Copper catalysts supported on porous aromatic frameworks for the hydrogenation of ethylene carbonate

Copper catalysts supported on porous aromatic frameworks for the hydrogenation of ethylene carbonate | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Copper catalysts supported on porous aromatic frameworks for the hydrogenation of ethylene carbonate Elizaveta Oskina, Daria Makeeva, Leonid Kulikov, Anton Maximov This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6803584/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract Hydrogenation of organic carbonates on heterogeneous catalysts is one of the ways of indirect conversion of carbon dioxide, which is essential for addressing the urgent problem of decarbonization. Cu-based catalysts are the most widely used in hydrogenation, but their properties strongly depend on the characteristics of the heterogeneous carriers used. Although SiO 2 -based catalysts are the most extensively studied, it is of interest to develop catalysts based on new types of carriers such as MOFs, COFs and PAFs. In the current work, a series of copper-based catalysts with different metal contents (2, 5, 10, 30 wt%) based on porous aromatic framework PAF-30 and its amino-functionalized derivative PAF-30-NH 2 were synthesized and investigated in the hydrogenation of ethylene carbonate. The influence of reaction temperature, hydrogen pressure, concentration of ethylene carbonate in its solution in THF, copper content in the catalysts and reduction conditions on the activity of the catalysts was systematically studied. hydrogenation ethylene carbonate ethylene glycol porous aromatic frameworks copper nanoparticles Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 1. Introduction The catalytic hydrogenation of non-toxic and renewable carbon dioxide (CO 2 ) into valuable petrochemicals and fuel components has attracted considerable attention in terms of environmental sustainability [1]. However, the industrial use of catalytic systems for direct hydrogenation of CO 2 (Cu-ZnO-Al 2 O 3 , Cu-ZnO/ZrO 2 , Cu-La/SBA-15, Pd/SiO 2 , etc.) is limited by relatively harsh reaction conditions (220–300 o C, 50–100 atm) resulted from the kinetic inertness and high thermodynamic stability of CO 2 molecule [2]. On the other hand, the indirect transformation of carbon dioxide via the hydrogenation of organic carbonates, carbamates and formates can be achieved under milder conditions [3]. In particular, the conversion of CO 2 -derived ethylene carbonate (EC) to methanol and ethylene glycol (EG) is an attractive approach as EC is industrially available from the well-established «Omega process», which involves cycloaddition of ethylene oxide (EO) with CO 2 [4]. Copper-based catalytic systems are widely used in hydrogenation of esters due to selective hydrogenation of C-O/C = O bonds and low activity toward C-C bond cleavage [5, 6]. Inert supports, such as carbon- and silica-based materials, are required for this reaction, as excessive surface acidity or basicity can lead to decarbonylation or decarboxylation of carbonates [7]. Thus, mesoporous silicas including KIT-6, MCM-41, SBA-15, HMS were investigated as the supports for copper nanoparticles (Cu NPs) in the hydrogenation of EC [8–10]. For example, full conversion of EC with EG and MeOH yields of 95% and 62%, respectively, was achieved over Cu/SBA-15 catalyst [8]. Despite numerous attempts to modify silica-supported catalysts [11–13], loss of silica species during the reaction with solvent at high temperature still a problem, which will lead to poor stability [14]. Hence, the design of nonsilica Cu-based catalysts is required to improve the long-term running stability. Considerably less research is devoted to catalysts based on carbon materials [15–17]. Meanwhile, carbon materials extensively utilised as supports for transition metal nanoparticles due to their thermal and chemical stability, functionalization variability, well-developed textural properties [18]. For example, Cu-catalysts supported on carbon nanotubes with oxygen-containing functional groups were tested in EC hydrogenation. 40Cu/CNTs catalyst demonstrated EС conversion of more than 99% with methanol and ethylene glycol yields of 83% and 99%, respectively, and remains active after 150 hours on stream [16]. Meanwhile, many new porous materials have been synthesized in the past 15 years, including metal-organic frameworks (MOFs) [19], covalent organic frameworks (COFs) [20], porous aromatic frameworks (PAFs) [21]. However, to date, their application as catalyst carriers for the hydrogenation of organic carbonates has hardly been considered. Thus, Lei et. al. [22] report the synthesis of Cu@MIL-101 catalyst and its application in the hydrogenation of EC. It is interesting to note that the composition of the hydrogenation products depended on the reaction temperature: at 180°C the main product was ethylene glycol (conversion 100 %, selectivity 2%), and at 160°C – 2-hydroxyethyl formate, 2-HEF (conversion 100 %, selectivity 2%). The authors note the important role of the interaction between the Cu 0 and Cr 3+ in the dissociation of H 2 and activation of C-O and C = O bonds in the esters, which makes Cu@MIL-101 highly active catalyst. However, no methanol formation was observed, which may be due to the Lewis acidity of the Cr 3+ species. In the current work, we study Cu catalysts based on another type of carriers, porous aromatic frameworks — polymers constructed by the assembly of organic building blocks through covalent coupling reactions [23]. They are characterised by high specific surface areas, adjustable porous structures, high thermal and chemical stability, which allowed to develop on their basis catalysts for hydrogenation of alkynes and dienes [24, 25], hydrodeoxygenation of lignin-based of lignin bio-oil compounds [26], oxidation of alkylaromatics [27]. We applied two types of materials, PAF-30 and its derivative with amino groups PAF-30-NH 2 , as carriers of copper nanoparticles, and tested the obtained catalysts in the hydrogenation of ethylene carbonate. 2. Experimental section 2.1. Materials 4,4′-biphenyldiboronic acid ((НО) 2 B-Ph-Ph-B(OH) 2 , ABCR, 97%), palladium (II) acetate (Pd(OAc) 2 , Aldrich, 99.9%), triphenylphosphine (PPh 3 , Aldrich, ReagentPlus®, 99%), dimethylformamide (DMF) (HC(O)NMe 2 , Ruskhim, high-purity grade), potassium carbonate (K 2 CO 3 , Reakhim, high-purity grade), hydrochloric acid (HCl, Sigma-tech, high-purity grade), hydrogen peroxide (H 2 O 2 , Prime Chemicals Group, 50 wt% aqueous solution), tetrahydrofuran (THF) (C 4 H 8 O, Khimmed, high-purity grade), ethanol (CH 3 CH 2 OH, IREA 2000, purum p.a.), dichloromethane (CH 2 Cl 2 , IREA 2000, analytical grade), tin (II) chloride dihydrate (SnCl 2 ×2H 2 O, Sigma-Aldrich, 98%), potassium hydroxide (KOH, Reakhim, 99%), copper (II) acetate (Cu(OAc) 2 , Sigma-Aldrich, 98%), ethylene carbonate (EC) ((CH 2 O) 2 CO, Sigma-Aldrich, 98%), p-xylene (C 6 H 4 (CH 3 ) 2 , Sigma-Aldrich, 98%), hydrogen (H 2 , 99.999%). 2.2. Synthesis of materials and catalysts Tetrakis-(p-bromophenyl)methane, tetrakis-(4-bromo-3-nitrophenyl)methane and PAF-30 were synthesized using the method described previously [28, 29]. 2.2.1. Synthesis of PAF-30-NO 2 -pre In a 250 mL round bottomed flask, equipped with the stir bar and silicone bath, tetrakis(4-bromo-3-nitrophenyl)methane (600 mg, 0.74 mmol) and 4,4′-biphenyldiboronic acid (364 mg, 1.5 mmol) were dissolved in 30 mL DMF and then 4.3 mL of aqueous K 2 CO 3 (2 mol/L) was added. After 3 cycles of vacuum/argon (degas/backfill), Pd(OAc) 2 (17 mg, 0.08 mmol) and PPh 3 (108 mg, 0.41 mmol) were quickly added to the solution. The mixture was then heated at 130℃ and the reaction was stirred at this temperature for 24 hours under static Ar atmosphere. After cooling to room temperature, the precipitate was filtered and washed with mixture of 520 µL H 2 O 2 and 40 mL HCl in 40 mL of water for 50 minutes the removal of the palladium residuals. Then it was filtered again and washed with water (50 mL×2), ethanol (50 mL×2), dichloromethane (50 mL×2), THF (50 mL×2) and dried under vacuum for 4 hours to give PAF-30-NO 2 -pre as beige powder (574 mg). 2.2.2. Synthesis of PAF-30-NH 2 In a 250 mL round bottomed flask, equipped with stir bar and reflux condenser, the suspension of PAF-30-NO 2 -pre (400 mg) in THF (90 mL) was prepared, then tin (II) chloride dihydrate (7.1 g, 31 mmol) was added. The resulting mixture was refluxed for 12 hours and cooled down afterwards. 200 mL of 10 wt% KOH aqueous solution was added, precipitate was filtrated and stirred several times in 10 wt% KOH solution for complete removal of tin residuals, then washed with water (50 mL×3), THF (50 mL×2) and ethanol (50 mL×2) and dried under vacuum at 50℃ for 8 hours. The product was obtained as a swamp-coloured powder (398 mg). 2.2.3. Synthesis of Cu-PAF catalysts Copper-based catalysts with different copper content (2, 5, 10 or 30 wt%) were prepared by impregnation of PAF-30 and PAF-30-NH 2 with the solution of copper (II) acetate in ethanol, which was subsequently reduced at 300 o C for 2 h under a H 2 flow with a ramp rate of 3 o C ×min − 1 , and available for catalytic evaluation and characterization. First, the desired amount of PAF-30 or PAF-30-NH 2 was drying in a vacuum at 60°C for 1 h. Then, support material was impregnated with required amount of a copper (II) acetate solution in ethanol in a round-bottom flask equipped with a magnetic stirrer anchor and a reflux condenser at room temperature under continuous stirring for 12 h. After that the solvent was evaporated in a vacuum at 40°C. The resulting solid was dried in a vacuum at 60°C for 6 hours and, finally, reduced at 300 o C for 2 h under H 2 flow with a ramp rate of 3 o C ×min − 1 with a flow rate of 25 mL×min − 1 . 