrical power generation, mass transportation, or industrial operations. They can also be emitted through natural processes, such as volcanic eruptions, swamps, decomposition of organic matter, and atmospheric photochemical reactions. The hazards that these gases pose to human health and the environment necessitate the development of low-power, rapid, reliable, and accurate sensors capable of continuous, on-site, and real-time monitoring of their concentrations in susceptible locations.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0028] However, current methods and systems for detecting analytes have numerous limitations. For instance, current methods for the detection of toxic gases constitute electrochemical, colorimetric, catalytic, and infrared based sensors. Yet, these technologies arc often limited by long analysis times, discontinuous monitoring capabilities, bulky instrumentation, high-power and / or temperature consumption, and the reliance on trained technicians, all of which compromises their utility and portability.

[0029] Alternatively, chemiresistive sensing serves as an effective method for the sensitive, selective, stable, portable, and low-power detection of H2S, NH3, SO2, and NO, ensuring environmental protection and industrial welfare. Recent advancements in chemiresistive sensor technologies have established promising utility of different semi-conducting materials including metal oxides, conducting polymers, carbon nanotubes, conductive covalent-organic frameworks (cMOFs), and covalent organic frameworks (COFs). These materials offer promising sensing applications in terms of robust, sensitive, and rapid detection of these gases.

[0030] Particularly, cMOFs allow the fabrication of sensing devices that require low-power consumption, sustain miniaturization, and provide tunable selectivity through simple nanostructural variations. Therefore, incorporating several devices into an array of chemiresistive sensors allows the combination of responses from multiple sensors through multivariate analyses to generate dimensionally unique recognizable pattern outputs to complex analyte mixtures.

[0031] Preceding reports have integrated cMOFs based on triphenylene, metallophthalocyanine (MPc), and metallonaphthalocyanine (MNPc) linkers, into chemiresistive sensing arrays for the distinction of small toxic gases and volatile organic compounds. However, these cMOFs can have extended or delayed response times and show similar responses towards a particular gaseous analyte, constricting the rapid differentiation of particular concentrations of analytes in their corresponding arrays.

[0032] In sum, current methods and systems for detecting analytes from samples have numerous limitations. The embodiments of the present disclosure aim to address the aforementioned limitations.

[0033] Compositions

[0034] In some embodiments, the present disclosure pertains to a composition that includes a covalent- organic framework. In some embodiments, the covalent-organic framework includes: (1) a plurality of first atoms; (2) a plurality of second atoms; and (3) a plurality of tetrapyrazinoporphyrazine-basedPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 ligands, where each of the tetrapyrazinoporphyrazine-based ligands is coordinated with a first atom and a second atom. As set forth in more detail herein, the compositions of the present disclosure can include numerous structures and components.

[0035] Tetrapyrazinoporphyrazine-based ligands

[0036] The covalent-organic frameworks of the present disclosure can include various tetrapyrazinoporphyrazine-based ligands. For instance, in some embodiments, the tetrapyrazinoporphyrazine-based ligands include, without limitation, octahydroxytetrapyrazinoporphyrazine, Cobalt(II) octahydroxytetrapyrazinoporphyrazine, Copper(II) octahydroxytetrapyrazinoporphyrazine, Nickel (II) octahydroxytetrapyrazinoporphyrazine, Zinc (II) octahydroxy tetrapyrazinoporphyrazine, or combinations thereof. In some embodiments, the tetrapyrazinoporphyrazine-based ligands include octahydroxytetrapyrazinoporphyrazine. In some embodiments, the tetrapyrazinoporphyrazine -based ligands are in free base form. In some embodiments, the tetrapyrazinoporphyrazine-based ligands include a fully conjugated and planar macrocyclic core containing four pyrazine units. In some embodiments, such a structure provides multiple electron-withdrawing nitrogen atoms, thereby enhancing the oxidation resistance of the resulting MOF and improving the reversibility and reusability in NO detection.

[0037] Atoms

[0038] The covalent-organic frameworks of the present disclosure can include various first and second atoms. For instance, in some embodiments, the first atoms and the second atoms each independently include, without limitation, non-metallic atoms, divalent metals, transition metals, hydrogen, iron, nickel, copper, cobalt, zinc, manganese, platinum, palladium, gold, bismuth, chromium, magnesium, tin, or combinations thereof. In some embodiments, the first atoms and the second atoms each independently include, without limitation, hydrogen, nickel, copper, cobalt, zinc, or combinations thereof. In some embodiments, the first atoms and the second atoms each independently include metals. In some embodiments, the metals includes, without limitation, nickel, copper, cobalt, zinc, manganese, platinum, palladium, gold, bismuth, chromium, magnesium, tin, or combinations thereof.

[0039] In some embodiments, the first atom is cobalt. In some embodiments, the second atom is zinc. In some embodiments, the first atom is nickel, and the second atom is copper. In some embodiments, the first atom is nickel, and the second atom is cobalt. In some embodiments, the first atom is nickel, and the second atom is zinc. In some embodiments, the first atom is cobalt, and the second atom isPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 copper. In some embodiments, the first atom is cobalt, and the second atom is nickel. In some embodiments, the first atom is cobalt and the second atom is zinc. In some embodiments, both the first and second atom is copper. In some embodiments, both the first and second atom is nickel. In some embodiments, both the first and second atom is cobalt. In some embodiments, both the first and second atom is zinc.

[0040] In some embodiments, the second atoms are different from the first atoms. In some embodiments, the second atoms are the same as the first atoms. In some embodiments, the first atom is nickel. In some embodiments, the second atom is copper.

[0041] Structures

[0042] The covalent-organic frameworks of the present disclosure can include various structures and arrangements. For instance, in some embodiments, the covalent-organic framework is in the form of a conductive and interconnected network. In some embodiments, the covalent-organic framework is in two-dimensional form. In some embodiments, the covalent-organic framework is in the form of a crystalline framework. In some embodiments, the covalent-organic framework is in the form of a square lattice. In some embodiments, the square lattice includes a plurality of square apertures.

[0043] In some embodiments, the covalent-organic framework is in three-dimensional form. In some embodiments, the covalent-organic framework is in the form of nanorods. In some embodiments, the covalent-organic framework is in the form of an array on a surface.

[0044] In some embodiments, the tetrapyrazinoporphyrazine-based ligands are bridged to one another through various linkages. For instance, in some embodiments, the tetrapyrazinoporphyrazine-based ligands are bridged to one another through first atoms and second atoms. In some embodiments, the tctrapyrazinoporphyrazinc-bascd ligands arc bridged to one another through mctal-bis(dioxolcnc) linkages. In some embodiments, the first atoms are coordinated with a central region of the tetrapyrazinoporphyrazine-based ligands, and the second atoms are coordinated with one or more peripheral regions of the tetrapyrazinoporphyrazine-based ligands. In some embodiments, the first atoms and the second atoms provide dual active-sites for chemical detection.

[0045] The covalent-organic frameworks of the present disclosure may have various surface areas. For instance, in some embodiments, the covalent-organic frameworks of the present disclosure may have a specific surface area in a range of about 200 to 600 m2 / g, about 250 to 550 m2 / g, about 300 toPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003500 m2 / g, or about 350 to 450 nr / g, based on their Brunauer-Emmett-Teller (BET) N sorption isotherms.

[0046] Electronic components

[0047] In some embodiments, the compositions of the present disclosure may be components of an electrode. For instance, in some embodiments, the covalent-organic frameworks of the present disclosure are associated with at least one electrode component. In some embodiments, the electrode component includes an electrode surface. In some embodiments, the covalent-organic frameworks of the present disclosure serve as an electrode surface.

[0048] In some embodiments, the covalent-organic frameworks of the present disclosure are a component of a sensor. In some embodiments, the covalent-organic frameworks of the present disclosure are a component of a dosimeter.

[0049] In some embodiments, the covalent-organic frameworks of the present disclosure are associated with a textile. In some embodiments, the textile includes a plurality of fibers and a plurality of pores. In some embodiments, the covalent-organic frameworks of the present disclosure are associated with the fibers of the textile.

[0050] In some embodiments, the covalent-organic frameworks of the present disclosure are a component of a personal protective equipment. In some embodiments, the covalent-organic frameworks of the present disclosure are a component of an air quality monitoring system.

[0051] Methods of detecting analytes in a sample

[0052] Additional embodiments of the present disclosure pertain to methods of detecting analytes in a sample. In some embodiments illustrated in FIG. 1, such methods include: associating the sample with a composition of the present disclosure, where the composition is in the form of a sensor (step 10); and detecting the presence of the analyte from the sample. The detection generally includes: detecting a change in a property of the sensor (step 12), and correlating the change in the property to the presence of the analyte (step 14). As set forth in more detail herein, the analyte detection methods of the present disclosure can include numerous embodiments.

[0053] Changes in property

[0054] The analyte detection methods of the present disclosure may detect and correlate various property changes of a sensor to the presence of an analyte. In some embodiments, the correlationPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 includes comparing the properties of the sensor to properties of the sensor in response to association with known analytes.

[0055] In some embodiments, a positive percentage change in the property of the sensor is correlated to the presence of the analyte. In some embodiments, a negative percentage change in the property of the sensor is correlated to the presence of the analyte.

[0056] In some embodiments, the change in the property of the sensor includes a change in normalized conductance over time ( G / Go). In some embodiments, a decrease in normalized conductance over time is correlated to the presence of the analyte. In some embodiments, an increase in normalized conductance over time is correlated to the presence of the analyte. In some embodiments, a decrease or an increase in normalized conductance may depend on the type of analyte, the type of first atom, the type of second atom, the type of covalent-organic frameworks, or combinations thereof.

[0057] In some embodiments, the change in the property of the sensor includes a change in current over time. In some embodiments, an increase in current over time is correlated to the presence of the analyte. In some embodiments, a decrease in current over time is correlated to the presence of the analyte. In some embodiments, a decrease or an increase in current over time may depend on the type of analyte, the type of first atom, the type of second atom, the type of covalent-organic frameworks, or combinations thereof.

[0058] Analytes

[0059] The methods of the present disclosure may be utilized to detect various types of analytes. For instance, in some embodiments, the analyte includes, without limitation, gases, ketones, alcohols, aromatic compounds, volatile organic compounds, water, neurotransmitters, hormones, proteins, sugars, metal ions, ionizing radiation, toxic gases, NO, CO, H2S, SO2, NH3, H2O, NO2, CO2, or combinations thereof. In some embodiments, the analyte includes, without limitation, NO, H2S, SO2, CO, NH3, NO2, CO2, or combinations thereof.

[0060] In some embodiments, the methods of the present disclosure may be utilized for the selective detection of analytes. For instance, in some embodiments, the methods of the present disclosure may be utilized for the selective detection of NO. In some embodiments, NO may be detected selectively over H2S, SO2, CO, NH3, CO2 and NO2. In some embodiments for detecting NO selectively (e.g., over H2S, SO2, CO, NH3, CO2, and NO2, in the covalent-organic framework), the first atom is nickel, and the second atom is copper. In some embodiments, the NO may be detectable with a limit ofPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 detection of less than 100 ppt, less than 10 ppt, less than 1 ppt, or at 0.47 ppt. In some embodiments, SO2 may be detected in, optionally humid, air, optionally using a covalent-organic framework wherein the first atom is cobalt, and the second atom is copper. In some embodiments, the SO2 may be detectable with a limit of detection of less than 100 ppb, less than 10 ppb, or at 3 ppb.

[0061] In some embodiments, the methods of the present disclosure may be utilized for the differential detection of analytes. For instance, in some embodiments, a positive percentage change in the property of the sensor may be correlated to at least one of H2S, SO2, CO, and NH3. In some embodiments, a negative percentage change in the property of the sensor may be correlated to at least one of NO and NO2.

[0062] In some embodiments, the methods of the present disclosure may be utilized to detect analytes at low concentrations. For instance, in some embodiments, analytes may be detectable at less than 40 parts per million (ppm). In some embodiments, analytes may be detectable at less than 1 part per million (ppm). For instance, in some embodiments, analytes may be detectable at less than 100 parts per billion (ppb). In some embodiments, analytes may be detectable at less than 1 part per billion (ppb). In some embodiments, analytes may be detectable at less than 100 parts per trillion (ppt). In some embodiments, analytes may be detectable at less than 10 parts per trillion (ppt). In some embodiments, analytes may be detectable at less than 1 pail per trillion (ppt). In some embodiments, analytes may be detectable at 0.47 parts per trillion (ppt).

[0063] In some embodiments, the exposure of analyte samples to the compositions of the present disclosure results in the reversible association of any analyte in the sample with the composition. In some embodiments, the association also results in the capture of the analytes by the sensor. In some embodiments, the methods of the present disclosure also include a step of releasing the analyte from the sensor.

[0064] Samples

[0065] Analytes may be associated with the compositions of the present disclosure in various forms. For instance, in some embodiments, a sample may be in gaseous form. In some embodiments, a sample may be in liquid form. In some embodiments, a sample may be in solid form.

