Nitrogen-enriched flexible metal–organic framework for CO₂ adsorption

Abstract

A novel MOF named [Zn₂(L)(DMF)] was synthesized using solvothermal methods from the reaction of the new linker (4,4′,4′′-(4,4′,4′′-(benzene-1,3,5-triyltris(methylene))tris(3,5-dimethyl-1H-pyrazole-4,1-diyl))tribenzoic acid) and Zn(NO₃)₂·6H₂O. This new MOF was characterized by means of different techniques: powder X-ray diffraction, N₂ adsorption and desorption isotherms, thermogravimetric analysis, and scanning electron microscopy. Furthermore, suitable crystals were obtained, which allowed us to perform the X-Ray structure determination of this MOF. The capability of these new MOF to adsorb CO₂ at different temperatures was measured and its isosteric enthalpy of adsorption was calculated. The novel MOF shows an uncommon node composed of a Zn₃(–COO)₆(DMF)₂, and the asymmetric unit contains one crystallographically independent linker, one DMF molecule, and two Zn atoms. The [Zn₂(L)(DMF)] MOF is a microporous material with high crystallinity and stability up to 250 °C. The multiple nitrogenated pyrazole linkers in its framework enhance its CO₂ adsorption capabilities. This material exhibits a low CO₂ isosteric enthalpy of adsorption (H_ads), comparable to previously reported values for similar nitrogenated materials. All the observed CO₂ adsorption capacities were further supported by DFT calculations.

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Introduction

The increase in greenhouse gas emissions into the atmosphere, mainly from burning fossil fuels, particularly carbon dioxide (CO₂), has been ascribed to the rise in world temperatures. The primary sources of industrial pollution are plants that produce cement, steel, and coal-fired electricity.^1–3 The most popular and established process for CO₂ capture in those industries is post-combustion gas absorption, performed using aqueous solutions of amino alcohols, such as monoethanolamine (MEA) or diethanolamine (DEA).^4–7 However, its regeneration requires high energy consumption, can cause equipment corrosion, and may reduce its effectiveness due to amine degradation.^7–9

Lately, coordination polymers and Metal–Organic Frameworks (MOF) have been recognized as some of the most promising alternatives for CO₂ adsorption.¹⁰ MOFs are a class of crystalline porous materials based on metal ions (nodes) coordinated with organic ligands that form ordered and specific structures.^11–14 They are characterized by their enormous internal surface area, which can be up to 10 000 m² g⁻¹; ultra-porosity, up to 90% of free volume, in nanometer-sized cavities or open channels; low densities, for example, 0.126 g cm⁻³,¹⁵ uniform spatial dispersion of components; tunable pore sizes; tunable topologies, hybrid organic–inorganic nature, and multi-functionality.¹⁶ The adsorption capacity of MOFs is mainly related to the surface area, but pressure and adsorption temperature play a vital role in the interaction with the adsorbent.³

To improve CO₂ adsorption capacity and selectivity using MOFs, two strategies have been widely reported: (1) incorporation of coordinately unsaturated metal sites. These sites on the structure favor the immobilization of CO₂ molecules by inducing dipole–quadrupole interactions. The interaction between the Lewis acid sites of the metal with CO₂ molecules is favored, providing high adsorption at very low pressures and selectivity of CO₂ over N₂.^17,18 (2) Decoration with basic Lewis sites. As CO₂ molecules have quadrupole moments, the presence of polar groups in MOFs improves the adsorption of CO₂ and the selectivity concerning gases such as CH₄, N₂, and H₂ (non-polar).³ The incorporation or functionalization of organic molecules with polar groups capable of interacting strongly with CO₂ can occur in the MOF's nodes or ligands. Examples of these groups are amine, phosphonate, and sulfonate. Amines are most generally studied due to their high affinity towards CO₂ molecules and selectivity. Among them are primary, secondary, or tertiary amines, tetrazole, triazine, imidazole, and pyrazole, among others.^19–21

The herein study synthesizes and characterizes a novel Zn(II) MOF using an innovative, flexible pyrazole carboxylate linker. The carboxylic acid moiety in the linker structure will play a key role in developing the three-dimensional structure, while unbound pyrazoles will enable nitrogen sites to bind with CO₂ molecules. Additionally, we aim to investigate the potential generation of Lewis acid sites within the MOF nodes through the desorption of coordinated solvent molecules on the node after activation. Also, the enthalpy of adsorption (ΔH_ads) by the Clausius Clapeyron equation was modeled at different temperatures. Finally, to explore the MOF–CO₂ interaction, DFT calculations over the interacting structure were performed.

