Comparison of ZIF-14 (qtz) and a One-pot Synthesized Superparamagnetic Iron Oxide/ZIF-14 (qtz) Composite for the Adsorption of Diclofenac

Comparison of ZIF-14 (qtz) and a One-pot Synthesized Superparamagnetic Iron Oxide/ZIF-14 (qtz) Composite for the Adsorption of Diclofenac | 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 Comparison of ZIF-14 (qtz) and a One-pot Synthesized Superparamagnetic Iron Oxide/ZIF-14 (qtz) Composite for the Adsorption of Diclofenac Erick Ramírez, Daniela Carmona-Pérez, J. F. Marco, Karla R. Sanchez-Lievanos, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3952171/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The global presence of pharmaceutical pollutants in water sources represents a burgeoning public health concern. Recent studies underscore the urgency of addressing this class of emerging contaminants. In this context, our work focuses on synthesizing a composite material, Fe x O y /ZIF-14 ( qtz ), through a streamlined one-pot reaction process, as an adsorbent for diclofenac, an emerging environmental contaminant frequently found in freshwater environments and linked to potential toxicity towards several organisms such as fish and mussels. A thorough characterization was performed to elucidate the structural composition of the composite. The material presents magnetic properties attributed to its superparamagnetic behavior, which facilitates the recovery efficiency of the composite post-diclofenac adsorption. Our study further involves a comparative analysis between the Fe x O y /ZIF-14 ( qtz ) and a non-magnetic counterpart, comprised solely of 2-ethylimidazolate zinc polymer. This comparison aims to discern the relative advantages and disadvantages of incorporating magnetic iron oxide nanoparticles in the contaminant removal process facilitated by a coordination polymer. Our findings reveal that even a minimal incorporation of iron oxide nanoparticles substantially enhanced the composite’s overall performance in pollutant adsorption. pharmaceuticals magnetic material coordination polymer water pollution Zeolitic Imidazolate Framework Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 1. Introduction According to the World Health Organization (WHO) the most important chemical hazards in drinking water derive from arsenic, fluoride, and nitrate [ 1 ]. Nevertheless, contaminants of emerging concern such as pharmaceuticals, pesticides, fluoroalkyl substances, and microplastics are getting more public attention [ 1 ]. After the recent sanitary emergency, there has been a notable increase in the accumulation of pharmaceutical contaminants in wastewater, as highlighted in recent studies [ 2 ]. Contaminants of emerging concern (CECs) are substances detected in the environment at low concentrations, yet there is not enough information regarding their potential harmful effects [ 3 ]. Diclofenac, a widely-used anti-inflammatory medication, has become a prominent example of these new contaminants, frequently detected in wastewater, surface water, and marine environments. Recent evidence has established the toxicity of diclofenac, as demonstrated in the well-documented vulture population decline case [ 4 , 5 ]. Metal oxides like TiO 2 and ZnO have been extensively used as photocatalysts for the degradation of contaminants due to their semiconductor properties. Nevertheless, their activity is affected by the low affinity of the metal oxide surface towards organic molecules, and the recombination of photogenerated electron/hole pairs (h + /e − ) [ 3 , 6 ]. Highly porous materials like Zeolitic Imidazolate Frameworks (ZIFs) are considered alternatives to contaminant removal from water by either photocatalytic degradation or sorption [ 7 – 11 ]. The literature reports a variety of ZIF composites, particularly those incorporating the widely studied ZIF-8 (a coordination polymer formed by 2-methylimidazole and zinc), mixed with materials such as metal oxides, fibers, metal nanoparticles, graphene, and enzymes [ 11 – 14 ]. ZIF-8 and its cobalt analogue, ZIF-67, are noted for their SOD-type topology and high specific area [ 15 , 16 ]. Despite over 100 zeolite-like topologies identified for ZIFs, research predominantly focuses on the above mentioned structures for sorption or catalytic applications[ 9 ]. However, separating ZIFs after-contaminant treatment in water poses challenges due to their small particle size, often necessitating centrifugation. Magnetic ZIF-8 composites, facilitating easier separation, are produced through multi-step synthesis processes, where the coordination polymer is synthetized in presence of the magnetic particles [ 12 , 17 ]. Alternatively, heterojunctions between two semiconductors with different redox energy levels offer a different synthesis approach [ 3 ]. Simplifying and accelerating the synthesis of ZIFs and their composites would greatly benefit their widespread application. In this work, we prepared a composite material combining ZIF-14 ( qtz ) and magnetic iron oxides (a mixture of maghemite and magnetite) using a straightforward one-pot methodology. This composite was developed for testing as a sorbent and photocatalytic material for removal of diclofenac. The composite exhibits superparamagnetic behavior, a property that does not compromise the main matrix characteristics. Importantly, only a minimal amount of iron oxide (5%) is required to enable magnetic-assisted separation. We compared this composite with ZIF-14 ( qtz ) alone to demonstrate the benefits and drawbacks of incorporating magnetic particles into the material. 2. Experimental 2.1 Chemicals Ferrous ammonium sulfate hexahydrate (98%) was purchased from Meyer reagents, 2-ethylimidazole (98%), zinc sulfate heptahydrate (99%), zinc acetate dihydrate (99%), and diclofenac sodium salt (98%) were purchased from Sigma Aldrich. All the reagents were used without further purification. Solutions were prepared with deionized water with a resistivity of 18 MΩ cm − 1 . 2.2 Preparation of ZIF-14 Precursors 2-ethylimidazole (1.202 g, 12.5 mmol) and zinc acetate dihydrate (0.110 mg, 0.5 mmol) were dissolved in separated beakers in 25 and 10 ml of deionized water, respectively. Then, the ligand solution was added to the zinc salt solution without stirring. After a few seconds, a white precipitated started to form. The formation of the solid is slow, which can be followed by the cloudiness of the reaction mixture that disappears, after aging for one week. The white precipitated was filtered under vacuum and washed exhaustively with deionized water to remove the remanent acetate and ligand excess. The product was dried at 60°C in a convection oven for 2 days to give a white powder 0.099 g, 77% of yield according to the zinc equivalents. 2.3 One pot preparation of composite Fe x O y /ZIF-14 (qtz) The ligand 2-ethylimidazole (1.202 g 12.5 mmol) was dissolved in 100 ml of deionized water in a round flask and N 2 was bubbled to the solution during 30 min. Separately, 25 ml of deionized water solution with ferrous ammonium sulfate hexahydrate (0.050 g 0.127 mmol) and zinc sulfate heptahydrate (0.1438 g 0.5 mmol) was prepared and bubbled also with N 2 during 15 min. Then the metal solution was added to the ligand solution under stirring and nitrogen atmosphere using a syringe. Immediately, a light green dispersion was formed. Nitrogen bubbling was maintained for 30 minutes. Stirring continued for two hours, after that the solution turned grey. Dispersion was let for one night at room temperature and no coloration changes were observed. After decantation, the solid was filtered under vacuum and washed with deionized water. Finally, the solid was dried at 60°C in a convection oven for one day yielding a light brown solid. Isolated product 0.130 g. 2.4 Characterization The materials were characterized by several analytical techniques: IR, X-ray powder diffraction, Mössbauer spectroscopy, XPS, magnetization vs field curves, SEM, EDS, Diffuse Reflectance, and nitrogen adsorption. IR measurements were taken in a Thermo-scientific FTIR Spectrophotometer Model Nicolet 6700 provided with a Smart iTR ATR accessory. The powder diffraction patterns were obtained in a Malvern Panalytical model Empyrean diffractometer with Cu Kα beam source. Rietveld refinement was performed with BGMN software [ 18 ] (user interface Profex 5.2.2 [ 19 ]) to calculate the percent composition of the composite using as reference ZIF-14 [ 20 ], magnetite [ 21 ], and maghemite [ 22 ] files obtained from monocrystal X-ray diffraction data. Refinement was carried out with 2 phases i) ZIF-14 ( qtz ) and ii) iron oxide, separately. The BET specific area was measured at 77 K with a Micromeritics ASAP 2020 instrument; samples were degassed at 150°C. 57 Fe Mössbauer data were recorded at room temperature using a 57 Co(Rh) source and a conventional constant acceleration spectrometer. The velocity scale was calibrated using a 6 µm thick iron foil. The chemical isomer shifts were referred to the centroid of the room temperature Mössbauer spectrum of α-iron. The spectrum was computer-fitted. Magnetization curves were taken at a Physical Property Measurement System DynaCool-9 in the range of 1.8 to 350 K and in the field range from − 40 to 40 kOe. X-ray Photoelectron Spectroscopy measurements were performed on three separate ZIF batches to ensure data reproducibility. Sample preparation was performed under ambient atmosphere. Powders were dispersed in ethylene glycol to obtain a concentrated dispersion. The dispersion was drop-casted onto cleaned Si wafers and subsequently dried in a conventional oven at 50°C for 30 min. Afterwards, the Si wafers were electrically grounded to the XPS sample bar by carbon tape. The XPS measurements were recorded with a Kratos Axis Ultra DLD system equipped with monochromatic Al Kα (hν = 1486.6 eV) X-ray source. During the measurements, pressure in the main chamber was kept below 1×10 − 7 bar. Charge compensation was carried out via a neutralizer running at a current of 7 µA, a charge balance of 5 V, and a filament bias of 1.3 V. The X-ray gun was set to 10 mA emission. Binding energies were referenced to C 1s peak arising from adventitious carbon with an emission energy of 284.8 eV. The C 1s, O 1s, N 1s, Fe 2p and Zn 2p core levels were recorded with an emission current of 10 mA, an accelerating voltage of 15 kV, and a pass energy of 80 eV. We collected three scans for iron, zinc, oxygen and nitrogen, and two scans for carbon. XPS analysis was performed with CasaXPS (Version 2.3.22PR1.0). The U Touggard function was used for background subtraction. The XPS signals were fitted with the CasaXPS Component Fitting tool. SEM micrographs were obtained using a Zeiss Auriga Scanning Electron Microscope with a beam energy of 25 kV. The composite samples were drop-casted onto silicon wafers from hexane dispersions. EDS elemental information was also obtained using a Zeiss Auriga Scanning Electron Microscope coupled to an EDS analyzer. Measurements were carried out using 25 kV electron beam energy. Semi-quantitative data analyses were performed using the EDAX Apex software. 2.5 Adsorption measurements The kinetic experiments were performed at 25°C placing respectively, 6.6 mg of ZIF-14 and composite in an amber vial, with 20 mL of diclofenac solution 20 mg L − 1 . Aliquots were taken from different vials at different times. In the diclofenac/ZIF-14 system, vials were firstly shaken in an orbital shaker at 200 rpm for 5 min and then, let statically until aliquots were taken. For the diclofenac/composite system, shaking was performed all time. The adsorption capacity was determined by the known equation: q = (( C i - C f )V)/ m , where q is the adsorbed quantity, C i is the initial and C f the final concentration, V is the volume of diclofenac solution, and m is the adsorbent mass. The concentration changes in the solutions during the adsorption experiments were measured by RP-HPLC using an Agilent 1200 Infinity series chromatograph equipped with a Multiple Wave Detector 1260 Infinity II. The chromatographic column Zorbax C18 (4.6 × 100 mm, 3.5 µm) was used at 30°C under isocratic conditions at a flow rate of 1 mL min − 1 , the eluent was a mixture of CH 3 CN and H 2 O (55:45) with 0.2% of formic acid. The adsorption experiments were carried out at 25°C in the concentration range within 1 mg L − 1 and 40 mg L − 1 . The amount of adsorbent was 6.6 mg set in 20 mL of diclofenac solution in an amber vial. The systems were shaken for 5 min in the case of ZIF-14 and for two hours in the experiments with the composite Fe x O y /ZIF-14. The diclofenac concentration changes were monitored by RP-HPLC under conditions described above. 