[0066] In some embodiments, a sample may be derived from an environment. In some embodiments, a sample may represent an environment. In some embodiments, the sample may include, without limitation, an air stream, an atmosphere, a water source, a gas source, soil, or combinations thereof.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0067] The samples of the present disclosure may be associated with the compositions of the present disclosure in various manners. For instance, in some embodiments, association includes incubating the sample with a composition of the present disclosure. In some embodiments, the association includes flowing the sample through a composition of the present disclosure.

[0068] Applications and Advantages

[0069] The methods and compositions of the present disclosure have numerous advantages. For instance, in some embodiments, the compositions of the present disclosure can detect various analytes (e.g., toxic gases, such as NO) in an ultrasensitive, selective, and rapid manner. Moreover, the high modularity offered by the covalent-organic frameworks of the present disclosure can be utilized to generate structurally analogous materials with orthogonal responses that prove valuable in selective detection and differentiation of various analytes in low power sensing.

[0070] As such, the methods and compositions of the present disclosure can have numerous applications. For instance, in some embodiments, the methods and compositions of the present disclosure can be utilized for analyte detection for various purposes, such as for indoor air quality monitoring, ensuring industrial safety, and protecting health and safety of first responders.

[0071] Additional embodiments

[0072] Reference will now be made to more specific embodiments of the present disclosure and experimental results that provide support for such embodiments. However, Applicant notes that the disclosure below is for illustrative purposes only and is not intended to limit the scope of the claimed subject matter in any way.

[0073] Example 1. Metallotetrapyrazinoporphyrazine-based conductive metal-organic frameworks for the detection and differentiation of toxic gases

[0074] This Example describes the synthesis of novel cMOFs constructed from metallotetrapyrazinoporphyrazine (MTPz) derivatives bridged with copper ions in bis(dioxolene) linkages, and the efficiency of an array composed of these materials in differentiating a suite of toxic gases. Applicant has previously developed a novel cMOF based on NiTPz, which exhibited exceptional part-per-trillion (ppt)-level sensitivity towards NO, along with, reversibility, reusability, and rapid saturation. Herein, structural modifications of the MTPz metal center (M = Co, Ni, or Cu), allow for the emergence of different analogs with unique and selective sensing responses towards H2S, SO2, NH3, and NO with low theoretical limits of detection within less than 10 minutes of analytePCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 exposure at room temperature and at a low driving voltage of 0.1 V. Applicant also reports the mechanism of interaction between the MOF material and gaseous analytes through diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and X-ray photoclcctron spectroscopy (XPS) analyses for the MOFs exposed to the analytes. In addition, principal component analysis of the sensing traces showed the ability of an array formed of these three MOF analogues to differentiate chemiresistive signals from H2S, SO2, NH3, and NO across a range of concentrations between 1 and 40 ppm with collective limits of detections in the ppb-range. This wide scope of ppb to ppm concentrations permits the usage of this MTPz-MOF array in applications ranging from industrial air quality monitoring to exhaled human breath analysis

[0075] Example 1.1. MOF Synthesis and Characterization

[0076] Applicant used a modular procedure, previously developed for the preparation of octahydroxysubstituted NiTPz, to generate other analogs of octahydroxy-substituted MTPz monomers, denoted by MTPz(OH)g with M = Co, Ni, or Cu. Tetrahedron Lett. 1995, 36 (42), 7583-7586. The synthetic intermediates and final products were characterized by ’I I-NMR,13C-NMR, and low- and high- resolution mass spectra. Applicant then synthesized a series of MTPz-Cu-MOFs using solvothermal means by the coordination of the three different monomers with copper (II) ions in bis(dioxolene) linkages (FIG. 2A). Generally, Applicant reacted the monomers in an inert atmosphere with copper (II) nitrate and ethylene diamine (EDA) in anhydrous dimethyl sulfoxide (DMSO) at 85°C for 15 hours to yield crystalline material. Assessing the crystallinity of the MOF particles using powder X-ray diffraction (PXRD) revealed significant diffraction patterns at 20 values of 3.9°, 5.6°, 7.9°, and 27.5°, corresponding to the (100), (110), (200), and (001 ) facets, respectively. These peaks correlate well with the simulated eclipsed stacking pattern of the MTPz-Cu-MOF structure rather than the simulated staggered one, as shown in FIG. 2B.

[0077] Applicant evaluated the morphology, crystallinity, and long-range order on the nanoscale of all MOFs by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively, which are shown in FIGS. 2C-D. Energy dispersive X-ray (EDX) spectroscopy on each of the MOF analogues confirmed the presence of all the expected elements distributed evenly across the crystal. TEM images validated the experimental interspacing distances between the (100) planes of the square-like pores to be around 2.2 nm. Applicant also calculated these interspacing distancesPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 of (100) planes as well as the interlayer distances between the (001) planes from the PXRD diffraction patterns using Bragg’s Law to be around 2.23 nm and 0.33 nm, respectively.

[0078] In efforts to confirm the chemical composition of the three frameworks, Applicant performed different experiments, namely CHN combustion analysis, inductively -coupled plasma mass spectrometry (ICP-MS), and thermogravimetric analysis (TGA). Applicant gathered the results in order to portray an understanding of the elemental composition for each of the three MOF analogues, which confirmed the presence of water molecules as well as DMSO and / or EDA molecules within the unit cell of the framework. In addition, to confirm the formation of coordination bonds, Applicant studied the attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra of the MTPz(OH)s monomers and their corresponding MOFs. Applicant was able to designate significant bands to C-0 between 1244-1257 cm"1, isoindole between 1400-1480 cm"1, C=C between 1560-1580 cm"1, and C=N stretching vibrations between 1626 and 1646 cm"1.

[0079] From the XPS, in addition to confirming the presence of the C=N and C=N— M bonds from the TPz core and the semi-quinoidal ligand state through the approximate equal presence of C=O to C-O, Applicant noted the minor differences in the oxidation state of the copper bridging ions. The ratio of Cu(I) to Cu(II) varies slightly from 55:45 to 60:40 and 49:51 for CoTPz-Cu-MOF, NiTPz-Cu-MOF and CuTPz-Cu-MOF, respectively. The paramagnetic nature of the d9Cu(II) ions was affirmed by the electron paramagnetic resonance (EPR) spectra of the three MOFs at g = 2.06.

[0080] Four-point probe conductivity measurements were determined to be 7.59 x 10"4, 2.59 x 10"6, and 9.66 x 10"7S / cm for CoTPz-Cu-MOF, NiTPz-Cu-MOF, and CuTPz-Cu-MOF, respectively, affirming the semiconductive properties of these layered MOF structures. Evaluating the porosity of the materials using Brunaucr-Emmctt-Tcllcr (BET) isotherm analyses revealed that the surface areas are 313, 396, and 347 m2 / g for CoTPz-Cu-MOF, NiTPz-Cu-MOF, and CuTPz-Cu-MOF, respectively, based on their N2 sorption isotherms.

[0081] Example 1,2, Chemiresistive Sensing Responses of MTPz-Cu-MOFs

[0082] Applicant tested the chemiresistive sensing responses of the three MOFs towards several small toxic gases, namely H2S, NH3, SO2, and NO. While these gases are important to sense in real-life applications, they also constitute surface probes that can provide spectroscopic evidence for the surface chemistry of the materials and can portray distinct material- analyte interactions.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0083] Briefly, Applicant drop-casted suspensions of the activated MOFs in Milli-Q water (1 mg / mL) onto 5-pm or 10-pm gold interdigitated electrodes. Applicant tested the sensing response of these devices towards the different gases at concentrations of 40, 20, 10, 5 and 1 ppm of gas analyte in dry nitrogen atmosphere. The recorded measurements constituted of a steady nitrogen flow for 10 minutes, exposure to the specific concentration of gas analyte for 10 minutes, followed by a recovery period of solely nitrogen gas flow for 30 minutes. Applicant computed the normalized change in response from the recorded change in current during the measurement period. Sensing responses of each of the MOFs towards the different concentrations of gases are shown in FIGS. 3A-3L.

[0084] The MOFs responded distinctively towards different gases. In particular, NiTPz-Cu-MOF and CuTPz-Cu-MOF showed a remarkable decrease in the normalized sensing response towards H2S, a reducing gas, reaching values of -100,000 % and -500,000%, respectively, after 10 minutes of exposure to 40 ppm (FIG. 4A). In contrast, CoTPz-Cu-MOF showed an increase of 70 % after the same exposure time and concentration of FhS, highlighting a key difference in its sensing response with respect to the other analogues (FIG. 4A). Surprisingly, testing the sensing responses towards NH3, another reducing gas, showed an increase in -AG / Go for all three MOFs (FIG. 4B). Unlike CoTPz-Cu-MOF that showed a relatively slow increase in response to a maximum of 18% after 10 minutes of NH3 exposure, Applicant observed preeminent responses for NiTPz-Cu-MOF and CuTPz- Cu-MOF through a rapid response that saturated at around 80 % and 90 %, respectively, within 1-to- 3 minutes of exposure towards 40, 20, and 10 ppm of NH3 (FIG. 4B).

[0085] The MOFs responded to SO2 in a similar way to their responses to NH3. CoTPz-Cu-MOF showed a maximum response of 18% to 40 ppm of SO2 after 10 minutes of exposure, whereas NiTPz- Cu-MOF and CuTPz-Cu-MOF showed a maximum of 90% and 65%, respectively, saturated within five minutes of exposure (FIG. 4C). Towards NO, an oxidizing gas, however, all three MOFs showed a decrease in -AG / Go (FIG. 4D). The initial rate of response upon exposure showed complete saturation at high concentrations (mainly 20 and 40 ppm of NO) within l-to-2 minutes of exposure followed by an increase in -AG / Go throughout the exposure time. All MOFs showed partial reversibility towards the different gases while flowing the devices with nitrogen after exposure to the analytes.

[0086] From the concentration-dependent sensing responses, Applicant computed the limits of detection (LODs) of the MOFs towards the four gases, and Applicant studied the initial rates of theirPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 responses. Applicant determined theoretical LOD values as low as 16.5, 3.2, and 0.62 ppb for CoTPz-, NiTPz-, and CuTPz-Cu-MOF, respectively, at 10 minutes of exposure to H2S. LODs for NH3 and SO2 were in the low ppm-rangc with values ranging from 0.068 to 2.0 ppm for NH at only 0.8 minutes of exposure, and 0.16 to 0.75 ppm of SO2 at 2 minutes of exposure. Similarly, towards NO, theoretical LOD calculations of 5.8, 2.0, and 0.58 ppb, respectively, were determined after 1 minute of exposure to gaseous analyte. For the initial rates of response, Applicant generally observed a linear trend when plotting the rate of response of each MOF towards the different gases across the various concentrations of gases.

[0087] Subsequently, Applicant examined the recyclability of these MOFs towards the different gases by performing alternating 10 minutes of 20 ppm gaseous analyte dosing and recovery for up to 13 cycles. Applicant noted that the first exposure towards the analyte gas was the most prominent and the greatest in response intensity, followed by either consistent change in response in the following cycles, as is the case upon exposure to NH3, or continuously decreasing % response after each cycle, similar to what is observed for H2S, SO2, and NO. Applicant ascribed this decrease in response across succeeding cycle to partial device recovery, where active sites remain occupied with pre-adsorbed analyte gas. To highlight this point, Applicant computed the percentage recovery of the MTPz-MOFs after exposure the different gases.

[0088] Briefly, the most significant results include 100% recovery of CoTPz-Cu-MOF towards NH3, while Applicant noted values in the range of 80-90% for NiTPz- and CuTPz-Cu-MOFs towards 20 ppm of H2S and NO. All three analogues retain moderate recovery, namely 60 to 80%, after exposure to 20 ppm of SO2.

[0089] Example 1,3. Sensing Mechanism Study by DRIFTS

[0090] To gain insight into these distinct responses from the MTPz-Cu-MOF analogues which simply differ from each other by the central metal ion, Applicant sought to perform DRIFTS experiments (FIGS. 5A-5D) and post-exposure MOF characterization in an effort to probe the mechanism of interaction upon gas analyte subjection. In DRIFTS, Applicant noted the presence of water appearing throughout exposure as a common observation in most spectra, determined by the appearance of new absorption bands at around 3500 and 1650 cm’1, assigned to the O-H stretching and bending vibrations of water, respectively. In addition, Applicant pointed out broad absorbance increases or decreases in the baseline of the spectra, particularly between 4000 and 1700 cm’1, allotted to changes in thePCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 electronic properties of the MOF structure upon exposure to gaseous analytes. These electronic features may result from probable changes in the electron-population of the conduction band, possible shallow-trapped electrons, or plausible inter- valence charge transfer reactions.

