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Article

Development and Characterization of PVA Membranes Modified with In(BTC) Metal–Organic Framework for Sustainable Pervaporation Separation of Isopropanol/Water

by
Vladimir Polyakov
1,
Mariia Dmitrenko
2,*,
Meri Kalmakhelidze
1,
Anna Kuzminova
2,
Roman Dubovenko
2,
Elizaveta Mukhanova
1,
Alexander Soldatov
1 and
Anastasia Penkova
1,2,*
1
The Smart Materials Research Institute, Southern Federal University, 105/42 Bolshaya Sadovaya Str., Rostov-on-Don 344090, Russia
2
St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia
*
Authors to whom correspondence should be addressed.
Sustainability 2024, 16(23), 10257; https://doi.org/10.3390/su162310257
Submission received: 17 October 2024 / Revised: 14 November 2024 / Accepted: 18 November 2024 / Published: 23 November 2024
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Abstract

:
In this study, pervaporation membranes from synthetic biodegradable polyvinyl alcohol (PVA) with improved properties for isopropanol dehydration were developed through modification with a synthesized In(BTC) metal–organic framework. The improvement in the PVA membrane properties was achieved by varying the In(BTC) concentration (2.5–7 wt.%) in the PVA matrix to allow us to select the optimal concentration for the membrane, which was further chemically cross-linked with maleic acid to increase the resistance, and developing a cross-linked supported membrane from the optimal PVA/5%In(BTC) composite for promising industrial applications. The synthesized In(BTC) and membranes were characterized by using spectroscopic, microscopic, X-ray diffraction, and thermogravimetric analysis methods, as well as swelling degree, contact angle measurements, and the Brunauer–Emmett–Teller adsorption model. The obtained regularities were confirmed by quantum chemical calculations. The cross-linked supported membrane from PVA/5%In(BTC) had optimal transport properties for isopropanol dehydration (20–90 wt.% water), 99.9–89.0 wt.% water in the permeate, and 0.142–0.341 kg/(m2h) of permeation flux, the rate of which was four times higher compared to the PVA membrane in separating 20–30 wt.% water/isopropanol.

1. Introduction

Membrane processes are currently actively related to sustainable processes [1]. The use of selective membranes in industry for the sorption [2], filtration [3,4], and separation [5,6] of liquids and gases makes it possible to significantly simplify classical technological processes, particularly to reduce energy consumption, eliminate the use of highly toxic solvents and expensive extractants, minimize equipment, etc. [7]. One of the simplest and most promising methods for separating low-molecular-weight liquid components is pervaporation. This is a separation process in which two- or multi-component homogeneous liquids on one side come into contact with a membrane (as a rule, a non-porous one), and on the other side, a vacuum is created, facilitating penetration through the membrane. The components of the mixture are sorbed on the membrane, diffuse through it, and are desorbed into the vapor phase. The resulting vapor is called the “permeate” [8]. The advantage of pervaporation is that the separation is not based on the thermodynamic equilibrium between the vapor and liquid phases, as in distillation, but is determined by the diffusion rate and solubility of the components in the membrane. Also, some of the main advantages of pervaporation for sustainable development compared to traditional separation processes are its waste-free nature and ability to separate azeotropic mixtures without the use of additional toxic agents, which subsequently leads to an additional purification stage [9]. As a result, pervaporation is actively used, for example, for the dehydration of various organic solvents [10,11].
Membrane technology is growing continuously and the membrane market is reaching billions of dollars. However, currently available membranes are not sustainable, as they come from polymers based on fossil fuels [12]. Significant environmental pollution has become a great driver for the development and research of membrane materials made of biodegradable polymers that can replace traditional ones. Biodegradable polymers are classified into (a) natural biopolymers (cellulose, starch, etc.), (b) polymers obtained via microbial fermentation, and (c) synthetic biodegradable polymers (polyvinyl alcohol (PVA), poly(ε-caprolactone), etc.) [13]. PVA has attracted considerable attention for membrane technology (in particular, pervaporation dehydration [14,15]) due to its large-scale production, low cost, high hydrophilicity, chemical resistance, tensile strength, and complete biodegradability. The safety of PVA has been confirmed as it is recognized as a food additive and a component of packaging material [13]. However, PVA also has a significant shortcoming—its high solubility in water—which limits its use in separating diluted aqueous solutions. To overcome this drawback of PVA-based membrane materials, cross-linking with various agents (such as maleic, fumaric acids, glutaraldehyde, etc. [5,16]) and the introduction of various particles into the polymer matrix (such as carbon nanoparticles [15,17], zeolites [18], metal–organic frameworks (MOFs), etc.) are used.
One of the most promising classes of substances used as membrane modifiers are MOFs [19]. This is a relatively new class of compounds consisting of metal ions or metal–oxygen clusters linked to each other by a bridging organic molecule—a linker. As a result, a highly porous 3D framework structure is formed, penetrated by cavities and channels. Varying the type and size of the linker, as well as its functional groups, allows us to adjust the pore size, increasing or decreasing the sorption selectivity. High values of specific surface area (SSA) and thermal and chemical stability determine a wide range of applications of MOFs, including sensing [20], sorption [21], gas storage, heterogeneous catalysis [22], chemical separation [23], and targeted drug delivery [24]. The preparation of mixed-matrix membranes (MMMs) with MOFs is an actively developing direction. Due to the presence of organic molecules in the MOF structure, their excellent compatibility with the membrane material is achieved. An MMM from PVA was developed through modification with MOFs such as aluminum fumarate [25], UiO-66 and UiO-67 [26], UiO-66-NH2 [27], MOF-303 [28], Cu(BTC) [29], MOF-801 [30], and MIL-140A [31]. To the best of our knowledge, there is no information about the development and study of pervaporation PVA membranes modified with an Indium (In)-based MOF.
The choice of an In-based MOF as a modifier is due to the fact that it is a nontoxic metal element [32] and can thus maintain the environmental friendliness of the MMM. It has good light transmittance and exhibits more versatile coordination modes and clustering among high-valence metal ions [33]. The use of In can be advantageous for the design and synthesis of stable MOFs with tailored properties. In trimesylates are a class of MOFs that include several individual phases built from In ions and 1,3,5-benzenetricarboxylic (trimesic) acid, but with different structures. It is known that the coordination sphere of In3+ is capable of binding to four carboxyl groups, forming a secondary building unit with a distorted tetrahedral geometry, which can then bind to carboxylate linkers to form a wide variety of anionic frameworks such as R3[In3(BTC)4]. The organic cation R+ usually acts as a counterion, and its size directly affects the phase composition of the resulting framework. The largest cations, such as tetrapropylammonium (Pr4N+) or tetrabutylammonium (Bu4N+), can form a rhombohedral phase with the space group R3c, whereas smaller cations are capable of forming a cubic lattice with the space group I43d [34]. Under certain conditions, the formation of frameworks with different structures [R+[In3O(BTC)2(H2O)3]2[In3(BTC)4]·solvents] occurs. These are designated in the literature as CPM-5 (R = (CH3)2NH2) and CPM-6 (R = CH3NH3), containing both anionic [In3(BTC)4]3− and cationic [In3O(BTC)2(H2O)3]+ framework units [35]. Due to the unique charged framework structure, the surface of In trimesylate nanoparticles enables the formation of numerous sorption centers on their surface, which can significantly improve the characteristics of PVA pervaporation membranes.
The aim of this study was to develop and study of MMMs from biodegradable PVA modified with synthesized In(BTC) for enhanced sustainable pervaporation dehydration. The synthesized In(BTC) was characterized by TEM microscopy, Fourier-transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), and the Brunauer–Emmett–Teller (BET) N2 adsorption model to estimate the SSA and pore size distribution. The effect of introducing different concentrations of In(BTC) into the PVA matrix on the properties of the PVA-based MMM was studied to select the optimal content of the modifier. To increase the dissolution resistance, a dense PVA/5% In(BTC) membrane with optimal characteristics was chemically cross-linked with maleic acid. To further increase the permeability for promising industrial applications, cross-linked supported membranes with a thin selective layer of a PVA/5% In(BTC) composite deposited onto a porous substrate were developed and studied. The structure and physicochemical properties of the developed composites and MMM were investigated by FTIR spectroscopy, scanning electron (SEM) and atomic force (AFM) microscopy, thermogravimetric analysis (TGA), swelling degree, and contact angle measurements. The obtained changes were confirmed by quantum chemical calculations. The pervaporation performance of the membranes was evaluated in the separation of water/isopropanol mixtures in a wide composition range.

2. Materials and Methods

2.1. Materials

To prepare membranes, polyvinyl alcohol (PVA) with a molecular weight of 103 kDa (NevaReaktiv, St. Petersburg, Russia) was used. The In(BTC) MOF (SSA of 87 m2/g, total pore volume of 0.077 cm3/g) was used as a modifier. In(BTC) synthesis technique, TEM, and XRD investigations are presented in the Supplementary Materials. A porous membrane based on aromatic polysulfonamide (UPM, pore size 200 Å) was purchased from Vladipor (Vladimir, Russia) and used as the membrane support. Indium (III) nitrate hydrate (In(NO3)3·H2O), 1,3,5-benzenetricarboxylic (trimesic) acid (H3BTC), dimethylformamide (DMF), isopropanol (IPA), ethanol, and maleic acid (MA) purchased from Sigma-Aldrich and Vekton (St. Petersburg, Russia) were used without additional purification.

