Unsaturated Metal Sites Research Articles

A wet impregnation approach to synthesize MIL-101(Cr) with open metal sites and their application in the adsorption of volatile organic compounds

The simple wet impregnation method reported a series of MIL-101(Cr) materials doped with copper acetate paddle wheel species. Powder X-ray diffraction and SEM studies showed the MOF frameworks remained intact during wet impregnation, and SEM- EDX, XPS, and N2 adsorption analyses confirmed the successful copper acetate loading. Volatile organic compounds adsorption capabilities of these materials were further examined, and it found that copper acetate doped MIL-101 (Cr) possesses up to 61% improvement in toluene uptake as compared to pristine MIL-101 (Cr) at a low partial pressure of P/P0 = 0.10 under 298.1 K. This performance improvement is attributed to the unsaturated open metal sites introduced by molecular copper acetate with a paddle wheel structure. This study provides not only a new series of promising VOC removal MOFs with unsaturated Cu(II) open metal sites but also a simple, widely applicable method for introducing Cu(II) open metal sites into MOFs by using molecular copper species with predefined paddle wheel structure.

Designing coordinatively unsaturated metal sites in bimetallic organic frameworks for oxygen evolution reaction

Metal organic frameworks (MOFs) are developing as promising catalysts for oxygen evolution reactions. A bimetallic electrocatalyst MOF using Ni and Cu as metal sources and 1,4-benzene dicarboxylic acid as a linker has been synthesized and evaluated for oxygen evolution reaction. Compared to monometallic MOFs, bimetallic MOFs participate more actively in electrocatalysis due to the higher abundance of active sites, local crystallinity, and lower long-range disorder. When utilized as oxygen evolution catalysts, Ni–Cu MOFs have a low overpotential of 340 mV at 10 mA/cm2 and a low Tafel slope of 65 mV/dec. The study paves the way for the development of highly efficient catalysts for water splitting applications.

Facile synthesis of bimetallic MIL-100(Fe, Al) for enhancing CO2 Adsorption performance

Bimetallic metal-organic frameworks, having two different metal species in the framework metal sites, demonstrate higher effectiveness in CO2 capture and separation performance than their monometallic counterpart. For this reason, a series of bimetallic MIL-100(Fe, Al) was synthesized using a hydrothermal reaction system in the presence of Fe and Al metal precursors with various molar ratios. The physicochemical characterizations of the products were influenced by adding Al species in the starting materials, inducing the successful incorporation of a certain amount of Al species inside the framework. The effect of Al incorporation was analyzed by inductively coupled plasma, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, NH3-temperature program desorption, and a N2 porosimetry. Among the investigated samples, MIL-100(Fe, Al)#2 showed the highest CO2 adsorption capacity of 3.27 mmol g−1 with an IAST-CO2/N2 selectivity of 76.5 at 25 °C and 1 bar. Compared to the MIL-100(Fe) parent sample, the results improved by approximately 26% for CO2 uptake amount and by 1.5-fold for CO2/N2 selectivity due to the increment of micropore volume and presence of the new adsorptive sites of unsaturated metal sites (Al3+) and H+ from the bridges between tiny particles of AlOOH and –COOH groups. This facile synthetic route for bimetallic MOFs has the potential to enhance CO2 adsorption performance.

Computational Discovery of Stable Metal-Organic Frameworks for Methane-to-Methanol Catalysis.

The challenge of direct partial oxidation of methane to methanol has motivated the targeted search of metal-organic frameworks (MOFs) as a promising class of materials for this transformation because of their site-isolated metals with tunable ligand environments. Thousands of MOFs have been synthesized, yet relatively few have been screened for their promise in methane conversion. We developed a high-throughput virtual screening workflow that identifies MOFs from a diverse space of experimental MOFs that have not been studied for catalysis, yet are thermally stable, synthesizable, and have promising unsaturated metal sites for C-H activation via a terminal metal-oxo species. We carried out density functional theory calculations of the radical rebound mechanism for methane-to-methanol conversion on models of the secondary building units (SBUs) from 87 selected MOFs. While we showed that oxo formation favorability decreases with increasing 3d filling, consistent with prior work, previously observed scaling relations between oxo formation and hydrogen atom transfer (HAT) are disrupted by the greater diversity in our MOF set. Accordingly, we focused on Mn MOFs, which favor oxo intermediates without disfavoring HAT or leading to high methanol release energies─a key feature for methane hydroxylation activity. We identified three Mn MOFs comprising unsaturated Mn centers bound to weak-field carboxylate ligands in planar or bent geometries with promising methane-to-methanol kinetics and thermodynamics. The energetic spans of these MOFs are indicative of promising turnover frequencies for methane to methanol that warrant further experimental catalytic studies.

