Stepwise Dehydration Research Articles

Latent Solvent Induced Reliable Interfacial Chemistry Toward Highly Reversible Zn Anodes

AbstractAqueous zinc‐ion batteries have garnered renewed interest owing to their inherent safety and cost‐effectiveness. However, Zn anode suffers from notorious side reactions and dendrite growth, compromising the battery performance. Designing anion‐containing solvation structures to facilitate the in situ formation of a solid electrolyte interphase (SEI) layer proves effective in protecting Zn anode, yet balancing the inherent interactions between the cations‐solvents and cations–anions remains a significant challenge. Herein, latent solvent (hexafluoroisopropanol) with specific anion‐philic and cation‐phobic properties is introduced, which can remarkably increase Zn(TFSI)2 solubility in water and induce anion‐containing solvation structures. The introduction of latent solvent enables anions to preferentially decompose, giving rise to an anion‐derived SEI layer. More interestingly, the direct anion‐cation interaction endows Zn2+ species with stepwise dehydration, minimizing the adsorption of water on Zn anode. The anion‐derived SEI layer and optimized de‐solvation process work in synergy to enable homogeneous Zn deposition and ensure high reversibility. When coupled with a NaV3O8·1.5H2O (NVO) cathode, the resultant full cell delivers a high‐capacity retention of 87.8% after 2000 cycles at 1 A g−1. This work provides valuable insights into the advanced latent solvent electrolyte design and beyond.

Cryopreservation of Abies alba × A. numidica and Pinus nigra embryogenic tissues by stepwise dehydration method

BackgroundCryopreservation makes it possible to preserve plant biodiversity for thousands of years in ex situ storage. The stepwise dehydration method is a simple and versatile cryopreservation technique based on the vitrification phenomenon. However, the commonly used dimethyl sulfoxide (DMSO) in this cryopreservation technique is considered harmful for plant material, thus alternative methods are needed to be applied.ResultsIn this study, the possibility of cryopreservation of embryogenic tissues (ETs) of Abies alba x A. numidica and Pinus nigra was investigated. Before freezing, ETs were partially dehydrated in the presence of increasing concentrations of sucrose (from 0.25 to 1.0 M) for 7 days, followed by desiccation of the tissues over silica gel for 2 and 2.5 h, respectively. After these pretreatments, the plant material was frozen in liquid nitrogen (LN; –196 °C). For both coniferous trees the ET survival rate was high and reached 84.4% for A. alba x A. numidica (28 days) and 86.7% for P. nigra (35 days) after recovery of the tissues from liquid nitrogen (LN). The regenerated tissue of A. alba x A. numidica was characterized by more intense growth after storage in LN compared to tissue that had not been cryopreserved (control). The tissue of this tree also undertook relatively rapid growth after thawing from LN. In turn, the ET growth of P. nigra was significantly lower after thawing compared to the other treatment.ConclusionsThe present study demonstrated, that the stepwise dehydration method could be successfully applied to the cryostorage of ETs of both studied trees. To the best of our knowledge, this is the first report on ET cryopreservation based on this method for Abies and Pinus genus representatives, which may be the alternative way for efficient, long-term preservation of germplasm in LN.

Emission characteristic of OVOCs, I/SVOCs, OC and EC from wood combustion at different moisture contents

Wood combustion is an important source of organic compounds, and its emission characteristics are affected by many factors, among which fuel moisture content (MC) is poorly understood. In this study, wood with MC of 2.5%, 10.9%, 19.2%, 31.4%, and 43.2% were prepared by stepwise dehydration of fresh pine, and burned separately in a quartz tube furnace at different ignition temperatures (400, 600, and 800 °C), in order to discuss the effects of MC on the emission characteristics of gas- and particle-phase organic compounds. The results showed that the effects of MC on the emission factors (EFs) of organic compounds were significant. When MC was close to 10%, the average EFs of carbonyl compounds (CCs), intermediate volatile organic compounds (IVOCs), polycyclic aromatic hydrocarbons (PAHs), n-alkanes, organic carbon (OC), and elemental carbon (EC) were 832.0 ± 518.5, 439.3 ± 111.6, 44.3 ± 6.6, 59.3 ± 9.3 mg/kg, and 2.4 ± 0.2, 0.8 ± 0.8 g/kg, respectively whereas when MC was near 30%, all the EFs reached the maximum and were 2.4, 3.1, 2.6, 4.2, and 3.1 times the lowest values, respectively. The MC and ignition temperature together affected the composition of organic compounds, with different organic profiles observed at various MCs when the temperature increased from 400 to 800 °C. For example, at MC ≈ 10%, the proportion of unresolved complex mixture (UCM) in IVOCs decreased from 59.7% to 43.4%, while the proportion of 5-6-ring PAHs increased from 7.4% to 35.4%. However, at MC ≈ 30%, formaldehyde and acetaldehyde in CCs decreased from >60% to ∼40%. In brief, the influence of MC may explain to a large extent the differences in organic emission characteristics of wood burned in the stove and open burning, and MC should be further considered in the experiments on the measurement of organic compound emissions from biomass burning.