2.2. Membrane Preparation

2.2.1. Dense Membrane

Unmodified membranes were prepared from 2 wt.% aqueous solutions of PVA, which were prepared by heating for 5 h at 85 °C and vigorous stirring. MMM were obtained as follows: the PVA and In(BTC) powders were mixed and ground in an agate mortar in modifier quantities from 2.5 to 7.5 wt.% relative to the amount of PVA. Then, the resulting mixtures were dissolved in water under conditions similar to those of the PVA solution. The resulting PVA solution and PVA/In(BTC) composite were subjected to ultrasound for 20 min and transferred to Petri dishes to form membranes by solvent evaporation at 40 °C in an oven for 24 h.
To use membranes in the separation of dilute solutions, the developed PVA and PVA/In(BTC) membranes were cross-linked with MA. MA powder was added to the PVA solution and PVA/In(BTC) composite in an amount equal to 35 wt.% relative to the PVA weight, followed by stirring for 2 h. Cross-linked membranes were prepared in accordance with the procedure described above. After molding, the membranes with MA were heated in an oven at 110 °C for 2 h for chemical cross-linking [36].

2.2.2. Supported Membranes

A PVA solution or PVA/In(BTC) composite containing MA was cast on the surface of a porous UPM substrate to form a selective thin dense polymer layer by drying in air for 24 h. The membranes were then heated in an oven at 110 °C for 2 h for chemical cross-linking.
The marking of all the obtained membranes is presented in Table 1.

2.3. Pervaporation Experiment

The performance of all resulting PVA and PVA/In(BTC) membranes was studied using a laboratory pervaporation setup at room temperature (20 °C) and a vacuum of ˂10−1 mmHg. The water content in the permeate was estimated using a gas chromatograph Chromatec Crystal 5000.2 (Chromatec, Nizhny Novgorod, Russia) equipped with a thermal conductivity detector and a “Hayesep R” column.
The permeation flux J [kg/(m2·h)] of the membranes was calculated using Equation (1) [37]:
J = W A · t ,
where W [kg] is the permeate weight, A [m2] is the effective membrane area (9.6 × 10−4 m2), and t [h] is the measurement time.
Measurements at each point were repeated at least 3 times, and the results were averaged.

2.4. Fourier-Transform Infrared Spectroscopy (FTIR)

The chemical composition of the PVA and PVA/In(BTC) membranes were studied using an IRAffinity-1S spectrometer (Shimadzu, St. Petersburg, Russia) with Attenuated Total Reflectance (ATR) geometry. The measurement was performed at 25 °C in the range of 500–4000 cm−1.
A Bruker Vertex 70 spectrometer (Bruker, Germany) was applied for In(BTC) investigation. The Attenuated Total Reflectance (ATR) geometry with air was used as the reference. The spectra were collected with a resolution of 1 cm–1 and 128 scans were performed in the range from 4000 to 500 cm−1 on an MCT detector and a Bruker Platinum ATR attachment.

2.5. Specific Surface Area Measurement

The specific surface area (SSA) was calculated using the Brunauer–Emmett–Teller (BET) model based on N2 adsorption isotherms measured on a TOP 200 Surface Area and Pore Size Analyzer (Altamira Instruments, China) at 77 K. Samples were activated at 250 °C for 12 h under a dynamic vacuum in a Prep J4 Vacuum Degasser (Altamira Instruments, China) before the measurements.

2.6. Scanning Electron Microscopy (SEM)

The cross-section and surfaces of the PVA and PVA/In(BTC) membranes were studied using a Zeiss AURIGA Laser (Carl Zeiss SMT, Oberhochen, Germany) at 1 kV. Cross-sections of the samples were obtained by breaking the membrane in liquid nitrogen.

2.7. Atomic Force Microscopy (AFM)

The surface of the PVA and PVA/In(BTC) membranes was studied using an NT-MDT NTegra Maximus atomic force microscope (NT-MDT Spectrum Instruments, Moscow, Russia) with standard silicon cantilevers and a rigidity of 15 N·m–1 in tapping mode.

2.8. Contact Angle Measurements

To study the hydrophilicity/hydrophobicity of the obtained membrane surfaces, contact angles of water were measured using a Goniometer LK-1 (NPK Open Science Ltd., Krasnogorsk, Russia) via the sessile drop method. The software “DropShape” was used to calculate the contact angle.

2.9. Swelling Degree

To estimate the swelling degree (sorption), samples of both uncross-linked and cross-linked dense membranes based on the PVA and PVA/5%In(BTC) composite were placed in water/IPA (20/80 and 30/70 wt.%) mixtures and in pure water (for only cross-linked dense membranes). The weight of each membrane was regularly checked until a constant swelling weight was achieved. To calculate the swelling degree S [%], Equation (2) was used:
S = m s − m 0 m 0 · 100 %
where m0 (g) is the weight of the dry membrane, and ms (g) is the weight of the swollen membrane.

2.10. Thermogravimetric Analysis (TGA)

The thermochemical stability of dense PVA and PVA/In(BTC) membranes was studied using Thermobalance TG 209 F1 Libra (Netzsch, Leuna, Germany) in a temperature range of 30–586 °C and a heating rate of 10 °C/min in Ar atmosphere.

2.11. Computational Methods

All model structures were subjected to geometry optimization using Gaussian 16 W software [38]. The optimization process employed the B3LYP method [39,40,41] in conjunction with a 6-311++G** basis set. All model systems exhibited a singlet ground state configuration. The optimization process was conducted without the imposition of symmetry constraints, and the Hessian matrices confirmed the presence of true minima with no imaginary frequencies. The thermodynamic parameters were estimated at 298.15 K and 1 atm. Bader’s Quantum Theory of Atoms in Molecules (QTAIM) analysis and bond order calculations were facilitated by a multifunctional wavefunction analyzer (Multiwfn 3.8) [42]. Furthermore, non-covalent interaction plots (NCIplots) [43] were generated in VMD [44] software (version 1.9.4a53 (29 June 2021)) with an isovalue of 0.5 (e1/3 bohr)−1 and a color scale range of [−0.04, 0.02] e bohr−3.

3. Results and Discussion

3.1. Dense PVA and PVA/In(BTC) Membrane Investigation

3.1.1. Transport Characteristics in Pervaporation Dehydration of IPA

To determine the optimal MOF content in the polymer matrix, 2.5, 5, and 7.5 wt.% of In(BTC) were introduced into the PVA membrane, and the performance of the obtained uncross-linked membranes was tested in the pervaporation separation of water/IPA mixtures (20 and 30 wt.% of water). The results are presented in Figure 1.
The graph in Figure 1a demonstrates a tendency for the rise in permeation flux with increasing water content for all membranes due to the enhanced swelling in water (confirmed by swelling degree below). The introduction of In(BTC) into the PVA matrix also increased the permeation flux of the modified membranes. It may be explained by the porous and anionic In(BTC) structure, structural changes in membrane morphology (the formation of cross-sectional irregularities and “granular” surface, confirmed by SEM and AFM data below) and increased surface hydrophilicity (confirmed by contact angle data, Table 2) during modification, causing enhanced swelling in the feed and the rise in membrane permeability. The decreased permeation flux of the PVA/7.5%In(BTC) membrane compared with the other modified membranes may be caused by the appearance of MOF clusters in the inner membrane structure (confirmed by SEM data below), which can prevent the penetration of feed components through the membrane, forming impassable zones.
The water content in the permeate for all membranes was 99.9 wt.% due to the low water content in the feed. However, the modified membranes demonstrated lower selectivity compared to the pristine PVA membrane in the pervaporation dehydration of IPA with 30 wt.% water, which decreased with increasing the modifier content in the PVA matrix. This may be due to two reasons: (1) the trade-off between permeability and selectivity, as well as (2) a more effective interaction of the BTC ligand from MOF with the feed components than that from PVA (confirmed by computational investigation in Section 3.2.1), resulting in simultaneous component penetration and reduced selectivity. Thus, the PVA/5%In(BTC) membrane demonstrates optimal performance due to the highest permeation flux (~2 times higher compared to the pristine PVA membrane) and high selectivity.
Because PVA tends to dissolve in water and industrial processes are carried out in a wide range of water concentration, dense PVA and PVA/5%In(BTC) membranes were chemically cross-linked with MA. The pervaporation performance of the cross-linked membranes in the separation of water/IPA mixtures (20–90 wt.% water) is presented in Figure 2.
The cross-linking of membranes leads to a slight increase in the permeation flux compared with the uncross-linked ones (Figure 1a), maintaining the same level of selectivity. It may be associated with a greater cross-sectional and surface roughness (confirmed by SEM and AFM data below) resulting in enhanced permeability. At the same time, a relatively closely packed structure was formed due to the cross-linking effect (the formation of ester bonds, confirmed by FTIR data, Figure 3c) with reduced swelling ability (confirmed by swelling data, Table 3), resulting in a high membrane selectivity degree [45]. The modification of the cross-linked PVAMA membrane with 5% of In(BTC) leads to an even greater increase in the permeation flux (0.063 to 0.235 kg/(m2·h)) and water content in the permeate (99.9–98.7.0 wt.%).