Stepwise Assembly of Quinary Multivariate Metal-Organic Frameworks via Diversified Linker Exchange and Installation.

Multivariate MOFs (MTV-MOFs) constructed from multiple components with atomistic precision hold the promise for many fascinating developments in both fundamental sciences and applications. Sequential linker installation can be an effective method to introduce different functional linkers into an MOF that contains coordinatively unsaturated metal sites. However, in many cases, these linkers must be installed according to a specific sequence and the complete synthetic flexibility and freedom is yet to be realized. Here, we rationally decreased the size of the primary ligand used in NPF-300, a Zr-MOF with scu topology (NPF = Nebraska Porous Framework), and synthesized its isostructure, NPF-320. NPF-320 exhibits optimized pocket sizes which allow for the post-synthetic installation of three secondary linkers in all six permuted sequences via both linker exchange and installation, forming a final quinary MTV-MOF via single-crystal-to-single-crystal transformation. With the functionalization of the linkers from the quinary MOF system, one will be able to construct MTV-MOFs not only with variable porosity but also with unprecedented complexity and encoded synthetic sequence information. The utility of sequential linker installation was further demonstrated by the construction of a donor-acceptor pair-based energy transfer system.

Synthesis, characterization, and selective gas adsorption performance of hybrid NH2-MIL-101(Fe)/ZIF-8 metal organic framework (MOF)

In this paper, an efficient NH2-MIL-101(Fe)/ZIF-8 metal organic framework (MOF) with tunable pore architecture was synthesized by an internal extended growth approach, using polyvinylpyrrolidone (PVP) as a regulator. In the resultant structure, the larger-pore MOF (NH2-MIL-101(Fe)) provides the facilitated transport pathways and the smaller-pore MOF (ZIF-8) acts as the shell, enhancing the molecular sieving properties. The synthesized MOFs were characterized by FESEM, EDS, HRTEM, FTIR, XRD, TGA, and BET analyses, and the hybrid structure formation was accordingly approved. Furthermore, the pure gas adsorption measurements were conducted for CO2, N2, CH4, C2H6, and C2H4 gases at 298 and 328 K and equilibrium pressures up to 4 bar. The CO2 adsorption capacity of 3.982 mmol g−1 at 298 K for NH2-MIL-101(Fe)/ZIF-8 was obtained, which is ∼43% and ∼127% higher than the values for the individual MOFs, respectively. This increase is mainly attributed to the favorable CO2 interactions with the unpaired electrons of nitrogen (amine functional groups and imidazole nitrogen) as well as oxygen atoms along with unsaturated metal sites present in the both MOFs. In addition, the beneficial size exclusion effect of the shell MOF, resulted in improved gas adsorption selectivity values. The synthesized hybrid structure displayed considerably higher CO2/N2 and CO2/CH4 adsorption selectivities, which were ∼3.8 and 1.7 times greater than those of the pristine NH2-MIL-101(Fe) MOF, respectively. Furthermore, the C2H6/C2H4 selectivity of NH2-MIL-101(Fe)/ZIF-8 was raised by ∼48%, compared to the NH2-MIL-101(Fe) MOF, owning to the molecular sieving effect of ZIF-8 for C2H6 with larger kinetic diameter compared to C2H4.

Bibonding Constructing Coordinatively Unsaturated Zni+(0 < i < 2) Sites for Enhanced Photo‐Fenton Activity

AbstractThe coordinatively unsaturated metal sites (CUMSs) have attracted widespread attention for enhancing catalytic activity. This study reports a controllable “bibonding” method to construct the coordinatively unsaturated Zni+ (0 < i < 2) active sites by forming N(g‐C3N4)‐Zn—N(imidazole) under mild experimental conditions. The catalysts with Zni+ are used for the photo‐Fenton reaction to degrade methylene blue (MB) without any oxidant. The degradation efficiency is positively correlated with Zni+. The Zni+ improved the Fe2+/Fe3+ conversion efficiency and the H2O2 generation ability of the catalyst. The optimized catalysts with 2.27% of Zni+ present a photo‐Fenton degradation efficiency of MB as 73.45 mg g−1 at pH 7 and 78.54 mg g−1 at pH 4. This strategy can be used to construct CUMSs for a series of narrow bandgap semiconductor materials containing nitrogen atoms.