[0091] Upon exposure to H2S, DRIFTS spectra of NiTPz-Cu-MOF and CuTPz-Cu-MOF showed patterns different from that of CoTPz-Cu-MOF. Briefly, positive Kubelka-Munk peaks at around 1540, 1474, 1400, 1333, 960, 860, 690, 645, and 605 cm"1were observed for the two former analogues (FIG. 5A). Applicant attributed the bands at 1540, 1474, 1400, and 1333 cm"1to perturbations in the TPz ligand structure, particularly aromatic C-C stretching for the first two bands and C-H bending for the latter two bands. Applicant ascribed the other bands to oxidized sulfurous species formed upon the catalytic oxidation of H2S in the presence of the MOF material, specifically to sulfite species (M-SOa2" at 960 and 645 cm"1) and sulfate species (M-SO42' at 860 cm"1), in addition to the formation of M-S sulfide bond (690 and 605 cm"1). Applicant also confirmed these observations by performing XPS analysis spectra on the MOF powder after being exposed to H S for 2 hours, where Applicant observed newly-developed S 2p peaks deconvoluted into sulfate (9% at binding energy = 168.8 eV), sulfite (17% at 167.4 eV), sulfide (7% at 162.0 eV), as well as H2S-M interactions (around 68% at 164.8 and 163.1 eV). In contrary, Applicant noted a different trend for the CoTPz-Cu-MOF analogue where decreasing Kubelka-Munk peaks at 1430, 1356, 1051 and 887 cm"1are presented, indicating disruption within the TPz ligand. In addition, Applicant reasoned that the shift from 1115 to 1144 cm"1results from deviations in the skeletal core of the central ligand structure, and the positive 611 cm"1band from the formation of an M-S bond. Interestingly, for CoTPz-Cu-MOF, Applicant noticed the partial reduction of the Cu(II) centers to Cu(I) from a 45:55 to a 37:63 ratio, further affirming the unique mechanism of CoTPz-Cu-MOF compared to the other Ni- and Cu- analogues.

[0092] Similarly, with NH3, Applicant sighted distinct mechanistic observations for NiTPz- and CuTPz-Cu-MOF in comparison with those of CoTPz-Cu-MOF, which may pose as a plausible explanation for the significant difference in the magnitude and rate of the sensing responses, as well as the trends in recovery (FIG. 5B). However, bands arising from gaseous NH3 are present in all spectra, notably those that shoulder at around 3220 cm"1corresponding to NH3 asymmetric stretching, at 1626 cm"1to NH3 symmetric bending, at 966 and 930 cm"1to NH3 symmetric bending, and at 490 cm"1to M-N stretching upon the coordination of NH3 molecules onto the metal, most probably copper, sites. In NiTPz- and CuTPz-Cu-MOF DRIFTS spectra, Applicant attributed the evolution of positivePCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 bands at around 1472, 1419, 1290, and 712 cm'1to vibrational modes of the TPz ligand, while those at 650 and 594 cm'1correspond to NH3 rocking. For DRIFTS spectra of CoTPz-Cu-MOF, however, Applicant observed decreasing Kubclka-Munk bands at 1513, 1379, 1312, 607, and 551 cm'1and assigned them to distortions within the aromatic TPz ligand and within the bis(dioxolene) linkage of the MOF, resulting from the interaction of NH3 with the metal center(s).

[0093] In regards to SO2, Applicant distinguished the newly-emerging bands at 1373, 1359, and 1344 cm’1as gas-phase SO2 asymmetric stretching and those at 1160 and 1140 cm’1as the corresponding symmetric stretching vibrations (FIG. 5C). For the DRIFTS spectra of all three MOFs, Applicant noticed bands relating to metal-bound SO2 (M-SO2) interactions, where the vibrations from CU-SO2 appeared in all the spectra of all analogues at around 1220 cm’1as asymmetric Cu-SCh stretching and 1040 cm’1as symmetric Cu-SCh stretching. In addition to the latter bands, DRIFTS spectra of NiTPz- Cu-MOF contained Ni-SCh asymmetric and symmetric stretching at 1270 and 1060 cm’1, whereas that of CoTPz-Cu-MOF contained the corresponding CO-SO2 vibrations at 1263 and 1033 cm’1, respectively. Furthermore, for NiTPz- and CoTPz-Cu-MOFs, Applicant noted the formation of sulfite and sulfate species, confirmed by the bands at 963, 857, and 655 cm’1, respectively, as well as by analyzing their XPS spectra after exposure in which peaks at binding energies 168.8 and 167.6 eV emerged. The oxidation of the sulfurous species is complemented by the partial reduction of the TPz ligand, observed as an increase in the semiquinoidal C=O to C-0 ratio from 55:41 to 38:58 in NiTPz- Cu-MOF and from 51:45 to 44:54 for CoTPz-Cu-MOF, respectively. CuTPz-Cu-MOF only showed peaks relating to sulfite species, further affirming the interaction of SO2 with the Ni and Co centers of the TPz ligand, observed in the DRIFTS spectra.

[0094] Upon exposure to NO, the common scries of peaks emerging from the presence of gaseous analyte include 2240 and 2209 cm'1due to trace nitrous oxide (N2O) in the stream, and 1907, 1875, and 1847 cm’1from gaseous NO (FIG. 5D). In addition, Applicant discerned copper-nitrosyl (Cu-NO) binding interactions identified by the peaks at 1733, 1738, and 1732 cm’1for spectra from NiTPz-, CoTPz- and CuTPz-Cu-MOF, respectively. Applicant also noted the formation of nitrite (NO2') ions in NiTPz-Cu as well as CuTPz-Cu at wavenumbers 1340 and 1220 cm’1in the DRIFTS spectra and at a binding energy of 403.5 eV in their N Is XPS spectra. Applicant allocated the other bands at 1539, 1282, and 856 cm’1observed for the three MOF analogues to stretching or bending vibrations resulting from electronic alterations within the framework upon the interaction with NO.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0095] Example 2. Molecular Engineering of a Conductive Metal-Organic Framework for Ultrasensitive, Rapid, Selective, and Reversible Sensing of Nitric Oxide

[0096] The selective, sensitive, low power, and portable detection of nitric oxide (NO) is important for environmental monitoring, industrial safety, and medical diagnostics. While tremendous progress has been made in detecting NO, existing technologies exhibit significant tradeoffs in sensitivity, selectivity, portability, and power requirements for broad implementation. This Example presents the first synthesis of a novel class of two-dimensional conductive tetrapyrazinoporphyrazine-based metalorganic frameworks (MOFs) interconnected with Cu (NiTPz-Cu-MOF & FETPz-Cu-MOF) and Zn ions (NiTPz-Zn-MOF) with unprecedented chemiresistive performance towards NO detection. NiTPz- Cu-MOF achieves ultralow detection limit [0.47 parts-per-trillion (ppt)], rapid response (within seconds), high selectivity of NO over H2S, SO2, CO, NH3, and NO2, excellent reversibility, operation at room temperature, and low power requirements. The novel structural features and material-analyte interactions of NiTPz-Cu-MOF with NO represents a significant conceptual advance in molecular engineering of materials for NO detection, with potential applications in environmental monitoring, industrial safety, and medical diagnostics.

[0097] This Example describes the synthesis of a novel class of two-dimensional, intrinsically conductive metal-organic frameworks (cMOFs) through the coordination of nickel(II) octahydroxytetrapyrazinoporphyrazine [NiTPz-(OH)s] with copper ions (NiTPz-Cu-MOF) and zinc ions (NiTPz-Zn-MOF), as well as the coordination of the metal-free ligand octahydroxytetrapyrazinoporphyrazine [H2TPz-(OH)s] with copper ions (FETPz-Cu-MOF). The molecular design of these cMOFs is based on a novel metallotetrapyrazinoporphyrazine (MTPz) ligand, an analog of mctallophthalocyaninc (MPc), where the a-position carbon atoms arc replaced with nitrogen. This substitution offers two strategic advantages for designing a highly reversible and sensitive sensor: (1) The replacement of a-position carbon atoms with electronegative nitrogen in NiTPz increases its oxidation potential by lowering the energy of its highest occupied molecular orbital (HOMO); (2) A monomer building block that in Applicant’ s preliminary studies showed strong sensitivity and reversibility toward chemiresistive NO detection, compared to MPc analog. By leveraging the high porosity and conductivity of cMOFs, Applicant reasoned that incorporating the NiTPz building block into a two-dimensional conductive MOF would enhance NO detection by achieving fast response times, improved sensitivity, and reversibility at low driving voltages. ToPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 understand the structure-property relationships in material- analyte interactions, Applicant systematically compared NiTPz-Cu-MOF with control materials NiTPz-Zn-MOF and FETPz-Cu- MOF to investigate how variations in the bridging ion and complex metal center influence MOF interactions with NO.

[0098] NiTPz-Cu-MOF exhibits good conductivity (3 x 106S cm *), a large surface area (396 m2g *), low dimensionality, and ordered presentation of binding sites to the gases. This material enables four major innovations in chemical sensing: (1) ultra- sensitive NO detection, with a theoretical limit of 0.47 parts-per-trillion (ppt) within 5 minutes of gas exposure and an initial response rate surpassing 100,000% per minute at 1 ppm NO, both the highest among all chemiresistive NO sensors made from metal oxides, dichalcogenides, nanocomposites, and cMOFs, (2) short saturation time (<5 min) and a broad dynamic range at low ppb levels (10-1000 ppb), uncommon in previously reported NO gas sensors; (3) exceptional selectivity, with distinct resistance changes for reducing and oxidizing gases and a 250-fold stronger response to NO over NO2 within 5 minutes at 1 ppm; and (4) unparalleled reversibility and reusability for NO detection at room temperature compared to most of the NO gas sensors. These achievements showcase the tremendous power of molecular engineering through precise selection of molecular building blocks to obtain conductive MOFs with tailored function, that when combined with the rapid and lower power detection, make NiTPz-Cu-MOF a promising material for versatile applications of continuous monitoring of NO. Building on former reports on reversible NO sensing, this Example introduces a conceptually novel design strategy based on a previously unreported, oxidation-resistant monomer that enables exceptional reversibility and reusability without requiring high crystallinity. The dual-active-site ligand allows tunable.

[0099] Example 2,1, MOF Synthesis and Characterization

[0100] Applicant synthesized NiTPz-Cu-MOF using NiTPz-(OH)s, which is prepared in 6 steps from 4,5-dimethoxybenzene-l,2-diamine (FIG. 6A). Optimization studies indicated that a low concentration of NiTPz-(OH)s and excess ethylenediamine (EDA), which slows down the nucleation process, were important for crystallinity. A reaction mixture of NiTPz-(OH)g (0.44 mM), Cu(NO3)2(2.1 equivalents), and EDA (1600 equivalents) in anhydrous dimethylsulfoxide (DMSO) at 85 °C for 2 days yielded the desired crystalline product. Similarly, Applicant synthesized NiTPz-Zn-MOF and H2TPz-Cu-MOF by reacting NiTPz-(OH)8with Zn(NO3)2and H2TPz-(OH)8with Cu(NO3)2respectively. The MOF preparation followed a procedure like that of NiTPz-Cu-MOF.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0101] Powder X-ray diffraction (PXRD) analysis suggested the 2D framework structures of NiTPz- Cu-MOF, NiTPz-Zn-MOF and ILTPz-Cu-MOF with peaks at 20 = 3.9°, 5.6°, 7.8°, and 27.5° (FIG. 6B), matching the (100), (110), (200), and (001) facets. These results aligned with simulations based on the P4 / mmm space group, assuming AA-stacked NiTPz subunits. Scanning electron microscopy (SEM) revealed nanoscale cubic crystallites of NiTPz-Cu-MOF (FIG. 6D), NiTPz-Zn-MOF (FIG. 6E), and FETPz-Cu-MOF (FIG. 6F). High-resolution transmission microscopy (HR-TEM) visualized 2.2-2.3 nm square pores in all three MOFs FIGS. 6D-F, with corresponding fast Fourier transform (FFT) patterns, confirming MOF formation.

[0102] The chemical composition of NiTPz-Cu-MOF, NiTPz-Zn-MOF and H2TPz-Cu-MOF was analyzed using combustion analysis, inductively coupled plasma mass spectrometry (ICP-MS), and thcrmogravimctric analysis (TGA). The results indicated the presence of EDA and water within the crystal lattice of all MOFs. The presence of EDA is likely due to chelating interaction of EDA with the bridging ions, while the water content is attributed to the hydrophilic nature of the MOF pores, which absorb moisture from the atmosphere. X-ray photoelectron spectroscopy (XPS) of NiTPz-Cu- MOF identified C, O, N, Ni, and Cu, with the Ni 2p to Cu 2p peak area ratio aligning with theoretical expectations (1:2). The Cu 2p3 / 2 peak revealed partial reduction of Cu(II) (934.0 eV) to Cu(I) (932.5 eV) in a 4:6 ratio. The presence of C-0 and C=O bonds in the O ls region supported the semiquinone structure of the MOF, and -NH2 groups in the N Is region suggested the presence of EDA. The XPS spectra of NiTPz-Zn-MOF and HzTPz-Cu-MOF exhibited similar patterns in the O Is and N Is regions, demonstrating the chemical similarity among the three MOFs. Electron paramagnetic resonance (EPR) spectroscopy of NiTPz-Cu-MOF and H2TPZ-CU-MOF exhibited a broad symmetric line shape attributed to a Cu-centered radical, while the EPR spectrum of NiTPz-Zn-MOF closely resembled that of its monomer. The charge neutrality of the material was confirmed by dye uptake experiments, where neither positively-charged nor negatively-charged dyes were absorbed by NiTPz- Cu-MOF overnight.