Experimental section

Materials

All reagents and solvents were commercially purchased from commercial suppliers and used as received without further purification. 1,3,5-tris(bromomethyl)benzene (97%), acetylacetone (≥99%), acetone (≥97%), benzene (99.8%), hexane (95%), magnesium sulfate anhydrous (≥98%), potassium (98%), potassium iodide (≥99%), tert-butyl alcohol (≥99.5%) and tetrahydrofuran (99.9%) were purchased from Sigma Aldrich. 4-Hydrazinobenzoic acid (97%) was purchased from Fisher Chemical. N,N-Dimethylformamide (DMF) (99%) was purchased from Acros organics, and zinc(II) nitrate hexahydrate (98%) was purchased from Strem Chemicals.

Synthesis of the linker

The linker, whose structure is shown in Fig. 1, was synthesized in a two-step synthetical procedure. An intermediate tris-β diketonic was produced according to a previous report,²² where the 1,3,5-tris (bromomethyl) benzene reacted with potassium tert-butoxide and acetylacetone. Then, this compound reacted with 4-hydrazinobenzoic acid to obtain the final linker. Detailed synthetic procedures and structural characterizations of the precursor and linker are provided in the ESI (Scheme S1 and Fig. S1–S16†).

Fig. 1 Chemical structure of the novel linker.

Synthesis of [Zn₂(L)DMF] single crystal

In a 3-dram vial, the linker (190.60 mg, 0.25 mmol, 1 equiv.) was dissolved in N,N′-dimethylformamide (DMF) (8.0 mL) using an ultrasonic water bath. Meanwhile, in another 3-dram vial, Zn(NO₃)₂·6H₂O (47.30 mg, 0.16 mmol, 0,6 equiv.) was also dissolved in DMF (8.0 mL). Both solutions were mixed in a 6-dram vial, capped, and placed in an oven preheated to 100 °C for 48 hours. After cooling down to room temperature, the product was obtained by centrifugation at 8500 rpm for 10 minutes. The solid was washed three times with DMF (10 mL) and three times with acetone (10 mL) every two hours. Finally, it was soaked with acetone overnight, centrifuged, and dried in air to give a light-yellow powder.

Physical measurements

Single-crystal X-ray crystallography. A suitable crystal was selected and mounted on a glass fiber with Paratone oil on a XtaLAB Synergy, single source at offset/far, HyPix diffractometer. During data collection, the crystal was kept at 100 K. The structure was solved using Olex2 ²³ with the ShelXT²⁴ structure solution program using intrinsic phasing and refined with the XL²⁵ refinement package using least squares minimization. The refinement result is summarized in Table S1.† Crystallographic data for the [Zn₂(L)DMF] structure in CIF format has been deposited in the Cambridge Crystallographic Data Centre (CCDC) under deposition numbers CCDC 2355199.†

Powder X-ray diffraction (PXRD). PXRD patterns were recorded on a STOE-STADIMP powder diffractometer equipped with an asymmetrically curved Germanium monochromator (CuKα1 radiation, λ = 1.54056 Å) and a one-dimensional silicon strip detector (MYTHEN2 1K from DECTRIS) at room temperature on the IMSERC X-ray Facility at Northwestern University. The line-focused Cu X-ray tube was operated at 40 kV and 40 mA. The activated MOF powder was packed in a 3 mm metallic mask, sandwiched between two polyimide layers of tape, and measured in transmission geometry in a rotating holder. Intensity data from 1 to 34 degrees 2θ were collected over 7 minutes. The instrument was calibrated against a NIST Silicon standard (640d) prior to the measurement.

N₂ adsorption and desorption isotherms. Before each analysis, samples were thermally treated at 120 °C for 16 h under a high vacuum on a Smart VacPrep from Micromeritics. Then, using the Micromeritics Tristar II 3020 (Micromeritics, Norcross, GA) N₂ adsorption and desorption isotherms were measured at 77 K and pore-size distributions were obtained from density functional theory (DFT). Around 50 mg of sample was used in each measurement and Brunauer–Emmett–Teller (BET) surface area was calculated in the region P/P₀ = 0.005–0.05.