3. Results and discussion 3.1 Compositional and topological identification 3.1.1 Vibrational spectroscopy Comparison of the ATR-FTIR spectra of ZIF-14 ( qtz ) and its iron composite is shown in Fig. 1 . They show the typical bands corresponding to the imidazole: C-H stretching at 3008, 2974, 2938 cm − 1 , C = C stretching at 1601 cm − 1 , C = N stretching at 1449, 1321, 1308 cm − 1 , C-H out of the plane bending at 1049, 757, 739 cm − 1 , and for the ring deformation out of the plane bending at 660 cm − 1 [ 23 ]. The spectra of ZIF-14 ( qtz ) and Fe x O y /ZIF-14 ( qtz ) are almost identical, whereas the main difference between the synthesis products and the free ligand is the absence of the broad band of N-H stretching in the high energy region of the spectra and N-H deformation mode at 1570 cm − 1 that corroborate formation of the imidazolate anion. As shown in Fig. 1 , the iron oxide bands have such low intensity that they do not appear in the spectrum, which is congruent with the low portion of the iron oxide in the composite. 3.1.2 Topology and crystallinity analyzed by Powder X-Ray Diffraction The diffractogram of ZIF-14 ( qtz ) was simulated, using the Mercury software with the cif file of the monocrystal structure taken from the CCDC database of a previous reported work [ 20 ]. The diffraction patterns of ZIF-14 ( qtz ) and Fe x O y /ZIF-14 ( qtz ) show the presence of characteristic peaks at 2θ from 10 to 35 degrees corresponding to the planes (1 \(\stackrel{-}{1}\) 0), (1 \(\stackrel{-}{1}\stackrel{-}{1}\) ), (1 \(\stackrel{-}{1}\stackrel{-}{2}\) ), (2 \(\stackrel{-}{1}\) 0), (2 \(\stackrel{-}{1}\stackrel{-}{1}\) ), (2 \(\stackrel{-}{2}\) 0), (2 \(\stackrel{-}{2}\stackrel{-}{1}\) ), (2 \(\stackrel{-}{2}\stackrel{-}{2}\) ), (2 \(\stackrel{-}{1}\stackrel{-}{3}\) ), ( \(\stackrel{-}{2}\) 23), and (3 \(\stackrel{-}{1}\stackrel{-}{1}\) ) of ZIF-14 ( qtz ). Comparison of the diffraction patterns obtained with the simulated ZIF-14 ( qtz ) agree with the presence of the qtz topology. Crystallinity of pure ZIF-14 ( qtz ) is relatively higher than that of the composite, but they show almost identical diffractograms (Fig. 2 b and c ). The principal difference is a very low intensity peak, marked with astherisk in the inset of Fig. 2 c, at the diffraction angle 2θ = 35.7 ° that corresponds, as expected, to the magnetite or maghemite (311) plane in the composite. Concerning the iron oxide present in the composite, quantification of the magnetite/maghemite relationship was not conducted because other techniques surpass the XRD method for this purpose [ 24 ]. Therefore, we consider both phases of iron oxide in our approach to study the structure of the materials (Table 1 ). The Fe x O y /ZIF-14 diffraction pattern fitting was approximately 95% ZIF-14 ( qtz ) and 5% of magnetite and maghemite respectively (Fig. 3 ). As shown in Table 1 , the cell parameters were not significantly affected by the selection of one of these iron phases for the refinement and the low portion agrees with the ATR-FTIR spectrum information. In addition, crystallite mean size below 50 nm agrees with the existence of small domains that exhibit superparamagnetic behavior. The refinement of ZIF-14 ( qtz ) gives a bigger crystallite size (around 93 nm) and a wider distribution (k1 parameter in Table 1 ) than the ZIF-14 ( qtz ) phase in the composite Fe x O y /ZIF-14 ( qtz ). Table 1 Selected refinement parameters obtained by the Rietveld method of ZIF-14 ( qtz ) and the composite, considering magnetite or maghemite for the refinement. k1 is a normalized parameter of crystallite size broadening (smaller k1 values correspond to a wide distribution [ 25 ]), R wp is the weighted residual square sum, R exp is the possible minimum value for R wp , and GoF is the goodness-of-fit. Parameters ZIF-14 Composite Fe x O y /ZIF-14 ( qtz ) Composite Fe x O y /ZIF-14 ( qtz ) ZIF-14 ( qtz ) Magnetite Fe 3 O 4 ZIF-14 ( qtz ) Maghemite Fe 2 O 3 Space group P6 4 P6 4 F4 1 /d \(\stackrel{-}{3}\) 2 /m P6 4 P4 1 32 Cell parameters a (nm) 0.8483(2) 0.8497(4) 0.8395(4) 0.8498(4) 0.8397(4) c (nm) 1.2852(3) 1.2858(6) ‒ 1.2859(6) ‒ k1 0 1 1 1 1 Crystallite size (nm) 93(3) 48.3(9) 24(1) 48.3(9) 23(1) 93(3) 48.3(9) 24(1) 48.3(9) 23(1) 126(11) 77(8) 24(1) 78(8) 23(1) Composition (%) 95.2(2) 4.8(2) 94.3(3) 5.7(3) R wp 9.03 7.56 7.50 R exp 4.53 2.87 2.87 GoF 1.99 2.63 2.61 3.2 Iron oxide phase characterization and magnetic properties of the composite 3.2.1 Magnetite/maghemite identification by Mössbauer spectroscopy Results of ATR-FTIR spectroscopy and PXRD show that the main component of the composite Fe x O y /ZIF-14 ( qtz ) is the coordination polymer, and for the identity clarification of the iron oxide phase, Mössbauer and magnetization experiments were performed. The room temperature Mössbauer spectrum recorded from Fe x O y /ZIF-14 ( qtz ) is depicted in Fig. 4 . The spectrum shows a main broad, asymmetric magnetic component and a smaller quadrupole contribution. The spectrum is characteristic of a system experiencing superparamagnetic relaxation associated to a distribution of iron oxide small particle sizes. The spectrum was fitted to a model considering three different magnetic contributions and a quadrupole doublet. The hyperfine parameters obtained from the fit of the spectrum are collected in Table 2 . Table 2 Hyperfine parameters obtained from the fit of the spectrum recorded at room temperature from sample Fe x O y /ZIF-14 ( qtz ). Site/species δ (mms − 1 ) Δ or 2ε (mms − 1 ) H (T) Area (%) Doublet 0.34 0.63 -- 8 Sextet 1 0.32 -0.01 47.3 39 Sextet 2 0.45 0.04 41.5 36 Sextet 3 0.66 0.39 26.2 17 Δ: isomer shift; Δ: quadrupole splitting (doublet); 2ε: quadrupole shift (sextets); H: hyperfine magnetic field. The narrower sextet (spectrum in magenta) has parameters which can be associated with maghemite (γ-Fe 2 O 3 ) [ 26 ]. While the isomer and quadrupole shifts of this sextet match those characteristic of this iron oxide, the hyperfine magnetic field is significantly smaller: 47.3 T vs. the “canonical” 49.9 T value [ 26 ]. It has been reported that the phenomenon of superparamagnetism is often reflected in a smaller value of the hyperfine magnetic field due to the occurrence of collective magnetic excitations [ 27 , 28 ]. This implies that, at room temperature, the size of the maghemite particles, although large enough as to show a well-developed magnetic sextet, is not sufficient to overcome completely the superparamagnetic relaxation, hence the smaller hyperfine magnetic field. The second most intense magnetic component (blue) has an isomer shift (0.45 mms − 1 ) which is quite large as to be due solely to the presence of an Fe 3+ oxide [ 26 , 29 ]. It is well-known that the room temperature Mössbauer spectrum of magnetite, Fe 3 O 4 , is composed of two different magnetic sextets, one accounting for the Fe 3+ sitting in the tetrahedral sites of the spinel-related structure and a second one arising from the Fe 2+ /Fe 3+ located in the corresponding octahedral sites in that structure [ 26 – 29 ]. As a consequence of electron hopping, the chemical isomer shift of this second sextet (0.72 mms − 1 ) is intermediate between that expected for an octahedral high spin Fe 3+ ion (∼0.35 mms − 1 ) and that characteristic of an octahedral high spin Fe 2+ ion (∼1.1 mms − 1 ) and then it is often referred as the Fe 2.5+ octahedral component of the Mössbauer spectrum of magnetite. Therefore, the present results suggest that the broad blue sextet might arise from a fraction of small particle magnetite, as the increase in the value of the isomer shift respect to that expected for Fe 3+ would suggest the participation of Fe 2+ ions through an electron hopping mechanism. It has been also reported that superparamagnetic particles can not only show smaller hyperfine magnetic field values but also smaller isomer shifts [ 28 , 30 ]. Both circumstances are concurring here, hence the assignment of this sextet as to be due to superparamagnetic magnetite. We must not discard, however, that, because the spectrum is clearly characteristic of the occurrence of a distribution of particle sizes, a fraction of small-particle maghemite (that with sizes smaller than that responsible for the narrower magenta sextet) is also contributing to the blue sextet, providing a second, concomitant reason for its intermediate isomer shift value. The presence of magnetite was confirmed further by the presence of the third magnetic component (Fig. 4 and Table 2 , dark green component) whose with an isomer shift is closer to that of the Fe 2.5+ component of magnetite. It is also a well-proven fact that in the absence of an external applied magnetic field, it is difficult to discern the sextet corresponding to the tetrahedral Fe 3+ in magnetite from the Fe 3+ sextet corresponding to maghemite. Since the Fe 2.5+ /Fe 3+ sextet area ratio in the spectrum of stoichiometric magnetite is 1.9 [ 29 ], the fact that the (blue + green)/magenta sextet area ratio in the spectrum of the present sample is around 1.35, points out to the occurrence in this sample of a mixture of superparamagnetic magnetite and maghemite. Finally, the quadrupole doublet (light orange in Fig. 4 ) has hyperfine parameters characteristic of a high spin Fe 3+ ion in octahedral oxygen coordination. Apart from corresponding to an octahedral high spin Fe 3+ species, the nature of a doublet like this is quite unspecific since it might arise from the presence of a large number of different phases. It might correspond, for example, to a fraction of very small maghemite particles such that, due to superparamagnetic effects, the magnetic interactions have totally collapsed at room temperature or to any other kind of microcrystalline/amorphous Fe 3+ phase which went undetected by XRD. The composite corresponds to a mixture of maghemite and magnetite having a distribution of particle sizes: from small enough as to show a completely paramagnetic spectrum at room temperature to large enough as to give a well-developed sextet with parameters close, but not quite, to those shown by bulk specimens. The data would be consistent with a magnetite core surrounded by a maghemite shell. Besides the superparamagnetic effects due to the small sizes of the particles, the concomitant surface and interface effects would explain most of the phenomenology observed in the spectrum. 3.2.2 X-ray photoelectron spectroscopy studies The surface chemistry of our composite was studied by X-ray photoelectron spectroscopy (XPS). XPS data were dominated mainly by the carbon and zinc signals arising from the ZIF framework which encapsulates and surrounds the iron oxide nanoparticles. Given the characteristics of the composite, and the low amount or iron oxide load (5%), it was difficult to obtain a Fe 2p spectrum with a reasonable statistic as to extract unambiguous conclusions. Figure 5 shows representative Fe 2p and Zn 2p spectra. As explained above, the Fe 2p spectrum presents a poor signal-to-noise ratio. The main photoemission Fe 2p 3/2 peak at 709 eV and the shoulder observed at 711.8 suggest the concomitant presence of Fe 2+ and Fe 3+ , respectively. However, the quality of the data precludes its rigorous deconvolution making difficult to separate both contributions (Fig. 5 a). The Zn 2p spectrum consists of a narrow spin-orbit doublet with BEs Zn 2p 3/2 =1019 eV and Zn 2p 1/2 =1042 eV which is consistent with the presence of Zn 2+ [8] . This analysis enhances our understanding of the surface characteristics and chemical states of iron and zinc in the composite, providing valuable insights into its chemical properties and potential applications. 3.2.3 Magnetic properties of the composite Fe x O y /ZIF-14 (qtz) Magnetic curves M vs H of the composite Fe x O y /ZIF-14 ( qtz ) are shown in Fig. 6 . The curves do not show hysteresis loop (Hc value close to zero) which is a confirmation of the superparamagnetic behavior as it was mentioned before in the discussion of Mössbauer spectroscopy results. The magnetization saturation (Ms) changed from 4.79 to 7.45 emu g − 1 in the studied temperature range and the low values are due to the small percent of iron oxide (⁓ 5%) in the composite. Magnetic response to a magnetic field was tested by placing a commercial magnet beside a vial with an aqueous dispersion of the composite, Fig. 6 inset shows the initial dispersion and the solid totally agglomerated after 90 seconds, whereas ZIF-14 ( qtz ) remains dispersed for days in an aqueous system until sedimentation of the solid is completed. It can be inferred all the coordination polymer particles have magnetic iron oxide particles embedded. 