[0103] Conductivity measurements of NiTPz-Cu-MOF, NiTPz-Zn-MOF and H2TPZ-CU-MOF at ambient conditions using a four-point probe method yielded values of 3 ± 1 x 106S cm1(n = 7), 2 ± 1 x 106S cm1(n = 7) and 2 ± 1 x 107S cm1(n = 7), respectively. These values represent a two- order magnitude improvement over their corresponding monomers: NiTPz-(OH)s: 5 ± 3 x 10 S cm1(n = 7) and H2TPz-(OH)s: 6 ± 3 x 109S cm1(n = 7). Gas adsorption analysis revealedPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003Brunauer-Emmett-Teller (BET) surface areas of 396 m2 / g, 305 m2 / g, and 408 m2 / g for NiTPz-Cu- MOF, NiTPz-Zn-MOF and H2TPz-Cu-MOF, respectively.

[0104] Example 2,2, Chemiresistive Response of NiTPz-Cu-MOF and its control materials

[0105] Each sensing experiment was performed using at least three devices to ensure reproducibility. Additionally, Applicant repeatedly conducted sensing experiments using different batches of NiTPz- Cu-MOF to ensure batch-to-batch consistency and minimize human error. To illustrate the chemiresistive gas sensing ability of NiTPz-Cu-MOF, Applicant tested six analytes: NO, FES, SO2, CO, NHs, and NO2, which are toxic pollutants or biological signaling molecules. NiTPz-Cu-MOF can easily distinguish reducing gases and oxidizing gases, as shown in FIG. 7A, with distinct positive percentage changes in normalized sensing response toward reducing gases (H2S, SO2, CO, and NH3) and negative percentage changes in normalized sensing response toward oxidizing gases (NO and NO2). Among the tested oxidizing gases, NiTPz-Cu-MOF exhibited a 250-fold stronger response to NO than to NO2 at 1 ppm over 5 minutes. This exceptional selectivity for NO over NO2, based on response magnitude, is unprecedented among the reported MOF sensors.

[0106] As shown in FIG. 7B, NiTPz-Cu-MOF demonstrated rapid response and excellent reversibility. The response to 1 ppm NO reached saturation within 5 min, a significant improvement over previously reported MPc-based cMOFs (>30 min). The initial response rates of NiTPz-Cu-MOF over the first minute of exposure at 20-1000 ppb NO ranged from 370 to 102,000 % min 370-2600 times faster than prior MPc-based cMOFs. To further investigate the kinetics between NiTPz-Cu-MOF and NO, Applicant plotted the initial response rate over the first minute of exposure against NO concentration. A linear relationship [R2= 0.98] suggests a pseudo-first-order reaction with a rate constant of 118 min-1, around 3000 times greater than other MPc-based cMOFs. Through comparison of saturation time and analysis of initial response rates, NiTPz-Cu-MOF demonstrates an exceptionally fast response to extremely low concentrations of NO. NiTPz-Cu-MOF exhibited high sensitivity, detecting 10 ppb NO with a -1500% normalized sensing response change (FIG. 7B), significantly outperforming all chemiresistive NO sensors. The calculated limit of detection ranged from 0.47 to 6.20 parts-per-trillion (ppt) for 1-5 minute exposures, among the lowest reported for NO sensors. Additionally, NiTPz-Cu-MOF showed almost full reversibility, recovering 83-96% of its response within 30 minutes in nitrogen, a notable improvement over most of the NO gas sensors.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0107] To investigate the role of NiTPz and Cu bridging ion on NO sensitivity, NO sensing experiments were conducted using two isoreticular MOFs, NiTPz-Zn-MOF and FLTPz-Cu-MOF. NiTPz-Zn-MOF was used as a control because Zn(II) ions cannot form stable nitrosyl complexes, meaning its electronic signal primarily arises from the interaction between NiTPz and NO. FFTPz-Cu- MOF was selected as another control, as the organic ligand should not interact strongly with NO, meaning its electronic signal should originate from interactions between Cu bridging ions and NO. As shown in FIG. 7C, MOFs with single active sites produced significantly weaker changes in normalized sensing response (NiTPz-Cu-MOF: -184,000%, NiTPz-Zn-MOF: -57,000%, FFTPz-Cu- MOF: -107,000%). The combined response of the single active site MOFs remained below that of NiTPz-Cu-MOF, showing that embedding dual active sites within a single MOF enables a synergistic effect, significantly enhancing NO detection sensitivity.

[0108] The reusability of NiTPz-Cu-MOF as an NO sensor was evaluated through a 5 -cycle exposure-recovery experiment (5-min exposure and 30-min recovery) (FIG. 7D) and a 15-cycle test (5-min exposure and 10-min recovery). In both experiments, the initial responses in the first cycle were comparable (-205,000% in the 5-cycle test vs. -201,000% in the 15-cycle test). The maximum responses were observed in the third cycle (-279,000% and -284,000%, respectively), followed by a gradual decline in subsequent cycles. Under the 5-cycle conditions, NiTPz-Cu-MOF maintained full sensitivity (i.e. , maximum -AG / Go comparable to the first cycle) throughout all five cycles. In the 15- cycle test with shortened recovery time, full sensitivity was retained for the first four cycles. Collectively, these results demonstrate the reproducibility and reusability of NiTPz-Cu-MOF across different sample batches and testing conditions.

[0109] The performance of NiTPz-Cu-MOF under humid conditions is shown in FIG. 7E. The sensor response sharply decreased from -183,000% to -7,400% as relative humidity (RH) increased from 0% to 15%, then stabilized in the RH range of 40-98% (-120% to -146%). Despite the significant drop, the signal-to-noise ratio of NiTPz-Cu-MOF remains robust when compared to previously reported NO sensors such as Cm(HHTP)2 and NiPc-CuMOF, both of which exhibited negligible response to 1 ppm NO under 98% RH in N2. Notably, NiTPz-Cu-MOF exhibited reversible and consistent responses over eight exposure-recovery cycles under these humid conditions (FIG. 7F). The average responses over eight cycles remained highly reproducible: RH 40%: -121 ± 7%; RH 70%: -118 ± 7%; RH 98%: -143 ± 8%. This observation can be interpreted based on the waterPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 adsorption isotherm, which shows that pore filling begins at approximately 13% RH. Below this threshold, the MOF pores remain accessible to NO, allowing strong interactions with the active sites (bridging ions and the central TPz ion), resulting in high sensitivity. Above 13% RH, water molecules begin to block the pores and compete with NO for binding at the metal sites, sharply reducing the response. At RH above 40%, multilayer water films form on the MOF. In this regime, NO interacts weakly with the MOF surface rather than the metal nodes, resulting in lower but stable and reversible sensing responses.

[0110] In addition to humidity, oxygen is another atmospheric component that can influence sensing performance. Response of NiTPz-Cu-MOF in air was examined using 1 ppm NO. The maximum normalized response within 5 minutes in air (-176,000%) was comparable to that in dry nitrogen (-183,000%), but with a significantly faster response time in air. This result indicates that oxygen does not interfere with NO detection. The long-term stability of NiTPz-Cu-MOF was further evaluated using a sample stored under ambient conditions for 5 months. When tested with 1 ppm NO in nitrogen, the aged sample showed a slightly reduced overall response (-156,000%, -85% of the original), but retained the same saturation time (5 min) and recovery rate (96%) as freshly prepared samples. These findings confirm the excellent long-term stability and reliability of NiTPz-Cu-MOF for practical sensing applications.

[0111] Applicant employed ex-situ PXRD, EPR and XPS spectroscopy to investigate the structural and redox stability of NiTPz-Cu-MOF in 1 ppm NO. After exposure to 1 ppm NO in N2 for 2 hours, followed by a 15-minute N2 purge, the PXRD spectra remained almost identical to the pristine MOF (FIG. 8A), confirming its structural stability. The EPR signal exhibited only a slight 4% increase (FIG. 8B), indicating minimal oxidation of Cu(I) to Cu(II). XPS spectroscopy further confirmed the redox stability of NiTPz-Cu-MOF at 1 ppm NO exposure: (1) Cu 2p spectra (FIG. 8C) showed only 0.2% of Cu(I) ions oxidized to Cu(II) ions, indicating minimal redox changes; (2) N Is spectra (FIG. 8D) showed similar peak areas for the C=N and C=N — Ni regions before and after NO exposure, supporting MOF stability. However, a small new peak (2.4%) appeared at 403.0 eV, corresponding to amine / V-oxidc, while the -NH2 peak area decreased. These minor changes may be attributed to ethylenediamine oxidation; (3) O Is spectra (FIG. 8E) indicated minimal MOF oxidation, with only a slight 0.2% decrease in the C-0 bond peak area. The peak area at 532.4 eV increased by 1.1%, likely due to the overlap of amine A-oxide binding energies with the C=O bond region. Overall, the EPR andPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003XPS results demonstrated the high redox stability of NiTPz-Cu-MOF after 1 ppm NO exposure, aligning with the exceptional reversibility and reusability observed in the sensing experiments.

[0112] In the DRIFTS experiments, a 1% NO concentration was used to enhance the detection of subtle spectroscopic changes upon NO exposure. Additionally, experiments were conducted at a lower NO concentration (100 ppm) to better simulate conditions in NO detection. As shown in FIG. 9A, the spectra obtained from both experiments were largely similar, except for the absence of the NO(g) band at 1900 cm1in the lower concentration case, likely due to weak signal intensity. The DRIFTS spectra revealed four distinct spectral regions of interest: (1) the metal-heteroatom bond stretching region (<800 enr1), (2) the aromatic ring vibration and C-0 bond stretching regions (800-1600 cmthe N-0 bond stretching region of the metal nitrosyl complex (M---N-0) and the C=O bond stretching region (1600-2000 cmand (4) the broad electronic absorbance (BEA) region (>2000 cm

[0113] The BEA region is associated with changes in the conduction band electron population and charge-transfer reactions. Upon exposure to 1% NO, an increase in BEA intensity was observed within the first minute (FIG. 9A), followed by a gradual decrease to its original absorbance level after 10 minutes. This pattern mirrors the response decay observed in the consecutive exposure-recovery sensing experiments (FIG. 7D). During the second through fifth cycles, the normalized response decayed after reaching its peak during NO exposure. The response decay during exposure typically indicates secondary interactions between the material and NO after saturation. The combined results from DRIFTS and sensing experiments suggest that electronic properties of NiTPz-Cu-MOF may recover through secondary interactions with NO. A similar pattern was observed with 100 ppm NO exposure. However, while the BEA region initially increased, it did not fully return to its original absorbance after 15 minutes (FIG. 9A). When NO was replaced with N2, the BEA intensity continued to decrease over time. In the aromatic and metal-ligand regions (FIG. 9B), spectral shifts to higher wavenumbers were observed at 1206 cm1(C-0 stretching), 892 cm1(aromatic C-H bending), and 555 cm1(Cu-0 stretching), showing a change of the chemical environment upon NO interaction with NiTPz-Cu-MOF.

[0114] In the M---N O and C=O stretching regions (FIG. 9C), the NiTPz-Cu-MOF spectrum exhibited a broad absorption feature between 1666 cm1and 1748 cm *. To clarify the nature of this band, Applicant examined structural analogs NiTPz-Zn-MOF, H2TPZ-CU-MOF, and NiTPz-(OH)8. A distinct peak at 1694 cm1was observed in the spectra of NiTPz-Cu-MOF (NiTPz-CuMOF), NiTPz-PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003Zn-MOF (NiTPz-ZnMOF), and NiTPz-(OH)8, but was absent in H2TPz-Cu-MOF (H2TPz-CuMOF). Since the former three materials contain Ni, the peak at 1694 cm1is likely associated with the Ni---N- O interaction. However, in typical octahedral or square pyramidal Ni(II) nitrosyl complexes, the N-0 stretching frequency is generally observed near the NO(g) frequency (1850-1920 cm '). making it indistinguishable from free NO(g). If the Ni(II) ion partially distorts from the TPz ligand cavity, forming a 3-coordinated (1570-1820 cm ') or 4-coordinated (1690-1780 cm ') nitrosyl complex, it could potentially exhibit an N-0 stretching signal at 1694 cm Additionally, a weak band at 1717 cm1was detected in NiTPz-Cu-MOF and H2TPz-Cu-MOF but was absent in NiTPz-Zn-MOF and NiTPz-(OH)8, suggesting an association with Cm- -N-0 interactions in the Cu-containing materials NiTPz-Cu-MOF and H2TPz-Cu-MOF. The Cu(II)--N-0 species typically exhibit sharp peaks in the 1855-1920 cm1range, while Cu(I)---N-0 complexes tend to form weak peaks around 1730 cm *, Based on the peak position and intensity, the 1717 c1peak is more likely to correspond to a Cu(I)-"N-0 interaction. These findings suggest that the broad absorption band in NiTPz-Cu-MOF includes two distinct and independent contributions, a sharp peak at 1694 cm1(purple dotted line) and a weaker peak at 1717 cm1(orange dotted line). Applicant employed DFT calculations to probe potential material-analyte interactions responsible for the highly sensitive and reversible detection of NO.