2.3. Catalytic tests Hydrogenation of EC was carried out in a stainless-steel batch reactor equipped with magnetic stirrer. To begin, the autoclave was charged with EC, catalyst and THF. p-Xylene was also added to the reaction mixture as the internal standard. After flushing with H 2 three times, the autoclave was pressurized with H 2 at room temperature, and then heated to the desired temperature with vigorous mechanical stirring of 800 rpm. After the reaction, the autoclave was cooled to room temperature and depressurized. Reaction products were analysed by gas chromatography. All experiments were performed at least twice; the experimental error did not exceed 5%. The calculation method of the conversion of EC, yields of products are described as follows [30]: $$\:\begin{array}{c}Conversion\:\left(\text{E}\text{C}\right)=\:\frac{\text{m}\text{o}\text{l}\:\text{o}\text{f}\:\text{E}\text{C}\:\text{c}\text{h}\text{a}\text{r}\text{g}\text{e}\text{d}-\text{m}\text{o}\text{l}\:\text{o}\text{f}\:\text{E}\text{C}\:\text{l}\text{e}\text{f}\text{t}}{\text{m}\text{o}\text{l}\:\text{o}\text{f}\:\text{E}\text{C}\:\text{c}\text{h}\text{a}\text{r}\text{g}\text{e}\text{d}}·100\%\:\#\left(1\right)\end{array}$$ $$\:\begin{array}{c}Yield\:\left(\text{A}\right)=\frac{\text{m}\text{o}\text{l}\:\text{o}\text{f}\:\text{p}\text{r}\text{o}\text{d}\text{u}\text{c}\text{t}\left(\text{A}\right)}{\text{m}\text{o}\text{l}\:\text{o}\text{f}\:\text{E}\text{C}\:\text{c}\text{h}\text{a}\text{r}\text{g}\text{e}\text{d}\:}·100\%\#\left(2\right)\end{array}$$ 2.4. Characterization Nitrogen adsorption-desorption isotherms were recorded at 77 K on a Micromeritics Gemini VII 2390 instrument. The samples were out-gassed at 110°C for 6 hours before measurements. The surface area (S BET ) was calculated by the Brunauer–Emmett–Teller (BET) method based on adsorption data in a range of relative pressures P/P 0 = 0.05–0.2. Pore volume and pore size distribution were determined from the adsorption branches of isotherms using the non-local density functional theory (NLDFT) pore model for carbon slit pores. The total pore volume (V tot ) was calculated from the amount of nitrogen adsorbed at a relative pressure of P/P 0 = 0.965. Fourier transform infrared (FTIR) spectra were taken with a Nicolet IR200 (Thermo Scientific) instrument using multiple distortion of the total internal reflection method with multi-reflection HATR accessories, containing a 45˚ZnSe crystal for different wavelengths with a resolution of 4 cm − 1 in the range of 4000–500 cm − 1 .All spectra were taken by averaging 500 scans. Transmission electron microscopy (TEM) analysis was conducted on a JEM-2100 microscope with accelerating voltage of 200 kV. The processing of the micrographs and the calculation of the average particle size were conducted using the ImageJ software program. The analysis was performed in the center “Materials Science and Metallurgy” of NUST MISiS. The copper content in the catalysts was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) on an ICPE-9000 spectrometer (SHIMADZU) in Center for Collective Usage «Analytical Center for the Problems of Deep Refining of Oil and Petrochemistry» of A.V. Topchiev Institute of Petrochemical Synthesis, RAS. X-ray photoelectron spectroscopy (XPS) studies were performed on a PHI VersaProbe II 5000 instrument using excitation with Al K α X-ray radiation at 1486.6 eV. The calibration of photoelectron peaks was based on the C1s line with a binding energy of 284.5 eV (Figure S1 ). Deconvolution of XPS spectra was performed using CasaXPS v. 2.3.19PR1.0 software. The analysis was conducted at the center “Materials Science and Metallurgy” of NUST MISiS. The liquid products were analysed by Meta-Chrom Crystallux-4000M chromatograph equipped with a flame-ionization detector and a Rxi-17Sil MS column (30 m × 0.25 mm × 0.25 µm). Chromatograms were recorded and analysed using specialized software. 3. Result and discussion 3.1. General characterization In this work, porous aromatic frameworks PAF-30 and PAF-30-NH 2 were prepared using the Suzuki-Miyaura cross-coupling reaction (Fig. 1 ) [31]. Both materials were characterised by FTIR spectroscopy, low-temperature nitrogen adsorption-desorption, and the nitrogen content in PAF-30-NH 2 was determined by CNHS elemental analysis. FTIR of PAF-30-NH 2 exhibits an absorption band in the region of 1612 cm − 1 corresponding to amino groups (Fig. 2 a). In addition, the absorption bands of the symmetric and asymmetric valence vibration of nitro groups in aromatic compounds (at 1534 and 1348 cm − 1 , respectively) weren’t detected in the spectrum of PAF-30-NH 2 , indicating the complete reduction of these functional groups in material [24, 32]. Notably, no absorption band corresponding to C-Br bond vibrations (1080 cm⁻¹) was detected, demonstrating the completeness of the Suzuki-Miyaura cross-coupling reaction. The low-temperature nitrogen adsorption-desorption isotherms (Fig. 2 b) of PAF-30 and PAF-30-NH 2 materials revealed an abrupt absorption of nitrogen in low relative pressure range (P/P 0 = 0-0.05), indicating the well-developed porosity of these materials. Moreover, in the range of relative pressures P/P 0 = 0.2–0.9 the adsorption isotherms of these materials gradually increase without exhibiting a plateau; a hysteresis loop between the adsorption and desorption curves is found, demonstrating the presence of micro/mesopores in the structure of the obtained polymers. In addition, the steep adsorption of nitrogen in the region of P/P 0 = 0.9–0.97 for PAF-30-NH 2 material may indicate the presence of pores larger than 20 nm. It should be noted that PAF-30-NH 2 is characterized by higher average specific surface area (S BET = 793 m 2 /g) and pore volume (V p = 0.55 cm 3 /g) compared with those values for PAF-30 (S BET = 483 m 2 /g; V p = 0.28 cm 3 /g), that can be caused by more intensive framework interpenetration in case of PAF-30 material [33] (Table 1 ). Furthermore, PAF-30-NH 2 has higher micropore ratio (S t−plot / S BET = 64%) than PAF-30 (S t−plot / S BET = 49%). According to elemental analysis, the nitrogen content of PAF-30-NH 2 was 5.39 wt%. Table 1 Low-temperature N 2 adsorption-desorption and elemental analysis for the synthesized PAFs. Material S BET , m 2 /g S t−plot , m 2 /g S t−plot / S BET, % V tot , cm 3 /g ω N , wt% PAF-30 483 239 49 0.28 — PAF-30-NH 2 793 506 64 0.55 5.39 Using PAF-30 и PAF-30-NH 2 , we synthesized copper catalysts with nominal metal contents of 2, 5, 10 and 30 wt% by impregnating the support material with a solution of copper (II) acetate in ethanol followed by metal reduction in a hydrogen flow at 300 o C (Fig. 3 ). The composition of the catalysts was studied by means of XPS, TEM and ICP-AES. TEM images of the catalysts are illustrated in Fig. 4 . All catalysts contain well-distinct Cu nanoparticles of spherical shape and their size distribution is close to an asymmetric normal distribution. At the same time, large (up to 0.5 µm) particles or agglomerates of copper particles are present on the surface of catalysts with high metal content (more than 10 wt%). Their formation may be due to sintering of metal particles during reduction by cause of low Hüttig temperature for copper (134 o C) [22]. Also, with increasing metal content in the catalysts the distribution graph becomes wider, the proportion of large (more than 13 nm) nanoparticles and the average size of copper particles increase. Thus, the maximum of metal particle size distribution for 2Cu-PAF-30-NH 2 catalyst is 7 nm, for 5Cu-PAF-30-NH 2 – 10 nm, for 10Cu-PAF-30-NH 2 – 13 nm, for 30Cu-PAF-30-NH 2 – 16 nm and for 30Cu-PAF-30–19 nm. Hence, the average particle size increased with cooper loading [34, 35]. Table 2 XPS and ICP-AES data for catalysts Method ICP-AES XPS, Cu LMM AES XPS, N 1s Parameter Cu, wt% Binding energy, eV \(\:\frac{{\text{C}\text{u}}^{+}}{{\text{C}\text{u}}^{+}+{\text{C}\text{u}}^{0}},\:\%\) Binding energy, eV / Content, % Cu 0 Cu + RNH 2 RNH 2 →Cu 30Cu-PAF-30 32.68 570.31 573.21 23 — — 30Cu-PAF-30-NH 2 28.82 570.16 573.45 18 399.0 / 50% 400.3 / 50% 10Cu-PAF-30-NH 2 8.84 570.65 573.26 24 399.3 / 57% 399.9 / 43% 5Cu-PAF-30-NH 2 5.28 570.64 573.04 19 399.3 / 47% 399.9 / 53% 2Cu-PAF-30-NH 2 3.34 570.47 573.24 31 399.5 / 71% 400.3 / 29% The copper content in the catalysts and its chemical state on the surface of the freshly reduced catalysts were determined by ICP-AES and XPS methods, respectively (Table 2 , Figs. 5 and 6 ). The actual copper content of obtained Cu catalysts was close to nominal values. The Cu 2p XPS spectra of 30Cu-PAF-30, 30Cu-PAF-30-NH 2 , 10Cu-PAF-30-NH 2 catalysts (Fig. 5 a) lack a peak at 940–945 eV that is characteristic of the Cu 2+ satellite, indicating successful reduction of the catalysts [36, 37]. However, weak satellite peak at 941–950 eV was found in spectra of 5Cu-PAF-30-NH 2 and 2Cu-PAF-30-NH 2 catalysts, which may be derived from oxidation of copper species when the catalysts with low content of Cu are exposed to the atmosphere [13]. It should be mentioned that some Cu 2+ can be converted to Cu 0 and Cu + during hydrogenation reaction [38]. Also, very weak satellite peaks between 942.0 and 948.0 eV in spectra of the abovementioned catalysts can be attributed to Cu + [39]. Due to the similar binding energy of Cu + and Cu 0 species, Auger electron spectroscopy (AES) of Cu LMM are performed to determine the different copper species (Table 2 , Fig. 5 b). The XPS analysis revealed comparable Cu⁺/(Cu⁰ + Cu⁺) ratio for all catalysts (18–31%). Additional information of the structure of the catalysts and coordination of Cu particles by amino groups is provided by N 1s XPS spectra (Fig. 6 ). There are two peaks with maxima at 399.0-399.5 eV and 399.9-400.3 eV in the spectra of all obtained Cu-catalysts based on amino-modified PAF. The first one is characteristic peak corresponding to nitrogen atoms in amino groups bonded to phenyl rings [40] and the second peak at higher binding energy corresponds to positively charged species (–NH + 2 ), attributed to the donation of unshared electron pairs from the –NH 2 group to the metal ions [41]. 3.2. Catalytic performance The synthesized catalysts were tested in the hydrogenation of ethylene carbonate. Figure 7 shows the possible reactions occurring during the hydrogenation of EC [42, 43]. The most favourable reaction is hydrogenation of ethylene carbonate to methanol and ethylene glycol (reaction 2). At the same time, incomplete hydrogenation of EC with formation of carbon monoxide (reaction 1) is also possible. Undesirable reactions include hydrolysis of ethylene carbonate in the presence of trace amounts of water in the solvent (reaction 5), and thermal decomposition of EC (reaction 4), which generally occurs at temperatures above 200–250℃ [44]. Decarboxylation of EC to ethanol and carbon dioxide (reaction 3) may also proceed, which is also an interesting route for CO 2 -derived carbonates conversion. To prevent possible hydrolysis of EC (reaction 5), dried solvent was used in the reaction. First, the effect of temperature (150–250 ℃), hydrogen pressure (30–70 atm) and EC/Cu molar ratio (10–400) on the composition of hydrogenation products was investigated. The conversion of ethylene carbonate increases with increasing temperature (Fig. 8 a), with ethylene glycol and ethanol being the main products. In addition, traces of ethylene oxide were detected in reaction products at temperatures of 200 ℃ and 250 ℃. Also, ethanol yield increases sharply at 250 ℃ due to possible hydrogenation of ethylene glycol [45, 46]. However, no formation of any reaction products was observed in the blank experiment (without catalyst), and the conversion of EC did not exceed 2% in the presence of PAF-30 or PAF-30-NH 