3.1.2. Structure and Physicochemical Properties

The structural changes in the cross-linked and uncross-linked membranes and In(BTC) were investigated by FTIR spectroscopy (Figure 3).
The FTIR spectrum of the synthesized In(BTC) was in agreement with the literature data [46]. This is a combination of the absorption bands of the trimesic linker, amines, and In–O bonds. In particular, the characteristic bands of the trimesic acid aromatic ring in-plane deformation, wagging, and torsional vibrations are observed in the range from 900 to 1050 cm−1. The band at 1556 cm−1 corresponds to ν C=C of the benzene ring, and the bands at 713 and 748 cm−1—to out-of-plane bending vibrations of aromatic C–H bonds. The vibrations of aromatic C–H bonds are in the range of 3000 to 3100 cm−1 and are weakly expressed due to overlapping with a wide absorption peak (2500–3500 cm−1) that corresponded to characteristics of water molecule hydrogen bonds in the In(BTC) pores. The carboxyl group of the linker corresponds to the bands at 1280 (ν C–O), 1355 (νs O–C=O), and 1614 cm−1 (νas O–C=O), as well as a weak absorption peak of carbonyl groups (ν C=O) at 1710 cm−1. The FTIR spectrum also shows characteristic bands of organic amines. Thus, the vibrations at 1106 cm−1 may be attributed to the stretching vibrations of C–N bonds, and the absorption bands at 1437 and 2968 cm−1 indicate νas and δas of aliphatic C–H (CH3) bonds, respectively. In addition, a broadened absorption peak at 3367 cm−1 is observed, related to νas of hydrogen bonds of the N–H groups. Finally, the vibration band at 530 cm−1 corresponds to the vibrations of In–O and further confirms the successful binding of the In3+ cations to trimesic acid.
The FTIR spectra of all dense membranes had a very similar profile due to the significant predominance of the vibration bands of PVA molecules (Figure 3b,c). In particular, vibrations of the C–H bonds of methylene groups can be observed at 1420 (bending vibrations), 1326 cm−1 (deformation vibrations), and in the region of 2900–2950 cm−1 (symmetric and asymmetric stretching vibrations). In addition, an intense absorption band of C–O bonds (1087 cm−1) and vibrations of the C–C bonds of the PVA carbon skeleton (848 cm−1) are observed [47,48,49,50]. The most intense absorption in the range of 3000–3500 cm−1 is characteristic of hydrogen bonds of alcohol –OH groups, and water molecules. The presence of so-called “bound” water is also indicated by low-intensity peaks in the range of 1600–1750 cm−1 [50]. Due to the superposition of the peaks of In(BTC) and PVA, a broadening, shift and/or intensity decrease in the following peaks at 3289, 2918, 2853, 1711, and 1086 cm−1 were observed for the In(BTC)-modified membranes. The significant change is the decrease in the intensity of the hydrogen bond peak. These changes may be associated with both the coordination of indium ions by the PVA groups and the decrease in the proportion of bound water.
The cross-linking of PVA chains with MA leads to more significant changes (Figure 3b,c). More intense absorption appears, which may be associated with asymmetric vibrations of the –C–O–C= ester groups, characteristic of the condensation products of MA with –OH groups [51]. The increased absorption bands of the carbonyl groups C=O (1711 and 1707 cm−1) of MA and -CO-CH=CH- stretching (1659 and 1639 cm−1) related to the formation of an unsaturated ester between PVA and MA due to cross-linking [52] appeared for the cross-linked PVAMA and PVA/5% In(BTC)MA membranes.
Figure 4 shows the N2 adsorption/desorption isotherms of the In(BTC) sample and their pore size distribution.
The isotherm shape (Figure 4a) corresponds to type II according to the IUPAC nomenclature, which is characteristic of microporous materials. In the region of low relative pressures, a sharp jump in the amount of adsorbed nitrogen is observed, which is characteristic of the process of filling micropores with adsorbate molecules. In the region of high relative pressures, a small hysteresis loop appears, caused by the capillary condensation of nitrogen in the space between uniformly sized particles. The pore size distribution diagram (Figure 4b) shows an intense peak in the range of 1–2 nm, corresponding to micropores. In addition, small peaks from 2 to 4.5 nm are also observed, which are related to mesopores. They are probably formed as defects on the In(BTC) crystal surface. The SSA of the sample was low (87 m2/g) because the pores of the anionic framework were filled with large dimethylammonium cations, while the total pore volume was 0.077 cm3/g.
To investigate the inner structure and surface of the obtained membranes, cross-sectional and surface SEM microphotographs and AFM images of the uncross-linked and cross-linked membranes are shown in Figure 5 and Figure 6, respectively.
As can be seen from the presented images, the uncross-linked membrane based on pristine PVA is characterized by a smooth and uniform cross-sectional and surface structure (Figure 5a). The In(BTC) particles up to 7.5 wt.% were uniformly distributed in the PVA matrix: there are no significant interphase defects. This may be due to the great affinity of PVA to the BTC linker (confirmed by computational investigation in Section 3.2.1). The introduction of In(BTC) into the PVA matrix only leads to the appearance of cross-sectional and surface irregularities (“plastic deformations”). The number of cross-sectional irregularities increased with increasing modifier content. In particular, for the PVA/7.5%In(BTC) membrane, clusters can be observed along the cross-sectional structure because of possible MOF agglomeration [53]. The formation of agglomerates of MOF (ZIF-8) with higher content in the PVA matrix bulk (cross-sectional structure) was also previously confirmed [54]. The surface roughness of the modified membranes was relatively similar (with “granular” structure), which may indicate a uniform dispersion of the MOF in the volume of the PVA matrix and may be due to a slight difference in the concentrations of the introduced modifier.
The cross-linking of the PVA membrane with MA (PVAMA) resulted in significant roughness of the cross-sectional structure (Figure 6a) [36]. This may be due to the formation of a relatively closely packed structure because of the cross-linking of polymer chains [55]. The introduction of In(BTC) and cross-linking with MA leads to an even greater degree of roughness of the cross-section and surface structures of the PVA/5%In(BTC)MA membrane, which significantly affects the transport parameters of the modified membrane during pervaporation.
For a more explicit assessment of the surface membrane structure and its changes during modification, the average roughness (Ra) and root-mean-square roughness (Rq) of the membrane surfaces calculated based on the AFM images (Figure 5 and Figure 6) and the contact angle of water are presented in Table 2. The change in surface properties is a complex process, including the effect of membrane roughness, and the presence of functional groups of the modifier, which may modulate the hydrophilicity/hydrophobicity of the membrane surface.
There is a tendency for the average and root-mean-square roughness to increase insignificance with increasing In(BTC) content in the PVA-based membranes. At the same time, the modified membranes had roughness parameter values similar to those of the pristine PVA membrane (within the margin of error). Thus, the introduction of In(BTC) into the PVA matrix only results in a modification of the membrane surface by the formation of different irregularities (more “granular” structure, confirmed by SEM in Figure 5), maintaining the same level of roughness. It is also worth noting that the modifier addition was relatively small, and In(BTC) was well dispersed in the PVA matrix owing to the linker, causing minor changes in the surface roughness. However, these changes may also contribute to an increase in sorption center numbers and facilitate mass transfer through the membrane during pervaporation [56]. For the cross-linked membranes (PVAMA and PVA/5%In(BTC)MA), the surface roughness differed more significantly from that of the uncross-linked membranes (Table 2). This may be due to the cross-linking effect of MA [55], and it is also consistent with the SEM data (Figure 6).
It was found that the introduction of In(BTC) and its increase in its content in the PVA membrane led to an increase in the surface hydrophilicity (the decrease in the contact angle of water). This may be due to the hydrophilic nature of In and In-based MOFs, which can be controlled by selecting the solvent during synthesis [57]. Cross-linking with MA does not significantly change the hydrophilic–hydrophobic balance of the cross-linked membrane surface [36].
Since the first two stages of the pervaporation mechanism—sorption and diffusion—are important and limiting, the swelling degree of the membranes was measured in the feed of water/IPA (20 and 30 wt.% water) and pure water. The swelling of uncross-linked PVA and PVA/5%In(BTC) membranes was studied only in mixtures because they tended to dissolve in dilute aqueous solutions without cross-linking. The results are presented in Table 3.
The obtained data show that the swelling degree of the cross-linked and uncross-linked membranes trends to increase with increasing water content in the feed. At the same time, the addition of a modifier slightly increased the swelling degree. This may be associated an increase in the sorption center number on the modified membrane surfaces due to structural changes, increased inner roughness (confirmed by SEM, Figure 5 and Figure 6), as well as with an increase in the surface hydrophilicity (confirmed by contact angle data, Table 2). Cross-linking with MA results in the stability of the cross-linked membranes in pure water and a reduction in the swelling degree in mixtures due to the cross-linking of polymer chains, causing a decrease in the free volume between them [13].
To evaluate the thermal stability of the obtained uncross-linked and cross-linked membranes, TGA curves are presented in Figure 7.
For uncross-linked membranes, three weight loss regions can be observed on the curves. The first weight loss up to 130 °C indicates the removal of bound water molecules and moisture loss from the samples. The second stage of weight loss in the 250–350 °C range was associated with the dehydration of polymer hydroxyl groups [31]. The PVA/5%In(BTC) membrane exhibits higher thermal stability than the pristine PVA membrane (a loss of 75.7% up to 350 °C) because of less weight loss (a loss of 51.5% up to 350 °C). Then, the final matrix decomposition stage begins [58], which is completed at approximately 500 °C for both samples [59]. The product of the thermal decomposition of pure PVA membrane in an inert atmosphere is a carbon matrix with a weight of 4.8%. At the same time, the weight of the undecomposed product in the case of the PVA/5%In(BTC) membrane is significantly higher (24%). This is due to the formation of a product containing, in addition to the carbon matrix, an In-containing MOF pyrolysis product, which cannot be removed from the matrix under these conditions.
After cross-linking with MA, a more complex picture of membrane thermal decomposition is observed. The TGA curves of the cross-linked membranes contains four stages of weight loss. The first is associated with the removal of bound water molecules from the matrices, as in the case of uncross-linked membranes. After this, three stages of decomposition process begin [60], including the process of PVA dehydration, decarboxylation of maleic acid, and, finally, carbon matrix formation [61]. Note that the cross-linked membranes demonstrated higher stability up to 200 °C compared to the uncross-linked membranes, which may be due to the presence of bonds with MA. However, they further have a greater mass loss up to approximately 390 °C compared to the PVA/5%In(BTC) membrane. It may be because in this temperature regime, there is the degradation of bonds between PVA and MA [55]. It was concluded from the TGA data that the In(BTC)-modified membranes have higher thermal stability, demonstrating their potential for use at temperatures as high as 200 °C.