[0115] To inspect the mechanism of sensing in NiTPz-Cu-MOF and its structural analogs, density functional theory simulations using the PBEsol functional were employed to probe the thermodynamics of binding between the MOF sensors and NO. After structural optimization, NO was initialized at different sites on the framework and further relaxed; upon binding, the NO vibrational frequency was computed using the finite differences method. In NiTPz-Cu-MOF, NO binding at both Ni and Cu was observed. The Ni--NO bond was slightly endothermic (Eads = +360 meV) and gave an NO stretching mode of 1834 cm"1, close to free NO. At bridging metal sites in the framework (Cu for NiTPz-Cu-MOF and H2TPz-Cu-MOF and Zn for NiTPz-Zn-MOF), NO desorbed. However, these bridging metals are all nominally in the +2 oxidation state. To model the majority population of Cu(I) by XPS, as well as the incorporation of EDA suggested by XPS and ICP-MS, a ribbon model of NiTPz-Cu-MOF was constructed which contained Cu(I) edge sites coordinated by EDA (FIG. 10). At these Cu(I) edge sites, a slightly exothermic Cu--NO bond formed (Eads= -308 meV) with an NO stretching mode of 1685 cm"1, in excellent agreement with the experimental DRIFTS spectra. NOPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 binding at these isolated Cu(I) edge sites adds a new manifold of conduction band states associated with N-0 7i* orbitals, but the bulk transport properties of the material remain unperturbed. Additional molecular models were developed to search for similar vibrational features in non-periodic examples, but only EDA-coordinated Cu(I) yielded the appropriate match to experiment. This analysis suggests that NO adsorption at EDA-coordinated edge sites contributes to the sensing performance for this group of materials.

[0116] Example 2,3. Conclusion and outlook

[0117] In conclusion, this Example presents the synthesis and characterization of NiTPz-Cu-MOF, NiTPz-Zn-MOF, and FETPz-Cu-MOF, a novel class of 2D cMOF. Among them, NiTPz-Cu-MOF demonstrates remarkable NO sensitivity, with a detection limit as low as 0.47 ppt within 5 minutes and rapid response rates exceeding 100,000% per minute at 1 ppm NO. It shows high selectivity for NO over other reactive gases (e.g., FES, SO2, CO, NFE, NO2). Notably, NiTPz-Cu-MOF offers outstanding reversibility and reusability, maintaining sensitivity across multiple cycles and stable performance in low humid conditions, promising for real-time and continuous monitoring. Furthermore, PXRD analysis confirms the structural stability of NiTPz-Cu-MOF, while XPS and EPR results demonstrate its redox stability, supporting its durability in NO detection. DRIFTS analysis, supported by DFT calculation, suggests that Cu(I)--NO interactions play a crucial role in MOF---NO interactions. This Example demonstrates the importance of molecular engineering of linkers in tuning structure-function relationships of MOFs. This approach provides a distinct molecular design strategy for creating materials with tailored sensing function, merging high sensitivity and reversibility. While NiTPz-Cu-MOF is highly promising for sensing applications, practical deployment will require addressing challenges such as synthetic complexity, potential environmental interferences, and device fragility. However, only microgram-scale quantities are needed per device, making the material feasible for integration. In addition, sensor arrays based on structurally tunable TPz-based analogs can mitigate cross-reactivity in complex gas mixtures. Together, these insights highlight the high potential utility of NiTPz-Cu-MOF in continuous and distributed NO monitoring systems.

[0118] Example 3. Reusable and Humidity- Tolerant Sulfur Dioxide Chemiresistive Sensor Based on a Tetrapyrazinoporphyrazine-Linked Metal-Organic Framework

[0119] With the increasing release of atmospheric pollutants, such as sulfur dioxide (SO2) gas, into the atmosphere, there is an urgent need for low-power, reliable sensing platforms capable of accuratelyPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 detecting trace concentrations of such contaminants under real- world conditions. However, achieving stable and reproducible sensing performance using multifunctional conductive materials, particularly under varying humidity levels, remains a challenge. This Example reports a novel, highly-crystallinc, conductive, tetrapyrazinoporphyrazine (TPz)-based metal-organic framework (MOF), designated as CoTPz-Cu-MOF, which exhibits rapid, robust, and humidity-resistant chemiresistive responses toward SO2 in various environments. Notably, the sensor, which features limits of detection in the parts-per-billion range, maintains consistent performance at relative humidity levels ranging from 0 to 98%, even at SO2 concentrations of 5 ppm — the permissible exposure limit set by the Occupational Safety and Health Administration. The sensor also demonstrates excellent reusability in humid air, retaining stable responses upon repeated exposures, even at saturated humidity. In situ and ex situ spectroscopic analyses reveal the underlying mechanisms governing the enhanced reversibility in air compared to nitrogen. Taken together, this Example presents CoTPz-Cu-MOF, as a robust and reliable SO2 chemiresistive sensor, suitable for deployment in diverse atmospheric conditions and across a wide humidity range, offering significant potential applications in occupational safety and environmental monitoring.

[0120] In this Example, Applicant reports the synthesis and characterization of a novel cMOF based on TPz for the reliable detection of SO2 under real- world conditions. The developed cMOF, coined as CoTPz-Cu-MOF, exhibits stable chemiresistive performance at SO2 concentrations as low as 5 ppm, the PEL for SO2 set by OSHA. Importantly, the sensor maintains its performance in challenging environments, including ambient air and a wide range of relative humidity (RH) levels, from 0 to 98%. CoTPz-Cu-MOF features cobalt-centered TPz units bridged via bis(dioxolene) linkages coordinated to copper ions, yielding a long-range ordered robust 2D architecture with enhanced crystallinity and conductivity compared to its other analogs. This material demonstrates rapid response times (on the order of seconds), high sensitivity at low detection limits (as low as 3 ppb in air), and excellent reversibility and reusability across multiple sensing cycles (up to six cycles with consistent performance). With meticulous linker design, Applicant harnesses the structural modularity of cMOFs to achieve stable, humidity-tolerant, and sensitive chemiresistive sensor for SO2 detection, paving the way for practical deployment in environments prone to variable moisture levels and pollutant exposure.

[0121] Example 3.1. MOF Synthesis and CharacterizationPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0122] Applicant synthesized CoTPz-Cu-MOF from a novel octahydroxy-functionalized TPz linker with a central cobalt ion, CoTPz(OH)s, coordinated to a copper bridging ion through bis(dioxolene) linkages. Building upon optimization efforts conducted for other TPz-bascd MOFs, Applicant showed that a reaction including 0.44 mM concentration of CoTPz(OH)s monomer in anhydrous dimethyl sulfoxide (DMSO), 2.1 equivalence of copper (II) nitrate hemipentahydrate as a copper salt precursor, and 400 equivalence of ethylene diamine (EDA) as a base additive heated at 85 °C for 15 hours would yield crystalline framework material of CoTPz-Cu-MOF (FIG. 11A). Powder X-ray diffraction (PXRD) suggested the high crystallinity of CoTPz-Cu-MOF with sharp diffraction peaks at 20 = 3.9°, 5.6°, 7.9°, and 27.5°, corresponding the (100), (110), (200), and (001) facet planes, respectively, which are well-aligned with the simulated eclipsed packing structure of CoTPz-Cu-MOF (FIG. 11B). Scanning electron microscopy (SEM) images revealed sheet-like morphology of crystallites with diameters of around 100 nm across different synthetic batches of CoTPz-Cu-MOF (FIG. 11C). Transmission electron microscopy (TEM) images further confirmed the grain size of CoTPz-Cu-MOF, where the images showed a uniform distribution of 2.16 nm square pores with long-range crystalline order extended across the surface of the crystallites (FIGS. 11D-E).

[0123] While energy dispersive X-ray (EDX) spectroscopy, inductively coupled plasma-mass spectrometry (ICP-MS), CHN combustion analysis, and thermogravimetric analysis (TGA) elucidated the elemental composition of CoTPz-Cu-MOF, attenuated total reflectance Fourier-transform infrared (ATR-FTIR), electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS) revealed the coordination network and oxidation states of the components. In particular, the linker moieties in CoTPz-Cu-MOF possess semi-quinoidal structures, deduced from the approximate 50:50 distribution of C-0 to C=O binding energies within the O ls XPS range, which is accommodated by the bridging ions through a 45:55 ratio of Cu(II) to Cu(I). The presence of an electron paramagnetic resonance (EPR) peak at g = 2.068 corroborated Applicant’s findings regarding the presence of paramagnetic Cu(II) ions in the framework. Evaluating the porosity of this 2D cMOF, through N2 sorption isotherms at 77K identified a BET surface area of 313 m2g’1, and its conductivity using four- point probe revealed a conductivity of 7.6 x 10"4S cm"1, which suggested that CoTPz-Cu-MOF would be suitable for gas sensing applications.

[0124] Example 3.2. Chemiresistive Sensing Responses of CoTPz-Cu-MOFPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0125] To examine the gas sensing properties of CoTPz-Cu-MOF towards SO2, Applicant prepared sensing devices by dropcasting 25 pL of MOF suspension in water (1 mg / mL) onto gold interdigitated electrodes with 10 pm-widc gaps and drying them in a vacuum chamber for 2 hours. Owing to the good conductivity of CoTPz-Cu-MOF, the resulting electrodes possessed resistance values in the range of 40-70 kQ, allowing for utilization of a low driving voltage of 0.1 V in the chronoamperometric sensing experiments. For precise delivery of particular gas concentrations, Applicant controlled flow rates of gases through mass flow controllers directed into a Teflon chamber equipped with a gas inlet and outlet, in which the electrodes are enclosed. Applicant evaluated the response of CoTPz-Cu-MOF using the negative normalized conductance (-AG / Go) which revealed a concentration-dependent increase in response percentages towards SO2 across concentrations ranging from 2 to 40 ppm in dry nitrogen (N2) and dry air atmospheres (FIGS. 12A-B). Though with minimal variation in the initial rates and magnitudes of responses, the overall sensing ability of CoTPz-Cu- MOF is retained in the presence of interferent gaseous species in the dry air environment, with an expected composition of N2 (78.0%), oxygen gas (O2, 20.9%), argon (Ar, 0.9%), carbon dioxide (CO2, 0.03%), and others (<0.2%), as compared to pure dry N2 environment.

[0126] Since SO2 is prone to oxidation into sulfur trioxide (SO3) and sulfuric acid (H2SO4) under certain environmental conditions, Applicant had carefully considered the stability of SO2 under the various atmospheric conditions incorporated in this Example. Based on previous reports in the literature, in the absence of a photocatalyst and irradiation, SO2 has been proven relatively stable during the time of exposure (10 minutes) at room temperature and in the absence of sunlight or irradiation under dry as well as low humid conditions. Also, in relation to the sulfur cycle, the conversion of SO2 into SO3 in the presence of irradiation and oxygen would require hours or days, which can then be transformed into H2SO4, thus posed unlikely under the conditions of Applicant’s conducted sensing experiments. At higher humidity levels, however, the possibility of SO2 solvation into water vapor and the subsequent formation of sulfurous acid (H2SO3) increases, which may hint to some differences in sensing trends or mechanisms.

[0127] Based on this assumption, Applicant evaluated the reversibility of response, theoretical detection limits (LODs) of CoTPz-Cu-MOF, and initial rate of response (RoR) towards SO2 under dry N2 and air atmospheric conditions. Notably, while reversibility in dry nitrogen is random across different SO2 concentrations (FIG. 12C), sensing responses in dry air showed excellent recoveryPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003(averaged around 100% for the 2 - 40 ppm range of SO2 concentrations), hinting towards the possible role of interferences from air in enhancing the recovery. In addition, plotting the concentrationdependent magnitudes of response at 2 and 5 minutes of exposure to SO2 displayed linear relationships (FIGS. 12D-E), allowing for the calculation of theoretical LODs of CoTPz-Cu-MOF towards SO2 upon 5 minutes of exposure with low values of 220 ± 12 ppb in dry N2 atmosphere and 57 ± 12 ppb in dry air atmosphere. Since these values are lower than the recommended PEL limits, CoTPz-Cu- MOF allows for tracking real-time concentrations of SO2 in ambient atmosphere prior to exceeding hazardous levels that may cause serious health and environmental impacts. In addition, evaluating initial ROR revealed the ability of CoTPz-Cu-MOF of rapid sensing within less than the first minute of exposure towards different concentrations of SO2 (FIG. 12F).