3.3 Morphology and elemental composition of the surface The morphology and composition of the composite and the ZIF were analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectra (EDS). Differences in the particle size of the ZIF and the composite were observed by SEM. Figure 7 shows that the particle size is lower for the composite material and the size distribution is narrow and centered at 1.2 µm. ZIF-14 ( qtz ) presents a more dispersed particle size. Figure 8b shows the overall polyhedron/sphere-like morphology of the obtained composite. Figure 8d displays the EDS spectra of this composite material confirming the presence of all expected elements. 3.4 Optical properties: reflectance and band gap Reflectance diffuse spectra show in Fig. 9 , the comparison of the E g value estimated by making the baseline correction to the Tauc’s plot method [ 31 ] and taking the first derivative to find the inflection point. The band gap energy value of the composite Fe x O y /ZIF-14 ( qtz ) of 5.21 eV is basically the same as that of ZIF-14 ( qtz ) (5.23 eV), which implies that the material is a composite, and it is not an iron-doped material. These E g values are very similar to that obtained by theoretical calculations [ 32 , 33 ]. Also, experimental data [ 8 ] for ZIF-8 are approximately 5 eV since 2-ethylimidazole and 2-methylimidazole are very similar ligands in terms of electron density donation. Additionally, the composite Fe x O y /ZIF-14 ( qtz ) shows a broad absorption band at energies below 5 eV corresponding to the absorption of iron oxides. Because of the width of that band, it is not possible to extrapolate the linear region to determine the E g value; however, the reported value for magnetite and maghemite is close to 2 eV [ 34 , 35 ]. A larger absorption at low energy in the composite is more evident in the absorbance spectra (not shown but can be inferred from the reflectance spectrum) due to the ability of iron oxide to absorb in the visible region of the spectra. This ability can enhance the photocatalytic properties of the composite by a semiconductor heterojunction [ 3 ]. 3.5 Textural properties Nitrogen adsorption isotherms were measured to evaluate the specific surface area of the samples (Fig. 10 ). The ZIF-14 ( qtz ) sample shows a type IV adsorption isotherm with a BET surface area of 17.9 m 2 g − 1 , where the hysteresis loop closing at p/p 0 > 0.4 indicates the material presents pores in the mesopore range. Several slopes in the desorption isotherm within the hysteresis loop move the isotherm away from a characteristic behavior and may reflect a complex system of pores. The composite Fe x O y /ZIF-14 ( qtz ) shows a type IIb adsorption isotherm with non-rigid pores or cavities between agglomerates and a BET specific surface area of 13.3 m 2 g − 1 . Nitrogen was less adsorbed by the composite than by the ZIF due probably to pore blocking and both samples exhibit a sub-step at p/p 0 0.4 only in the desorption isotherm, and less intense in the composite. This fact suggests that it is not associated with changes in interglobular voids, but with the polymer matrix. The specific surface is slightly reduced during the process of integration of the magnetic particles in the coordination polymer matrix. However, the decrement is not substantial (compared with the acquired magnetic properties). The low magnitudes of the specific surface area are congruent with the formation of a compact phase. The changes in the nitrogen adsorption isotherm of the iron-ZIF composite with respect the ZIF indicate that the textural characteristics are sensitive to the presence of the magnetic particles. In the comparative graph (Fig. 10 b), three linear segments are shown in the adsorption curve. The first shows that the adsorption isotherms of both materials agree only at very low pressures. Then, the lower slope in the mesopore region indicates less adsorption ability of the composite. The opposite behavior is observed in the high-pressure region. 3.6 Adsorption of diclofenac by ZIF-14 (qtz) and Fe x O y /ZIF-14 (qtz) Kinetic results of diclofenac adsorption at 25°C from aqueous solution were fitted to both pseudo -first and pseudo -second-order rate law equations (Fig. 11 ). The results are summarized in Table 3 . The ZIF-14 ( qtz ) data fit as well with the pseudo -first-order law as with the pseudo -second-order law. However, the calculated adsorbed amount at equilibrium q e,calc is closer to the experimental data for the pseudo -first order than for the pseudo -second order. A different situation concerns the data fit for Fe x O y /ZIF-14 ( qtz ), since the correlation coefficient is acceptable for both orders that yield calculated q e,calc similar to the experimental q e,exper . Hence, in this case, more studies are needed for the exact determination of the kinetic order during adsorption under the given conditions. It should be noted that the kinetic constants k 1 and k 2 are larger for the composite, which implies that the adsorption equilibrium is reached faster and the affinity towards diclofenac improves with the presence of magnetic metal oxide particles. Table 3 Experimental and calculated kinetic parameters for the adsorption of diclofenac (20 mg L − 1 ) using a pseud o-first-order and pseudo -second-order rate law fitting at 25°C. ZIF-14 ( qtz ) Fe x O y /ZIF-14 ( qtz ) Pseudo- first-order q e,exper (mg g − 1 ) 5.8 7.5 q e,calc (mg g − 1 ) 5.6 ± 0.1 7.1 ± 0.2 k 1 × 10 3 (s − 1 ) 1.1 ± 0.1 9.9 ± 4.0 R 2 0.997 0.985 Pseudo -second-order q e,calc (mg g − 1 ) 6.2 ± 0.1 7.2 ± 0.2 k 2 × 10 3 ( g mg − 1 s − 1 ) 0.2 ± 0.02 6.2 ± 5.5 R 2 0.998 0.986 The diclofenac adsorption isotherms were measured also in aqueous solution. They were adjusted to the Langmuir-Freundlich and Freundlich equations and the resulting parameters are shown in Table 4 . The calculated curves fitted well with experimental values and the maximal adsorption capacity ( q m ) predicted for ZIF-14 ( qtz ) with the Langmuir-Freundlich equation resulted beyond the experimental measurement range, because the adsorbent did not achieve saturation. In contrast, the q m value of 14.7 mg g − 1 was obtained for the composite Fe x O y /ZIF-14 ( qtz ) and it is similar to the experimental value. This equation reflects a clear different heterogeneity of both materials since n 1 for Fe x O y /ZIF-14 ( qtz ). However, it is not possible to make a direct comparison of both materials by observing the parameters from the Langmuir-Freundlich equation. Then, with the Freundlich equation, the ZIF-14 ( qtz ) and Fe x O y /ZIF-14 ( qtz ) fitting parameters of the adsorption isotherm fitted similarly. Comparison of the constant k F suggests that affinity towards diclofenac is higher for the composite Fe x O y /ZIF-14 ( qtz ) than for ZIF-14 ( qtz ), although the adsorption capacity is lower. The last implies that some cavities in the coordination polymer are blocked by iron oxide particles changing not only the specific surface area but also the affinity towards diclofenac in the composite. Table 4 Langmuir-Freundlich and Freundlich parameters for diclofenac adsorption from aqueous solution at 25°C on ZIF-14 ( qtz )and the composite. ZIF-14 ( qtz ) Fe x O y /ZIF-14 ( qtz ) Langmuir-Freundlich q m (mg g -1 ) 55.5 ± 60.9 14.7 ± 1.4 k LF (mg g -1 ) 0.02 ± 0.02 0.05 ± 0.01 n 0.75 ± 0.17 1.19 ± 0.14 R LF 2 0.992 0.997 Freundlich k F (mg g -1 )(L mg -1 ) 1/ n 1.4 ± 0.2 1.8 ± 0.3 n 0.62 ± 0.03 0.53 ± 0.05 R F 2 0.991 0.982 4. Conclusions The comprehensive characterization of our synthesized materials, utilizing techniques such as ATR-FTIR, N 2 adsorption, powder XRD, Mössbauer spectroscopy, SEM, EDS, diffuse reflectance, XPS, and magnetization, reveals that magnetic particles (a mix of magnetite and maghemite) are effectively embedded within the ZIF-14 (qtz) matrix. This incorporation stabilizes the small iron oxide domains, necessary to provide the superparamagnetic behavior to the composite. Our findings indicate that while Fe x O y /ZIF-14 ( qtz ) composite exhibits a lower diclofenac adsorption capacity compared to ZIF-14 ( qtz ), likely due to iron oxide particles occupying some of the cavities it exhibits a higher affinity for diclofenac, as evidenced by the analysis of k LF , k F , k 1 and k 2 values. Moreover, the composite can be easily recovered with the assistance of a common commercial magnet. A higher photocatalytic activity is also expected in the composite due to the presence of iron oxides. The thorough characterization and adsorption experiments were important to evaluate the effect of adsorption, even if modest, and will be involved in future photocatalytic studies, including the identification of photo-induced by-products and understanding the role of iron species. In summary, the presence of superparamagnetic particles improves the adsorption performance of the ZIF, and the “ one-pot ” synthesis method should be considered as a straightforward approach for the synthesis of ZIF and MOF composites in aqueous solutions. Declarations Competing interests The authors declare no competing interests. Funding This work was supported by Consejo Nacional de Humanidades Ciencias y Tecnologías (CONAHCYT) and the National Science Foundation (NSF). Data Availability The datasets generated during the current study are available from the corresponding author on reasonable request. Author Contribution E. R. Z.: Conceptualization, methodology, validation, formal analysis, investigation, writing of the original draft, visualization, writing, review, editing of the published work. D. C. P.: Methodology, review, and editing. J. F. M.: Measurements, discussion and review of the final manuscript. K. R. S. 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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-3952171","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":272657576,"identity":"eb545d73-5a12-447f-a362-30f453146190","order_by":0,"name":"Erick Ramírez","email":"data:image/png;base64,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","orcid":"","institution":"Benemérita Universidad Autónoma de Puebla","correspondingAuthor":true,"prefix":"","firstName":"Erick","middleName":"","lastName":"Ramírez","suffix":""},{"id":272657577,"identity":"853f3e70-c36d-4ba7-bef3-e735c7253c9b","order_by":1,"name":"Daniela Carmona-Pérez","email":"","orcid":"","institution":"Benemérita Universidad Autónoma de Puebla","correspondingAuthor":false,"prefix":"","firstName":"Daniela","middleName":"","lastName":"Carmona-Pérez","suffix":""},{"id":272657578,"identity":"9f2f4683-9bd8-4b1d-aab1-5a0324f9d340","order_by":2,"name":"J. 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Elizalde-González","email":"","orcid":"","institution":"Benemérita Universidad Autónoma de Puebla","correspondingAuthor":false,"prefix":"","firstName":"María","middleName":"P.","lastName":"Elizalde-González","suffix":""}],"badges":[],"createdAt":"2024-02-12 23:16:30","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3952171/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3952171/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":51187139,"identity":"b99b3337-303d-4cd3-bb1a-39d269803f05","added_by":"auto","created_at":"2024-02-15 16:06:52","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":182392,"visible":true,"origin":"","legend":"\u003cp\u003eATR-FTIR spectra of 2-ethylimidazole (up), Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (qtz) (middle), and ZIF-14 (qtz) (bottom).\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/e2e05990aa279b9cef58f7d4.jpg"},{"id":51187141,"identity":"087e04db-ee73-4368-b5be-3acdd1b7b8e7","added_by":"auto","created_at":"2024-02-15 16:06:52","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":227694,"visible":true,"origin":"","legend":"\u003cp\u003eDiffraction patterns from 10 to 50 ° of a) simulated ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e), b) synthesized ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e), and c) Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e). Inset: intensity amplification in logarithmic scale in the range from 31 to 38°.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/a0d159931c626381ef8a7d03.jpg"},{"id":51187148,"identity":"9d7098cf-98d6-4b9a-84f7-c958c2fb3d5c","added_by":"auto","created_at":"2024-02-15 16:06:53","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":180400,"visible":true,"origin":"","legend":"\u003cp\u003eRietveld refinement of the composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (qtz).