3.2. Computational Investigation

The selection of the polymer–modifier pair is of paramount importance in the fabrication of MMMs because it directly affects both the structure and the separation efficiency of the resulting material. With regard to the filler, the properties of the resulting MMM are typically influenced by the chemical composition and macroscopic parameters, including the pore shape, surface characteristics, and particle size distribution of the filler material [62]. Interfacial interactions are frequently attributed to the formation of defects at the filler/polymer interface. The first type involves the formation of interfacial voids (referred to as “sieve-in-a-cage” morphology) due to poor adhesion at the interface, which serve as additional non-selective transport channels. Another phenomenon involves the rigidification of the polymer layer surrounding the filler, associated with the immobilization of polymer chains at the filler/polymer interface due to strong interactions, which diminishes the performance of diffusion membranes [63]. Therefore, selecting the polymer/modifier pair not only based on macroscopic parameters and the compatibility of the two materials is crucial for developing membranes that strike a balance between permeability and selectivity.
In this research, the molecular geometries of the initial water, IPA, the model compound 1,3,5-benzenetricarboxylic acid (BTC) (the In(BTC) ligand), and the model trimeric units of the isotactic (PVAiso) and syndiotactic (PVAsin) polymers were optimized. Different stereoconfigurations of the polymer were studied to investigate the influence of stereoisomerism on the formation of non-covalent interactions. Hypothetical paired associates were generated and optimized to investigate non-covalent interactions. For complexes exhibiting the highest values of changes in thermodynamic potentials, topological analysis, NCI analysis, and bond order assessments were performed. The Cartesian coordinates for the structures discussed in this study are provided in Table S1 in the Supplementary Materials.

3.2.1. Formation of Hypothetical Associates

The geometries of hypothetical associates between the membrane components, the components of the system, and the feed mixture were obtained and optimized. The changes in thermodynamic potentials during the formation of the associates are presented in Table S2. Table 4 presents the changes in the isothermal–isobaric potential for the most energetically favorable associates.
The obtained data demonstrate that PVA has a greater affinity for the BTC linker than the feed components. This was evidenced by the favorable distribution of the modifier within the polymer matrix in the SEM images (Figure 5). Furthermore, we observed that the BTC ligand more effectively interacts with the components of the feed than PVA. This phenomenon elucidates the elevated degree of swelling (Table 3) and augmented permeability observed in the modified membranes (Figure 1). Consequently, the comparable energy changes during the formation of associates between BTC and the feed components may explain the reduced selectivity of the modified membranes during pervaporation separation as the In(BTC) concentration increases (Figure 1b). For the syndiotactic stereoconfiguration, more favorable interactions were observed, which may be attributed to the intramolecular bonds formed in the isotactic units that impede the formation of strong intermolecular interactions (Figure 8).

3.2.2. Non-Covalent Interaction Investigation

The investigation of non-covalent interactions associated with the formation of associates involved topological and bond order analyses using Multiwfn 3.8. The results of the topological analysis revealed the existence of bond critical points (BCPs) and bond paths, indicating the presence of non-covalent interactions (Figure 8). A comprehensive summary of the QTAIM parameters at the BCPs is available in Table S3 in the Supplementary Materials.
To assess the strength of these interactions, the Wiberg bond index (WBI) and the Fuzzy bond order (FBO) were employed. The WBI and FBO values, interaction length, and ratio of interaction length to the sum of van der Waals radii (R) are presented in Table 5.
Based on the data presented in Table 5, R values below 100% indicate stabilizing intermolecular interactions. Furthermore, WBI and FBO values below 0.2 indicate their noncovalent character [64]. The obtained bond-order metrics can also provide insights into the strength of such interactions. Specifically, higher WBI and FBO values were observed for water and IPA molecules associated with the BTC ligand compared with the PVA trimer. Analogous trends were identified through the determination of hydrogen bond energies using real space functions at critical points [65] (Table S3 in Supplementary Materials) and by correlating the interaction type from NCIplots (Figure 8). These findings corroborate the formation of stronger hydrogen bond, which in turn enhance the hydrophilicity of the membrane and its surface, as confirmed by swelling experiments and contact angle measurements (Table 2 and Table 3).

3.3. Supported PVA and PVA/In(BTC) Membrane Investigation

The permeability of the cross-linked dense membranes can be further increased by decreasing the thickness. However, a significant decrease in membrane thickness adversely affects its strength characteristics, which is important in industrial applications. To maintain the strength of the thin layer, it is necessary to form a supported membrane on a strong porous substrate, for example, on the commercial porous UPM substrate. The supported membranes with a cross-linked thin layer of PVA and PVA/5%In(BTC) were developed and tested in the pervaporation dehydration of IPA to compare with the cross-linked dense membranes (Figure 9).
Reducing the membrane thickness resulted in a significant increase (~2 times) in the permeation flux (Figure 9a) but a decrease in the membrane selectivity to water (Figure 9b). The water content in the permeate of the PVA/UPMMA membrane ranged from 99.9 to 89.5 wt.% and that of the PVA/5%In(BTC)/UPMMA membrane—from 99.9 to 89.0 wt.%. This may be due to the excessive swelling of the thin layer of the supported membranes, leading to an increase in the free volume between the PVA chains and the simultaneous penetration of two components. To evaluate the thin layer thickness and surface changes, supported membranes were studied by SEM and AFM methods (Figure 10).
The thin polymer layer adhered well to both supported membranes to the UPM substrate was observed. The thickness of the supported membranes was found to be 600 ± 300 nm. The calculated surface parameters for the supported membranes are presented in Table 6.
The surface roughness of the supported membranes was higher than the dense cross-linked membranes (Table 2). This may be due to the deposition of the thin PVA-based layer on the porous support, which follows the unevenness of the substrate [5,66].

3.4. Comparison of the Performance with PVA-Based Membranes

Table 7 presents a comparison of the pervaporation characteristics for the obtained cross-linked supported PVA/5%In(BTC)/UPMMA membrane and supported PVA-based membranes, as well as the commercial PVA-based analog PERVAPTM 1201, under close experimental conditions.
Based on the data presented in Table 7, it can be concluded that the trade-off between permeability and selectivity is a significant problem for supported PVA-based membranes. However, the cross-linked supported PVA/5%In(BTC)/UPMMA membrane demonstrates good pervaporation performance in the separating of the IPA/water mixture. It should also be noted that the developed membrane exhibits a higher permeation flux than the commercial PERVAPTM 1201 membrane. Thus, the PVA/5%In(BTC)/UPMMA membrane is promising for IPA dehydration under industrial conditions.