Engineering 3D Interpenetrated ZIF-8 Network in Poly(ethylene oxide) Composite Electrolyte for Fast Lithium-Ion Conduction and Effective Lithium-Dendrite Inhibition

A novel 3D ZIF-8 network-reinforced polyethylene oxide (PEO) composite polymer electrolyte (Z-C-PAN-PEO) is successfully built, in which the network with an interpenetrated structure is tactfully developed by in situ assembling ZIF-8 nanoparticles on electrospinning carboxylated polyacrylonitrile (C-PAN) nanofiber surfaces. ZIF-8 with high porosity and unsaturated open metal sites will act as the bridge between C-PAN nanofibers and the PEO matrix. It is proven that the selected ZIF-8 can play a significant role in facilitating Li+ conduction and transference by effectively interacting with the oxygen atoms of C–O–C to promote the segmental movement of PEO and immobilizing TFSI– anions to release more free Li+. The 3D interpenetrating structure of Z-C-PAN further enables the conduction channels more consecutive and long-ranged, endowing the Z-C-PAN-PEO electrolyte with an optimum ionic conductivity of 4.39 × 10–4 S cm–1 and a boosted Li+ transference number of 0.42 at 60 °C. Other improvements occurring in the reinforced electrolytes are the broaden electrochemical stability window of ∼4.9 V and sufficient mechanical strength. Consequently, the stable Li-plating/stripping for 1000 cycles at 0.1 mA cm–1 witnesses the splendid compatibility against Li dendrite. The cycling performance of LiFePO4/Z-C-PAN-PEO/Li cells with a reversible capacity of 116.2 mAh g–1 after 600 cycles at 0.2 C guarantees the long-term running potential in lithium metal batteries. This study puts forward new insights in designing and exploiting the active role of MOFs for high-performance solid polymer electrolytes.

Highly water-stable MOF-74 synthesized by in-situ trace polymer modification

MOF-74 family is unstable in humid environment because its coordination bond between metal ions and oxygen atoms is relatively weak. This limits the practical application of MOF-74 material. Therefore, improving the water vapor/water stability of MOF-74 is crucial for their use in practical applications. In this work, we propose a strategy involving a trace polymer in-situ modified MOF-74. During the in-situ synthesis, polyvinylamineacid (PCH) was introduced into the structure of MOF-74 (PCH-MOF-74, PMOF-74) to form a hydrophobic environment around the unsaturated metal sites to enhance water stability. After immersion in water or acid, PMOF-74 can maintain most of the original crystal structure and gas adsorption capacity. The experimental results show that the successful incorporation of PCH into MOF can effectively improve the water vapor/water stability of MOF structures, and it is also worth further improving and enhancing the structural stability of other MOF materials with metal sites.

Simulating water adsorption in metal–organic frameworks with open metal sites using the 12-6-4 Lennard–Jones potential

ABSTRACT Metal–organic frameworks (MOFs) with coordinatively unsaturated open metal sites (OMSs) are promising sorbent materials in atmospheric water harvesting (AWH) systems at low relative humidity (RH) due to their strong interactions with water molecules. However, accurate computational modelling of water adsorption in those materials are challenging, as standard force fields (FFs) based on the 12-6 Lennard–Jones (L–J) potential cannot properly describe the water–OMS interactions. In biomolecular simulations, the 12-6-4 L–J potential has been successfully used to model metal ion–water interactions in which the extra 1/r 4-term is for charge-induced dipole electrostatics. In this work, we adopted this strategy and used the 12-6-4 L–J potential to model water–OMS interactions in MOFs for low RH AWH applications. Without any modifications, the parameters used for aqueous metal ions were able to greatly improve the accuracy in predicting water adsorption isotherms in MOF-74, which highlights the simplicity and transferability of this method.