2 . It is worth noting the sharp increase in conversion at 200 ℃, indicating that high temperature is favourable for the activation of a stable EC molecule [47]. The obtained data agree with the results of thermodynamic calculations, according to which higher temperature is not beneficial for the target reaction (2), and more advantageous for reactions (1) and (3) [47]. Thus, we consider the temperature of 200℃ to be the optimal temperature for the reaction, since at this temperature a high conversion of EC is achieved, and the probability of its decomposition is minimal. Figure 8 b shows the composition of hydrogenation products of ethylene carbonate at different hydrogen pressures. The dependence of EC conversion, as well as yields of ethylene glycol and ethanol, has a volcano-like shape: it increases in the range of 30–50 atm, and decreases in the range of 50–70 atm. Such decrease in yield of hydrogenation products may be associated with competitive adsorption of hydrogen on the catalyst surface, hampering the adsorption of substrate. Thus, maximum conversion (86%) was achieved at 50 atm with EG yield of 69%, EtOH yield of 14% and EO yield of 3%. The results of EC hydrogenation at different substrate:metal ratios are shown in Fig. 9 . The conversion was practically unchanged when the EC/Cu ratio was increased from 10:1 to 200:1 mol/mol (and EC concentration – from 0.15 M to 1 M). However, at the EC/Cu ratio of 400:1 mol/mol and EC concentration of 2 M the conversion dropped sharply, which may be due to the limited catalytic capacity of the catalyst. It is noteworthy, that small amount of methanol (3%) was obtained at the EC/Cu ratio of 10:1 mol/mol. Based on the obtained results, we assume that reactions (1) and (3) are competitive, and the ratio of their rates depends more on the reaction temperature and the structure of the catalyst surface than on the substrate concentration or hydrogen pressure. The main reaction (2) is suppressed under selected reaction conditions and proceeds only at low substrate concentration. Ethanol formation is possible both during decarboxylation of EC and hydrogenation of EG [43, 47]. Therefore, we tested the feasibility of the hydrogenation of EG over a 10Cu-PAF-30-NH 2 catalyst. However, the reaction products did not contain ethanol, which suggests its formation mainly during the reaction (3). The influence of Cu content in catalysts on the composition of reaction products was studied (Fig. 10 a). The comparison was carried out at a fixed EC/Cu value of 10, and the hydrogen pressure and reaction time were decided to be reduced to 40 atm and 4 h, respectively. All catalysts demonstrated high activity in hydrogenation of EC: while EG remained the main reaction product, the yields of ethanol and methanol over the catalysts differed. Thus, the methanol yield decreases with decreasing copper content in the catalyst: it was 8% on the 30Cu-PAF-30-NH 2 catalyst, 3% on the 10Cu-PAF-30-NH 2 catalyst, and in the case of 5Cu-PAF-30-NH 2 and 2Cu-PAF-30-NH 2 its formation was not observed. The ethanol yield decreases in the series of catalysts 2Cu-PAF-30-NH 2 , 5Cu-PAF-30-NH 2 and 10Cu-PAF-30-NH 2 from 22 to 8%, but increases sharply to 28% in the case of catalyst 30Cu-PAF-30-NH 2 . We hypothesize that obtained results can be interpreted as follows. It is known that during hydrogenation, the EC molecule is coordinated by carbonyl oxygen on Cu + species perpendicular to the catalyst surface, while dissociative adsorption of H 2 occurs on the Cu 0 surface [48]. However, in the case of the synthesized catalysts, most of the particles are located inside the pores of the carrier, due to which this type of adsorption of the EC molecule appears to be sterically hindered. With increasing Cu content in the catalyst, the amount of nanoparticles not encapsulated in the pores of the carrier also increased, and the formation of methanol apparently occurs on them. At the same time, the ethanol yield, correlates with the size of Cu particles in the catalyst (Fig. 10 b), or probably with the total copper surface available for EC adsorption. Thus, in the case of 2Cu-PAF-30-NH 2 , 5Cu-PAF-30-NH 2 and 10Cu-PAF-30-NH 2 catalysts, most of the nanoparticles are located inside the pores of the carrier and the ethanol yield decreases linearly with increasing their size. The significantly higher ethanol yield on catalyst 30Cu-PAF-30-NH 2 , despite the larger average particle size, may be due to the presence of small copper nanoparticles (up to 10 nm) readily available for EC, even though their relatively small fraction in the total nanoparticle distribution. To test the described hypotheses, the influence of the reduction conditions of the 30Cu-PAF-30-NH 2 catalyst on its activity was studied (Figure S2). The highest conversion of EC (94%) as well as the highest yields of ethanol (28%) and methanol (8%) were obtained when the catalyst was reduced at 300℃ for 2 hours. Increasing both the temperature and time of catalyst reduction leads to a decrease in its activity, which may be due to the enlargement of copper nanoparticles because of the low value of the Hüttig temperature for copper (134 o C). At the lower reduction temperature (250℃), the EC conversion was less (65%). However, increasing the recovery time of the catalyst to 4 hours resulted in an increase in its activity, which can be explained by a more complete reduction of the metal under these conditions. Finally, the reusability of 30Cu-PAF-30-NH 2 was tested using the 30Cu-PAF-30 catalyst based on unmodified PAF-30 carrier as a comparison (Fig. 11 ). Both catalysts showed high activity. However, EC conversion on the 30Cu-PAF-30-NH 2 catalyst was higher (94% vs. 52% in Cycle 1), and methanol was present in the reaction products. Nevertheless, despite the lower activity, 30Cu-PAF-30 was much more stable: the EC conversion and product yields were virtually unchanged by reaction cycle 5. At the same time, the 30Cu-PAF-30-NH 2 catalyst gradually loses its activity and at cycle 5, the yields of EG, EtOH and MeOH were 49, 7 and 1%, respectively. This decrease in activity may be due to the washout of metal from the carrier surface, especially those not anchored in the pores of the nanoparticles. 4. Conclusions Copper catalysts based on porous aromatic frameworks PAF-30 and PAF-30-NH 2 with different metal content (2, 5, 10, 30 wt%) were synthesized. The average size of Cu NPs increased from 7 to 16 nm with increasing metal loading from 2–30%, while their surface composition was similar according to the XPS results (Cu + /(Cu + + Cu 0 ) = 18–31%). The obtained catalysts exhibited high activity in the hydrogenation of ethylene carbonate, and the main products were ethylene glycol and ethanol. It is assumed that the low yield of methanol is due to the impossibility of perpendicular adsorption of ethylene carbonate molecule on the surface of copper nanoparticles due to steric hindrance caused by the carrier. The highest conversion of ethylene carbonate was obtained on catalyst 30Cu-PAF-30-NH 2 at 40 atm H 2 , 200℃ and EC/Cu = 10:1 mol/mol: under these conditions for 4 hours the yields of ethylene glycol, ethanol and methanol were 58, 28 and 8%, respectively. Abbreviations EC Ethylene carbonate EG Ethylene glycol EO Ethylene oxide NPs Nanoparticles MOFs Metal-organic frameworks COFs Covalent organic frameworks PAFs Porous aromatic frameworks 2-HEF 2-Hydroxyethyl formate BET Brunauer–Emmett–Teller NLDFT Non-local density functional theory FTIR Fourier transform infrared TEM Transmission electron microscopy ICP-AES Inductively coupled plasma atomic emission spectrometry XPS X-ray photoelectron spectroscopy AES Auger electron spectroscopy Declarations Ethics and Consent to Participate Not applicable. Consent for Publication Not applicable. Conflict of Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Author Contributions Elizaveta Oskina: investigation, writing - original draft. Leonid Kulikov: writing - review and editing, visualization. Daria Makeeva: analysis, supervision. Anton Maximov: formal analysis, methodology, supervision. Funding There was no funding for this research. Data Availability No data was used for the research described in the article. Acknowledgements The study was conducted under the state assignment of Lomonosov Moscow State University, project № 121031300092-6. References Fayisa BA, Yang Y, Zhen Z, et al (2022) Engineered chemical utilization of CO 2 to methanol via direct and indirect hydrogenation pathways: a review. Ind Eng Chem Res. https://doi.org/10.1021/acs.iecr.2c00402 Lian C, Ren F, Liu Y, et al (2015) Heterogeneous selective hydrogenation of ethylene carbonate to methanol and ethylene glycol over a copper chromite nanocatalyst. Chemical Communications. https://doi.org/10.1039/c4cc08247h Balaraman E, Gunanathan C, Zhang J, et al (2011) Efficient hydrogenation of organic carbonates, carbamates and formates indicates alternative routes to methanol based on CO 2 and CO. 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Journal of Physical Chemistry C. https://doi.org/10.1021/jp3119633 Peñas-Garzón M, Sampaio MJ, Wang YL, et al (2022) Solar photocatalytic degradation of parabens using UiO-66-NH 2 . Sep Purif Technol. https://doi.org/10.1016/j.seppur.2022.120467 Figueroa-Quintero L, Cordero-Lanzac T, Ramos-Fernandez E V., et al (2025) Tailoring catalysts for CO 2 hydrogenation: synthesis and characterization of NH 2 –MIL–125 frameworks. Molecules. https://doi.org/10.3390/molecules30071458 Fayisa BA, Yang Y, Zhen Z, et al (2022) Engineered chemical utilization of CO 2 to methanol via direct and indirect hydrogenation pathways: a review. Ind Eng Chem Res. https://doi.org/10.1021/acs.iecr.2c00402 Kim J, Pfänder N, Prieto G (2020) Recycling of CO 2 by hydrogenation of carbonate derivatives to methanol: tuning copper–oxide promotion effects in supported catalysts. ChemSusChem. https://doi.org/10.1002/cssc.202000166 Fernandes Y, Bry A, de Persis S (2019) Thermal degradation analyses of carbonate solvents used in Li-ion batteries. J Power Sources. https://doi.org/10.1016/j.jpowsour.2018.12.077 Gong J, Yue H, Zhao Y, et al (2012) Synthesis of ethanol via syngas on Cu/SiO 2 catalysts with balanced Cu 0 -Cu + sites. J Am Chem Soc. https://doi.org/10.1021/ja3034153 Ai P, Tan M, Ishikuro Y, et al (2017) Design of an autoreduced copper in carbon nanotube catalyst to realize the precisely selective hydrogenation of dimethyl oxalate. ChemCatChem. https://doi.org/10.1002/cctc.201601503 Yang Y, Zhang M, Fayisa BA, et al (2024) Towards understanding the reaction network in the hydrogenation of CO 2 -derived ethylene carbonate. Chem Eng Sci. https://doi.org/10.1016/j.ces.2024.119701 Liu J, He P, Wang L, et al (2018) An efficient and stable Cu/SiO 2 catalyst for the syntheses of ethylene glycol and methanol via chemoselective hydrogenation of ethylene carbonate. Chinese Journal of Catalysis. https://doi.org/10.1016/S1872-2067(18)63032-3 Additional Declarations No competing interests reported. Supplementary Files SupplementaryInformation.