4. Conclusions

In the present work, membranes from synthetic biodegradable PVA modified with the synthesized In(BTC) MOF with improved characteristics were developed for the sustainable pervaporation dehydration of IPA.
The increase in In(BTC) content (2.5–7.5 wt.%) in the PVA matrix led to an increase in permeation flux with a slight decrease in selectivity in the pervaporation dehydration of IPA (20 and 30 wt.% water). This was due to the formation of inner and surface irregularities of the membranes and increased surface hydrophilicity (confirmed by SEM, AFM, contact angle measurements) during modification with the porous anionic In(BTC) modifier. The dense PVA/5%In(BTC) membrane was optimal because it had the highest permeation flux among all modified membranes and was ~2-fold higher than the pristine PVA membrane. Further, this membrane was chemically cross-linked with MA, which led to membrane stability during IPA dehydration over a wide concentration range (up to 90 wt.% water) and a slight increase in permeation flux, maintaining the same level of selectivity.
The creation of a cross-linked supported membrane from an optimal PVA/5% In(BTC) composite onto a commercial porous UPM substrate allowed us to increase the permeation flux by four times compared to the dense pristine PVA membrane in the pervaporation of 20 and 30 wt.% water/IPA mixtures. Thus, this cross-linked supported PVA/5%In(BTC) membrane is promising for industrial dehydration applications even at elevated temperatures (confirmed by TGA).

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/su162310257/s1, Figure S1: (a) TEM image of the synthesized In(BTC) sample; (b) particle size distribution of In(BTC) obtained from TEM image analysis; Figure S2: XRD pattern of the synthesized In(BTC); Table S1: The Cartesian atomic coordinates; Table S2: Changes in thermodynamic potential values during the association of components; Table S3: Electron density ρ(r) (e bohr−3), Laplacian ∇2ρ(r) (e bohr−5), potential energy density V(r) (Hartree), and Lagrangian kinetic energy G(r) (Hartree) at the bond CP (3, −1), corresponding to noncovalent interactions. aE, bE, cE, and dE (kJ mol−1) are counted values of interaction energy in case of correlation with a—ρ(r), b—G(r), c—V(r), and d—∇2ρ(r). References [34,70,71] are presented in Supplementary Materials.

Author Contributions

Conceptualization, A.P. and M.D.; methodology, A.P., M.D., A.K. and E.M.; validation, A.P. and M.D.; formal analysis, M.D. and V.P.; investigation, V.P., M.D., A.K., R.D. and M.K.; data curation, M.D., A.K. and A.P.; writing—original draft preparation, M.D., V.P., R.D. and A.P.; writing—review and editing, M.D. and A.P.; visualization, V.P., M.D. and R.D.; supervision, A.P. and A.S.; project administration, A.P. and A.S., funding acquisition, A.P. All authors have read and agreed to the published version of the manuscript.

Funding

The research was supported by the Strategic Academic Leadership Program of the Southern Federal University (“Priority 2030”) for the development and investigation of metal–organic framework and membranes. The authors acknowledge Saint-Petersburg State University for a research grant 102591880 that provided financial support for theoretical consideration using computational methods.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are contained within the article and Supplementary Materials.