Design of metal-organic frameworks for improving pseudo-solid-state magnesium-ion electrolytes: Open metal sites, isoreticular expansion, and framework topology

The design criteria for metal-organic frameworks (MOFs) have been established by evaluating the relationship between their key characteristics and magnesium-ion conductivity based on three types of secondary building blocks (Zn4O(CO2)6: MOF-5 and MOF-177; Cu2(CO2)4: MOF-199, MOF-143, MOF-14, and MOF-399; Cu2O2(CO2)2: Cu-MOF-74) to achieve pseudo-solid-state magnesium-ion conduction. We found that open-metal sites and channel layouts play a pivotal role in promoting magnesium-ion transport dynamics at reduced activation energy, transforming MOF scaffolds into ionic-channel analogs. X-ray absorption spectroscopy combined with Raman and Fourier-transform infrared spectroscopy predicted the chemical environment, solvents, and anions that occupied coordinatively unsaturated metal sites. The chemical compositions of electrolytes determined by 1H-NMR (nuclear magnetic resonance) and organic elemental analysis confirmed that isoreticular expansion increases the molar percentage of charge carriers, providing high conductivity. The current research systematically reveals the impacts of different MOF characteristics on ionic conduction performance, paving the way for the construction of a new class of fast and selective multivalent-ion pseudo-solid electrolytes.

Shine a light on the defect evolution over the TiO2 surface

In a recent issue of Chem Catalysis, He et al. quantify the evolution of surface unsaturated metal site and oxygen vacancy over TiO2 upon calcination treatment under different atmospheres using 31P solid-state nuclear magnetic resonance (NMR) spectroscopy with trimethylphosphine as a probe. The quantitative results are correlated with the H2 yield in the water-splitting reaction.

Carbon-Anchored Molybdenum Oxide Nanoclusters as Efficient Catalysts for the Electrosynthesis of Ammonia and Urea.

The electrochemical NO3 - reduction and its coupling with CO2 can provide novel and clean routes to synthesize NH3 and urea, respectively. However, their practical application is still impeded by the lack of efficient catalysts with desirable Faradaic efficiency (FE) and yield rate. Herein, we report the synthesis of molybdenum oxide nanoclusters anchored on carbon black (MoOx /C) as electrocatalyst. It affords an outstanding FE of 98.14 % and NH3 yield rate of 91.63 mg h-1 mgcat. -1 in NO3 - reduction. Besides, the highest FE of 27.7 % with a maximum urea yield rate of 1431.5 μg h-1 mgcat. -1 toward urea is also achieved. The formation of electron-rich MoOx nanoclusters with highly unsaturated metal sites in the MoOx /C heterostructure is beneficial for enhanced catalytic performance. Studies on the mechanism reveal that the stabilization of *NO and *CO2 NOOH intermediates are critical for the NH3 and urea synthesis, respectively.

Carbon‐Anchored Molybdenum Oxide Nanoclusters as Efficient Catalysts for the Electrosynthesis of Ammonia and Urea

AbstractThe electrochemical NO3− reduction and its coupling with CO2 can provide novel and clean routes to synthesize NH3 and urea, respectively. However, their practical application is still impeded by the lack of efficient catalysts with desirable Faradaic efficiency (FE) and yield rate. Herein, we report the synthesis of molybdenum oxide nanoclusters anchored on carbon black (MoOx/C) as electrocatalyst. It affords an outstanding FE of 98.14 % and NH3 yield rate of 91.63 mg h−1 mgcat.−1 in NO3− reduction. Besides, the highest FE of 27.7 % with a maximum urea yield rate of 1431.5 μg h−1 mgcat.−1 toward urea is also achieved. The formation of electron‐rich MoOx nanoclusters with highly unsaturated metal sites in the MoOx/C heterostructure is beneficial for enhanced catalytic performance. Studies on the mechanism reveal that the stabilization of *NO and *CO2NOOH intermediates are critical for the NH3 and urea synthesis, respectively.