Thermogravimetric analysis (TGA). The TGA measurement was performed on a TGA/DCS 1 system (Mettler-Toledo AG, Schwerzenbach, Switzerland), which runs on a PC with STARe software. Samples were heated from 25 to 600 °C at 10 °C min⁻¹ under nitrogen with a flow rate of 20 mL min⁻¹.

Scanning electron microscopy (SEM). Before imaging, the samples were coated with OsO₄ to ∼9 nm thickness in a Denton Desk III TSC Sputter Coater. SEM images were collected on a Hitachi SU8030 FE-SEM (Dallas, TX) microscope.

CO₂ sorption measurements. Before analyses, the sample was activated by heating 120 °C under dynamic vacuum on a Smart Vacprep from Micromeritics until the outgassing rate was <5 μmHg min⁻¹ using a mass of approximately 50 mg. Then, CO₂ adsorption experiments were performed by using Micromeritics ASAP 2020 surface area analyzer. The isotherms were measured around standard conditions at 273 K, 288 K, and 298 K from 0 to 800 mbar (0–80 kPa). The experiment temperatures were maintained employing a Micromeritics Iso Controller. The Clausius–Clapeyron equation (eqn (1)) was used to calculate the isosteric enthalpy of CO₂ adsorption (ΔH_ads, kJ mol⁻¹).²⁶where p is pressure, T is temperature, and R is the ideal gas constant (8.314 J mol⁻¹ K⁻¹).

Theoretical calculations

Density functional theory calculations in the scalar relativistic framework were carried out using the ADF 2019.01 code^27,28 with the ZORA Hamiltonian.^29–31 Triple-ξ Slater basis set (STO-TZP) for valence electrons was employed³² with the functional RPBE³³ including dispersion correction (Grimme D3).³⁴ Using Versluis and Ziegler's analytical energy gradient method, no symmetry restraints were considered for the equilibrium geometries.³⁵ The nature of the binding interaction was studied in the representation of the MOF simplified pore model with different amounts of CO₂ molecules through the Morokuma–Ziegler decomposition scheme. In this scheme, the binding energy is determined by applying a fragmentation of the molecular structure, which allows the decomposition of the interaction energy (ΔE_Int) among the fragments. Therefore, this compound was studied as two fragments constituting the system: the MOF pore simplified model and the surrounding CO₂ molecules (considering from 2 up to 8 CO₂ molecules interacting with the MOF). The interaction energy can be decomposed as:³⁶

ΔE_Int = ΔE_Pauli + ΔE_Elec + ΔE_Orb + ΔE_Disp (2)

The ΔE_Pauli refers to the Pauli repulsion (exchange repulsion). This energy is responsible for any steric repulsion. The remaining three terms correspond to the classical electrostatic interaction (ΔE_Elec), the dispersive contribution (ΔE_Disp), and the effect of the orbital interaction and polarization effects (ΔE_Orb). All these terms have a stabilizing contribution to the interaction energy.

Results and discussion

After activation and washing, the novel [Zn₂(L)(DMF)] MOF is a fine white powder with light-marron crystals (Fig. S17b†). The SEM picture (Fig. S17c†) depicts the particle distribution as irregularly formed clusters with an average particle size ranging from 10 to 100 μm.

Crystal structure analysis

The synthesized MOF structure was elucidated by single-crystal X-ray diffraction (XRD) (Table S1†). The analysis revealed that [Zn₂(L)DMF] crystallizes in the monoclinic P21/n space group. The asymmetric unit of [Zn₂(L)DMF] contains one crystallographically independent linker, one DMF molecule, and two Zn(II) atoms (Fig. 2a). Also, it showed that the framework is composed of a Zn₃(–COO)₆(DMF)₂ node (Fig. 2b). The central Zn(II) shows octahedral coordination with carboxylate oxygen atoms, and the other two Zn(II) show distorted trigonal bipyramidal geometry coordinated to four carboxylate linkers (Fig. 2c). The remaining positions are bound to the oxygen of a DMF molecule, which was used as a solvent in the reaction. This uncommon type of node has already been reported for the MOF Zn₃(BDC)₃·6CH₃OH (BDC: 1,4-benzenedicarboxylate).^37,38

Fig. 2 For [Zn₂(L)(DMF)], (a) asymmetric unit, (b) coordination environment for Zn²⁺, (c) node structure.