[0128] Prompted by the stability and enhanced reversibility of CoTPz-Cu-MOF responses towards SO2 in air, Applicant sought to study its sensing response features in humid environments. Remarkably, even with a high relative humidity (RH) of 98%, the sensing response of CoTPz-Cu- MOF is not decreased due to interference of water vapor molecules at a much higher concentration of around 26,000 ppm, at least 650 folds greater than the concentration of SO2 (FIG. 13A). Upon evaluating the concentration-dependent response (FIG. 13B), Applicant calculated the LOD in 98% RH humid air to be as low as 3 ppb upon 5 minutes of exposure to SO2 with initial rates of responses capable of SO2 detection within less than a minute as well at concentrations above 5 ppm, OSHA’s PEL of SO2. Upon multiple exposure-recovery cycles, CoTPz-Cu-MOF shows retainment of response magnitude of around 50% for up to 5 cycles even at low concentrations of 10 ppm (FIG. 13C). These results highlight the practical reusability and accuracy of utilizing the same sensor device across multiple exposures of SO2 in humid air. Compared to recyclability in dry nitrogen and dry air atmospheres CoTPz-Cu-MOF shows enhanced recyclability in humid air than the other two conditions in which the responses considerably decrease upon consecutive exposure-recovery cycles.

[0129] Then, Applicant sought to evaluate the sensing responses of CoTPz-Cu-MOF across varying humidity levels (0-98% RH) in both N2 and air atmospheres. While the magnitude of response increases gradually from 40 to 80% upon exposure to 10 ppm of SO2 with N2 as the background gas, Applicant noted constant response magnitudes at the same SO2 concentration in air with values of around 50% across varying humidity levels (FIG. 13D). In addition, the sensing responses in humid N2 environments across varying humidity levels show no reversibility of response after exposure toPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-00310 ppm of SO2, unlike the responses in humid air from which Applicant calculated reversibility percentages reaching up to 90%. Notably, Applicant also observed similar enhanced performance metrics in humid air at 5 ppm of SO2, the PEL level established by OSHA, even when the concentration of water molecules is 5,200 folds greater (with a 26,000 ppm concentration at 98% RH), in which the magnitude of sensing response (around 20%) remains constant across varying % RH levels. Collectively, these results highlight the superior performance of CoTPz-Cu-MOF described by its stable magnitude of response to SO2 across varying humidity levels, even up to 5,200 folds greater than the concentration of analyte, in N2 as well as in the presence of interferences in air.

[0130] Example 3.3. Spectroscopic Insights into Material-Analyte Interactions

[0131] In efforts to understand the reason behind the difference in sensing responses in dry and humid air conditions with respect to those in nitrogen, Applicant sought to perform in situ and ex situ spectroscopic investigations of CoTPz-Cu-MOF upon exposure to SO2 under these various conditions. Applicant collected in situ DRIFTS spectra at several time points while exposing a composite of CoTPz-Cu-MOF with potassium bromide (KBr) to 400 ppm of SO2 in both N2 and air atmospheres (FIG. 14A), whereas Applicant performed ex situ XPS analyses after exposing CoTPz-Cu-MOF samples to 40 ppm of SO2 in dry N2, dry air, and 98% RH humid air atmospheres for three hours (FIGS. 14B-D). Due to the hygroscopic nature of KBr, and since the DRIFTS setup is composed of KBr windows and a KBr-based composite, Applicant was not able to perform DRIFTS spectra under humid conditions. Collectively, the spectroscopic analyses revealed four key insights into the interactions between SO2 and CoTPz-Cu-MOF. First, Applicant observed a peak shift, visibly seen as a decrease in the difference spectrum at 1570 cm"1and an increase at 1520 cm"1, as well as two newly- appearing peaks at 1458 and 1313 cm"1, which Applicant has attributed to perturbations within the TPz ligands of the framework upon the exposure of CoTPz-Cu-MOF to SO2 in N2 and air environments (FIG. 14A). Second, in addition to the presence of gaseous SO2 peaks at 1400-1340 and 1185-1142 cm"1, Applicant noted the presence of SO2 molecules bound to copper ions (Cu-SCE) at 1215 and 860 cm"1in spectra of both N2 and air background. Third, however, Applicant noted the formation of sulfite ( SO?2-) and sulfate (SCL2") species only in the case when the background gas is N2. Applicant identified these two species with the bands at 962 and 646 cm"1and the bands at 758 and 696 cm"1corresponding to vibrations of SCE2" and SCU2", respectively. High-resolution XPS spectra performed upon exposure of CoTPz-Cu-MOF to 40 ppm of SO2 in N2 confirmed the presencePCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 of 63% SO32" (at 167.8 eV) and 37% SO " (at 169.0 eV) in the S 2p region (FIG. 14D). However, these peaks were absent when the sample is exposed to 40 ppm of SO2 in air, further corroborating the findings from DRIFTS. Instead, Applicant noted the presence of sulfide species including poly sulfide (4% Sxat 163.4 eV), copper deficient non- stoichiometric sulfide (25% CuxSyat 162.3 eV), and copper sulfide (CuiS at 161.2 eV) in the XPS spectra that Applicant was not able to identify from DRIFTS due to the high signal-to-noise ratio at wavenumbers below 620 cm"1in the IR spectra. Fourth, Applicant noted the slight reduction of copper ions from a 46:54 ratio of Cu(II):Cu(I) to a 33:67 ratio upon exposure to N2 (FIG. 14B). On the contrary, in dry air and humid air environments, exposure to SO2 yielded an oxidation of copper bridging ions to 76:24 and 71:29 ratios, respectively (FIG. 14B). Moreover, this oxidation is accompanied by the emergence of an extra peak at 529.0 eV in the O Is high-resolution XPS spectrum, presumably referring to copper oxide lattice oxygen, and thus attributed to the formation of metal oxide species (M-O) (FIG. 14C). Since the signal from gaseous SO2 bands (at 1400-1340 and 1185-1142 cm"1) were relatively weak when DRIFTS experiment was performed at 400 ppm, Applicant also performed the spectra upon exposing the sample to 1% of SO2 in background gas. The results revealed clearer gaseous SO2 peaks with similar observations from other bands within the difference spectra. Altogether, these studies highlight the difference in interaction mechanisms between CoTPz-Cu-MOF and SO2 in N2, air, or humid air conditions, yielding varying reversibility and recyclability yet consistent sensing responses at different humidity levels.

[0132] Example 3.4, Conclusion

[0133] In conclusion, this Example demonstrates the synthesis and sensing capabilities of a novel highly crystalline, and intrinsically conductive MOF, CoTPz-Cu-MOF, based on TPz ligand. As a chcmircsistivc sensor for SO2, CoTPz-Cu-MOF exhibits robust, reversible, and humidity-tolerant responses across a wide range of environmental conditions, addressing a critical challenge in real- world gas sensing settings, where atmospheric humidity fluctuates regularly. Its high sensitivity, with limits of detection in the ppbrange, and consistent signal output across varying relative humidities (0 - 98% RH) make it a competitive platform for trace-level SO2 monitoring. Notably, the sensor maintains partial to full reversibility depending on the environment, with enhanced performance in air compared to nitrogen, and remains reusable for at least five cycles under high humidity conditions — an appealing trait for repeated exposure.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0134] Beyond its performance metrics, this Example underscores the impact of targeted molecular design in developing new-generation cMOFs capable of overcoming limitations observed in existing materials. The improved humidity tolerance and air reversibility of CoTPz-Cu-MOF, relative to structurally analogous frameworks such as NiTPz-Cu-MOF, suggest that subtle differences in coordination environment may impact charge transport and host-guest interactions, leading to significantly different sensing behaviors. Future studies aimed at systematically comparing analogous cMOFs, incorporating controlled variations in metal centers, ligand functionality, electronic structure, and pore environments, could yield deeper insights into the governing mechanisms of signal transduction and gas recognition among interferences. Collectively, this Example not only introduces a promising sensor material for SO2 detection in real-life conditions, but also contributes to the broader understanding of how rational design of conductive frameworks can enable next-generation sensing technologies suitable for environmental monitoring, occupational safety, and public health applications.

[0135] Example 4. Humidity-Modulated Dual Ionic-Electronic Conduction in a 2D conductive MOF for Selective SO2 Detection

[0136] This Example describes the development and characterization of a new member of metalorganic frameworks, which exhibit dual moisture-triggered switchable electronic and protonic conduction.

[0137] Example 4,1, MOF Synthesis and Characterization

[0138] A reaction mixture containing NiTPz-(OH)s (2.2 mM), Co(NOs)2 (2.5 equivalents), and EDA (400 equivalents) in anhydrous dimethyl sulfoxide (DMSO) was heated at 85 °C for 24 hours, yielding the desired crystalline product (FIG. 15A).

[0139] Powder X-ray diffraction (PXRD) analysis confirmed the formation of a 2D framework structure for NiTPz-Co-MOF, with characteristic peaks at 29 = 3.9°, 5.6°, 7.8°, and 26.5°, corresponding to the (100), (110), (200), and (001) facets, respectively (FIG. 15B). These experimental patterns closely match simulated patterns based on the P4 / mmm space group, assuming AA-stacked NiTPz subunits. Notably, the (001) peak at 26.5° appears at a lower angle than in other NiTPz-Cu-MOF series MOFs (-27.5°), indicating a larger interplanar distance. This expansion is likely due to axial coordination by Co(II), which may bind solvent, EDA, or water molecules along the axial direction, increasing the spacing between layers. In addition to the expanded interlayerPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 distance, NiTPz-Co-MOF also differs morphologically from other NiTPz-Cu-MOF series MOFs. While members of the series typically adopt cubic shapes, NiTPz-Co-MOF exhibits a nanorod morphology with lengths around 100 nm (FIG. 15D). High-resolution transmission electron microscopy (HR-TEM) further confirmed the rod-shaped crystallites, revealing well-defined, parallel crystal lattices (FIG. 15E).

[0140] The Brunauer-Emmett-Teller (BET) surface area of NiTPz-Co-MOF was measured to be 345 m2 / g, comparable to other MOFs in the NiTPz-Cu-MOF series (300-400 m2 / g). Four-point probe conductivity measurements under ambient conditions revealed that NiTPz-Co-MOF exhibits an electronic conductivity of (8.2 ± 2.8) x 10 S cm1(n = 7), consistent with values reported for other NiTPz-Cu-MOF series MOFs (lO^-lO5S cm1).

[0141] The repeating unit formula of NiTPz-Co-MOF was determined using a combination of combustion analysis, inductively coupled plasma mass spectrometry (ICP-MS), and thermogravimetric analysis (TGA). Initial analysis using a general formula of (NiTPz)iCo2 showed deviations greater than 2% in C, H, and N content compared to experimental values. Considering the presence of water and ethylenediamine (EDA) molecules observed in other NiTPz-Cu-MOF series MOFs, a revised formula, (NiTPz)iCo2-2EDA-6H2O, was proposed. This updated formula reduced the deviation to less than 1% and was further supported by TGA results. The theoretical combined mass of EDA and water in this composition is approximately 15%. The TGA curve of NiTPz-Co- MOF under nitrogen flow showed an initial mass loss of -14% around 100 °C, consistent with the evaporation of EDA and water. These findings indicate that NiTPz-Co-MOF incorporates EDA and water molecules within its crystal lattice, similar to other members of the NiTPz-Cu-MOF series, albeit in varying proportions.

[0142] The chemical environments of the elements and spin states of Co(II) ion in NiTPz-Co-MOF were further investigated using X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) spectroscopy. The XPS survey spectrum confirmed the presence of C, O, N, Ni, and Co, consistent with elemental mapping via SEM-EDX. High-resolution scans of the O Is region revealed three peaks at binding energies of 530.3 eV, 531.8 eV, and 533.1 eV, attributed to C-O, C=O, and adsorbed water, respectively. The peak area ratio of C-0 to C=O (62:27) suggests the presence of a semiquinone-like structure within the framework.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0143] Similarly, high-resolution scans of the N Is region revealed three distinct environments, with peaks at 398.3 eV, 399.6 eV, and 400.6 eV, corresponding to C=N, C=N--Ni, and hydrogen -bonded -NHz, respectively. The presence of the latter peak supports the incorporation of EDA. Additionally, the peak area ratio of C=N to C=N---Ni was 63:21, consistent with the expected 1:3 ratio of noncoordinated to Ni-coordinated nitrogen atoms in the NiTPz unit.

[0144] The Co 2p region displayed a sharp peak at 780.7 eV and a broad satellite peak at 782.4 eV, characteristic of Co(II) ions. EPR spectroscopy was employed to determine the spin state of Co(II). A broad signal with a multiplet feature between g = 1.93 and 2.09 was observed. The g-factor range and distinct splitting pattern confirm that the bridging Co(II) ions arc in the high-spin state, as low-spin Co(II) typically exhibits weak or EPR-silent behavior.