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 08 Jul, 2025 Reviews received at journal 07 Jul, 2025 Reviews received at journal 02 Jul, 2025 Reviews received at journal 27 Jun, 2025 Reviewers agreed at journal 15 Jun, 2025 Reviewers agreed at journal 15 Jun, 2025 Reviewers agreed at journal 13 Jun, 2025 Reviewers invited by journal 13 Jun, 2025 Editor assigned by journal 05 Jun, 2025 Submission checks completed at journal 05 Jun, 2025 First submitted to journal 02 Jun, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6803584","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":471662238,"identity":"e70c90e9-fa2d-4753-a9ef-739c1b50f00a","order_by":0,"name":"Elizaveta Oskina","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxUlEQVRIiWNgGAWjYFACNoYDYPp4AwNDQgFJWs4AqQQDIrVAwI0EIEGMFn7+Y4mHC2oY5Phuvk788MCAId/gAAEtkjPSDhyecYzBWPJ27mYJoMMsNxDSYnCDveEwDxtD4obbuRtAWgwI2mJw/jhQyz+G+g03z27+QZyWA0CH8bYBw+oG7zbibAH6JeEwbx+D4cwzudssEgwkDCQJaQGGmPFnnm8M8nzHz26++aPCxoCPkBYo+A9jSBCnfhSMglEwCkYBfgAAXcZCyty9l7cAAAAASUVORK5CYII=","orcid":"","institution":"Lomonosov Moscow State University","correspondingAuthor":true,"prefix":"","firstName":"Elizaveta","middleName":"","lastName":"Oskina","suffix":""},{"id":471662239,"identity":"77b06192-4e57-4de8-b575-37313a79c252","order_by":1,"name":"Daria Makeeva","email":"","orcid":"","institution":"Lomonosov Moscow State University","correspondingAuthor":false,"prefix":"","firstName":"Daria","middleName":"","lastName":"Makeeva","suffix":""},{"id":471662243,"identity":"a4d0b792-564c-4a92-88da-04f5339f30ca","order_by":2,"name":"Leonid Kulikov","email":"","orcid":"","institution":"Lomonosov Moscow State University","correspondingAuthor":false,"prefix":"","firstName":"Leonid","middleName":"","lastName":"Kulikov","suffix":""},{"id":471662244,"identity":"4fe9d2cb-e628-4787-999a-568bf4cd9bf0","order_by":3,"name":"Anton Maximov","email":"","orcid":"","institution":"A.V. Topchiev Institute of Petrochemical Synthesis","correspondingAuthor":false,"prefix":"","firstName":"Anton","middleName":"","lastName":"Maximov","suffix":""}],"badges":[],"createdAt":"2025-06-02 15:23:22","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6803584/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6803584/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84789161,"identity":"5990c7c5-6136-4b29-bb65-b19f74efd919","added_by":"auto","created_at":"2025-06-17 11:04:23","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":44999,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic synthesis of PAF-30 and PAF-30-NH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/a3a0412fbf7ebc1a2cebe3e4.png"},{"id":84790762,"identity":"30ad5594-e6a4-47c3-86a4-5c14a7d44541","added_by":"auto","created_at":"2025-06-17 11:20:24","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":84696,"visible":true,"origin":"","legend":"\u003cp\u003eIR spectra (a) and N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherms (b) of PAF-30 and PAF-30-NH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/16da11bfe92189d302553784.png"},{"id":84790249,"identity":"64caf3ce-3b9e-45ef-a494-32258bdfdd57","added_by":"auto","created_at":"2025-06-17 11:12:23","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":74659,"visible":true,"origin":"","legend":"\u003cp\u003eThe scheme of copper nanoparticles encapsulation in the pores of PAF-30-NH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/2abd32903c8bcc186f0d69a4.png"},{"id":84791627,"identity":"b24dea17-bae2-4819-9543-3f778fd38053","added_by":"auto","created_at":"2025-06-17 11:28:24","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2410377,"visible":true,"origin":"","legend":"\u003cp\u003eTEM images and particle size distributions for (a) 30Cu-PAF-30, (b) 30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e, (c) 10Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e, (d) 5Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e, (e) 2Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/f449bf86c1a49d9bd300ea8e.png"},{"id":84789165,"identity":"08f64144-9783-46a2-a7ca-e5054594269f","added_by":"auto","created_at":"2025-06-17 11:04:24","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":117376,"visible":true,"origin":"","legend":"\u003cp\u003eXPS Cu 2p (a) and AES Cu LMM (b) spectra of the catalysts\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/d32c263269965a22242b67f7.png"},{"id":84790250,"identity":"9cf3d798-b720-4e89-b116-26ae5873c78f","added_by":"auto","created_at":"2025-06-17 11:12:24","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":82632,"visible":true,"origin":"","legend":"\u003cp\u003eXPS N 1s spectra of the PAF-30-NH\u003csub\u003e2\u003c/sub\u003e-based catalysts\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/4b139b5f18ac4141508a9749.png"},{"id":84789163,"identity":"408b916d-0a6d-4606-93ea-28808781494b","added_by":"auto","created_at":"2025-06-17 11:04:24","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":19092,"visible":true,"origin":"","legend":"\u003cp\u003ePossible reactions during the EC hydrogenation: (1) Decarbonylation; (2) Hydrogenation; (3) Decarboxylation; (4) Decomposition; (5) Hydrolysis\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/9072ed7f1068e028bcf24492.png"},{"id":84789172,"identity":"4c5c3771-2022-44fa-b5f9-d72679e29869","added_by":"auto","created_at":"2025-06-17 11:04:24","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":25391,"visible":true,"origin":"","legend":"\u003cp\u003eEC hydrogenation at different temperatures (a) and hydrogen pressures (b).\u003cbr\u003e\n\u003cem\u003eReaction conditions\u003c/em\u003e: 5 mg of catalyst (10Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e), EC/Cu=200:1 mol/mol, C(EC) = 1\u0026nbsp;M, 1.5 mL EC solution in ТHF, 5h; hydrogen pressure in (a) – 50 atm H\u003csub\u003e2\u003c/sub\u003e;\u003cbr\u003e\nreaction temperature in (b) – 200°C.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/de1b3d451b323ed92515a8fe.png"},{"id":84789177,"identity":"5cd805f1-f30e-4c41-83bf-6a3413cfb09d","added_by":"auto","created_at":"2025-06-17 11:04:24","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":17102,"visible":true,"origin":"","legend":"\u003cp\u003eEC hydrogenation at different EC/Cu ratio (different EC concentration). \u003cem\u003eReaction\u0026nbsp;conditions\u003c/em\u003e: 5 mg of catalyst (10Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e), 0.75 mL EC solution in ТHF, 5 h, 50\u0026nbsp;atm H\u003csub\u003e2\u003c/sub\u003e, 200°C.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/82fb6f0a44cc82d898acdb19.png"},{"id":84790258,"identity":"b7e0ead0-dd1e-445e-b06c-4452d23f9c3b","added_by":"auto","created_at":"2025-06-17 11:12:24","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":31148,"visible":true,"origin":"","legend":"\u003cp\u003eEC hydrogenation on xCu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e catalysts, where x= 2; 5; 10; 30 wt% Cu. \u003cem\u003eReaction conditions\u003c/em\u003e: EC/Cu=10:1 mol/mol, C(EC) = 0.15\u0026nbsp;M, 0.75 mL EC solution in THF, 4 h, 40\u0026nbsp;atm H\u003csub\u003e2\u003c/sub\u003e, 200℃.\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/83652188e7c01a0b06e53f74.png"},{"id":84789174,"identity":"c17eacbb-d5dc-4f43-b0ae-215f2e8d38a1","added_by":"auto","created_at":"2025-06-17 11:04:24","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":24983,"visible":true,"origin":"","legend":"\u003cp\u003eReusability of (a) 30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e and (b) 30Cu-PAF-30.\u003cbr\u003e\n\u003cem\u003eReaction conditions\u003c/em\u003e: EC/Cu=10:1 mol/mol, C(EC) = 0.15\u0026nbsp;M, 0.75 mL EC solution in THF, 4 h, 40\u0026nbsp;atm H\u003csub\u003e2\u003c/sub\u003e, 200℃.\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/37505cfc223893f8f7396de0.png"},{"id":84791990,"identity":"b05454a2-1371-461e-85f5-ea5863ad0264","added_by":"auto","created_at":"2025-06-17 11:36:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4080979,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/9ea5a26f-96ed-4ffa-9266-fe99ea72f199.pdf"},{"id":84790252,"identity":"4d492256-e8e1-4ab1-9874-2f05de5360de","added_by":"auto","created_at":"2025-06-17 11:12:24","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":290509,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6803584/v1/2158fe2db0a762d04204b40a.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Copper catalysts supported on porous aromatic frameworks for the hydrogenation of ethylene carbonate ","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe catalytic hydrogenation of non-toxic and renewable carbon dioxide (CO\u003csub\u003e2\u003c/sub\u003e) into valuable petrochemicals and fuel components has attracted considerable attention in terms of environmental sustainability [1]. However, the industrial use of catalytic systems for direct hydrogenation of CO\u003csub\u003e2\u003c/sub\u003e (Cu-ZnO-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, Cu-ZnO/ZrO\u003csub\u003e2\u003c/sub\u003e, Cu-La/SBA-15, Pd/SiO\u003csub\u003e2\u003c/sub\u003e, etc.) is limited by relatively harsh reaction conditions (220\u0026ndash;300 \u003csup\u003eo\u003c/sup\u003eC, 50\u0026ndash;100 atm) resulted from the kinetic inertness and high thermodynamic stability of CO\u003csub\u003e2\u003c/sub\u003e molecule [2]. On the other hand, the indirect transformation of carbon dioxide via the hydrogenation of organic carbonates, carbamates and formates can be achieved under milder conditions [3]. In particular, the conversion of CO\u003csub\u003e2\u003c/sub\u003e-derived ethylene carbonate (EC) to methanol and ethylene glycol (EG) is an attractive approach as EC is industrially available from the well-established \u0026laquo;Omega process\u0026raquo;, which involves cycloaddition of ethylene oxide (EO) with CO\u003csub\u003e2\u003c/sub\u003e [4].\u003c/p\u003e \u003cp\u003eCopper-based catalytic systems are widely used in hydrogenation of esters due to selective hydrogenation of C-O/C\u0026thinsp;=\u0026thinsp;O bonds and low activity toward C-C bond cleavage [5, 6]. Inert supports, such as carbon- and silica-based materials, are required for this reaction, as excessive surface acidity or basicity can lead to decarbonylation or decarboxylation of carbonates [7]. Thus, mesoporous silicas including KIT-6, MCM-41, SBA-15, HMS were investigated as the supports for copper nanoparticles (Cu NPs) in the hydrogenation of EC [8\u0026ndash;10]. For example, full conversion of EC with EG and MeOH yields of 95% and 62%, respectively, was achieved over Cu/SBA-15 catalyst [8]. Despite numerous attempts to modify silica-supported catalysts [11\u0026ndash;13], loss of silica species during the reaction with solvent at high temperature still a problem, which will lead to poor stability [14]. Hence, the design of nonsilica Cu-based catalysts is required to improve the long-term running stability.