The central octahedral structure in the node's MOF shows no distortion, and the angles correspond to the theoretical ones, 90° for each measured angle. However, the trigonal bipyramidal structures are not in the equatorial position (as the O–Zn–O angles should be 120°), showing distorted angles with values of 104.29°, 117.46°, and 133.81°. On the other hand, the angles O–Zn–O between the equatorial and axial oxygen should have a value of 90°; however, as shown in Fig. S18d,† the structure is distorted and no 90° angles were found (Fig. S18a†). This distortion is attributed to the central octahedron's stability and the linker's rigidity. Each linker connects six Zn²⁺ ions, resulting in a three-dimensional (3D) porous (not interpenetrated) network due to its flexibility (Fig. 3). Removing the weak bound DMF molecules by activation offers an opportunity to achieve a porous material with unsaturated zinc centers, which may benefit CO₂ adsorption.³⁹ Zn–O bond lengths ranged from 1.948 to 2.293 Å. These values are consistent with those previously reported for Zn(II)-based MOFs.^37,40–42

Fig. 3 3D view of the [Zn₂(L)DMF].

Powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA)

The structural stability of [Zn₂(L)DMF] sample was confirmed by the sharp and clear diffraction peaks in PXRD patterns after activation under dynamic vacuum at 120 °C for 16 h, activation by supercritical CO₂, and after CO₂ adsorption at 273, 288 and 298 K (Fig. 4a). The simulated PXRD pattern was obtained from the single-crystal structure using the Mercury 2021.1.0 software, and the phase purity was determined through the as-synthesized sample. After activation treatments and CO₂ adsorption, the PXRD pattern was compared with the simulated PXRD pattern to check structure stability.

Fig. 4 For [Zn₂(L)(DMF)]. (a) PXRD patterns after several treatments. (b) TGA curve.

[Zn₂(L)DMF] MOF showed that the thermal activation with vacuum evacuation at 120 °C caused a phase a slight crystalline loss or a phase transition. Supercritical CO₂ drying (scCO₂), a mild activation technique, was chosen to prove the amorphization. scCO₂ activation is based on avoiding the liquid-to-gas phase transition associated with capillary forces.⁴³ This activation has been successfully used for MOFs built from flexible linkers when conventional thermal activation causes the MOF's collapse or if the solvent exchange is unsuccessful.⁴⁴ However, after scCO₂ activation, a mixture of phases emerged, combining characteristics from both the “as-synthesized” and “activated at 120 °C” patterns.

Liu et al. reported that scCO₂ activation followed by conventional activation was highly effective in promoting the disruption of the coordination bond between the metal and the solvents that act as ligands, generating more efficient sites for CO₂ adsorption.⁴⁵

The thermal stability of [Zn₂(L)DMF] was evaluated by TGA (Fig. 4b). The initial weight loss over 270 °C can be attributed to the loss of DMF molecules coordinated to the Zn(II) in the nodes. Previous reports have demonstrated that DMF remained coordinated up to 260 °C in other MOFs.⁴⁶ The weight loss from 290 °C to 500 °C may be due to linker decomposition and collapse of the MOF structure. A plausible explanation for the temperature decomposition for the second and third events is the energy required to break different types of bonds. Benzene and pyrazole rings of the linker required lower energy than the coordinate bonds formed between the carboxylates and the zinc atoms. Also, breaking 14 Zn–O bonds in the node MOF is necessary.

The final remaining percentage of mass could be expected to be the node structure of the MOF. In this sense, the node Zn₃(–COO)₆ corresponds to ∼23% of the whole network's weight. For previously reported trinuclear Zn-based MOFs, the decomposition temperature and residue percentage were over 400 °C and around 25%, respectively.⁴⁷

Nitrogen (N₂) adsorption studies

The N₂ adsorption isotherm at 77 K up to 1 atm was measured on the [Zn₂(L)DMF] sample. Previously, the MOF pores were fully evacuated by scCO₂ activation followed by thermal activation at 50 °C to remove possibly retained CO₂ molecules in the network. As can be observed in Fig. 5a, the N₂ adsorption isotherm on the activated sample resembles a typical type-I(a) isotherm according to the IUPAC classification,⁴⁸ typical for microporous materials. This profile indicates that at low relative pressure (P/P⁰ < 0.015), the available micropores are occupied due to enhanced adsorbent–adsorptive interactions in narrow micropores, increasing substantially the quantity of N₂ adsorbed. The adsorbed gas quantity approaches a limiting value due to the lack of an external surface area rather than an internal surface area.^48,49 The BET surface area found was 402 m² g⁻¹. Furthermore, no hysteresis was observed upon desorption of gas from the pores. Fig. 5b shows the pore size distribution analysis based on DFT, which reveals a narrow distribution of micro-sized pores between 10–15 Å, with the maximum percentage at 12.5 Å. This result correlates well with the type of isotherm found.