Acid–Base Property of Tetragonal YNbO4 with Phosphate Groups and Its Catalysis for the Dehydration of Glucose to 5‐Hydroxymethylfurfural

Acid–base properties of amphoteric crystalline YNbO4, which is synthesized by co‐precipitation method using a water‐soluble Nb peroxo complex, are adjusted by the impregnation of phosphate groups. The resulting phosphate–YNbO4 materials are tested for glucose dehydration to 5‐hydroxymethylfurfural (HMF). Both activity and selectivity increase by the introduction of phosphate groups, giving the optimal catalyst with five phosphate groups per nm2 of surface (5P‐YNbO4). 5P‐YNbO4 shows ≈50% selectivity at 75% conversion. Pyridine adsorption experiments show that 5P‐YNbO4 exclusively possesses Lewis acidity. NH3‐ and CO2‐temperature programmed desorption measurements confirm that phosphoric acid treatment increases acid strength and acid density with concurrent loss of basicity. Experiments using isotope‐labeled glucose clarify that HMF is formed on 5P‐YNbO4 through the stepwise dehydration reaction mechanism. Recyclability experiments show an accumulation of carbon deposits at the end of each reaction causing deactivation, but the activity can be completely recovered by successive washing with water and subsequent calcination at 400 °C in air.

Stepwise dehydration of thomsonite (THO) with disordered Si/Al distribution: A new partially hydrated phase

The structural transformations occurring as a function of increasing temperature in zeolites are of interest because the porous structure, and therefore the physical properties, can significantly change.Zeolites with THO framework type are small-pore materials, which received attention because of their applications in catalytic processes. The majority of THO zeolites (synthetic and natural) are characterized by an ordered distribution of the cations at the tetrahedral sites. To date, few cases of disordered thomsonite have been reported. In this study, we investigated the dehydration behaviour of a natural thomsonite with disordered Si/Al distribution and chemical composition Ca3·34Na2·66Si11Al9O40∙12H2O. The structure was determined from room temperature (RT) to 698 K in order to compare the thermal behaviour with that reported for the ordered variety. Accurate structural analysis was performed by in situ single crystal X-ray diffraction. The dehydration starts at 348 K. Up to 498 K, thomsonite gradually releases four H2O. From 498 to 573 K, additional four H2O are lost and the space group changes from orthorhombic (Pbmn) to monoclinic (P21/n). This partially hydrated phase is characterized by a unit-cell volume contraction of −3% with respect to the RT phase and by a rearrangement of the extraframework cations in the zeolitic pores. The thermally treated thomsonite is able to reabsorb 50% of the lost H2O and transforms to the orthorhombic phase, equivalent to that observed at lower temperatures. However, the diffraction pattern analysis indicated a high degree of mosaicity, most probably due to the residual stress accumulated during the phase transformation.

Mechanism elucidation of stepwise dehydration of pharmaceutical hydrate crystals by structure determination from powder diffraction data

Mechanism elucidation of stepwise dehydration of pharmaceutical hydrate crystals by structure determination from powder diffraction data

Mycoremediation and toxicity assessment of textile effluent pertaining to its\xa0possible correlation with COD

Globally, textile industries are one of the major sectors releasing dye pollutants. This is the first report on the positive correlation between toxicity and chemical oxygen demand (COD) of textile effluent along with the proposed pathway for enzymatic degradation of acid orange 10 using Geotrichum candidum within a very short stretch of time (18 h). Removal efficiency of this mycoremedial approach after 18 h in terms of chemical oxygen demand, biological oxygen demand, total suspended solids, salinity, color and dye concentration in the treated effluent reached to 98.5%, 56.3%,73.2%, 64%, 89% and 87% respectively. Also there was a decrease in pH of the treated effluent. FTIR analysis of the treated effluent confirmed biodegradation. The LCMS analysis showed the degradation of acid orange 10, which was confirmed by the formation of two biodegradation products, 7-oxo-8-iminonapthalene-1,3-disulfonate and nitrosobenzene, which subsequently undergoes stepwise hydrogenation and dehydration to form aniline via phenyl hydroxyl amine as intermediate. The X-ray diffraction studies showed that heavy metal content in the treated effluent has reduced along with decrease in % crystallinity, indicating biodegradation. The connection between toxicity and COD was also inveterated using Pearson’s correlation coefficient. Further the toxicological studies indicated the toxicity of raw textile effluent and relatively lower toxic nature of metabolites generated after biodegradation by G. candidum.