\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/bf1250ed08866c4e0697ab17.jpg"},{"id":51187143,"identity":"9076a5e7-1098-42a7-aac9-7c7015ad2e4e","added_by":"auto","created_at":"2024-02-15 16:06:52","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":192912,"visible":true,"origin":"","legend":"\u003cp\u003eMössbauer spectrum recorded at room temperature of Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e).\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/bf391ff0ca9c53954eb8c532.jpg"},{"id":51187135,"identity":"e866e58c-cf22-4e08-82a1-2c6a90012571","added_by":"auto","created_at":"2024-02-15 16:06:52","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":187003,"visible":true,"origin":"","legend":"\u003cp\u003ea)\u003cstrong\u003e \u003c/strong\u003eRepresentative HR-XPS Fe 2p region spectra of the composite material. b)\u003cstrong\u003e \u003c/strong\u003eRepresentative HR-XPS Zn 2p region spectra of the composite material.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/e66f4a0d90392d048b19cd99.jpg"},{"id":51187420,"identity":"26193204-313c-4144-8dda-82a2149ff21d","added_by":"auto","created_at":"2024-02-15 16:14:53","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":196500,"visible":true,"origin":"","legend":"\u003cp\u003eMagnetization (M) versus applied magnetic field at different temperatures of Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (qtz). Inset: initial dispersion (upper picture) and the solid magnetically separated (lower picture).\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/375f4e3f2807691f420ffca9.jpg"},{"id":51187142,"identity":"482c36a6-539e-48cb-8019-09b960d5712e","added_by":"auto","created_at":"2024-02-15 16:06:52","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":271679,"visible":true,"origin":"","legend":"\u003cp\u003eParticle size distribution of a) ZIF-14 (qtz) and b) composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (qtz).\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/c9ea18eacea5ddba12f570bd.jpg"},{"id":51187149,"identity":"3c9b9a89-1439-433b-a92b-2865aa34ea8c","added_by":"auto","created_at":"2024-02-15 16:06:53","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":483711,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative SEM micrographs of a)\u003cstrong\u003e \u003c/strong\u003eZIF-14 (qtz) (scale bar = 10 μm) and b) nanostructured composite (scale bar = 4 μm).\u003cstrong\u003e \u003c/strong\u003eEDS spectrum of c) ZIF-14 (qtz) and d) the composite material showcasing the presence of all expected elements in their structures.\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/324425cf238a4c48cbd588d5.jpg"},{"id":51187419,"identity":"db9eb960-c781-490b-8a85-8e563d8024e0","added_by":"auto","created_at":"2024-02-15 16:14:52","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":176067,"visible":true,"origin":"","legend":"\u003cp\u003eSolid-state optical diffuse-reflection spectra of ZIF-14 (qtz), and Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF (qtz) (left side). Tauc’s plot of\u0026nbsp; ZIF-14 (qtz), and\u0026nbsp; Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (qtz) (right side).\u003c/p\u003e","description":"","filename":"9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/f74520635095309b0f89538e.jpg"},{"id":51187146,"identity":"e8f81017-c36b-47cd-9b4e-c9950a0f8390","added_by":"auto","created_at":"2024-02-15 16:06:53","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":235947,"visible":true,"origin":"","legend":"\u003cp\u003ea) Nitrogen adsorption-desorption isotherms of ZIF-14 (qtz) and Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF (qtz). Full symbols: adsorption, empty symbols: desorption. Inset: desorption isotherms in the 0.4 \u0026lt; p/p\u003csub\u003e0\u003c/sub\u003e \u0026lt; 0.6 range. b) Comparative isotherm of nitrogen adsorbed (cm\u003csup\u003e3\u003c/sup\u003eg\u003csup\u003e-1\u003c/sup\u003e) by the two materials.\u003c/p\u003e","description":"","filename":"10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/5dde0c83bd5ed99c909b07c4.jpg"},{"id":51187147,"identity":"5025f5fe-a663-44b1-950e-99f9c5190f2c","added_by":"auto","created_at":"2024-02-15 16:06:53","extension":"jpg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":124839,"visible":true,"origin":"","legend":"\u003cp\u003eKinetic curves of diclofenac adsorption experiments at 25 °C on a) ZIF-14 (qtz) and b) Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (qtz). Symbols: experimental values. Continuous line: pseudo-first order fitting and dotted line: pseudo-second-order fitting.\u003c/p\u003e","description":"","filename":"11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/b8105eddf16facf20d5ec63b.jpg"},{"id":51187145,"identity":"bdd1eb77-6103-496b-a5b3-a9cc1958ed75","added_by":"auto","created_at":"2024-02-15 16:06:53","extension":"jpg","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":144637,"visible":true,"origin":"","legend":"\u003cp\u003eDiclofenac adsorption isotherms on a) ZIF-14 (qtz) and b) Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (qtz). Red dash lines correspond to the Langmuir-Freundlich fitting and black dash lines correspond to the Freundlich fitting.\u003c/p\u003e","description":"","filename":"12.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/a82af2f95a764d53a1017cd9.jpg"},{"id":51708554,"identity":"5dfc23d5-62fb-405b-8b60-74059e8537a7","added_by":"auto","created_at":"2024-02-27 17:11:41","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1479250,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3952171/v1/96faa664-9bbb-4c9f-b85e-737e598adee7.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Comparison of ZIF-14 (qtz) and a One-pot Synthesized Superparamagnetic Iron Oxide/ZIF-14 (qtz) Composite for the Adsorption of Diclofenac","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eAccording to the World Health Organization (WHO) the most important chemical hazards in drinking water derive from arsenic, fluoride, and nitrate [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Nevertheless, contaminants of emerging concern such as pharmaceuticals, pesticides, fluoroalkyl substances, and microplastics are getting more public attention [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. After the recent sanitary emergency, there has been a notable increase in the accumulation of pharmaceutical contaminants in wastewater, as highlighted in recent studies [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Contaminants of emerging concern (CECs) are substances detected in the environment at low concentrations, yet there is not enough information regarding their potential harmful effects [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Diclofenac, a widely-used anti-inflammatory medication, has become a prominent example of these new contaminants, frequently detected in wastewater, surface water, and marine environments. Recent evidence has established the toxicity of diclofenac, as demonstrated in the well-documented vulture population decline case [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMetal oxides like TiO\u003csub\u003e2\u003c/sub\u003e and ZnO have been extensively used as photocatalysts for the degradation of contaminants due to their semiconductor properties. Nevertheless, their activity is affected by the low affinity of the metal oxide surface towards organic molecules, and the recombination of photogenerated electron/hole pairs (h\u003csup\u003e+\u003c/sup\u003e/e\u003csup\u003e\u0026minus;\u003c/sup\u003e) [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Highly porous materials like Zeolitic Imidazolate Frameworks (ZIFs) are considered alternatives to contaminant removal from water by either photocatalytic degradation or sorption [\u003cspan additionalcitationids=\"CR8 CR9 CR10\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The literature reports a variety of ZIF composites, particularly those incorporating the widely studied ZIF-8 (a coordination polymer formed by 2-methylimidazole and zinc), mixed with materials such as metal oxides, fibers, metal nanoparticles, graphene, and enzymes [\u003cspan additionalcitationids=\"CR12 CR13\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eZIF-8 and its cobalt analogue, ZIF-67, are noted for their SOD-type topology and high specific area [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Despite over 100 zeolite-like topologies identified for ZIFs, research predominantly focuses on the above mentioned structures for sorption or catalytic applications[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. However, separating ZIFs after-contaminant treatment in water poses challenges due to their small particle size, often necessitating centrifugation. Magnetic ZIF-8 composites, facilitating easier separation, are produced through multi-step synthesis processes, where the coordination polymer is synthetized in presence of the magnetic particles [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Alternatively, heterojunctions between two semiconductors with different redox energy levels offer a different synthesis approach [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Simplifying and accelerating the synthesis of ZIFs and their composites would greatly benefit their widespread application.\u003c/p\u003e \u003cp\u003eIn this work, we prepared a composite material combining ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) and magnetic iron oxides (a mixture of maghemite and magnetite) using a straightforward \u003cem\u003eone-pot\u003c/em\u003e methodology. This composite was developed for testing as a sorbent and photocatalytic material for removal of diclofenac. The composite exhibits superparamagnetic behavior, a property that does not compromise the main matrix characteristics. Importantly, only a minimal amount of iron oxide (5%) is required to enable magnetic-assisted separation. We compared this composite with ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) alone to demonstrate the benefits and drawbacks of incorporating magnetic particles into the material.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n\u003ch2\u003e2.1 Chemicals\u003c/h2\u003e\n\u003cp\u003eFerrous ammonium sulfate hexahydrate (98%) was purchased from Meyer reagents, 2-ethylimidazole (98%), zinc sulfate heptahydrate (99%), zinc acetate dihydrate (99%), and diclofenac sodium salt (98%) were purchased from Sigma Aldrich. All the reagents were used without further purification. Solutions were prepared with deionized water with a resistivity of 18 M\u0026Omega; cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n\u003ch2\u003e2.2 Preparation of ZIF-14\u003c/h2\u003e\n\u003cp\u003ePrecursors 2-ethylimidazole (1.202 g, 12.5 mmol) and zinc acetate dihydrate (0.110 mg, 0.5 mmol) were dissolved in separated beakers in 25 and 10 ml of deionized water, respectively. Then, the ligand solution was added to the zinc salt solution without stirring. After a few seconds, a white precipitated started to form. The formation of the solid is slow, which can be followed by the cloudiness of the reaction mixture that disappears, after aging for one week. The white precipitated was filtered under vacuum and washed exhaustively with deionized water to remove the remanent acetate and ligand excess. The product was dried at 60\u0026deg;C in a convection oven for 2 days to give a white powder 0.099 g, 77% of yield according to the zinc equivalents.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n\u003ch2\u003e2.3 One pot preparation of composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (qtz)\u003c/h2\u003e\n\u003cp\u003eThe ligand 2-ethylimidazole (1.202 g 12.5 mmol) was dissolved in 100 ml of deionized water in a round flask and N\u003csub\u003e2\u003c/sub\u003e was bubbled to the solution during 30 min. Separately, 25 ml of deionized water solution with ferrous ammonium sulfate hexahydrate (0.050 g 0.127 mmol) and zinc sulfate heptahydrate (0.1438 g 0.5 mmol) was prepared and bubbled also with N\u003csub\u003e2\u003c/sub\u003e during 15 min. Then the metal solution was added to the ligand solution under stirring and nitrogen atmosphere using a syringe. Immediately, a light green dispersion was formed. Nitrogen bubbling was maintained for 30 minutes. Stirring continued for two hours, after that the solution turned grey. Dispersion was let for one night at room temperature and no coloration changes were observed. After decantation, the solid was filtered under vacuum and washed with deionized water. Finally, the solid was dried at 60\u0026deg;C in a convection oven for one day yielding a light brown solid. Isolated product 0.130 g.