Fig. 5 (a) Nitrogen sorption isotherm at 77 K and (b) DFT calculated pore size distributions for [Zn₂(L)(DMF)].

CO₂ adsorption studies

In order to know the efficiency of the [Zn₂(L)DMF] MOF as CO₂ adsorber, the CO₂ sorption isotherms were measured from 0 to 75 kPa at 298 K, 288 K, and 273 K. The CO₂ uptake amounts were 3.0 wt% (15.41 cm³ g⁻¹, 0.69 mmol g⁻¹), 4.2 wt% (21.60 cm³ g⁻¹, 0.96 mmol g⁻¹), and 6.9 wt% (35.23 cm³ g⁻¹, 1.57 mmol g⁻¹), respectively (see Fig. 6a). One or more of the following mechanisms could be responsible for the CO₂ adsorption in the MOF. First, CO₂ oxygen atoms may interact with hydrogens and metal atoms of the framework, particularly with coordinatively unsaturated metal centers or open metal sites (OMS). Second, the CO₂ carbon atom may be attracted to the negatively charged nitrogens of the pyrazole linkers.¹⁷ It had been established that amine molecules and open nitrogen sites present high affinity toward CO₂ adsorption; thus pyrazole molecules act as Lewis basic sites and CO₂ molecules as the Lewis acids.³ Finally, flexible and microporous MOFs are suitable for CO₂ adsorption.⁵⁰

Fig. 6 For [Zn₂(L)(DMF)], (a) CO₂ adsorption isotherms at 273, 288 and 298 K, and (b) isosteric enthalpy of adsorption of CO₂.

Comparable values, ranging between 16.67–35.84 cm³ g⁻¹ and 13.08–28.22 cm³ g⁻¹ at 273 K and 298 K, respectively, observed at 75 kPa have been reported for MOFs with structures based on a very similar flexible pyrazole carboxylate ligands, using triethylenediamine and 4,4-bipyridine as pillars.⁵¹ These MOFs exhibit interpenetration and have a greater nitrogen content; however, the uptake values are not appreciably higher than those found here.

The interaction's strength between the framework and the CO₂ molecules was calculated by enthalpy of adsorption (ΔH_ads) by the Clausius Clapeyron equation at 273 K, 288 K, and 298 K. Before using the Clausius–Clapeyron approach, the isotherms at three temperatures must be fitted with the same continuous function. As most MOFs exhibit a Freundlich–Langmuir-type isotherm,²⁶eqn (3) was used.

where n is the amount of CO₂ adsorbed (the loading) in mmol g⁻¹, p is the pressure in kPa, a is the maximal loading in mmol g⁻¹, b is the affinity constant (1/kPac), and c is the heterogeneity exponent. As shown in Fig. S19–S21,† the Freundlich–Langmuir fit with the obtained experimental data; therefore, the Clausius–Clapeyron equation can predict the ΔH_ads. The value for CO₂ at zero coverage was calculated to be 27 kJ mol⁻¹ (Fig. 6b). As mentioned above, this value may be the average result of different types of interactions. Only the interaction between CO₂ and OMS sites accounts for the hybridization of the molecular orbitals, electrostatics, van der Waals forces, and Pauli repulsion.³ The profile shows that ΔH_ads value slightly increases at higher pressures, which could be associated with intermolecular interaction between CO₂ molecules. On the other hand, at lower pressure, the adsorbate molecules are not close enough for an adequate interaction between them.⁵² A quite similar ΔH_ads value (29.3–27.7 kJ mol⁻¹) was already reported for the MOF SNU-100′ ([Zn₃(TCPT)₂(HCOO)][NH₂(CH₃)₂])⁵³ which has a trinuclear Zn node and nitrogen atoms in its structure similar to the herein report for the [Zn₂(L)DMF] MOF.