\u003c/p\u003e \u003cp\u003eConsiderably less research is devoted to catalysts based on carbon materials [15\u0026ndash;17]. Meanwhile, carbon materials extensively utilised as supports for transition metal nanoparticles due to their thermal and chemical stability, functionalization variability, well-developed textural properties [18]. For example, Cu-catalysts supported on carbon nanotubes with oxygen-containing functional groups were tested in EC hydrogenation. 40Cu/CNTs catalyst demonstrated EС conversion of more than 99% with methanol and ethylene glycol yields of 83% and 99%, respectively, and remains active after 150 hours on stream [16].\u003c/p\u003e \u003cp\u003eMeanwhile, many new porous materials have been synthesized in the past 15 years, including metal-organic frameworks (MOFs) [19], covalent organic frameworks (COFs) [20], porous aromatic frameworks (PAFs) [21]. However, to date, their application as catalyst carriers for the hydrogenation of organic carbonates has hardly been considered. Thus, Lei et. al. [22] report the synthesis of Cu@MIL-101 catalyst and its application in the hydrogenation of EC. It is interesting to note that the composition of the hydrogenation products depended on the reaction temperature: at 180\u0026deg;C the main product was ethylene glycol (conversion 100 %, selectivity 2%), and at 160\u0026deg;C \u0026ndash; 2-hydroxyethyl formate, 2-HEF (conversion 100 %, selectivity 2%). The authors note the important role of the interaction between the Cu\u003csup\u003e0\u003c/sup\u003e and Cr\u003csup\u003e3+\u003c/sup\u003e in the dissociation of H\u003csub\u003e2\u003c/sub\u003e and activation of C-O and C\u0026thinsp;=\u0026thinsp;O bonds in the esters, which makes Cu@MIL-101 highly active catalyst. However, no methanol formation was observed, which may be due to the Lewis acidity of the Cr\u003csup\u003e3+\u003c/sup\u003e species.\u003c/p\u003e \u003cp\u003eIn the current work, we study Cu catalysts based on another type of carriers, porous aromatic frameworks \u0026mdash; polymers constructed by the assembly of organic building blocks through covalent coupling reactions [23]. They are characterised by high specific surface areas, adjustable porous structures, high thermal and chemical stability, which allowed to develop on their basis catalysts for hydrogenation of alkynes and dienes [24, 25], hydrodeoxygenation of lignin-based of lignin bio-oil compounds [26], oxidation of alkylaromatics [27]. We applied two types of materials, PAF-30 and its derivative with amino groups PAF-30-NH\u003csub\u003e2\u003c/sub\u003e, as carriers of copper nanoparticles, and tested the obtained catalysts in the hydrogenation of ethylene carbonate.\u003c/p\u003e"},{"header":"2. Experimental section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Materials\u003c/h2\u003e \u003cp\u003e4,4\u0026prime;-biphenyldiboronic acid ((НО)\u003csub\u003e2\u003c/sub\u003eB-Ph-Ph-B(OH)\u003csub\u003e2\u003c/sub\u003e, ABCR, 97%), palladium (II) acetate (Pd(OAc)\u003csub\u003e2\u003c/sub\u003e, Aldrich, 99.9%), triphenylphosphine (PPh\u003csub\u003e3\u003c/sub\u003e, Aldrich, ReagentPlus\u0026reg;, 99%), dimethylformamide (DMF) (HC(O)NMe\u003csub\u003e2\u003c/sub\u003e, Ruskhim, high-purity grade), potassium carbonate (K\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e, Reakhim, high-purity grade), hydrochloric acid (HCl, Sigma-tech, high-purity grade), hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, Prime Chemicals Group, 50 wt% aqueous solution), tetrahydrofuran (THF) (C\u003csub\u003e4\u003c/sub\u003eH\u003csub\u003e8\u003c/sub\u003eO, Khimmed, high-purity grade), ethanol (CH\u003csub\u003e3\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003eOH, IREA 2000, purum p.a.), dichloromethane (CH\u003csub\u003e2\u003c/sub\u003eCl\u003csub\u003e2\u003c/sub\u003e, IREA 2000, analytical grade), tin (II) chloride dihydrate (SnCl\u003csub\u003e2\u003c/sub\u003e\u0026times;2H\u003csub\u003e2\u003c/sub\u003eO, Sigma-Aldrich, 98%), potassium hydroxide (KOH, Reakhim, 99%), copper (II) acetate (Cu(OAc)\u003csub\u003e2\u003c/sub\u003e, Sigma-Aldrich, 98%), ethylene carbonate (EC) ((CH\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e2\u003c/sub\u003eCO, Sigma-Aldrich, 98%), p-xylene (C\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e4\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, Sigma-Aldrich, 98%), hydrogen (H\u003csub\u003e2\u003c/sub\u003e, 99.999%).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Synthesis of materials and catalysts\u003c/h2\u003e \u003cp\u003eTetrakis-(p-bromophenyl)methane, tetrakis-(4-bromo-3-nitrophenyl)methane and PAF-30 were synthesized using the method described previously [28, 29].\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e \u003ch2\u003e2.2.1. Synthesis of PAF-30-NO\u003csub\u003e2\u003c/sub\u003e-pre\u003c/h2\u003e \u003cp\u003eIn a 250 mL round bottomed flask, equipped with the stir bar and silicone bath, tetrakis(4-bromo-3-nitrophenyl)methane (600 mg, 0.74 mmol) and 4,4\u0026prime;-biphenyldiboronic acid (364 mg, 1.5 mmol) were dissolved in 30 mL DMF and then 4.3 mL of aqueous K\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e (2 mol/L) was added. After 3 cycles of vacuum/argon (degas/backfill), Pd(OAc)\u003csub\u003e2\u003c/sub\u003e (17 mg, 0.08 mmol) and PPh\u003csub\u003e3\u003c/sub\u003e (108 mg, 0.41 mmol) were quickly added to the solution. The mixture was then heated at 130℃ and the reaction was stirred at this temperature for 24 hours under static Ar atmosphere. After cooling to room temperature, the precipitate was filtered and washed with mixture of 520 \u0026micro;L H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e and 40 mL HCl in 40 mL of water for 50 minutes the removal of the palladium residuals. Then it was filtered again and washed with water (50 mL\u0026times;2), ethanol (50 mL\u0026times;2), dichloromethane (50 mL\u0026times;2), THF (50 mL\u0026times;2) and dried under vacuum for 4 hours to give PAF-30-NO\u003csub\u003e2\u003c/sub\u003e-pre as beige powder (574 mg).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.2.2. Synthesis of PAF-30-NH\u003csub\u003e2\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eIn a 250 mL round bottomed flask, equipped with stir bar and reflux condenser, the suspension of PAF-30-NO\u003csub\u003e2\u003c/sub\u003e-pre (400 mg) in THF (90 mL) was prepared, then tin (II) chloride dihydrate (7.1 g, 31 mmol) was added. The resulting mixture was refluxed for 12 hours and cooled down afterwards. 200 mL of 10 wt% KOH aqueous solution was added, precipitate was filtrated and stirred several times in 10 wt% KOH solution for complete removal of tin residuals, then washed with water (50 mL\u0026times;3), THF (50 mL\u0026times;2) and ethanol (50 mL\u0026times;2) and dried under vacuum at 50℃ for 8 hours. The product was obtained as a swamp-coloured powder (398 mg).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.2.3. Synthesis of Cu-PAF catalysts\u003c/h2\u003e \u003cp\u003eCopper-based catalysts with different copper content (2, 5, 10 or 30 wt%) were prepared by impregnation of PAF-30 and PAF-30-NH\u003csub\u003e2\u003c/sub\u003e with the solution of copper (II) acetate in ethanol, which was subsequently reduced at 300 \u003csup\u003eo\u003c/sup\u003eC for 2 h under a H\u003csub\u003e2\u003c/sub\u003e flow with a ramp rate of 3 \u003csup\u003eo\u003c/sup\u003eC \u0026times;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and available for catalytic evaluation and characterization.\u003c/p\u003e \u003cp\u003eFirst, the desired amount of PAF-30 or PAF-30-NH\u003csub\u003e2\u003c/sub\u003e was drying in a vacuum at 60\u0026deg;C for 1 h. Then, support material was impregnated with required amount of a copper (II) acetate solution in ethanol in a round-bottom flask equipped with a magnetic stirrer anchor and a reflux condenser at room temperature under continuous stirring for 12 h. After that the solvent was evaporated in a vacuum at 40\u0026deg;C. The resulting solid was dried in a vacuum at 60\u0026deg;C for 6 hours and, finally, reduced at 300 \u003csup\u003eo\u003c/sup\u003eC for 2 h under H\u003csub\u003e2\u003c/sub\u003e flow with a ramp rate of 3 \u003csup\u003eo\u003c/sup\u003eC \u0026times;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with a flow rate of 25 mL\u0026times;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Catalytic tests\u003c/h2\u003e \u003cp\u003eHydrogenation of EC was carried out in a stainless-steel batch reactor equipped with magnetic stirrer. To begin, the autoclave was charged with EC, catalyst and THF. p-Xylene was also added to the reaction mixture as the internal standard. After flushing with H\u003csub\u003e2\u003c/sub\u003e three times, the autoclave was pressurized with H\u003csub\u003e2\u003c/sub\u003e at room temperature, and then heated to the desired temperature with vigorous mechanical stirring of 800 rpm. After the reaction, the autoclave was cooled to room temperature and depressurized. Reaction products were analysed by gas chromatography. All experiments were performed at least twice; the experimental error did not exceed 5%. The calculation method of the conversion of EC, yields of products are described as follows [30]:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\begin{array}{c}Conversion\\:\\left(\\text{E}\\text{C}\\right)=\\:\\frac{\\text{m}\\text{o}\\text{l}\\:\\text{o}\\text{f}\\:\\text{E}\\text{C}\\:\\text{c}\\text{h}\\text{a}\\text{r}\\text{g}\\text{e}\\text{d}-\\text{m}\\text{o}\\text{l}\\:\\text{o}\\text{f}\\:\\text{E}\\text{C}\\:\\text{l}\\text{e}\\text{f}\\text{t}}{\\text{m}\\text{o}\\text{l}\\:\\text{o}\\text{f}\\:\\text{E}\\text{C}\\:\\text{c}\\text{h}\\text{a}\\text{r}\\text{g}\\text{e}\\text{d}}\u0026middot;100\\%\\:\\#\\left(1\\right)\\end{array}$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:\\begin{array}{c}Yield\\:\\left(\\text{A}\\right)=\\frac{\\text{m}\\text{o}\\text{l}\\:\\text{o}\\text{f}\\:\\text{p}\\text{r}\\text{o}\\text{d}\\text{u}\\text{c}\\text{t}\\left(\\text{A}\\right)}{\\text{m}\\text{o}\\text{l}\\:\\text{o}\\text{f}\\:\\text{E}\\text{C}\\:\\text{c}\\text{h}\\text{a}\\text{r}\\text{g}\\text{e}\\text{d}\\:}\u0026middot;100\\%\\#\\left(2\\right)\\end{array}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Characterization\u003c/h2\u003e \u003cp\u003eNitrogen adsorption-desorption isotherms were recorded at 77 K on a Micromeritics Gemini VII 2390 instrument. The samples were out-gassed at 110\u0026deg;C for 6 hours before measurements. The surface area (S\u003csub\u003eBET\u003c/sub\u003e) was calculated by the Brunauer\u0026ndash;Emmett\u0026ndash;Teller (BET) method based on adsorption data in a range of relative pressures P/P\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.05\u0026ndash;0.2. Pore volume and pore size distribution were determined from the adsorption branches of isotherms using the non-local density functional theory (NLDFT) pore model for carbon slit pores. The total pore volume (V\u003csub\u003etot\u003c/sub\u003e) was calculated from the amount of nitrogen adsorbed at a relative pressure of P/P\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.965.