[0145] Applicant previously demonstrated that two members of the NiTPz-Cu-MOF series (NiTPz- Cu-MOF and DC- 103) exhibit humidity-mediated proton conductivity, attributed to the waterchelating ability of the TPz ligand. Given the structural similarity, NiTPz-Co-MOF is expected to exhibit comparable behavior upon water absorption. Prior to evaluating its humidity-dependent proton conductivity, the water uptake behavior of NiTPz-Co-MOF was investigated. Pelletized samples (mass: 50-65 mg; diameter: 6.04-6.05 mm; thickness: 1.1-1.4 mm) were placed in a humid chamber maintained at 98% relative humidity (RH). Over three days, the mass of NiTPz-Co-MOF increased by 15 ± 5% (n = 2), accompanied by a dimensional expansion of 18 ± 5% (n = 2), confirming its hydrophilic nature.

[0146] Proton conductivity was measured using alternating current (AC) electrochemical impedance spectroscopy (EIS) on pelletized samples. Under anhydrous conditions at 303 K, NiTPz-Co-MOF exhibited negligible conductivity, indicating the critical role of water in facilitating proton transport. When exposed to humidified air at 98% RH, Nyquist plots collected over the temperature range of 303 to 333 K (FIG. 16A) revealed temperature-dependent conductivity. NiTPz-Co-MOF displayed proton conductivities ranging from 5.6 x 10 to 1.7 x 105S cm *. To probe the conduction mechanism, the activation energy (Ea) was extracted by fitting the temperature-dependent conductivity data to the Arrhenius equation (FIG. 16B). The resulting Ea of 0.37 eV (n = 2) is consistent with a Grotthuss-type proton conduction mechanism, where protons propagate through a hydrogen-bonded network of water molecules confined within the MOF pores.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0147] In addition to proton transport, semiconducting materials may exhibit changes in charge carrier concentration and type upon doping. To assess the effect of water on charge carrier characteristics in NiTPz-Co-MOF, Sccbcck coefficient measurements were performed on both dry (NiTPz-Co-MOF@dry) and water-saturated (NiTPz-Co-MOF ©FkO) samples. NiTPz-Co-MOF @ dry was prepared by placing pellets under vacuum at room temperature for 3 hours to remove residual moisture, and all subsequent measurements were conducted under vacuum. NiTPz-Co-MOF ©FFO was obtained by placing the pellets in a 98% RH chamber overnight, with measurements performed under ambient conditions (-60% RH).

[0148] The NiTPz-Co-MOF @ dry sample exhibited an average positive Seebeck coefficient (a) of +25.06 pV K1(FIG. 16C), indicating that holes are the majority charge carriers (p-type behavior). In contrast, NiTPz-Co-MOF @H2O displayed a negative Seebeck coefficient of -13.71 pV I< *, with a corresponding negative slope in the Seebeck curve (FIG. 16D), indicating n-type semiconducting behavior. These results suggest that water doping alters the electronic structure of NiTPz-Co-MOF, switching its dominant charge carriers from holes to electrons.

[0149] Inspired by the humidity-induced proton conductivity and the switching of charge carrier polarity observed in NiTPz-Co-MOF, Applicant hypothesized that selective chemiresistive gas sensing could be achieved by tuning the balance between electronic and ionic conduction mechanisms.

[0150] Applicant first explored how water-induced charge carrier switching affects the detection of ammonia. Ammonia (NHs) was selected due to the following reasons: (1) it is an alkaline gas and does not generate protons upon dissolution in water; (2) it possesses a low ionization constant in water (1.8 x 105), and (3) its ionization products (NHT and OH ) are bulky polyatomic ions that require high activation energy to migrate, rendering ion conduction may not be feasible at room temperature. Thus, under Applicant’s testing conditions (25 °C), the chemiresistive response of NiTPz-Co-MOF toward NHs should stem purely from electronic interactions.

[0151] Under dry nitrogen, NiTPz-Co-MOF exhibited a normalized response of +42% upon 5- minute exposure to 40 ppm NH3. The positive normalized response confirms p-type semiconductor behavior, in agreement with Seebeck measurements. Remarkably, upon introducing water vapor to the gas chamber, the normalized response reversed from positive to negative values, indicating a transition from p-type to n-type conduction. Additionally, the magnitude of the response increased significantly from -7% at 25% RH to -336% at 98% RH. These observations suggest that humidity-induced chargePCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 carrier switching in NiTPz-Co-MOF directly affects the direction and magnitude of its sensing response to NH3.

[0152] Next, Applicant investigated the role of humidity-mediated proton conduction in the detection of carbon dioxide. CO2 was selected to demonstrate this property because CO2 is only slightly soluble in water (Khydration = 1.7 x 103) and its dissociation in water is weak (Ka= 4.3 x 107mol dm-3), suggesting that its interaction with NiTPz-Co-MOF under dry or low RH conditions should primarily involve electronic effects and proton conduction becomes significant only in highly humid environments. Based on these properties, Applicant expected that any chemiresistive response to CO2 at high RH would result solely from proton conduction.

[0153] Indeed, NiTPz-Co-MOF exhibited no measurable response to 4000 ppm CO2 under dry nitrogen or at 25% RH, confirming CO2 cannot induce any electronic changes to NiTPz-Co-MOF. However, at RH levels above 50%, weak responses ranging from -3% to -15% were observed. This is attributed to the small number of protons generated from CO2 hydration and dissociation, which lower the resistance of the material through proton conduction. Notably, NiTPz-Co-MOF consistently produced negative responses under these conditions, aligning with the proton-mediated mechanism.

[0154] Encouraged by these results, Applicant extended the investigation to evaluate the ability of NiTPz-Co-MOF to differentiate between NO2 and SO2 under varying humidity conditions. In dry nitrogen, NiTPz-Co-MOF showed a normalized response of +75% to SO2 (a reducing gas) and -2700% to NO? (an oxidizing gas), consistent with p-type behavior. At 25% RH, the normalized response to SO2 switched to -400%, indicating a shift to n-type conduction. Meanwhile, the response to NO2 decreased to -1300%, likely due to a reduced hole carrier concentration, making the NiTPz- Co-MOF less sensitive to oxidizing species.

[0155] At 75% RH, NiTPz-Co-MOF showed a dramatic response of -3100% to SO2, surpassing that of NO2 (-200%). This enhanced sensitivity to SO2 is attributed to the combined effect of water-induced n-type conduction and proton conduction resulting from SO2 hydration and dissociation. The protons lower the resistance of NiTPz-Co-MOF, further amplifying the negative response. In contrast, NO2 hydration also generates protons, but the oxidizing property of NO2 tends to increase resistance of a n-type semiconductor. The opposing contributions from electronic and ionic effects effectively cancel each other, suppressing the response in NO2 detection.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003

[0156] At 98% RH, NiTPz-Co-MOF gave a strikingly high response of -9500% to SO2 compared to -62% for NO2, demonstrating a 150-fold enhancement in sensitivity. These results show that by exploiting the interplay between electronic and ionic conduction, NiTPz-Co-MOF enables highly selective detection of SO2 over NO2 under humid conditions (RH > 75%) and also offers clear discrimination under dry conditions (RH < 25%) (FIG. 17A).

[0157] Since extremely dry environments (RH < 25%) are uncommon in real- world applications, Applicant focused subsequent analysis on SO2 sensing under wet conditions. As shown in FIG. 17B, NiTPz-Co-MOF remained highly sensitive to low concentrations of SO2 at 98% RH, delivering normalized responses of -570% and -100% within 5 minutes at 5 ppm and 2 ppm SO2, respectively. These values fall well within the occupational exposure limits set by Occupational Safety and Health Administration (OSHA) and National Institute for Occupational Safety and Health (NIOSH) (5 and 2 ppm, respectively), indicating the practical viability of NiTPz-Co-MOF for workplace SO2 detection.

[0158] The initial response rates of NiTPz-Co-MOF in the first minute of exposure ranged from 5 to 1100 % min1across the 2-40 ppm concentration range. To further understand the sensing kinetics, the normalized response was plotted as a function of SO2 concentration over 1-5 minutes (FIG. 17C). A linear correlation was observed in the 2-20 ppm range, suggesting pseudo-first-order kinetics between NiTPz-Co-MOF and SO2 under humid conditions. The calculated limits of detection (LOD) ranged from 18 to 2 parts-per-billion (ppb) for exposure times between 1 and 5 minutes.

[0159] The reusability of NiTPz-Co-MOF for SO2 detection was evaluated through repeated exposure-recovery cycles under 98% RH with 20 ppm SO2. As shown in FIG. 17D, NiTPz-Co-MOF exhibited a rapid response of -3100% in the 1stcycle. Although only partial recovery was observed, the 2ndcycle still demonstrated strong responses (-7300%). In 3rd-6thcycles, the response stabilized, showing 15-34% changes per cycle (FIG. 17D, red bar chart), indicating reasonable durability and potential for reuse in practical applications.

[0160] Applicant employed ex-situ PXRD, EPR, and XPS spectroscopy to investigate the structural and redox changes of NiTPz-Co-MOF upon exposure to 40 ppm SO2 in 98% RH N2. After a 15-minute exposure followed by a 5-minute N2 purge, the PXRD patterns showed that the (100), (110), and (200) facets remained nearly unchanged, whereas the (001) facet shifted to higher angles and split into a doublet at 29 = 26.67° and 26.96° (FIG. 18A), indicating a contraction of the interlayer spacing upon wet SO2 exposure. After a second cycle of 15-minute SO2 exposure and 5-minute N2 purge, the peakPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 at 26.67° disappeared, and a broad single peak remained at 26.96°. Further exposure to wet SO2 for 30 additional minutes did not alter the PXRD pattern, with the broad (001) reflection at 26.96° persisting. This reduction in intcrplanar distance may facilitate charge transport and reduce the electrical resistance of NiTPz-Co-MOF under humid SO2 conditions.

[0161] EPR analysis revealed no significant change in signal intensity or g-factor after 1 hour of exposure to 40 ppm SO2 in 98% RH N2 (FIG. 18B), suggesting that the redox state and high-spin Co(II) configuration of NiTPz-Co-MOF remain stable under these conditions.

[0162] XPS analysis, however, indicated redox-related chemical changes. In the S 2p region (FIG. 18C), a new peak at 167.5 eV emerged, corresponding to sulphite (SO32) species. In the N Is region (FIG. 18D), a new peak at 401.5 eV appeared alongside a decrease in intensity of the original 400.4 eV peak, which are assigned to protonated EDA and neutral EDA, respectively. These results suggest that SO2 reacts with water to form H2SO3, which is then neutralized by EDA trapped within the lattice, leading to the formation of protonated EDA and SO32. Other spectral regions in the XPS remained largely unchanged compared to the pristine sample.

[0163] To further probe chemical interactions during SO2 exposure, Applicant conducted in-situ DRIFTS measurements under dry conditions due to the vulnerability of the KBr window in moist environments. Upon exposure to 1% SO2 in dry N2, several key changes were observed (FIG. 18E): (1) The broad electronic absorption (BEA) region from 1800-3000 cm1increased in intensity, indicating altered electronic properties and charge-transfer processes. This change was irreversible upon switching back to dry N2, consistent with the irreversibility observed in the dry SO2 sensing response; (2) a reversible doublet at 1132 and 1165 cm1appeared, corresponding to the S=O stretching mode of a CO-SO2 adduct, which vanished after SO2 removal; and (3) a new, irreversible band at 955 cm1emerged, attributed to the S=O stretching vibration of SO32, supporting the findings from XPS.

[0164] Example 4.2, Conclusion

[0165] In summary, Applicant has developed and characterized a new member of the NiTPz-Cu- MOF series, NiTPz-Co-MOF, which exhibits dual moisture-triggered switchable electronic and protonic conduction. This dual-mode behavior enables humidity-controlled modulation of charge carrier type, switching from p-type to n-type conduction, and facilitates proton transport. Both factors are critical for selective chemiresistive gas sensing. Notably, NiTPz-Co-MOF demonstrates anPCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 exceptionally strong and selective response to SO2 under humid conditions, characterized by a short response time (5 minutes), low detection limits down to single-digit ppb levels, and clear discrimination against other gases. Structural and spectroscopic analyses reveal that SO2 exposure induces interlayer contraction, EDA protonation, and formation of sulfite species, all of which contribute to the sensing mechanism. Together, these findings position NiTPz-Co-MOF as a promising platform for next-generation MOF-based chemiresistive sensors with tunable electronic and ionic transport properties.