Acknowledgments

The experimental work of this study was facilitated by the equipment from the Chemical Analysis and Materials Research Centre, Magnetic Resonance Research Centre, Centre for Innovative Technologies of Composite Nanomaterials, Nanophotonics Centre, Cryogenic department, Computing Centre, Centre for Physical of Surface Investigation, Thermogravimetric and Calorimetric Research Centre, and the Interdisciplinary Resource Centre for Nanotechnology at the St. Petersburg State University.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Issaoui, M.; Jellali, S.; Zorpas, A.A.; Dutournie, P. Membrane technology for sustainable water resources management: Challenges and future projections. Sustain. Chem. Pharm. 2022, 25, 100590. [Google Scholar] [CrossRef]
  2. Akhmetshina, A.I.; Petukhov, A.N.; Gumerova, O.R.; Vorotyntsev, A.V.; Nyuchev, A.V.; Vorotyntsev, I.V. Solubility of H2S and CO2 in imidazolium-based ionic liquids with bis(2-ethylhexyl) sulfosuccinate anion. J. Chem. Thermodyn. 2019, 130, 173–182. [Google Scholar] [CrossRef]
  3. Anokhina, T.S.; Pleshivtseva, T.S.; Ignatenko, V.Y.; Antonov, S.V.; Volkov, A.V. Fabrication of composite nanofiltration membranes from cellulose solutions in an [Emim]OAc–DMSO mixture. Pet. Chem. 2017, 57, 477–482. [Google Scholar] [CrossRef]
  4. Plisko, T.V.; Bildyukevich, A.V.; Burts, K.S.; Ermakov, S.S.; Penkova, A.V.; Kuzminova, A.I.; Dmitrenko, M.E.; Hliavitskaya, T.A.; Ulbricht, M. One-Step Preparation of Antifouling Polysulfone Ultrafiltration Membranes via Modification by a Cationic Polyelectrolyte Based on Polyacrylamide. Polymers 2020, 12, 1017. [Google Scholar] [CrossRef]
  5. Dmitrenko, M.; Kuzminova, A.; Zolotarev, A.; Ermakov, S.; Roizard, D.; Penkova, A. Enhanced Pervaporation Properties of PVA-Based Membranes Modified with Polyelectrolytes. Application to IPA Dehydration. Polymers 2019, 12, 14. [Google Scholar] [CrossRef]
  6. Dmitrenko, M.E.; Penkova, A.V.; Missyul, A.B.; Kuzminova, A.I.; Markelov, D.A.; Ermakov, S.S.; Roizard, D. Development and investigation of mixed-matrix PVA-fullerenol membranes for acetic acid dehydration by pervaporation. Sep. Purif. Technol. 2017, 187, 285–293. [Google Scholar] [CrossRef]
  7. Osman, A.I.; Chen, Z.; Elgarahy, A.M.; Farghali, M.; Mohamed, I.M.A.; Priya, A.K.; Hawash, H.B.; Yap, P. Membrane Technology for Energy Saving: Principles, Techniques, Applications, Challenges, and Prospects. Adv. Energy Sustain. Res. 2024, 5, 2400011. [Google Scholar] [CrossRef]
  8. Van der Bruggen, B.; Luis, P. Chapter Four—Pervaporation. In Progress in Filtration and Separation; Tarleton, S., Ed.; Oxford University Press: Oxford, UK, 2015; pp. 101–154. ISBN 012384746X. [Google Scholar]
  9. Dai, Y.; Li, S.; Meng, D.; Yang, J.; Cui, P.; Wang, Y.; Zhu, Z.; Gao, J.; Ma, Y. Economic and Environmental Evaluation for Purification of Diisopropyl Ether and Isopropyl Alcohol via Combining Distillation and Pervaporation Membrane. ACS Sustain. Chem. Eng. 2019, 7, 20170–20179. [Google Scholar] [CrossRef]
  10. Raza, W.; Wang, J.; Yang, J.; Tsuru, T. Progress in pervaporation membranes for dehydration of acetic acid. Sep. Purif. Technol. 2021, 262, 118338. [Google Scholar] [CrossRef]
  11. Chapman, P.D.; Oliveira, T.; Livingston, A.G.; Li, K. Membranes for the dehydration of solvents by pervaporation. J. Membr. Sci. 2008, 318, 5–37. [Google Scholar] [CrossRef]
  12. Hua, D.; Ong, Y.K.; Wang, Y.; Yang, T.; Chung, T.-S. ZIF-90/P84 mixed matrix membranes for pervaporation dehydration of isopropanol. J. Membr. Sci. 2014, 453, 155–167. [Google Scholar] [CrossRef]
  13. Oun, A.A.; Shin, G.H.; Rhim, J.-W.; Kim, J.T. Recent advances in polyvinyl alcohol-based composite films and their applications in food packaging. Food Packag. Shelf Life 2022, 34, 100991. [Google Scholar] [CrossRef]
  14. Liu, L.; Kentish, S.E. Pervaporation performance of crosslinked PVA membranes in the vicinity of the glass transition temperature. J. Membr. Sci. 2018, 553, 63–69. [Google Scholar] [CrossRef]
  15. Dmitrenko, M.; Penkova, A.; Kuzminova, A.; Missyul, A.; Ermakov, S.; Roizard, D. Development and characterization of new pervaporation PVA membranes for the dehydration using bulk and surface modifications. Polymers 2018, 10, 571. [Google Scholar] [CrossRef] [PubMed]
  16. Huang, Z.; Guan, H.; Qiao, X.; Kulprathipanja, S. Pervaporation study of aqueous ethanol solution through zeolite-incorporated multilayer poly (vinyl alcohol) membranes: Effect of zeolites. J. Membr. Sci. 2006, 276, 260–271. [Google Scholar] [CrossRef]
  17. Falath, W. Novel stand-alone PVA mixed matrix membranes conjugated with graphene oxide for highly improved reverse osmosis performance. Arab. J. Chem. 2021, 14, 103109. [Google Scholar] [CrossRef]
  18. Sheng, F.; Afsar, N.U.; Zhu, Y.; Ge, L.; Xu, T. PVA-Based Mixed Matrix Membranes Comprising ZSM-5 for Cations Separation. Membranes 2020, 10, 114. [Google Scholar] [CrossRef]
  19. Agafonov, M.A.; Alexandrov, E.V.; Artyukhova, N.A.; Bekmukhamedov, G.E.; Blatov, V.A.; Butova, V.V.; Gayfulin, Y.M.; Garibyan, A.A.; Gafurov, Z.N.; Gorbunova, Y.G.; et al. Metal-organic frameworks in Russia: From the synthesis and structure to functional properties and materials. J. Struct. Chem. 2022, 63, 671–843. [Google Scholar] [CrossRef]
  20. Halder, S.; Ghosh, P.; Rizzoli, C.; Banerjee, P.; Roy, P. Nitroaromatic explosives detection by a luminescent Cd(II) based metal organic framework. Polyhedron 2017, 123, 217–225. [Google Scholar] [CrossRef]
  21. Butova, V.V.; Bulanova, E.A.; Polyakov, V.A.; Guda, A.A.; Aboraia, A.M.; Shapovalov, V.V.; Zahran, H.Y.; Yahia, I.S.; Soldatov, A.V. The effect of cobalt content in Zn/Co-ZIF-8 on iodine capping properties. Inorganica Chim. Acta 2019, 492, 18–22. [Google Scholar] [CrossRef]
  22. Farrusseng, D.; Aguado, S.; Pinel, C. Metal–Organic Frameworks: Opportunities for Catalysis. Angew. Chem. Int. Ed. 2009, 48, 7502–7513. [Google Scholar] [CrossRef] [PubMed]
  23. Furukawa, H.; Cordova, K.E.; O’Keeffe, M.; Yaghi, O.M. The Chemistry and Applications of Metal-Organic Frameworks. Science 2013, 341, 1230444. [Google Scholar] [CrossRef] [PubMed]
  24. Horcajada, P.; Serre, C.; Maurin, G.; Ramsahye, N.A.; Balas, F.; Vallet-Regí, M.; Sebban, M.; Taulelle, F.; Férey, G. Flexible Porous Metal-Organic Frameworks for a Controlled Drug Delivery. J. Am. Chem. Soc. 2008, 130, 6774–6780. [Google Scholar] [CrossRef] [PubMed]
  25. Huang, Z.; Yang, G.; Zhang, J.; Gray, S.; Xie, Z. Dual-layer membranes with a thin film hydrophilic MOF/PVA nanocomposite for enhanced antiwetting property in membrane distillation. Desalination 2021, 518, 115268. [Google Scholar] [CrossRef]
  26. Wu, G.; Li, Y.; Geng, Y.; Lu, X.; Jia, Z. Adjustable pervaporation performance of Zr-MOF/poly(vinyl alcohol) mixed matrix membranes. J. Chem. Technol. Biotechnol. 2019, 94, 973–981. [Google Scholar] [CrossRef]
  27. Ashtiani, S.; Khoshnamvand, M.; Regmi, C.; Friess, K. Interfacial Design of Mixed Matrix Membranes via Grafting PVA on UiO-66-NH2 to Enhance the Gas Separation Performance. Membranes 2021, 11, 419. [Google Scholar] [CrossRef]
  28. Zhang, Y.; Yuan, H.; Chen, X.; Jiang, Z.; Lu, J.; Xin, F. Incorporating MXene@MOF-303 Composites into Poly(vinyl alcohol) (PVA) to Fabricate Pervaporation Membranes for Desalination. ACS Appl. Polym. Mater. 2024, 6, 8277–8290. [Google Scholar] [CrossRef]
  29. Sharma, U.; Shalini, S.; Basu, S.; Saravanan, P.; Jang, M. Active layer modification of commercial nanofiltration membrane using CuBTC/PVA matrix for improved surface and separation characteristics. J. Appl. Polym. Sci. 2021, 138, app50508. [Google Scholar] [CrossRef]
  30. Li, H.; Zhao, C.; Ying, Y.; Zhang, W. Improve MOF-801 dispersibility in PVA membranes by a pre-crosslinking strategy for enhanced pervaporation performance. J. Membr. Sci. 2023, 687, 122043. [Google Scholar] [CrossRef]
  31. Kuzminova, A.; Dmitrenko, M.; Zolotarev, A.; Myznikov, D.; Selyutin, A.; Su, R.; Penkova, A. Pervaporation Polyvinyl Alcohol Membranes Modified with Zr-Based Metal Organic Frameworks for Isopropanol Dehydration. Membranes 2022, 12, 908. [Google Scholar] [CrossRef]
  32. Hou, S.-Z.; Zhang, X.-D.; Yuan, W.-W.; Li, Y.-X.; Gu, Z.-Y. Indium-Based Metal–Organic Framework for High-Performance Electroreduction of CO2 to Formate. Inorg. Chem. 2020, 59, 11298–11304. [Google Scholar] [CrossRef] [PubMed]
  33. Ji, W.; Wang, G.; Wang, B.; Yan, B.; Liu, L.; Xu, L.; Ma, T.; Yao, S.; Fu, Y.; Zhang, L.; et al. A new indium-based MOF as the highly stable luminescent ultra-sensitive antibiotic detector. Chin. J. Struct. Chem. 2023, 42, 100062. [Google Scholar] [CrossRef]
  34. Chen, S.; Zhang, J.; Wu, T.; Feng, P.; Bu, X. Multiroute Synthesis of Porous Anionic Frameworks and Size-Tunable Extraframework Organic Cation-Controlled Gas Sorption Properties. J. Am. Chem. Soc. 2009, 131, 16027–16029. [Google Scholar] [CrossRef] [PubMed]
  35. Zheng, S.-T.; Bu, J.T.; Li, Y.; Wu, T.; Zuo, F.; Feng, P.; Bu, X. Pore Space Partition and Charge Separation in Cage-within-Cage Indium−Organic Frameworks with High CO2 Uptake. J. Am. Chem. Soc. 2010, 132, 17062–17064. [Google Scholar] [CrossRef] [PubMed]
  36. Penkova, A.V.; Acquah, S.F.A.; Dmitrenko, M.E.; Chen, B.; Semenov, K.N.; Kroto, H.W. Transport properties of cross-linked fullerenol–PVA membranes. Carbon N. Y. 2014, 76, 446–450. [Google Scholar] [CrossRef]
  37. Baker, R.W. Membrane Technology and Applications; McGraw-Hill: New York, NY, USA, 2000. [Google Scholar]
  38. Frisch, M.J. Gaussian 16, Revision A.03; Gaussian, Inc., Wallingford CT, 2016. Available online: https://gaussian.com/citation_a03/ (accessed on 17 October 2024).
  39. Becke, A.D. Density-functional thermochemistry. I. The effect of the exchange-only gradient correction. J. Chem. Phys. 1992, 96, 2155–2160. [Google Scholar] [CrossRef]
  40. Becke, A.D. Density-functional exchange-energy approximation with correct asymptotic behavior. Phys. Rev. A 1988, 38, 3098–3100. [Google Scholar] [CrossRef]
  41. Lee, C.; Yang, W.; Parr, R.G. Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. Phys. Rev. B 1988, 37, 785–789. [Google Scholar] [CrossRef]
  42. Lu, T.; Chen, F. Multiwfn: A multifunctional wavefunction analyzer. J. Comput. Chem. 2012, 33, 580–592. [Google Scholar] [CrossRef]
  43. Johnson, E.R.; Keinan, S.; Mori-Sánchez, P.; Contreras-García, J.; Cohen, A.J.; Yang, W. Revealing Noncovalent Interactions. J. Am. Chem. Soc. 2010, 132, 6498–6506. [Google Scholar] [CrossRef]
  44. Humphrey, W.; Dalke, A.; Schulten, K. VMD: Visual molecular dynamics. J. Mol. Graph. 1996, 14, 33–38. [Google Scholar] [CrossRef] [PubMed]
  45. Xu, S.; Shen, L.; Li, C.; Wang, Y. Properties and pervaporation performance of poly (vinyl alcohol) membranes crosslinked with various dianhydrides. J. Appl. Polym. Sci. 2018, 135, 46159. [Google Scholar] [CrossRef]
  46. Grigoropoulos, A.; Whitehead, G.F.S.; Perret, N.; Katsoulidis, A.P.; Chadwick, F.M.; Davies, R.P.; Haynes, A.; Brammer, L.; Weller, A.S.; Xiao, J.; et al. Encapsulation of an organometallic cationic catalyst by direct exchange into an anionic MOF. Chem. Sci. 2016, 7, 2037–2050. [Google Scholar] [CrossRef] [PubMed]
  47. Omkaram, I.; Sreekanth Chakradhar, R.P.; Lakshmana Rao, J. EPR, optical, infrared and Raman studies of VO2+ ions in polyvinylalcohol films. Phys. B Condens. Matter 2007, 388, 318–325. [Google Scholar] [CrossRef]
  48. Franca, T.; Goncalves, D.; Cena, C. ATR-FTIR spectroscopy combined with machine learning for classification of PVA/PVP blends in low concentration. Vib. Spectrosc. 2022, 120, 103378. [Google Scholar] [CrossRef]
  49. Bhat, N.V.; Nate, M.M.; Kurup, M.B.; Bambole, V.A.; Sabharwal, S. Effect of γ-radiation on the structure and morphology of polyvinyl alcohol films. Nucl. Instruments Methods Phys. Res. Sect. B Beam Interactions Mater. Atoms 2005, 237, 585–592. [Google Scholar] [CrossRef]
  50. Asran, A.S.; Henning, S.; Michler, G.H. Polyvinyl alcohol–collagen–hydroxyapatite biocomposite nanofibrous scaffold: Mimicking the key features of natural bone at the nanoscale level. Polymer 2010, 51, 868–876. [Google Scholar] [CrossRef]
  51. Zemzem, M.; Vinches, L.; Hallé, S. Morphological investigation of maleic anhydride-grafted nitrile/nanoclay nanocomposites. Mater. Res. Express 2022, 9, 085302. [Google Scholar] [CrossRef]
  52. Dmitrenko, M.; Atta, R.; Zolotarev, A.; Kuzminova, A.; Ermakov, S.; Penkova, A. Development of Novel Membranes Based on Polyvinyl Alcohol Modified by Pluronic F127 for Pervaporation Dehydration of Isopropanol. Sustainability 2022, 14, 3561. [Google Scholar] [CrossRef]
  53. Chen, R.; Chai, M.; Hou, J. Metal-organic framework-based mixed matrix membranes for gas separation: Recent advances and opportunities. Carbon Capture Sci. Technol. 2023, 8, 100130. [Google Scholar] [CrossRef]