\u003c/p\u003e \u003cp\u003eFourier transform infrared (FTIR) spectra were taken with a Nicolet IR200 (Thermo Scientific) instrument using multiple distortion of the total internal reflection method with multi-reflection HATR accessories, containing a 45˚ZnSe crystal for different wavelengths with a resolution of 4 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the range of 4000\u0026ndash;500 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.All spectra were taken by averaging 500 scans.\u003c/p\u003e \u003cp\u003eTransmission electron microscopy (TEM) analysis was conducted on a JEM-2100 microscope with accelerating voltage of 200 kV. The processing of the micrographs and the calculation of the average particle size were conducted using the ImageJ software program. The analysis was performed in the center \u0026ldquo;Materials Science and Metallurgy\u0026rdquo; of NUST MISiS.\u003c/p\u003e \u003cp\u003eThe copper content in the catalysts was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) on an ICPE-9000 spectrometer (SHIMADZU) in Center for Collective Usage \u0026laquo;Analytical Center for the Problems of Deep Refining of Oil and Petrochemistry\u0026raquo; of A.V. Topchiev Institute of Petrochemical Synthesis, RAS.\u003c/p\u003e \u003cp\u003eX-ray photoelectron spectroscopy (XPS) studies were performed on a PHI VersaProbe II 5000 instrument using excitation with Al \u003cem\u003eK\u003c/em\u003eα X-ray radiation at 1486.6 eV. The calibration of photoelectron peaks was based on the C1s line with a binding energy of 284.5 eV (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Deconvolution of XPS spectra was performed using CasaXPS v. 2.3.19PR1.0 software. The analysis was conducted at the center \u0026ldquo;Materials Science and Metallurgy\u0026rdquo; of NUST MISiS.\u003c/p\u003e \u003cp\u003eThe liquid products were analysed by Meta-Chrom Crystallux-4000M chromatograph equipped with a flame-ionization detector and a Rxi-17Sil MS column (30 m \u0026times; 0.25 mm \u0026times; 0.25 \u0026micro;m). Chromatograms were recorded and analysed using specialized software.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Result and discussion","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.1. General characterization\u003c/h2\u003e \u003cp\u003eIn this work, porous aromatic frameworks PAF-30 and PAF-30-NH\u003csub\u003e2\u003c/sub\u003e were prepared using the Suzuki-Miyaura cross-coupling reaction (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) [31]. Both materials were characterised by FTIR spectroscopy, low-temperature nitrogen adsorption-desorption, and the nitrogen content in PAF-30-NH\u003csub\u003e2\u003c/sub\u003e was determined by CNHS elemental analysis.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFTIR of PAF-30-NH\u003csub\u003e2\u003c/sub\u003e exhibits an absorption band in the region of 1612 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponding to amino groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). In addition, the absorption bands of the symmetric and asymmetric valence vibration of nitro groups in aromatic compounds (at 1534 and 1348 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively) weren\u0026rsquo;t detected in the spectrum of PAF-30-NH\u003csub\u003e2\u003c/sub\u003e, indicating the complete reduction of these functional groups in material [24, 32]. Notably, no absorption band corresponding to C-Br bond vibrations (1080 cm⁻\u0026sup1;) was detected, demonstrating the completeness of the Suzuki-Miyaura cross-coupling reaction.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe low-temperature nitrogen adsorption-desorption isotherms (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb) of PAF-30 and PAF-30-NH\u003csub\u003e2\u003c/sub\u003e materials revealed an abrupt absorption of nitrogen in low relative pressure range (P/P\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0-0.05), indicating the well-developed porosity of these materials. Moreover, in the range of relative pressures P/P\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.2\u0026ndash;0.9 the adsorption isotherms of these materials gradually increase without exhibiting a plateau; a hysteresis loop between the adsorption and desorption curves is found, demonstrating the presence of micro/mesopores in the structure of the obtained polymers. In addition, the steep adsorption of nitrogen in the region of P/P\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.9\u0026ndash;0.97 for PAF-30-NH\u003csub\u003e2\u003c/sub\u003e material may indicate the presence of pores larger than 20 nm. It should be noted that PAF-30-NH\u003csub\u003e2\u003c/sub\u003e is characterized by higher average specific surface area (S\u003csub\u003eBET\u003c/sub\u003e = 793 m\u003csup\u003e2\u003c/sup\u003e/g) and pore volume (V\u003csub\u003ep\u003c/sub\u003e = 0.55 cm\u003csup\u003e3\u003c/sup\u003e/g) compared with those values for PAF-30 (S\u003csub\u003eBET\u003c/sub\u003e = 483 m\u003csup\u003e2\u003c/sup\u003e/g; V\u003csub\u003ep\u003c/sub\u003e = 0.28 cm\u003csup\u003e3\u003c/sup\u003e/g), that can be caused by more intensive framework interpenetration in case of PAF-30 material [33] (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Furthermore, PAF-30-NH\u003csub\u003e2\u003c/sub\u003e has higher micropore ratio (S\u003csub\u003et\u0026minus;plot\u003c/sub\u003e/ S\u003csub\u003eBET\u003c/sub\u003e = 64%) than PAF-30 (S\u003csub\u003et\u0026minus;plot\u003c/sub\u003e/ S\u003csub\u003eBET\u003c/sub\u003e= 49%). According to elemental analysis, the nitrogen content of PAF-30-NH\u003csub\u003e2\u003c/sub\u003e was 5.39 wt%.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLow-temperature N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption and elemental analysis for the synthesized PAFs.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterial\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS\u003csub\u003eBET\u003c/sub\u003e, m\u003csup\u003e2\u003c/sup\u003e/g\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eS\u003csub\u003et\u0026minus;plot\u003c/sub\u003e, m\u003csup\u003e2\u003c/sup\u003e/g\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eS\u003csub\u003et\u0026minus;plot\u003c/sub\u003e/ S\u003csub\u003eBET,\u003c/sub\u003e %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eV\u003csub\u003etot\u003c/sub\u003e, cm\u003csup\u003e3\u003c/sup\u003e/g\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eω\u003csub\u003eN\u003c/sub\u003e, wt%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ePAF-30\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e483\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e239\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ePAF-30-NH\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e793\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e506\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.39\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eUsing PAF-30 и PAF-30-NH\u003csub\u003e2\u003c/sub\u003e, we synthesized copper catalysts with nominal metal contents of 2, 5, 10 and 30 wt% by impregnating the support material with a solution of copper (II) acetate in ethanol followed by metal reduction in a hydrogen flow at 300 \u003csup\u003eo\u003c/sup\u003eC (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The composition of the catalysts was studied by means of XPS, TEM and ICP-AES.\u003c/p\u003e \u003cp\u003eTEM images of the catalysts are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. All catalysts contain well-distinct Cu nanoparticles of spherical shape and their size distribution is close to an asymmetric normal distribution. At the same time, large (up to 0.5 \u0026micro;m) particles or agglomerates of copper particles are present on the surface of catalysts with high metal content (more than 10 wt%). Their formation may be due to sintering of metal particles during reduction by cause of low H\u0026uuml;ttig temperature for copper (134 \u003csup\u003eo\u003c/sup\u003eC) [22]. Also, with increasing metal content in the catalysts the distribution graph becomes wider, the proportion of large (more than 13 nm) nanoparticles and the average size of copper particles increase. Thus, the maximum of metal particle size distribution for 2Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e catalyst is 7 nm, for 5Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e \u0026ndash; 10 nm, for 10Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e \u0026ndash; 13 nm, for 30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e \u0026ndash; 16 nm and for 30Cu-PAF-30\u0026ndash;19 nm. Hence, the average particle size increased with cooper loading [34, 35].\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eXPS and ICP-AES data for catalysts\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMethod\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eICP-AES\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c5\" namest=\"c3\"\u003e \u003cp\u003eXPS, Cu\u0026nbsp;LMM\u0026nbsp;AES\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003eXPS, N\u0026nbsp;1s\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCu, wt%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eBinding energy, eV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{{\\text{C}\\text{u}}^{+}}{{\\text{C}\\text{u}}^{+}+{\\text{C}\\text{u}}^{0}},\\:\\%\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003eBinding energy, eV / Content, %\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCu\u003csup\u003e0\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCu\u003csup\u003e+\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eRNH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eRNH\u003csub\u003e2\u003c/sub\u003e\u0026rarr;Cu\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e30Cu-PAF-30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e570.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e573.