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n\u003ch2\u003e2.4 Characterization\u003c/h2\u003e\n\u003cp\u003eThe materials were characterized by several analytical techniques: IR, X-ray powder diffraction, M\u0026ouml;ssbauer spectroscopy, XPS, magnetization vs field curves, SEM, EDS, Diffuse Reflectance, and nitrogen adsorption.\u003c/p\u003e\n\u003cp\u003eIR measurements were taken in a Thermo-scientific FTIR Spectrophotometer Model Nicolet 6700 provided with a Smart iTR ATR accessory. The powder diffraction patterns were obtained in a Malvern Panalytical model Empyrean diffractometer with Cu K\u0026alpha; beam source. Rietveld refinement was performed with BGMN software [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e] (user interface Profex 5.2.2 [\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e]) to calculate the percent composition of the composite using as reference ZIF-14 [\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e], magnetite [\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e], and maghemite [\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e] files obtained from monocrystal X-ray diffraction data. Refinement was carried out with 2 phases \u003cem\u003ei)\u003c/em\u003e ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) and \u003cem\u003eii)\u003c/em\u003e iron oxide, separately. The BET specific area was measured at 77 K with a Micromeritics ASAP 2020 instrument; samples were degassed at 150\u0026deg;C.\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e57\u003c/sup\u003eFe M\u0026ouml;ssbauer data were recorded at room temperature using a \u003csup\u003e57\u003c/sup\u003eCo(Rh) source and a conventional constant acceleration spectrometer. The velocity scale was calibrated using a 6 \u0026micro;m thick iron foil. The chemical isomer shifts were referred to the centroid of the room temperature M\u0026ouml;ssbauer spectrum of \u0026alpha;-iron. The spectrum was computer-fitted. Magnetization curves were taken at a Physical Property Measurement System DynaCool-9 in the range of 1.8 to 350 K and in the field range from \u0026minus;\u0026thinsp;40 to 40 kOe.\u003c/p\u003e\n\u003cp\u003eX-ray Photoelectron Spectroscopy measurements were performed on three separate ZIF batches to ensure data reproducibility. Sample preparation was performed under ambient atmosphere. Powders were dispersed in ethylene glycol to obtain a concentrated dispersion. The dispersion was drop-casted onto cleaned Si wafers and subsequently dried in a conventional oven at 50\u0026deg;C for 30 min. Afterwards, the Si wafers were electrically grounded to the XPS sample bar by carbon tape. The XPS measurements were recorded with a Kratos Axis Ultra DLD system equipped with monochromatic Al K\u0026alpha; (h\u0026nu;\u0026thinsp;=\u0026thinsp;1486.6 eV) X-ray source. During the measurements, pressure in the main chamber was kept below 1\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e bar. Charge compensation was carried out via a neutralizer running at a current of 7 \u0026micro;A, a charge balance of 5 V, and a filament bias of 1.3 V. The X-ray gun was set to 10 mA emission. Binding energies were referenced to C 1s peak arising from adventitious carbon with an emission energy of 284.8 eV. The C 1s, O 1s, N 1s, Fe 2p and Zn 2p core levels were recorded with an emission current of 10 mA, an accelerating voltage of 15 kV, and a pass energy of 80 eV. We collected three scans for iron, zinc, oxygen and nitrogen, and two scans for carbon. XPS analysis was performed with CasaXPS (Version 2.3.22PR1.0). The U Touggard function was used for background subtraction. The XPS signals were fitted with the CasaXPS Component Fitting tool.\u003c/p\u003e\n\u003cp\u003eSEM micrographs were obtained using a Zeiss Auriga Scanning Electron Microscope with a beam energy of 25 kV. The composite samples were drop-casted onto silicon wafers from hexane dispersions. EDS elemental information was also obtained using a Zeiss Auriga Scanning Electron Microscope coupled to an EDS analyzer. Measurements were carried out using 25 kV electron beam energy. Semi-quantitative data analyses were performed using the EDAX Apex software.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n\u003ch2\u003e2.5 Adsorption measurements\u003c/h2\u003e\n\u003cp\u003eThe kinetic experiments were performed at 25\u0026deg;C placing respectively, 6.6 mg of ZIF-14 and composite in an amber vial, with 20 mL of diclofenac solution 20 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Aliquots were taken from different vials at different times. In the diclofenac/ZIF-14 system, vials were firstly shaken in an orbital shaker at 200 rpm for 5 min and then, let statically until aliquots were taken. For the diclofenac/composite system, shaking was performed all time. The adsorption capacity was determined by the known equation: \u003cem\u003eq\u003c/em\u003e = ((\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e-\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sub\u003e)V)/\u003cem\u003em\u003c/em\u003e, where \u003cem\u003eq\u003c/em\u003e is the adsorbed quantity, \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e is the initial and \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sub\u003e the final concentration, V is the volume of diclofenac solution, and \u003cem\u003em\u003c/em\u003e is the adsorbent mass. The concentration changes in the solutions during the adsorption experiments were measured by RP-HPLC using an Agilent 1200 Infinity series chromatograph equipped with a Multiple Wave Detector 1260 Infinity II. The chromatographic column Zorbax C18 (4.6 \u0026times; 100 mm, 3.5 \u0026micro;m) was used at 30\u0026deg;C under isocratic conditions at a flow rate of 1 mL min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the eluent was a mixture of CH\u003csub\u003e3\u003c/sub\u003eCN and H\u003csub\u003e2\u003c/sub\u003eO (55:45) with 0.2% of formic acid.\u003c/p\u003e\n\u003cp\u003eThe adsorption experiments were carried out at 25\u0026deg;C in the concentration range within 1 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 40 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The amount of adsorbent was 6.6 mg set in 20 mL of diclofenac solution in an amber vial. The systems were shaken for 5 min in the case of ZIF-14 and for two hours in the experiments with the composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14. The diclofenac concentration changes were monitored by RP-HPLC under conditions described above.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n\u003ch2\u003e3.1 Compositional and topological identification\u003c/h2\u003e\n\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n\u003ch2\u003e3.1.1 Vibrational spectroscopy\u003c/h2\u003e\n\u003cp\u003eComparison of the ATR-FTIR spectra of ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) and its iron composite is shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. They show the typical bands corresponding to the imidazole: C-H stretching at 3008, 2974, 2938 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, C\u0026thinsp;=\u0026thinsp;C stretching at 1601 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, C\u0026thinsp;=\u0026thinsp;N stretching at 1449, 1321, 1308 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, C-H out of the plane bending at 1049, 757, 739 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and for the ring deformation out of the plane bending at 660 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e[\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e]. The spectra of ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) and Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) are almost identical, whereas the main difference between the synthesis products and the free ligand is the absence of the broad band of N-H stretching in the high energy region of the spectra and N-H deformation mode at 1570 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e that corroborate formation of the imidazolate anion. As shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, the iron oxide bands have such low intensity that they do not appear in the spectrum, which is congruent with the low portion of the iron oxide in the composite.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n\u003ch2\u003e3.1.2 Topology and crystallinity analyzed by Powder X-Ray Diffraction\u003c/h2\u003e\n\u003cp\u003eThe diffractogram of ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) was simulated, using the Mercury software with the cif file of the monocrystal structure taken from the CCDC database of a previous reported work [\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e]. The diffraction patterns of ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) and Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) show the presence of characteristic peaks at 2\u0026theta; from 10 to 35 degrees corresponding to the planes (1\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\stackrel{-}{1}\\)\u003c/span\u003e\u003c/span\u003e0), (1\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\stackrel{-}{1}\\stackrel{-}{1}\\)\u003c/span\u003e\u003c/span\u003e), (1\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\stackrel{-}{1}\\stackrel{-}{2}\\)\u003c/span\u003e\u003c/span\u003e), (2\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\stackrel{-}{1}\\)\u003c/span\u003e\u003c/span\u003e0), (2\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\stackrel{-}{1}\\stackrel{-}{1}\\)\u003c/span\u003e\u003c/span\u003e), (2\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\stackrel{-}{2}\\)\u003c/span\u003e\u003c/span\u003e0), (2\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\stackrel{-}{2}\\stackrel{-}{1}\\)\u003c/span\u003e\u003c/span\u003e), (2\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\stackrel{-}{2}\\stackrel{-}{2}\\)\u003c/span\u003e\u003c/span\u003e), (2\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\stackrel{-}{1}\\stackrel{-}{3}\\)\u003c/span\u003e\u003c/span\u003e), (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\stackrel{-}{2}\\)\u003c/span\u003e\u003c/span\u003e23), and (3\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\stackrel{-}{1}\\stackrel{-}{1}\\)\u003c/span\u003e\u003c/span\u003e) of ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e). Comparison of the diffraction patterns obtained with the simulated ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) agree with the presence of the \u003cem\u003eqtz\u003c/em\u003e topology. Crystallinity of pure ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) is relatively higher than that of the composite, but they show almost identical diffractograms (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eb and \u003cstrong\u003ec\u003c/strong\u003e). The principal difference is a very low intensity peak, marked with astherisk in the inset of Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ec, at the diffraction angle 2\u0026theta;\u0026thinsp;=\u0026thinsp;35.7 \u0026deg; that corresponds, as expected, to the magnetite or maghemite (311) plane in the composite.\u003c/p\u003e\n\u003cp\u003eConcerning the iron oxide present in the composite, quantification of the magnetite/maghemite relationship was not conducted because other techniques surpass the XRD method for this purpose [\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e]. Therefore, we consider both phases of iron oxide in our approach to study the structure of the materials (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 diffraction pattern fitting was approximately 95% ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) and 5% of magnetite and maghemite respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). As shown in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, the cell parameters were not significantly affected by the selection of one of these iron phases for the refinement and the low portion agrees with the ATR-FTIR spectrum information. In addition, crystallite mean size below 50 nm agrees with the existence of small domains that exhibit superparamagnetic behavior. The refinement of ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) gives a bigger crystallite size (around 93 nm) and a wider distribution (k1 parameter in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e) than the ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) phase in the composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eSelected refinement parameters obtained by the Rietveld method of ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) and the composite, considering magnetite or maghemite for the refinement. k1 is a normalized parameter of crystallite size broadening (smaller k1 values correspond to a wide distribution [\u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e]), \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003ewp\u003c/em\u003e\u003c/sub\u003e is the weighted residual square sum, \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003eexp\u003c/em\u003e\u003c/sub\u003e is the possible minimum value for \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003ewp\u003c/em\u003e\u003c/sub\u003e, and \u003cem\u003eGoF\u003c/em\u003e is the goodness-of-fit.