  54. Liu, B.; Zhang, S.; Li, M.; Wang, Y.; Mei, D. Metal–Organic Framework/Polyvinyl Alcohol Composite Films for Multiple Applications Prepared by Different Methods. Membranes 2023, 13, 755. [Google Scholar] [CrossRef] [PubMed]
  55. Gohil, J.M.; Bhattacharya, A.; Ray, P. Studies on the Crosslinking of Poly (Vinyl Alcohol). J. Polym. Res. 2006, 13, 161–169. [Google Scholar] [CrossRef]
  56. Goodyer, C.E.; Bunge, A.L. Mass transfer through membranes with surface roughness. J. Membr. Sci. 2012, 409–410, 127–136. [Google Scholar] [CrossRef]
  57. Zhang, Y.; Lucier, B.E.G.; McKenzie, S.M.; Arhangelskis, M.; Morris, A.J.; Friščić, T.; Reid, J.W.; Terskikh, V.V.; Chen, M.; Huang, Y. Welcoming Gallium- and Indium-Fumarate MOFs to the Family: Synthesis, Comprehensive Characterization, Observation of Porous Hydrophobicity, and CO2 Dynamics. ACS Appl. Mater. Interfaces 2018, 10, 28582–28596. [Google Scholar] [CrossRef]
  58. Das, P.; Ray, S.K.; Kuila, S.B.; Samanta, H.S.; Singha, N.R. Systematic choice of crosslinker and filler for pervaporation membrane: A case study with dehydration of isopropyl alcohol–water mixtures by polyvinyl alcohol membranes. Sep. Purif. Technol. 2011, 81, 159–173. [Google Scholar] [CrossRef]
  59. Tamer, T.M.; Sabet, M.M.; Omer, A.M.; Abbas, E.; Eid, A.I.; Mohy-Eldin, M.S.; Hassan, M.A. Hemostatic and antibacterial PVA/Kaolin composite sponges loaded with penicillin–streptomycin for wound dressing applications. Sci. Rep. 2021, 11, 3428. [Google Scholar] [CrossRef]
  60. Zhang, L.; Yu, P.; Luo, Y. Dehydration of caprolactam–water mixtures through cross-linked PVA composite pervaporation membranes. J. Membr. Sci. 2007, 306, 93–102. [Google Scholar] [CrossRef]
  61. Xia, L.L.; Li, C.L.; Wang, Y. In-situ crosslinked PVA/organosilica hybrid membranes for pervaporation separations. J. Membr. Sci. 2016, 498, 263–275. [Google Scholar] [CrossRef]
  62. Jia, Z.; Wu, G. Microporous and Mesoporous Materials Metal-organic frameworks based mixed matrix membranes for pervaporation. Microporous Mesoporous Mater. 2016, 235, 151–159. [Google Scholar] [CrossRef]
  63. Lin, R.; Villacorta Hernandez, B.; Ge, L.; Zhu, Z. Metal organic framework based mixed matrix membranes: An overview on filler/polymer interfaces. J. Mater. Chem. A 2018, 6, 293–312. [Google Scholar] [CrossRef]
  64. Aakeroy, C.B.; Bryce, D.L.; Desiraju, G.R.; Frontera, A.; Legon, A.C.; Nicotra, F.; Rissanen, K.; Scheiner, S.; Terraneo, G.; Metrangolo, P.; et al. Definition of the chalcogen bond (IUPAC Recommendations 2019). Pure Appl. Chem. 2019, 91, 1889–1892. [Google Scholar] [CrossRef]
  65. Mata, I.; Alkorta, I.; Espinosa, E.; Molins, E. Relationships between interaction energy, intermolecular distance and electron density properties in hydrogen bonded complexes under external electric fields. Chem. Phys. Lett. 2011, 507, 185–189. [Google Scholar] [CrossRef]
  66. Dmitrenko, M.; Mikhailovskaya, O.; Dubovenko, R.; Kuzminova, A.; Myznikov, D.; Mazur, A.; Semenov, K.; Rusalev, Y.; Soldatov, A.; Ermakov, S.; et al. Pervaporation Membranes Based on Polyelectrolyte Complex of Sodium Alginate/Polyethyleneimine Modified with Graphene Oxide for Ethanol Dehydration. Polymers 2024, 16, 1206. [Google Scholar] [CrossRef] [PubMed]
  67. Dmitrenko, M.E.; Penkova, A.V.; Kuzminova, A.I.; Morshed, M.; Larionov, M.I.; Alem, H.; Zolotarev, A.A.; Ermakov, S.S.; Roizard, D. Investigation of new modification strategies for PVA membranes to improve their dehydration properties by pervaporation. Appl. Surf. Sci. 2018, 450, 527–537. [Google Scholar] [CrossRef]
  68. Chong, W.; Mohd Nawawi, M.; Sadikin, A. Pervaporation of isopropanol-water mixture using poly(vinyl) alcohol-zsm-5 membranes. J. Teknol. 2008, 49, 159–166. [Google Scholar]
  69. Sairam, M.; Naidu, B.V.K.; Nataraj, S.K.; Sreedhar, B.; Aminabhavi, T.M. Poly(vinyl alcohol)-iron oxide nanocomposite membranes for pervaporation dehydration of isopropanol, 1,4-dioxane and tetrahydrofuran. J. Membr. Sci. 2006, 283, 65–73. [Google Scholar] [CrossRef]
  70. Sabouni, R.; Kazemian, H.; Rohani, S. Microwave Synthesis of the CPM-5 Metal Organic Framework. Chem. Eng. Technol. 2012, 35, 1085–1092. [Google Scholar] [CrossRef]
  71. Muzart, J. N,N-Dimethylformamide: Much more than a solvent. Tetrahedron 2009, 65, 8313–8323. [Google Scholar] [CrossRef]
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Figure 1. Dependence of (a) the permeation flux and (b) water content in permeate on the water content in feed for uncross-linked PVA and PVA/In(BTC) membranes in the pervaporation separation of water/IPA mixtures.
Figure 1. Dependence of (a) the permeation flux and (b) water content in permeate on the water content in feed for uncross-linked PVA and PVA/In(BTC) membranes in the pervaporation separation of water/IPA mixtures.
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Figure 2. The dependence of the permeation flux and water content in permeate on the water content in feed for the cross-linked dense PVAMA and PVA/5%In(BTC)MA membranes in the pervaporation separation of water/IPA mixtures.
Figure 2. The dependence of the permeation flux and water content in permeate on the water content in feed for the cross-linked dense PVAMA and PVA/5%In(BTC)MA membranes in the pervaporation separation of water/IPA mixtures.
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Figure 3. FTIR spectra of (a) In(BTC), uncross-linked and cross-linked dense (b) PVA, and (c) PVA/5% In(BTC) membranes.
Figure 3. FTIR spectra of (a) In(BTC), uncross-linked and cross-linked dense (b) PVA, and (c) PVA/5% In(BTC) membranes.
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Figure 4. (a) N2 adsorption/desorption isotherm and (b) pore size distribution of the In(BTC) sample.
Figure 4. (a) N2 adsorption/desorption isotherm and (b) pore size distribution of the In(BTC) sample.
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Figure 5. Cross-sectional and surface SEM microphotographs and AFM images of the uncross-linked dense (a) PVA, (b) PVA/2.5%In(BTC), (c) PVA/5%In(BTC), and (d) PVA/7.5%In(BTC) membranes.
Figure 5. Cross-sectional and surface SEM microphotographs and AFM images of the uncross-linked dense (a) PVA, (b) PVA/2.5%In(BTC), (c) PVA/5%In(BTC), and (d) PVA/7.5%In(BTC) membranes.
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Figure 6. Cross-sectional and surface SEM microphotographs and AFM images of the cross-linked dense (a) PVAMA and (b) PVA/5%In(BTC)MA membranes.
Figure 6. Cross-sectional and surface SEM microphotographs and AFM images of the cross-linked dense (a) PVAMA and (b) PVA/5%In(BTC)MA membranes.
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Figure 7. TGA curves for uncross-linked and cross-linked PVA and PVA/5%In(BTC) membranes.
Figure 7. TGA curves for uncross-linked and cross-linked PVA and PVA/5%In(BTC) membranes.
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Figure 8. QTAIM distribution of bond critical points (CPs) (blue spheres) and bond paths among associates. The NCIplot index isosurface is also represented using an isovalue of 0.5 (e1/3 bohr)−1, and the color range is −0.04 e/bohr3 ≤ sign(λ2)ρ ≤ 0.02 e/bohr3. CPs and NCIplot surfaces for characterizing intermolecular interactions are presented for clarity.
Figure 8. QTAIM distribution of bond critical points (CPs) (blue spheres) and bond paths among associates. The NCIplot index isosurface is also represented using an isovalue of 0.5 (e1/3 bohr)−1, and the color range is −0.04 e/bohr3 ≤ sign(λ2)ρ ≤ 0.02 e/bohr3. CPs and NCIplot surfaces for characterizing intermolecular interactions are presented for clarity.
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Figure 9. Dependence of (a) the permeation flux and (b) water content in permeate on the water content in feed for the cross-linked supported PVA/UPMMA and PVA/5%In(BTC)/UPMMA membranes in the pervaporation separation of water/IPA mixtures compared with the dense cross-linked membranes.
Figure 9. Dependence of (a) the permeation flux and (b) water content in permeate on the water content in feed for the cross-linked supported PVA/UPMMA and PVA/5%In(BTC)/UPMMA membranes in the pervaporation separation of water/IPA mixtures compared with the dense cross-linked membranes.
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Figure 10. Cross-sectional SEM micrographs and surface AFM images of the cross-linked supported (a) PVA/UPMMA and (b) PVA/5%In(BTC)/UPMMA membranes.
Figure 10. Cross-sectional SEM micrographs and surface AFM images of the cross-linked supported (a) PVA/UPMMA and (b) PVA/5%In(BTC)/UPMMA membranes.
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Table 1. Designation of obtained membranes and additive amount.
Table 1. Designation of obtained membranes and additive amount.
Membrane DesignationAdditive Amount Relative to PVA, wt% UPM Support
In(BTC)MA
dense uncross-linked
PVA---
PVA/2.5%In(BTC)2.5
PVA/5%In(BTC)5
PVA/7.5%In(BTC)7.5
dense cross-linked
PVAMA-35-
PVA/5%In(BTC)MA5
supported cross-linked
PVA/UPMMA-35+
PVA/5%In(BTC)/UPMMA5
Table 2. Average (Ra), root-mean-square (Rq) roughness parameters, and contact angle of water for uncross-linked and cross-linked PVA and PVA/In(BTC) membranes.
Table 2. Average (Ra), root-mean-square (Rq) roughness parameters, and contact angle of water for uncross-linked and cross-linked PVA and PVA/In(BTC) membranes.
MembranesRa, nmRq, nmContact Angle of Water, °
PVA0.230.3167 ± 3
PVA/2.5%In(BTC)0.260.3465 ± 3
PVA/5%In(BTC)0.280.3562 ± 5
PVA/7.5%In(BTC)0.270.3459 ± 5
PVAMA0.280.3566 ± 2
PVA/5%In(BTC)MA0.330.4660 ± 5
Table 3. Swelling degree of uncross-linked and cross-linked dense PVA and PVA/5%In(BTC) membranes in water/IPA mixtures and water.
Table 3. Swelling degree of uncross-linked and cross-linked dense PVA and PVA/5%In(BTC) membranes in water/IPA mixtures and water.
MembraneSwelling Degree, %
Water/IPA MixtureWater
20/80 wt.%30/70 wt.%
PVA67106-
PVA/5%In(BTC)71113-
PVAMA4981109
PVA/5%In(BTC)MA5082123
Table 4. Gibbs energy change during the formation of the most energetically favorable associates.
Table 4. Gibbs energy change during the formation of the most energetically favorable associates.
∆Gmin, kJ/mol
B3LYP/6-311++G**BTCH2OIPA
PVAiso16.617.921.7
PVAsin−6.77.69.4
BTC~−1.0−0.8
H2O ~10.4
Table 5. WBI and FBO values, interaction lengths, and the ratio of interaction length to the sum of van der Waals radii.
Table 5. WBI and FBO values, interaction lengths, and the ratio of interaction length to the sum of van der Waals radii.
B3LYP/6-311++G**
AssociateInteractionWBIFBOd, ÅR, %
PVAisoBTCO///H(COOH)0.1310.0911.7916365.9%
H(OH)///O(CO)0.0290.0202.3628586.9%
H2OO///H0.0590.0512.116777.8%
O*///H0.0400.0362.3370485.9%
H(CH2)///O0.0140.0182.86991105.5%
IPA-2O(OH)///H(OH)0.0720.0621.9767672.7%
H*(O*H*)///O0.0940.0741.9032770.0%
IPA-4H(CH3)///O0.0160.0292.85031104.8%
H(CH2)///O0.0190.0302.5959895.4%
PVAsinBTCO*///H(COOH)0.1660.1131.6913362.2%
H(OH)///O(CO)0.0850.0651.9126870.3%
H2OO*///H0.1130.0841.8297667.3%
H(OH)///O0.1130.0901.8697368.7%
IPA-1H(CHOH)///O0.0290.0382.3190385.3%
H(OH)///O0.0800.0651.9750772.6%
O*(OH)///H(OH)0.0660.0572.0253774.5%
IPA-3H(CH2)///O0.0160.0252.73736100.6%
H*(C*H*2)///H(CH3)0.0010.0013.53497147.3%
BTCH2OO(CO)///H0.0750.0562.0365674.9%
H(OH)///O0.1430.1101.7689765.0%
IPAO(CO)///H0.0570.0452.1435378.8%
H(OH)///O0.1640.1121.7129963.0%
The notation of atoms O and O*, H and H* corresponds to atoms from different constitutional repeating units.
Table 6. Surface average roughness (Ra) and root-mean-square roughness (Rq) of the cross-linked supported membranes.
Table 6. Surface average roughness (Ra) and root-mean-square roughness (Rq) of the cross-linked supported membranes.
MembranesRa, nmRq, nm
PVA/UPMMA0.440.57
PVA/5%In(BTC)/UPMMA2.293.19
Table 7. Pervaporation characteristics of the supported cross-linked membrane with literature-described PVA-based membranes for the IPA/water (80/20) mixture separation.
Table 7. Pervaporation characteristics of the supported cross-linked membrane with literature-described PVA-based membranes for the IPA/water (80/20) mixture separation.
MembranesThickness, μmWater Content in Feed, wt.%Temperature, °CPermeation Flux, g/(m2h)Water Content in Permeate, wt.%References
PVA/5%In(BTC)/UPMMA0.6202214299.9This study
PERVAPTM 1201-20223499.9[67]
PVA/3% Pluronic F127/PA*MA1.5202229698.2[52]
PVA/20%chitosan/UPMMA1202223393.9[15]
PVA/5%fullerenol/20%chitosan/UPMMA1202224196.8
PVA/ZSM-5/PS **-2027.520066.7[68]
PVA/3%
Fe(II)/Fe(III)/polyester
fabrics		1020309892.3[69]
* PA—polyamide; ** PS—polysulfone.
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Polyakov, V.; Dmitrenko, M.; Kalmakhelidze, M.; Kuzminova, A.; Dubovenko, R.; Mukhanova, E.; Soldatov, A.; Penkova, A. Development and Characterization of PVA Membranes Modified with In(BTC) Metal–Organic Framework for Sustainable Pervaporation Separation of Isopropanol/Water. Sustainability 2024, 16, 10257. https://doi.org/10.3390/su162310257