Mixed-matrix membranes containing zero-dimension porphyrin-based complex for propylene/propane separation

The membrane-based technology for propylene/propane (C3H6/C3H8) separation is very promising due to its low-energy separation process with high effectiveness. Herein, we propose a new type of mixed-matrix membranes (MMMs) containing zero-dimension non-porous porphyrin-based complex (M-TMCPP, M = Zn2+, Cd2+, Ni2+) with coordinatively unsaturated metal sites. Density functional theory calculation results show that M-TMCPP can form π complexation with C3H6 and facilitate C3H6 molecule through membranes. Different from porous nanofillers, M-TMCPP exhibits zero-dimension non-porous molecular structure and can be dissolved in solvent at molecular lever under low concentration. Benefiting from the favorable interaction between C3H6 with metal sites and the uniform distribution of M-TMCPP particles and/or even independent M-TMCPP molecules in polymer, the porphyrin-based complexes are used as nanofillers in fluorinated polyimide (6FDA-DAM). The prepared MMMs exhibit an extraordinary C3H6/C3H8 ideal selectivity of up to 45.6 with a high C3H6 permeability of 70.3 Barrer, far surpassing the previously reported 6FDA-based polyimide MMMs and polymeric membranes. Membrane performances of three different M-TMCPP MMM were studied and the gas transportation mechanism was evaluated. This work provides a new conceptual approach of using non-porous zero-dimensional complexes with coordinatively unsaturated sites as fillers in mixed matrix membranes, which not only can accomplish olefin/alkane separation with ultrahigh performance, but also indicates its high potential for feasible usage.

Heterometallic YbCo–Organic Framework for Efficiently Catalyzing Cycloaddition of CO2 with Epoxides and Knoevenagel Condensation

Due to the excellent catalytic performance of Co-MOFs and Ln-MOFs on the chemical fixation of CO2, the self-assembly of microporous heterometallic compounds with the aid of designed functional ligands is carried out in our group. Herein, the solvothermal self-assembly of Co2+, Yb3+, and 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine (H5BDCP) generated a rarely reported {CoYb}n-chain-based framework of {[CoYb(BDCP)(H2O)]·3DMF·3H2O}n (NUC-70) with quasi-nanoporous channels (aperture ca. 11.4 Å) shaped by six rows of {CoYb(CO2)5(H2O)}n nodes. To the best of our knowledge, this is a rare 3d-4f heterometallic chain of {CoYb(CO2)5(H2O)}n with a staggered arrangement of Co2+ and Yb3+. After removing the associated water molecules, NUC-70a possesses the excellent characteristics of a large specific surface area, unsaturated open metal sites of Co2+ and Yb3+ as Lewis acid sites, and high heat/water-resistant physicochemical properties. Catalytic experiments showed that NUC-70a possessed a high catalytic activity on the cycloaddition reactions of epoxides with CO2 under mild conditions. Furthermore, the experiments performed confirmed that the Knoevenagel condensation reactions of aldehydes and malononitrile could be efficiently catalyzed by NUC-70a. This work illustrates that characteristic ligand design plays a key role in the self-assembly of MOFs with specific functions.

Efficient CO2 Capture under Humid Conditions on a Novel Amide-Functionalized Fe-soc Metal-Organic Framework.

CO2 is the main source of the greenhouse gases, and its capture from flue gas under humid conditions is challenging but important for promoting carbon neutrality. Herein, we report a novel soc topology Fe-based metal-organic framework (Fe-dbai) with highly efficient postcombusion CO2 capture performance by integrating multiple specific functionalities, such as unsaturated metal sites and amide functional groups. The CO2 adsorption capacity and CO2/N2 selectivity of Fe-dbai are high up to 6.4 mmol/g and 64 (298 K, 1 bar), respectively, superior to many other reported MOFs. More importantly, the CO2 working capacity of Fe-dbai under 60% RH conditions preserves 94% of that under dry conditions in the breakthrough experiments of CO2/N2 (15:85, v/v) mixtures. The molecular simulation highlights that the electronegative amide CO- group has a good affinity for CO2 and can improve the interaction between Fe UMS and CO2. Although H2O molecules will occupy a small fraction of the adsorption sites, the confinement effect it produces can enhance the adsorption affinity of the framework for CO2, which results in Fe-dbai retaining most of the CO2 adsorption capacity under humid conditions. The excellent CO2 capture performance makes Fe-dbai a potential candidate for the practical application of CO2 capture.