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e28.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e570.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e573.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e399.0 /\u003c/p\u003e \u003cp\u003e 50%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e400.3 / \u003c/p\u003e \u003cp\u003e50%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e570.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e573.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e399.3 / \u003c/p\u003e \u003cp\u003e57%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e399.9 / \u003c/p\u003e \u003cp\u003e43%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e570.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e573.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e399.3 / \u003c/p\u003e \u003cp\u003e47%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e399.9 / \u003c/p\u003e \u003cp\u003e53%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e570.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e573.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e399.5 / \u003c/p\u003e \u003cp\u003e71%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e400.3 / \u003c/p\u003e \u003cp\u003e29%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe copper content in the catalysts and its chemical state on the surface of the freshly reduced catalysts were determined by ICP-AES and XPS methods, respectively (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The actual copper content of obtained Cu catalysts was close to nominal values. The Cu 2p XPS spectra of 30Cu-PAF-30, 30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e, 10Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e catalysts (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea) lack a peak at 940\u0026ndash;945 eV that is characteristic of the Cu\u003csup\u003e2+\u003c/sup\u003e satellite, indicating successful reduction of the catalysts [36, 37]. However, weak satellite peak at 941\u0026ndash;950 eV was found in spectra of 5Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e and 2Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e catalysts, which may be derived from oxidation of copper species when the catalysts with low content of Cu are exposed to the atmosphere [13]. It should be mentioned that some Cu\u003csup\u003e2+\u003c/sup\u003e can be converted to Cu\u003csup\u003e0\u003c/sup\u003e and Cu\u003csup\u003e+\u003c/sup\u003e during hydrogenation reaction [38]. Also, very weak satellite peaks between 942.0 and 948.0 eV in spectra of the abovementioned catalysts can be attributed to Cu\u003csup\u003e+\u003c/sup\u003e [39]. Due to the similar binding energy of Cu\u003csup\u003e+\u003c/sup\u003e and Cu\u003csup\u003e0\u003c/sup\u003e species, Auger electron spectroscopy (AES) of Cu LMM are performed to determine the different copper species (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). The XPS analysis revealed comparable Cu⁺/(Cu⁰ + Cu⁺) ratio for all catalysts (18\u0026ndash;31%).\u003c/p\u003e \u003cp\u003eAdditional information of the structure of the catalysts and coordination of Cu particles by amino groups is provided by N 1s XPS spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). There are two peaks with maxima at 399.0-399.5 eV and 399.9-400.3 eV in the spectra of all obtained Cu-catalysts based on amino-modified PAF. The first one is characteristic peak corresponding to nitrogen atoms in amino groups bonded to phenyl rings [40] and the second peak at higher binding energy corresponds to positively charged species (\u0026ndash;NH\u003csup\u003e+\u003c/sup\u003e\u0026thinsp;\u003csub\u003e2\u003c/sub\u003e), attributed to the donation of unshared electron pairs from the \u0026ndash;NH\u003csub\u003e2\u003c/sub\u003e group to the metal ions [41].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Catalytic performance\u003c/h2\u003e \u003cp\u003eThe synthesized catalysts were tested in the hydrogenation of ethylene carbonate. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e shows the possible reactions occurring during the hydrogenation of EC [42, 43]. The most favourable reaction is hydrogenation of ethylene carbonate to methanol and ethylene glycol (reaction 2). At the same time, incomplete hydrogenation of EC with formation of carbon monoxide (reaction 1) is also possible. Undesirable reactions include hydrolysis of ethylene carbonate in the presence of trace amounts of water in the solvent (reaction 5), and thermal decomposition of EC (reaction 4), which generally occurs at temperatures above 200\u0026ndash;250℃ [44]. Decarboxylation of EC to ethanol and carbon dioxide (reaction 3) may also proceed, which is also an interesting route for CO\u003csub\u003e2\u003c/sub\u003e-derived carbonates conversion. To prevent possible hydrolysis of EC (reaction 5), dried solvent was used in the reaction.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFirst, the effect of temperature (150\u0026ndash;250 ℃), hydrogen pressure (30\u0026ndash;70 atm) and EC/Cu molar ratio (10\u0026ndash;400) on the composition of hydrogenation products was investigated. The conversion of ethylene carbonate increases with increasing temperature (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003ea), with ethylene glycol and ethanol being the main products. In addition, traces of ethylene oxide were detected in reaction products at temperatures of 200 ℃ and 250 ℃. Also, ethanol yield increases sharply at 250 ℃ due to possible hydrogenation of ethylene glycol [45, 46]. However, no formation of any reaction products was observed in the blank experiment (without catalyst), and the conversion of EC did not exceed 2% in the presence of PAF-30 or PAF-30-NH\u003csub\u003e2\u003c/sub\u003e. It is worth noting the sharp increase in conversion at 200 ℃, indicating that high temperature is favourable for the activation of a stable EC molecule [47]. The obtained data agree with the results of thermodynamic calculations, according to which higher temperature is not beneficial for the target reaction (2), and more advantageous for reactions (1) and (3) [47]. Thus, we consider the temperature of 200℃ to be the optimal temperature for the reaction, since at this temperature a high conversion of EC is achieved, and the probability of its decomposition is minimal.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003eb shows the composition of hydrogenation products of ethylene carbonate at different hydrogen pressures. The dependence of EC conversion, as well as yields of ethylene glycol and ethanol, has a volcano-like shape: it increases in the range of 30\u0026ndash;50 atm, and decreases in the range of 50\u0026ndash;70 atm. Such decrease in yield of hydrogenation products may be associated with competitive adsorption of hydrogen on the catalyst surface, hampering the adsorption of substrate. Thus, maximum conversion (86%) was achieved at 50 atm with EG yield of 69%, EtOH yield of 14% and EO yield of 3%.\u003c/p\u003e \u003cp\u003eThe results of EC hydrogenation at different substrate:metal ratios are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e9\u003c/span\u003e. The conversion was practically unchanged when the EC/Cu ratio was increased from 10:1 to 200:1 mol/mol (and EC concentration \u0026ndash; from 0.15 M to 1 M). However, at the EC/Cu ratio of 400:1 mol/mol and EC concentration of 2 M the conversion dropped sharply, which may be due to the limited catalytic capacity of the catalyst. It is noteworthy, that small amount of methanol (3%) was obtained at the EC/Cu ratio of 10:1 mol/mol. Based on the obtained results, we assume that reactions (1) and (3) are competitive, and the ratio of their rates depends more on the reaction temperature and the structure of the catalyst surface than on the substrate concentration or hydrogen pressure. The main reaction (2) is suppressed under selected reaction conditions and proceeds only at low substrate concentration.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eEthanol formation is possible both during decarboxylation of EC and hydrogenation of EG [43, 47]. Therefore, we tested the feasibility of the hydrogenation of EG over a 10Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e catalyst. However, the reaction products did not contain ethanol, which suggests its formation mainly during the reaction (3).\u003c/p\u003e \u003cp\u003eThe influence of Cu content in catalysts on the composition of reaction products was studied (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e10\u003c/span\u003ea). The comparison was carried out at a fixed EC/Cu value of 10, and the hydrogen pressure and reaction time were decided to be reduced to 40 atm and 4 h, respectively. All catalysts demonstrated high activity in hydrogenation of EC: while EG remained the main reaction product, the yields of ethanol and methanol over the catalysts differed. Thus, the methanol yield decreases with decreasing copper content in the catalyst: it was 8% on the 30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e catalyst, 3% on the 10Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e catalyst, and in the case of 5Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e and 2Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e its formation was not observed. The ethanol yield decreases in the series of catalysts 2Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e, 5Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e and 10Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e from 22 to 8%, but increases sharply to 28% in the case of catalyst 30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003eWe hypothesize that obtained results can be interpreted as follows. It is known that during hydrogenation, the EC molecule is coordinated by carbonyl oxygen on Cu\u003csup\u003e+\u003c/sup\u003e species perpendicular to the catalyst surface, while dissociative adsorption of H\u003csub\u003e2\u003c/sub\u003e occurs on the Cu\u003csup\u003e0\u003c/sup\u003e surface [48]. However, in the case of the synthesized catalysts, most of the particles are located inside the pores of the carrier, due to which this type of adsorption of the EC molecule appears to be sterically hindered. With increasing Cu content in the catalyst, the amount of nanoparticles not encapsulated in the pores of the carrier also increased, and the formation of methanol apparently occurs on them. At the same time, the ethanol yield, correlates with the size of Cu particles in the catalyst (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e10\u003c/span\u003eb), or probably with the total copper surface available for EC adsorption. Thus, in the case of 2Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e, 5Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e and 10Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e catalysts, most of the nanoparticles are located inside the pores of the carrier and the ethanol yield decreases linearly with increasing their size. The significantly higher ethanol yield on catalyst 30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e, despite the larger average particle size, may be due to the presence of small copper nanoparticles (up to 10 nm) readily available for EC, even though their relatively small fraction in the total nanoparticle distribution.