AMA Style

Polyakov V, Dmitrenko M, Kalmakhelidze M, Kuzminova A, Dubovenko R, Mukhanova E, Soldatov A, Penkova A. Development and Characterization of PVA Membranes Modified with In(BTC) Metal–Organic Framework for Sustainable Pervaporation Separation of Isopropanol/Water. Sustainability. 2024; 16(23):10257. https://doi.org/10.3390/su162310257

Chicago/Turabian Style

Polyakov, Vladimir, Mariia Dmitrenko, Meri Kalmakhelidze, Anna Kuzminova, Roman Dubovenko, Elizaveta Mukhanova, Alexander Soldatov, and Anastasia Penkova. 2024. "Development and Characterization of PVA Membranes Modified with In(BTC) Metal–Organic Framework for Sustainable Pervaporation Separation of Isopropanol/Water" Sustainability 16, no. 23: 10257. https://doi.org/10.3390/su162310257

APA Style

Polyakov, V., Dmitrenko, M., Kalmakhelidze, M., Kuzminova, A., Dubovenko, R., Mukhanova, E., Soldatov, A., & Penkova, A. (2024). Development and Characterization of PVA Membranes Modified with In(BTC) Metal–Organic Framework for Sustainable Pervaporation Separation of Isopropanol/Water. Sustainability, 16(23), 10257. https://doi.org/10.3390/su162310257

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