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eParameters\u003c/p\u003e\n\u003c/th\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eZIF-14\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eComposite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eComposite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eZIF-14 (\u003cem\u003eqtz\u003c/em\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eMagnetite Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eZIF-14 (\u003cem\u003eqtz\u003c/em\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eMaghemite Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSpace group\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eP6\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eP6\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eF4\u003csub\u003e1\u003c/sub\u003e/d\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\stackrel{-}{3}\\)\u003c/span\u003e\u003c/span\u003e\u003csub\u003e2\u003c/sub\u003e/m\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eP6\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eP4\u003csub\u003e1\u003c/sub\u003e32\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCell parameters\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"5\" align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003ea\u003c/em\u003e (nm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.8483(2)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.8497(4)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.8395(4)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.8498(4)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.8397(4)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003ec\u003c/em\u003e (nm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.2852(3)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.2858(6)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e‒\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.2859(6)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e‒\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ek1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCrystallite size (nm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"5\" align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;100\u0026gt;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e93(3)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e48.3(9)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e24(1)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e48.3(9)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e23(1)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;010\u0026gt;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e93(3)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e48.3(9)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e24(1)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e48.3(9)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e23(1)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;001\u0026gt;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e126(11)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e77(8)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e24(1)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e78(8)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e23(1)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eComposition (%)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e95.2(2)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.8(2)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e94.3(3)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.7(3)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eR\u003csub\u003ewp\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e9.03\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e7.56\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e7.50\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eR\u003csub\u003eexp\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.53\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e2.87\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e2.87\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGoF\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.99\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e2.63\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e2.61\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n\u003ch2\u003e3.2 Iron oxide phase characterization and magnetic properties of the composite\u003c/h2\u003e\n\u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n\u003ch2\u003e3.2.1 Magnetite/maghemite identification by M\u0026ouml;ssbauer spectroscopy\u003c/h2\u003e\n\u003cp\u003eResults of ATR-FTIR spectroscopy and PXRD show that the main component of the composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) is the coordination polymer, and for the identity clarification of the iron oxide phase, M\u0026ouml;ssbauer and magnetization experiments were performed. The room temperature M\u0026ouml;ssbauer spectrum recorded from Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) is depicted in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. The spectrum shows a main broad, asymmetric magnetic component and a smaller quadrupole contribution. The spectrum is characteristic of a system experiencing superparamagnetic relaxation associated to a distribution of iron oxide small particle sizes. The spectrum was fitted to a model considering three different magnetic contributions and a quadrupole doublet. The hyperfine parameters obtained from the fit of the spectrum are collected in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab2\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eHyperfine parameters obtained from the fit of the spectrum recorded at room temperature from sample Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSite/species\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u0026delta; (mms\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u0026Delta; or 2\u0026epsilon; (mms\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eH (T)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eArea (%)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eDoublet\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.34\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.63\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e--\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e8\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eSextet 1\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.32\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e47.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e39\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eSextet 2\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.45\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.04\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e41.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e36\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eSextet 3\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.66\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.39\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e26.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e17\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026Delta;: isomer shift; \u0026Delta;: quadrupole splitting (doublet); 2\u0026epsilon;: quadrupole shift (sextets); H: hyperfine magnetic field.\u003c/p\u003e\n\u003cp\u003eThe narrower sextet (spectrum in magenta) has parameters which can be associated with maghemite (\u0026gamma;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) [\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e]. While the isomer and quadrupole shifts of this sextet match those characteristic of this iron oxide, the hyperfine magnetic field is significantly smaller: 47.3 T \u003cem\u003evs.\u003c/em\u003e the \u0026ldquo;canonical\u0026rdquo; 49.9 T value [\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e]. It has been reported that the phenomenon of superparamagnetism is often reflected in a smaller value of the hyperfine magnetic field due to the occurrence of collective magnetic excitations [\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e]. This implies that, at room temperature, the size of the maghemite particles, although large enough as to show a well-developed magnetic sextet, is not sufficient to overcome completely the superparamagnetic relaxation, hence the smaller hyperfine magnetic field.\u003c/p\u003e\n\u003cp\u003eThe second most intense magnetic component (blue) has an isomer shift (0.45 mms\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) which is quite large as to be due solely to the presence of an Fe\u003csup\u003e3+\u003c/sup\u003e oxide [\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e]. It is well-known that the room temperature M\u0026ouml;ssbauer spectrum of magnetite, Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e, is composed of two different magnetic sextets, one accounting for the Fe\u003csup\u003e3+\u003c/sup\u003e sitting in the tetrahedral sites of the spinel-related structure and a second one arising from the Fe\u003csup\u003e2+\u003c/sup\u003e/Fe\u003csup\u003e3+\u003c/sup\u003e located in the corresponding octahedral sites in that structure [\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e]. As a consequence of electron hopping, the chemical isomer shift of this second sextet (0.72 mms\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) is intermediate between that expected for an octahedral high spin Fe\u003csup\u003e3+\u003c/sup\u003e ion (\u0026sim;0.35 mms\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and that characteristic of an octahedral high spin Fe\u003csup\u003e2+\u003c/sup\u003e ion (\u0026sim;1.1 mms\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and then it is often referred as the Fe\u003csup\u003e2.5+\u003c/sup\u003e octahedral component of the M\u0026ouml;ssbauer spectrum of magnetite. Therefore, the present results suggest that the broad blue sextet might arise from a fraction of small particle magnetite, as the increase in the value of the isomer shift respect to that expected for Fe\u003csup\u003e3+\u003c/sup\u003e would suggest the participation of Fe\u003csup\u003e2+\u003c/sup\u003e ions through an electron hopping mechanism. It has been also reported that superparamagnetic particles can not only show smaller hyperfine magnetic field values but also smaller isomer shifts [\u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e]. Both circumstances are concurring here, hence the assignment of this sextet as to be due to superparamagnetic magnetite. We must not discard, however, that, because the spectrum is clearly characteristic of the occurrence of a distribution of particle sizes, a fraction of small-particle maghemite (that with sizes smaller than that responsible for the narrower magenta sextet) is also contributing to the blue sextet, providing a second, concomitant reason for its intermediate isomer shift value. The presence of magnetite was confirmed further by the presence of the third magnetic component (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e and Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, dark green component) whose with an isomer shift is closer to that of the Fe\u003csup\u003e2.5+\u003c/sup\u003e component of magnetite.