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo test the described hypotheses, the influence of the reduction conditions of the 30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e catalyst on its activity was studied (Figure S2). The highest conversion of EC (94%) as well as the highest yields of ethanol (28%) and methanol (8%) were obtained when the catalyst was reduced at 300℃ for 2 hours. Increasing both the temperature and time of catalyst reduction leads to a decrease in its activity, which may be due to the enlargement of copper nanoparticles because of the low value of the H\u0026uuml;ttig temperature for copper (134\u003csup\u003eo\u003c/sup\u003eC). At the lower reduction temperature (250℃), the EC conversion was less (65%). However, increasing the recovery time of the catalyst to 4 hours resulted in an increase in its activity, which can be explained by a more complete reduction of the metal under these conditions.\u003c/p\u003e\u003cp\u003eFinally, the reusability of 30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e was tested using the 30Cu-PAF-30 catalyst based on unmodified PAF-30 carrier as a comparison (Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e11\u003c/span\u003e). Both catalysts showed high activity. However, EC conversion on the 30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e catalyst was higher (94% vs. 52% in Cycle 1), and methanol was present in the reaction products. Nevertheless, despite the lower activity, 30Cu-PAF-30 was much more stable: the EC conversion and product yields were virtually unchanged by reaction cycle 5. At the same time, the 30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e catalyst gradually loses its activity and at cycle 5, the yields of EG, EtOH and MeOH were 49, 7 and 1%, respectively. This decrease in activity may be due to the washout of metal from the carrier surface, especially those not anchored in the pores of the nanoparticles.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eCopper catalysts based on porous aromatic frameworks PAF-30 and PAF-30-NH\u003csub\u003e2\u003c/sub\u003e with different metal content (2, 5, 10, 30 wt%) were synthesized. The average size of Cu NPs increased from 7 to 16 nm with increasing metal loading from 2\u0026ndash;30%, while their surface composition was similar according to the XPS results (Cu\u003csup\u003e+\u003c/sup\u003e/(Cu\u003csup\u003e+\u003c/sup\u003e + Cu\u003csup\u003e0\u003c/sup\u003e)\u0026thinsp;=\u0026thinsp;18\u0026ndash;31%). The obtained catalysts exhibited high activity in the hydrogenation of ethylene carbonate, and the main products were ethylene glycol and ethanol. It is assumed that the low yield of methanol is due to the impossibility of perpendicular adsorption of ethylene carbonate molecule on the surface of copper nanoparticles due to steric hindrance caused by the carrier. The highest conversion of ethylene carbonate was obtained on catalyst 30Cu-PAF-30-NH\u003csub\u003e2\u003c/sub\u003e at 40 atm H\u003csub\u003e2\u003c/sub\u003e, 200℃ and EC/Cu\u0026thinsp;=\u0026thinsp;10:1 mol/mol: under these conditions for 4 hours the yields of ethylene glycol, ethanol and methanol were 58, 28 and 8%, respectively.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eEC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eEthylene carbonate\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eEG\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eEthylene glycol\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eEO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eEthylene oxide\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eNPs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eNanoparticles\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eMOFs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eMetal-organic frameworks\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eCOFs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eCovalent organic frameworks\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003ePAFs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003ePorous aromatic frameworks\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e2-HEF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003e2-Hydroxyethyl formate\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eBET\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eBrunauer\u0026ndash;Emmett\u0026ndash;Teller\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eNLDFT\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eNon-local density functional theory\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eFTIR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eFourier transform infrared\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eTEM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eTransmission electron microscopy\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eICP-AES\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eInductively coupled plasma atomic emission spectrometry\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eXPS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eX-ray photoelectron spectroscopy\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eAES\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 255px;\"\u003e\n \u003cp\u003eAuger electron spectroscopy\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics and Consent to Participate\u0026nbsp;\u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for Publication\u0026nbsp;\u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e Elizaveta Oskina: investigation, writing - original draft. Leonid Kulikov: writing - review and editing, visualization. Daria Makeeva: analysis, supervision. Anton Maximov: formal analysis, methodology, supervision.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003eThere was no funding for this research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u0026nbsp;\u003c/strong\u003eNo data was used for the research described in the article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003eThe study was conducted under the state assignment of Lomonosov Moscow State University, project № 121031300092-6.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eFayisa BA, Yang Y, Zhen Z, et al (2022) Engineered chemical utilization of CO\u003csub\u003e2\u003c/sub\u003e to methanol via direct and indirect hydrogenation pathways: a review. 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Chinese Journal of Catalysis. https://doi.org/10.1016/S1872-2067(18)63032-3\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"catalysis-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Catalysis Letters](https://link.springer.com/journal/10562)","snPcode":"10562","submissionUrl":"https://submission.springernature.com/new-submission/10562/3","title":"Catalysis Letters","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"hydrogenation, ethylene carbonate, ethylene glycol, porous aromatic frameworks, copper nanoparticles","lastPublishedDoi":"10.21203/rs.3.rs-6803584/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6803584/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eHydrogenation of organic carbonates on heterogeneous catalysts is one of the ways of indirect conversion of carbon dioxide, which is essential for addressing the urgent problem of decarbonization. Cu-based catalysts are the most widely used in hydrogenation, but their properties strongly depend on the characteristics of the heterogeneous carriers used. Although SiO\u003csub\u003e2\u003c/sub\u003e-based catalysts are the most extensively studied, it is of interest to develop catalysts based on new types of carriers such as MOFs, COFs and PAFs. In the current work, a series of copper-based catalysts with different metal contents (2, 5, 10, 30 wt%) based on porous aromatic framework PAF-30 and its amino-functionalized derivative PAF-30-NH\u003csub\u003e2\u003c/sub\u003e were synthesized and investigated in the hydrogenation of ethylene carbonate. The influence of reaction temperature, hydrogen pressure, concentration of ethylene carbonate in its solution in THF, copper content in the catalysts and reduction conditions on the activity of the catalysts was systematically studied.\u003c/p\u003e","manuscriptTitle":"Copper catalysts supported on porous aromatic frameworks for the hydrogenation of ethylene carbonate","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-17 11:04:19","doi":"10.21203/rs.3.rs-6803584/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-08T06:11:35+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-07T05:26:09+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-02T09:16:32+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-27T06:58:08+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"115924429276877103979440473807607833087","date":"2025-06-16T03:34:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"65316276937415232480720366553494972810","date":"2025-06-16T00:03:34+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"103704238207139935312410237015588465676","date":"2025-06-13T11:31:47+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-13T09:20:35+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-05T14:17:52+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-05T14:14:14+00:00","index":"","fulltext":""},{"type":"submitted","content":"Catalysis Letters","date":"2025-06-02T15:17:14+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"catalysis-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Catalysis Letters](https://link.springer.com/journal/10562)","snPcode":"10562","submissionUrl":"https://submission.springernature.com/new-submission/10562/3","title":"Catalysis Letters","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"ebedf2b4-0e45-4d96-a819-9c0eec3e4eb3","owner":[],"postedDate":"June 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-09-20T13:08:23+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-17 11:04:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6803584","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6803584","identity":"rs-6803584","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}