Theoretical modelling

To account for the adsorption enthalpy and the interaction that CO₂ has with the MOFs, DFT calculations were performed over a reduced model of the MOFs pore. The studied model considers the portion of interest of the MOF that might be interacting with the CO₂. Therefore, two to eight CO₂ molecules were included in the cavity and beside it and allowed to arrive at a minimum over the potential energy surface.

As observed in Table 1, dispersion energy is the most important contribution to the CO₂–MOF interaction. The dispersion interaction comes from the attractive forces between the induced dipoles of the studied fragments. Its contribution to the attractive energies (in percentage) decreases as the number of CO₂ molecules increases. On the other hand, the second most important contribution of the interaction energy corresponds to the electrostatic interaction between the CO₂ molecules and the MOF cavity. Finally, as the number of CO₂ molecules increases inside the MOF cavity, the contribution of the orbital interaction percentage increases while the dispersion contrition percentage decreases. The increase in the orbital energy might be attributed to the increased number of molecule-molecule interactions, forcing them to overlap their electronic clouds. As shown in the ESI (see Fig. S22†), the CO₂ molecules show orbital interaction with the MOFs orbitals, which is shown in every calculated CO₂ representation. Finally, the fukui function of the empty MOF was plotted. As observed in the ESI (see Fig. S23†), the f− and the f+ are located over the linker's aromatic rings, which supports the reactivity of the CO₂ molecules over the aromatic rings.

Table 1 Morokuma–Ziegler EDA in kcal mol⁻¹

	ΔEPauli	ΔEElec	ΔEOrb	ΔEDis	ΔEInt	Atract	% elect	% orb	% dis
2 CO2	23.0	−10.9	−5.2	−17.8	−10.8	−33.82	32	15	53
4 CO2	45.1	−23.8	−9.6	−27.1	−15.5	−60.58	39	16	45
6 CO2	75.0	−39.4	−16.3	−43.0	−23.8	−98.78	40	17	44
8 CO2	107.0	−53.2	−23.9	−55.1	−25.1	−132.1	40	18	42

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Conclusion

In conclusion, a novel Zn(II)-based metal–organic framework [Zn₂(L)(DMF)] has been successfully synthesized via a solvothermal method by mixing a carboxylate pyrazole-based linker (L) and a Zn metal salt. This MOF comprises a trimetallic Zn₃(–COO)₆(DMF)₂ node coordinated to two linkers and two DMF molecules. Notably, the material exhibits a microporous crystalline structure, displaying an average pore diameter of 12.5 Å and a BET surface area of 402 m² g⁻¹. The intrinsic flexibility of the linker employed in the [Zn₂(L)(DMF)] synthesis suggests that ‘breathing’ phenomena may be involved, giving attractive potential for gas adsorption applications. Notably, the recorded CO₂ uptake capacity reaches 35.23 cm³ at 273 K, while the isosteric enthalpy of CO₂ adsorption stands at 27 kJ mol⁻¹ at zero coverage.

Author contributions

All authors have given approval to the final version of the manuscript.

A. L.: Investigation, methodology, visualization, formal analysis, writing original draft. S. G.: Conceptualization, methodology, supervision. X. Z.: Investigation, formal analysis. E. S.: Investigation, formal analysis, resources, supervision, project administration. J. T. H.: Resources, supervision, project administration, funding acquisition.

Data availability

The data supporting this article have been included as part of the ESI.† Synthesis and characterization of the linker; crystal data and structure refinement for [Zn₂(L)DMF]; Freundlich–Langmuir fit for CO₂ adsorption isotherm on [Zn₂(L)DMF] at different temperatures; and the molecular structure of the CO₂ interacting systems models.

Crystallographic data for the [Zn₂(L)DMF] structure in CIF format has been deposited in the Cambridge Crystallographic Data Centre (CCDC) under deposition numbers CCDC 2355199.†

Conflicts of interest

The authors declare the following competing financial interest(s): J. T. H. has interest in NuMat Technologies, a company that commercializes MOFs.

Acknowledgements

This work was supported by ANID-Millennium Science Initiative Program-NCN2021_090. ANID/FONDAP/1523A0006. FONDECYT 1241917 and 1231194. ACT210057. FONDECYT Postdoctorado 3240504. At Northwestern, this work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences via grant DE-FG02-08ER15967.

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Footnote

† Electronic supplementary information (ESI) available. CCDC 2355199. For ESI and crystallographic data in CIF or other electronic format see DOI: https://doi.org/10.1039/d4dt01457j

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