\u003c/p\u003e\n\u003cp\u003eIt is also a well-proven fact that in the absence of an external applied magnetic field, it is difficult to discern the sextet corresponding to the tetrahedral Fe\u003csup\u003e3+\u003c/sup\u003e in magnetite from the Fe\u003csup\u003e3+\u003c/sup\u003e sextet corresponding to maghemite. Since the Fe\u003csup\u003e2.5+\u003c/sup\u003e/Fe\u003csup\u003e3+\u003c/sup\u003e sextet area ratio in the spectrum of stoichiometric magnetite is 1.9 [\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e], the fact that the (blue\u0026thinsp;+\u0026thinsp;green)/magenta sextet area ratio in the spectrum of the present sample is around 1.35, points out to the occurrence in this sample of a mixture of superparamagnetic magnetite and maghemite.\u003c/p\u003e\n\u003cp\u003eFinally, the quadrupole doublet (light orange in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e) has hyperfine parameters characteristic of a high spin Fe\u003csup\u003e3+\u003c/sup\u003e ion in octahedral oxygen coordination. Apart from corresponding to an octahedral high spin Fe\u003csup\u003e3+\u003c/sup\u003e species, the nature of a doublet like this is quite unspecific since it might arise from the presence of a large number of different phases. It might correspond, for example, to a fraction of very small maghemite particles such that, due to superparamagnetic effects, the magnetic interactions have totally collapsed at room temperature or to any other kind of microcrystalline/amorphous Fe\u003csup\u003e3+\u003c/sup\u003e phase which went undetected by XRD.\u003c/p\u003e\n\u003cp\u003eThe composite corresponds to a mixture of maghemite and magnetite having a distribution of particle sizes: from small enough as to show a completely paramagnetic spectrum at room temperature to large enough as to give a well-developed sextet with parameters close, but not quite, to those shown by bulk specimens. The data would be consistent with a magnetite core surrounded by a maghemite shell. Besides the superparamagnetic effects due to the small sizes of the particles, the concomitant surface and interface effects would explain most of the phenomenology observed in the spectrum.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n\u003ch2\u003e3.2.2 X-ray photoelectron spectroscopy studies\u003c/h2\u003e\n\u003cp\u003eThe surface chemistry of our composite was studied by X-ray photoelectron spectroscopy (XPS). XPS data were dominated mainly by the carbon and zinc signals arising from the ZIF framework which encapsulates and surrounds the iron oxide nanoparticles. Given the characteristics of the composite, and the low amount or iron oxide load (5%), it was difficult to obtain a Fe 2p spectrum with a reasonable statistic as to extract unambiguous conclusions. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e shows representative Fe 2p and Zn 2p spectra. As explained above, the Fe 2p spectrum presents a poor signal-to-noise ratio. The main photoemission Fe 2p\u003csub\u003e3/2\u003c/sub\u003e peak at 709 eV and the shoulder observed at 711.8 suggest the concomitant presence of Fe\u003csup\u003e2+\u003c/sup\u003e and Fe\u003csup\u003e3+\u003c/sup\u003e, respectively. However, the quality of the data precludes its rigorous deconvolution making difficult to separate both contributions (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea). The Zn 2p spectrum consists of a narrow spin-orbit doublet with BEs Zn 2p\u003csub\u003e3/2\u003c/sub\u003e=1019 eV and Zn 2p\u003csub\u003e1/2\u003c/sub\u003e=1042 eV which is consistent with the presence of Zn\u003csup\u003e2+ [8]\u003c/sup\u003e. This analysis enhances our understanding of the surface characteristics and chemical states of iron and zinc in the composite, providing valuable insights into its chemical properties and potential applications.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section3\"\u003e\n\u003ch2\u003e3.2.3 Magnetic properties of the composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (qtz)\u003c/h2\u003e\n\u003cp\u003eMagnetic curves M vs H of the composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) are shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e. The curves do not show hysteresis loop (Hc value close to zero) which is a confirmation of the superparamagnetic behavior as it was mentioned before in the discussion of M\u0026ouml;ssbauer spectroscopy results. The magnetization saturation (Ms) changed from 4.79 to 7.45 emu g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the studied temperature range and the low values are due to the small percent of iron oxide (⁓ 5%) in the composite. Magnetic response to a magnetic field was tested by placing a commercial magnet beside a vial with an aqueous dispersion of the composite, Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e inset shows the initial dispersion and the solid totally agglomerated after 90 seconds, whereas ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) remains dispersed for days in an aqueous system until sedimentation of the solid is completed. It can be inferred all the coordination polymer particles have magnetic iron oxide particles embedded.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n\u003ch2\u003e3.3 Morphology and elemental composition of the surface\u003c/h2\u003e\n\u003cp\u003eThe morphology and composition of the composite and the ZIF were analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectra (EDS). Differences in the particle size of the ZIF and the composite were observed by SEM. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e shows that the particle size is lower for the composite material and the size distribution is narrow and centered at 1.2 \u0026micro;m. ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) presents a more dispersed particle size. Figure\u0026nbsp;8b shows the overall polyhedron/sphere-like morphology of the obtained composite. Figure\u0026nbsp;8d displays the EDS spectra of this composite material confirming the presence of all expected elements.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\n\u003ch2\u003e3.4 Optical properties: reflectance and band gap\u003c/h2\u003e\n\u003cp\u003eReflectance diffuse spectra show in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e, the comparison of the \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eg\u003c/em\u003e\u003c/sub\u003e value estimated by making the baseline correction to the Tauc\u0026rsquo;s plot method [\u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e] and taking the first derivative to find the inflection point. The band gap energy value of the composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) of 5.21 eV is basically the same as that of ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) (5.23 eV), which implies that the material is a composite, and it is not an iron-doped material. These \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eg\u003c/em\u003e\u003c/sub\u003e values are very similar to that obtained by theoretical calculations [\u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e]. Also, experimental data [\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e] for ZIF-8 are approximately 5 eV since 2-ethylimidazole and 2-methylimidazole are very similar ligands in terms of electron density donation. Additionally, the composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) shows a broad absorption band at energies below 5 eV corresponding to the absorption of iron oxides. Because of the width of that band, it is not possible to extrapolate the linear region to determine the \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eg\u003c/em\u003e\u003c/sub\u003e value; however, the reported value for magnetite and maghemite is close to 2 eV [\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e]. A larger absorption at low energy in the composite is more evident in the absorbance spectra (not shown but can be inferred from the reflectance spectrum) due to the ability of iron oxide to absorb in the visible region of the spectra. This ability can enhance the photocatalytic properties of the composite by a semiconductor heterojunction [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\n\u003ch2\u003e3.5 Textural properties\u003c/h2\u003e\n\u003cp\u003eNitrogen adsorption isotherms were measured to evaluate the specific surface area of the samples (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e). The ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) sample shows a type IV adsorption isotherm with a BET surface area of 17.9 m\u003csup\u003e2\u003c/sup\u003eg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, where the hysteresis loop closing at p/p\u003csub\u003e0\u003c/sub\u003e \u0026gt; 0.4 indicates the material presents pores in the mesopore range. Several slopes in the desorption isotherm within the hysteresis loop move the isotherm away from a characteristic behavior and may reflect a complex system of pores. The composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) shows a type IIb adsorption isotherm with non-rigid pores or cavities between agglomerates and a BET specific surface area of 13.3 m\u003csup\u003e2\u003c/sup\u003eg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Nitrogen was less adsorbed by the composite than by the ZIF due probably to pore blocking and both samples exhibit a sub-step at p/p\u003csub\u003e0\u003c/sub\u003e 0.4 only in the desorption isotherm, and less intense in the composite. This fact suggests that it is not associated with changes in interglobular voids, but with the polymer matrix. The specific surface is slightly reduced during the process of integration of the magnetic particles in the coordination polymer matrix. However, the decrement is not substantial (compared with the acquired magnetic properties). The low magnitudes of the specific surface area are congruent with the formation of a compact phase. The changes in the nitrogen adsorption isotherm of the iron-ZIF composite with respect the ZIF indicate that the textural characteristics are sensitive to the presence of the magnetic particles. In the comparative graph (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003eb), three linear segments are shown in the adsorption curve. The first shows that the adsorption isotherms of both materials agree only at very low pressures. Then, the lower slope in the mesopore region indicates less adsorption ability of the composite. The opposite behavior is observed in the high-pressure region.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\n\u003ch2\u003e3.6 Adsorption of diclofenac by ZIF-14 (qtz) and Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (qtz)\u003c/h2\u003e\n\u003cp\u003eKinetic results of diclofenac adsorption at 25\u0026deg;C from aqueous solution were fitted to both \u003cem\u003epseudo\u003c/em\u003e-first and \u003cem\u003epseudo\u003c/em\u003e-second-order rate law equations (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e). The results are summarized in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e. The ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) data fit as well with the \u003cem\u003epseudo\u003c/em\u003e-first-order law as with the \u003cem\u003epseudo\u003c/em\u003e-second-order law. However, the calculated adsorbed amount at equilibrium \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003ee,calc\u003c/em\u003e\u003c/sub\u003e is closer to the experimental data for the \u003cem\u003epseudo\u003c/em\u003e-first order than for the \u003cem\u003epseudo\u003c/em\u003e-second order. A different situation concerns the data fit for Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e), since the correlation coefficient is acceptable for both orders that yield calculated \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003ee,calc\u003c/em\u003e\u003c/sub\u003e similar to the experimental \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003ee,exper\u003c/em\u003e\u003c/sub\u003e. Hence, in this case, more studies are needed for the exact determination of the kinetic order during adsorption under the given conditions. It should be noted that the kinetic constants \u003cem\u003ek\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003ek\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e are larger for the composite, which implies that the adsorption equilibrium is reached faster and the affinity towards diclofenac improves with the presence of magnetic metal oxide particles.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab3\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eExperimental and calculated kinetic parameters for the adsorption of diclofenac (20 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) using a \u003cem\u003epseud\u003c/em\u003eo-first-order and \u003cem\u003epseudo\u003c/em\u003e-second-order rate law fitting at 25\u0026deg;C.