In situ self-assembled macroporous interconnected nanosheet arrays of Ni-1,3,5-benzenetricarboxylate metal − organic framework on Ti mesh as high-performance oxygen evolution electrodes

Highly efficient metal–organic framework (MOF)-based oxygen evolution reaction (OER) catalysts are desirable for water splitting, but their development remains challenging due to poor accessibility of coordinatively unsaturated metal (cum) sites and low intrinsic activity. A large-area three-dimensional (3-D) macroporous interconnected nanosheet array of Ni-1,3,5-benzenetricarboxylate has been in situ self-assembled on Ti mesh (TM) by using ethanol as the solvent and high-affinity oxide layer on TM to promote in situ nucleation. The obtained nanoarchitecture exhibits much superior catalytic activity compared to most reported catalysts including MOF-based catalysts, other precious-metal-free ones, and Ir/Ru-based ones. Additionally, this electrode undergoes no current decay after 300 cyclic voltammetry (CV) cycles and can maintain at 250 mA cm−2 for over 266 h. The excellent catalytic performance is mainly due to the 3-D macroporous and interconnected nanosheet array structure improving cum site exposure and charge transport and in situ activated cum cations enhancing OH− adsorption. This work not only develops a facile and economical approach to synthesize 3-D macroporous interconnected MOF nanosheet arrays to simultaneously increase the number, exposure, and intrinsic activity of active sites and facilitate charge transport for high-performance eletrocatalysis, but provides scientific insights into the mechanisms for self-assembly of this unique nanoarchitecture and for the high OER performance.

Functionalization of Metal–Organic Framework Nanochannels for Water Transport and Purification

Artificial water nanochannels (AWCs) have drawn great attention due to their potential use in water purification. Herein, we propose an AWC design, which is based on coordinatively functionalizing unsaturated metal sites found in metal–organic frameworks (MOFs) with one-dimensional nanochannels. As a computational demonstration, we consider two MOFs, namely, Ni-CPO-27 and Ni-CPO-54, and graft proline, imidazolecarboxylic acid, imidazolecarboxaldehyde, pyrazolecarboxylic acid, and pyrazole carbaldehyde molecules into the MOF nanochannels. To assess the strength of the molecule-metal binding, binding energies were calculated using density functional theory. The results indicate that the MOFs containing either proline or 2-imidazolecarboxylic acid form water-stable AWCs with binding energies twice that of the binding energy of water. To shed light on the water diffusion mechanism in the proline-Ni-CPO-27/54 and 2-imidazolecarboxylic-Ni-CPO-27/54 AWCs, molecular dynamics simulations were performed to calculate the mean-squared displacement of water molecules and nonbonded interaction energies between select pairs of atoms in water and coordinated molecules were analyzed. It was found that the fastest water diffusion occurs in proline-Ni-CPO-54 with a self-diffusion coefficient of 7.2 ± 0.5 × 10–8 cm2/s. In comparison, the fastest water self-diffusion coefficient reported in a carbon nanotube-based AWC is 9 × 10–6 cm2/s. Nonbonded interactions between specific atom pairs regulate water diffusion in the functionalized MOF nanochannels. In particular, the change in water mean-squared displacement with changing water loading correlates well with the nonbonded energies between the partially positively charged hydrogen atoms in water and the partially negatively charged oxygen and nitrogen atoms in the proline and 2-imidazolecarboxylic acid molecules. The results presented herein indicate that water-stable MOFs could perform well as AWCs, thereby lending support to the further design and synthesis of MOF-based AWCs for water purification.

Ab Initio Study of Adsorption of Polymers on Metal–Organic Framework Surfaces

We present a computational study of metal–organic framework (MOF)/polymer interfaces in order to better understand the phenomena relevant to optimizing the design of MOF/polymer mixed-matrix membrane (MMM) materials. In this pursuit, we study adsorption of models of polymers Kapton and 6FDA-Durene to models of MOF surfaces both with and without coordinatively unsaturated metal sites existing on the surface (ZIF-8 and Co-BDC, respectively) at the density functional theory (DFT) level. To do this, we develop and tune models of polymers that are DFT-accessible, establishing a method for creating models of polymers that is transferable beyond these systems for use in studying MMMs, identifying some limits to this method. Through this work, we find that while polymer interactions with MOF surfaces may be expected to be dispersion-dominated, in the presence of coordinatively unsaturated metals on the surface, electronic and electrostatic effects may play a significant role, consistent with the previous literature in this area. We additionally find that while polymer model terminations often do not strongly affect the qualitative behavior at the MOF/polymer interface, an accurate electronic representation of the polymers may be critical for the development of force field-based tools to model MMMs and for a detailed understanding of the interactions in some cases.