[0166] Selected aspects of the present disclosure are as follows:1. A composition comprising: a covalent-organic framework, wherein the covalent-organic framework comprises: a plurality of first atoms; a plurality of second atoms; and a plurality of tetrapyrazinoporphyrazine-based ligands, wherein each of the tetrapyrazinoporphyrazine-based ligands is coordinated with a first atom and a second atom.2. The composition of aspect 1, wherein the tetrapyrazinoporphyrazine-based ligands are selected from the group consisting of octahydroxytetrapyrazinoporphyrazine, Cobalt(II) octahydroxytetrapyrazinoporphyrazine, Copper(II) octahydroxytetrapyrazinoporphyrazine, Nickel (II) octahydroxytetrapyrazinoporphyrazine, Zinc (II) octahydroxytetrapyrazinoporphyrazine, or combinations thereof.3. The composition of aspect 1 or 2, wherein the tetrapyrazinoporphyrazine-based ligands comprise octahydroxytetrapyrazinoporphyrazine.4. The composition of any one of aspects 1 to 3, wherein the covalent-organic framework is in the form of a square lattice, wherein the square lattice comprises a plurality of square apertures.5. The composition of any one of aspects 1 to 4, wherein the tetrapyrazinoporphyrazine-based ligands are bridged to one another through first atoms and second atoms.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-0036. The composition of aspect 5, wherein the tetrapyrazinoporphyrazine-based ligands are bridged to one another through mctal-bis(dioxolcnc) linkages.7. The composition of aspect 5 or 6, wherein the first atoms are coordinated with a central region of the tetrapyrazinoporphyrazine-based ligands, and wherein the second atoms are coordinated with one or more peripheral regions of the tetrapyrazinoporphyrazine-based ligands.8. The composition of any one of aspects 1 to 7, wherein the first atoms and the second atoms are each independently selected from the group consisting of non-metallic atoms, divalent metals, transition metals, hydrogen, iron, nickel, copper, cobalt, zinc, manganese, platinum, palladium, gold, bismuth, chromium, magnesium, tin, or combinations thereof.9. The composition of any one of aspects 1 to 8, wherein the first atoms and the second atoms are each independently selected from the group consisting of hydrogen, nickel, copper, cobalt, zinc, or combinations thereof.10. The composition of any one of aspects 1 to 9, wherein the second atoms are the same as the first atoms.11 . The composition of any one of aspects 1 to 9, wherein the second atoms are different from the first atoms.12. The composition of any one of aspects 1 to 9 or 11, wherein the first atom is nickel, and wherein the second atom is copper.13. The composition of any one of aspects 1 to 12, wherein the covalent-organic framework is a component of a sensor.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-00314. The composition of any one of aspects 1 to 13, wherein the covalent-organic framework is associated with a textile, wherein the textile comprises a plurality of fibers and a plurality of pores, and wherein the covalent-organic framework is associated with the fibers of the textile.15. The composition of any one of aspects 1 to 14, wherein the covalent-organic framework is a component of a personal protective equipment.16. The composition of any one of aspects 1 to 14, wherein the covalent-organic framework is a component of an air quality monitoring system.17. A method of detecting an analyte in a sample, said method comprising: associating the sample with a composition as defined in any one of aspects 1 to 12, wherein the composition is in the form of a sensor and comprises a covalent-organic framework, wherein the covalent-organic framework comprises: a plurality of first atoms, a plurality of second atoms, and a plurality of tetrapyrazinoporphyrazine-based ligands, wherein each of the tetrapyrazinoporphyrazine-based ligands is coordinated with a first atom and a second atom; and detecting the presence or absence of the analyte from the sample, wherein the detecting comprises: detecting a change in a property of the sensor, and correlating the change in the property to the presence of the analyte.18. The method of aspect 17, wherein a positive percentage change in the property of the sensor is correlated to the presence of the analyte.19. The method of aspect 17, wherein a negative percentage change in the property of the sensor is correlated to the presence of the analyte.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-00320. The method of any one of aspects 17 to 19, wherein the change in the property of the sensor comprises a change in normalized conductance over time (AG / Go).21. The method of aspect 20, wherein a decrease in normalized conductance over time is correlated to the presence of the analyte.22. The method of aspect 20, wherein an increase in normalized conductance over time is correlated to the presence of the analyte.23. The method of any one of aspects 17 to 19, wherein the change in the property of the sensor comprises a change in current over time.24. The method of aspect 23, wherein an increase in current over time is correlated to the presence of the analyte.25. The method of aspect 23, wherein a decrease in current over time is correlated to the presence of the analyte.26. The method of any one of aspects 17 to 25, wherein the analyte is selected from the group consisting of gases, ketones, alcohols, aromatic compounds, volatile organic compounds, water, neurotransmitters, hormones, proteins, sugars, metal ions, ionizing radiation, toxic gases, NO, CO, HoS, SO2, NH3, H2O, NO2, or combinations thereof.27. The method of any one of aspects 17 to 26, wherein the analyte is selected from the group consisting of NO, H2S, SO2, CO, NH3, NO2, or combinations thereof.28. The method of any one of aspects 17 to 27, wherein the method is utilized for the selective detection of analytes.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-00329. The method of any one of aspects 17 to 28, wherein the method is utilized for the differential detection of different analytes.30. The method of aspect 29, wherein the correlating comprises: correlating a positive percentage change in the property of the sensor to at least one of H2S, SO2, CO, and NH3, and correlating a negative percentage change in the property of the sensor to at least one of NO and NO2.31. The method of any one of aspects 17 to 30, wherein the analyte is detectable at less than 10 parts per trillion (ppt).32. The method of any one of aspects 17 to 31, wherein the analyte is in gaseous form.33. The method of any one of aspects 17 to 32, wherein the sample is derived from an environment.34. The method of any one of aspects 17 to 33, wherein the sample represents an environment.35. The method of any one of aspects 17 to 34, wherein the tetrapyrazinoporphyrazine-based ligands are selected from the group consisting of octahydroxytetrapyrazinoporphyrazine, Cobalt(II) octahydroxytetrapyrazinoporphyrazine, Copper(TI) octahydroxytetrapyrazinoporphyrazine, Nickel (II) octahydroxytctrapyrazinoporphyrazinc, Zinc (II) octahydroxytctrapyrazinoporphyrazinc, or combinations thereof.36. The method of any one of aspects 17 to 35, wherein the tetrapyrazinoporphyrazine-based ligands comprise octahydroxytetrapyrazinoporphyrazine.37. The method of any one of aspects 17 to 36, wherein the first atoms and the second atoms are each independently selected from the group consisting of non-metallic atoms, divalent metals,PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 transition metals, hydrogen, iron, nickel, copper, cobalt, zinc, manganese, platinum, palladium, gold, bismuth, chromium, magnesium, tin, or combinations thereof.38. The method of any one of aspects 17 to 37, wherein the first atoms and the second atoms arc each independently selected from the group consisting of hydrogen, nickel, copper, cobalt, zinc, or combinations thereof.

[0167] Without further elaboration, it is believed that one skilled in the art can, using the description herein, utilize the present disclosure to its fullest extent. The embodiments described herein are to be construed as illustrative and not as constraining the remainder of the disclosure in any way whatsoever. While the embodiments have been shown and described, many variations and modifications thereof can be made by one skilled in the ail without departing from the spirit and teachings of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims, including all equivalents of the subject matter of the claims. The disclosures of all patents, patent applications and publications cited herein are hereby incorporated herein by reference, to the extent that they provide procedural or other details consistent with and supplementary to those set forth herein.

Claims

PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003CLAIMS1. A composition comprising: a covalent-organic framework, wherein the covalent-organic framework comprises: a plurality of first atoms; a plurality of second atoms; and a plurality of tetrapyrazinoporphyrazine-based ligands, wherein each of the tetrapyrazinoporphyrazine-based ligands is coordinated with a first atom and a second atom.

2. The composition of claim 1, wherein the tetrapyrazinoporphyrazine -based ligands are selected from the group consisting of octahydroxytetrapyrazinoporphyrazine, Cobalt(II) octahydroxytetrapyrazinoporphyrazine, Copper(II) octahydroxytetrapyrazinoporphyrazine, Nickel (II) octahydroxytetrapyrazinoporphyrazine, Zinc (II) octahydroxytetrapyrazinoporphyrazine, or combinations thereof.

3. The composition of claim 1, wherein the tetrapyrazinoporphyrazine-based ligands comprise octahydroxytetrapyrazinoporphyrazine.

4. The composition of claim 1, wherein the covalent-organic framework is in the form of a square lattice, wherein the square lattice comprises a plurality of square apertures.

5. The composition of the claim 1, wherein the tetrapyrazinoporphyrazine-based ligands are bridged to one another through first atoms and second atoms.

6. The composition of claim 5, wherein the tetrapyrazinoporphyrazine -based ligands are bridged to one another through metal-bis(dioxolene) linkages.

7. The composition of claim 5, wherein the first atoms arc coordinated with a central region of the tetrapyrazinoporphyrazine-based ligands, and wherein the second atoms are coordinated with one or more peripheral regions of the tetrapyrazinoporphyrazine -based ligands.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-0038. The composition of claim 1, wherein the first atoms and the second atoms are each independently selected from the group consisting of non-metallic atoms, divalent metals, transition metals, hydrogen, iron, nickel, copper, cobalt, zinc, manganese, platinum, palladium, gold, bismuth, chromium, magnesium, tin, or combinations thereof.

9. The composition of claim 1, wherein the first atoms and the second atoms are each independently selected from the group consisting of hydrogen, nickel, copper, cobalt, zinc, or combinations thereof.

10. The composition of claim 1, wherein the second atoms are the same as the first atoms.

11. The composition of claim 1, wherein the second atoms are different from the first atoms.

12. The composition of claim 1, wherein the first atom is nickel, and wherein the second atom is copper.

13. The composition of claim 1, wherein the covalent-organic framework is a component of a sensor.

14. The composition of claim 1, wherein the covalent-organic framework is associated with a textile, wherein the textile comprises a plurality of fibers and a plurality of pores, and wherein the covalent- organic framework is associated with the fibers of the textile.

15. The composition of claim 1, wherein the covalent-organic framework is a component of a personal protective equipment.

16. The composition of claim 1, wherein the covalent-organic framework is a component of an air quality monitoring system.

17. A method of detecting an analyte in a sample, said method comprising:PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-003 associating the sample with a composition, wherein the composition is in the form of a sensor and comprises a covalent-organic framework, wherein the covalent-organic framework comprises: a plurality of first atoms, a plurality of second atoms, and a plurality of tetrapyrazinoporphyrazine-based ligands, wherein each of the tetrapyrazinoporphyrazine-based ligands is coordinated with a first atom and a second atom; and detecting the presence or absence of the analyte from the sample, wherein the detecting comprises: detecting a change in a property of the sensor, and correlating the change in the property to the presence of the analyte.

18. The method of claim 17, wherein a positive percentage change in the property of the sensor is correlated to the presence of the analyte.

19. The method of claim 17, wherein a negative percentage change in the property of the sensor is correlated to the presence of the analyte.

20. The method of claim 17, wherein the change in the property of the sensor comprises a change in normalized conductance over time (AG / Go).

21. The method of claim 20, wherein a decrease in normalized conductance over time is correlated to the presence of the analyte.

22. The method of claim 20, wherein an increase in normalized conductance over time is correlated to the presence of the analyte.PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-00323. The method of claim 17, wherein the change in the property of the sensor comprises a change in current over time.

24. The method of claim 23, wherein an increase in current over time is correlated to the presence of the analyte.

25. The method of claim 23, wherein a decrease in current over time is correlated to the presence of the analyte.

26. The method of claim 17, wherein the analyte is selected from the group consisting of gases, ketones, alcohols, aromatic compounds, volatile organic compounds, water, neurotransmitters, hormones, proteins, sugars, metal ions, ionizing radiation, toxic gases, NO, CO, H2S, SO2, NH3, H2O, NO2, CO2, or combinations thereof.

27. The method of claim 17, wherein the analyte is selected from the group consisting of NO, H2S, SO2, CO, NH3, NO2, CO2, or combinations thereof.

28. The method of claim 17, wherein the method is utilized for the selective detection of analytes.

29. The method of claim 17, wherein the method is utilized for the differential detection of different analytes.

30. The method of claim 29, wherein the correlating comprises: correlating a positive percentage change in the property of the sensor to at least one of H2S, SO2, CO, and NH3, and correlating a negative percentage change in the property of the sensor to at least one of NO and NO2.

31. The method of claim 17, wherein the analyte is detectable at less than 10 parts per trillion (ppt).PCT Application Attorney Docket No. AF60544.P058WODartmouth Ref. No. 2025-00332. The method of claim 17, wherein the analyte is in gaseous form.

33. The method of claim 17, wherein the sample is derived from an environment.

34. The method of claim 17, wherein the sample represents an environment.

35. The method of claim 17, wherein the tetrapyrazinoporphyrazine-based ligands are selected from the group consisting of octahydroxytetrapyrazinoporphyrazine, Cobalt(II) octahydroxytetrapyrazinoporphyrazine, Copper(II) octahydroxytetrapyrazinoporphyrazine, Nickel (II) octahydroxytetrapyrazinoporphyrazine, Zinc (II) octahydroxytetrapyrazinoporphyrazine, or combinations thereof.

36. The method of claim 17, wherein the tetrapyrazinoporphyrazine-based ligands comprise octahydroxytetrapyrazinoporphyrazine.

37. The method of claim 17, wherein the first atoms and the second atoms are each independently selected from the group consisting of non-metallic atoms, divalent metals, transition metals, hydrogen, iron, nickel, copper, cobalt, zinc, manganese, platinum, palladium, gold, bismuth, chromium, magnesium, tin, or combinations thereof.

38. The method of claim 17, wherein the first atoms and the second atoms are each independently selected from the group consisting of hydrogen, nickel, copper, cobalt, zinc, or combinations thereof.

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