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eZIF-14 (\u003cem\u003eqtz\u003c/em\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eFe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003ePseudo-\u003c/em\u003efirst-order\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003ee,exper\u003c/em\u003e\u003c/sub\u003e (mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.8\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003e7.5\u003c/em\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003ee,calc\u003c/em\u003e\u003c/sub\u003e (mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003ek\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e \u003cem\u003e\u0026times; 10\u003c/em\u003e\u003csup\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sup\u003e (s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e9.9\u0026thinsp;\u0026plusmn;\u0026thinsp;4.0\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.997\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.985\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003ePseudo\u003c/em\u003e-second-order\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003ee,calc\u003c/em\u003e\u003c/sub\u003e (mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003ek\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e \u003cem\u003e\u0026times; 10\u003c/em\u003e\u003csup\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sup\u003e \u003cem\u003e(\u003c/em\u003eg mg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.2\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.998\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.986\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eThe diclofenac adsorption isotherms were measured also in aqueous solution. They were adjusted to the Langmuir-Freundlich and Freundlich equations and the resulting parameters are shown in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. The calculated curves fitted well with experimental values and the maximal adsorption capacity (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e) predicted for ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) with the Langmuir-Freundlich equation resulted beyond the experimental measurement range, because the adsorbent did not achieve saturation. In contrast, the \u003cem\u003eq\u003c/em\u003e\u003csub\u003em\u003c/sub\u003e value of 14.7 mg g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was obtained for the composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) and it is similar to the experimental value. This equation reflects a clear different heterogeneity of both materials since n \u0026lt; 1 for ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) and n \u0026gt; 1 for Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e). However, it is not possible to make a direct comparison of both materials by observing the parameters from the Langmuir-Freundlich equation. Then, with the Freundlich equation, the ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) and Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) fitting parameters of the adsorption isotherm fitted similarly. Comparison of the constant \u003cem\u003ek\u003c/em\u003e\u003csub\u003eF\u003c/sub\u003e suggests that affinity towards diclofenac is higher for the composite Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) than for ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e), although the adsorption capacity is lower. The last implies that some cavities in the coordination polymer are blocked by iron oxide particles changing not only the specific surface area but also the affinity towards diclofenac in the composite.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab4\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eLangmuir-Freundlich and Freundlich parameters for diclofenac adsorption from aqueous solution at 25\u0026deg;C on ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e)and the composite.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eZIF-14 (\u003cem\u003eqtz\u003c/em\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eFe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eLangmuir-Freundlich\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e (mg g\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e55.5\u0026thinsp;\u0026plusmn;\u0026thinsp;60.9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e14.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.4\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003ek\u003c/em\u003e\u003csub\u003eLF\u003c/sub\u003e (mg g\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.02\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003en\u003c/em\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.19\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csub\u003eLF\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.992\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.997\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eFreundlich\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003ek\u003c/em\u003e\u003csub\u003eF\u003c/sub\u003e (mg g\u003csup\u003e-1\u003c/sup\u003e)(L mg\u003csup\u003e-1\u003c/sup\u003e)\u003csup\u003e1/\u003cem\u003en\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003en\u003c/em\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.62\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.53\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csub\u003eF\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.991\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.982\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe comprehensive characterization of our synthesized materials, utilizing techniques such as ATR-FTIR, N\u003csub\u003e2\u003c/sub\u003e adsorption, powder XRD, M\u0026ouml;ssbauer spectroscopy, SEM, EDS, diffuse reflectance, XPS, and magnetization, reveals that magnetic particles (a mix of magnetite and maghemite) are effectively embedded within the ZIF-14 (qtz) matrix. This incorporation stabilizes the small iron oxide domains, necessary to provide the superparamagnetic behavior to the composite. Our findings indicate that while Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) composite exhibits a lower diclofenac adsorption capacity compared to ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e), likely due to iron oxide particles occupying some of the cavities it exhibits a higher affinity for diclofenac, as evidenced by the analysis of \u003cem\u003ek\u003c/em\u003e\u003csub\u003eLF\u003c/sub\u003e, \u003cem\u003ek\u003c/em\u003e\u003csub\u003eF\u003c/sub\u003e, \u003cem\u003ek\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003ek\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e values. Moreover, the composite can be easily recovered with the assistance of a common commercial magnet. A higher photocatalytic activity is also expected in the composite due to the presence of iron oxides. The thorough characterization and adsorption experiments were important to evaluate the effect of adsorption, even if modest, and will be involved in future photocatalytic studies, including the identification of photo-induced by-products and understanding the role of iron species. In summary, the presence of superparamagnetic particles improves the adsorption performance of the ZIF, and the \u0026ldquo;\u003cem\u003eone-pot\u003c/em\u003e\u0026rdquo; synthesis method should be considered as a straightforward approach for the synthesis of ZIF and MOF composites in aqueous solutions.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eCompeting interests\u003c/h2\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eThis work was supported by Consejo Nacional de Humanidades Ciencias y Tecnolog\u0026iacute;as (CONAHCYT) and the National Science Foundation (NSF).\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eThe datasets generated during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eE. R. Z.: Conceptualization, methodology, validation, formal analysis, investigation, writing of the original draft, visualization, writing, review, editing of the published work. D. C. P.: Methodology, review, and editing. J. F. M.: Measurements, discussion and review of the final manuscript. K. R. S. L.: Measurements, discussion and review of the final manuscript. S. A. S. H.: Measurements, formal analysis, review of the final manuscript. K. E. K.: Methodology and resources. M. P. E. G: Conceptualization, methodology, formal analysis, validation, review, edition of the final manuscript and resources. All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgements\u003c/h2\u003e\n\u003cp\u003eThis work was supported by Consejo Nacional de Humanidades, Ciencias y Tecnolog\u0026iacute;as (CONAHCyT) via a postdoctoral grant (CVU 546339) and the National Science Foundation (CHE-2044462). We thank M. E. de Anda Reyes for magnetic measurements.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eWorld Health Organization (WHO), \u0026ldquo;Drinking-water,\u0026rdquo; (2023). https://www.who.int/news-room/fact-sheets/detail/drinking-water (accessed September 20, 2023).\u003c/li\u003e\n\u003cli\u003eG. Orive, U. Lertxundi, T. Brodin, P. Manning, Greening the pharmacy, Science 377 (2022) 259\u0026ndash;260. https://doi.org/10.1126/science.abp9554.\u003c/li\u003e\n\u003cli\u003eC.B. Anucha, I. Altin, E. Bacaksiz, V.N. Stathopoulos, Titanium dioxide (TiO₂)-based photocatalyst materials activity enhancement for contaminants of emerging concern (CECs) degradation: In the light of modification strategies, Chemical Engineering Journal Advances 10 (2022) 100262. https://doi.org/10.1016/j.ceja.2022.100262.\u003c/li\u003e\n\u003cli\u003eB. Bonnefille, E. Gomez, F. Courant, A. Escande, H. 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Yazdani, Influence of MWCNTs on the formation, structure and magnetic properties of magnetite, Mater Sci Semicond Process 40 (2015) 152\u0026ndash;157. https://doi.org/10.1016/j.mssp.2015.06.055.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"pharmaceuticals, magnetic material, coordination polymer, water pollution, Zeolitic Imidazolate Framework","lastPublishedDoi":"10.21203/rs.3.rs-3952171/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3952171/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe global presence of pharmaceutical pollutants in water sources represents a burgeoning public health concern. Recent studies underscore the urgency of addressing this class of emerging contaminants. In this context, our work focuses on synthesizing a composite material, Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e), through a streamlined \u003cem\u003eone-pot\u003c/em\u003e reaction process, as an adsorbent for diclofenac, an emerging environmental contaminant frequently found in freshwater environments and linked to potential toxicity towards several organisms such as fish and mussels. A thorough characterization was performed to elucidate the structural composition of the composite. The material presents magnetic properties attributed to its superparamagnetic behavior, which facilitates the recovery efficiency of the composite post-diclofenac adsorption. Our study further involves a comparative analysis between the Fe\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003ey\u003c/sub\u003e/ZIF-14 (\u003cem\u003eqtz\u003c/em\u003e) and a non-magnetic counterpart, comprised solely of 2-ethylimidazolate zinc polymer. This comparison aims to discern the relative advantages and disadvantages of incorporating magnetic iron oxide nanoparticles in the contaminant removal process facilitated by a coordination polymer. Our findings reveal that even a minimal incorporation of iron oxide nanoparticles substantially enhanced the composite\u0026rsquo;s overall performance in pollutant adsorption.\u003c/p\u003e","manuscriptTitle":"Comparison of ZIF-14 (qtz) and a One-pot Synthesized Superparamagnetic Iron Oxide/ZIF-14 (qtz) Composite for the Adsorption of Diclofenac","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-02-15 16:06:32","doi":"10.21203/rs.3.rs-3952171/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"ba50bdb8-f72b-4315-989a-821bbb337747","owner":[],"postedDate":"February 15th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-02-27T17:11:15+00:00","versionOfRecord":[],"versionCreatedAt":"2024-02-15 16:06:32","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3952171","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3952171","identity":"rs-3952171","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}