Stepwise dehydration of Cd-exchanged levyne: thermal stability and structural modifications

Zeolites show remarkable properties that can be tuned through cation exchange of their original extraframework content. In this respect, the response of the modified zeolite to the heating stimuli, in terms of structural modifications and thermal stability, can drastically change and is, therefore, an important factor to consider. In this study, the dehydration mechanism of a natural levyne previously exchanged with Cd2+ has been monitored in situ by single crystal X-ray diffraction. The initial dehydration trend between 50 and 175 °C is similar to that observed for the pristine material, levyne-Ca. The water loss is accompanied by extraframework cation migration within the zeolitic cavities and the unit-cell volume slightly contracts from 3503.8(1) to 3467.8(6) Å3. From 200 to 250 °C, a pronounced drop of the unit-cell volume (− 7%) is observed. The dehydrated structure at 250 °C corresponds to levyne B topology of natural levyne, characterized by the statistical rupture of the T–O–T bonds of the double six-ring membered cage. However, in contrast to levyne-Ca, the fraction of broken connections reached 50% instead of 37%, and no additional structural modifications were detected up to 350 °C. At 400 °C, diffraction data pointed to the onset of the structural collapse. At this temperature, the measured unit-cell volume was 8% smaller compared to that of the RT structure. The corresponding contracted structure did not rehydrate after exposure to humid conditions for 21 days.

Influence of Confinement on Barriers for Alkoxide Formation in Acidic Zeolites

AbstractThe influence of the confinement imposed by eight different zeotypes on the formation of the alkoxides of 13 primary alcohols is studied using dispersion corrected density functional theory calculations with the PBE‐D3 functional. Adsorption energies of the alcohols are computed along with barriers for formation of the alkoxides, which is the first step of the stepwise dehydration mechanism. We find that variations in the adsorption and transition state energies are largely governed by van der Waals interactions between substrates and the zeolite framework. Trends between different reactants, on the other hand, are largely due to the size of the molecules, which can be described quantitatively by the number of atoms constituting them. We find that the stabilization of adsorbates is largest for frameworks that are neither too small, leading to repulsive interaction, nor too spacious leading only to weak interaction.

Hydrates of calcium citrate and their interconversion in relation to calcium bioaccessibility

Calcium citrate tetrahydrate (CCT) and hexahydrate (CCH) precipitates from aqueous solutions of CaCl2 and sodium citrate above and below the transition temperature of 52 °C, respectively. The CCT, the dihydrate (CCD) and anhydrate (CCA) as obtained by a stepwise dehydration of solid CCH have enthalpy of dehydration of ΔH0CCH to CCT = 43.6, ΔH0CCT to CCD = 43.8, and ΔH0CCD to CCA = 88.1 kJ∙mol−1 as measured by DSC. WAXS measurements demonstrate a stepwise decrease in unit cell size upon dehydration, and a stronger binding of the two first water compared to additional. The increasing negative enthalpy of dissolution, as calculated from the temperature dependence of solubility (10–90 °C), +21 kJ∙mol−1 (CCH), –20 kJ∙mol−1 (CCT), –22 kJ∙mol−1 (CCD), and –40 kJ∙mol−1 (CCA) shows along the series of hydrates with increasing solubility, enthalpy–entropy compensation with an isoequilibrium temperature of 49 °C. Conversion of CCD and CCA in aqueous solutions yields the more soluble CCT, not the stable CCH in agreement with Ostwald’s stage law, increasing calcium bioaccessibility under physiological conditions in intestines.

Towards understanding and predicting the hydronium ion catalyzed dehydration of cyclic-primary, secondary and tertiary alcohols

The varying steric environment of zeolites subtly influences the rates of hydronium-ion-catalyzed dehydration of alcohols containing a cyclohexyl group in aqueous phase. The investigated primary, secondary, and tertiary alcohols show an increasing stabilization of an ionic transition state in this sequence, i.e., an increasing tendency to move from a concerted (E2 mechanism) to a stepwise dehydration (E1 mechanism). Hydronium ions confined in the micropores of MFI and BEA zeolites induced much higher catalyzed rates than those in the aqueous phase. Independent of the reaction mechanism and the environment, however, all alcohols investigated follow one compensation correlation between activation enthalpy and entropy for primary, secondary, and tertiary alcohols, respectively. For a given transition enthalpy, the rate of dehydration is the higher the larger the reaction space (translated to the reaction entropy). Surprisingly, all compensation relations intersect in one point. These dependences for the different alcohols are also reflected in the turnover rates, for which all alcohols also intersect in a common point, which appears to mark the highest reaction rate for dehydration catalyzed by hydronium ions at the investigated temperature.

Exploring Route for Pyrophosphate‐based Electrode Materials: Interplay between Synthesis and Structure

New sodium vanadium(III) hydrogenphosphate hydrate NaV(HPO4)2(H2O)0.5 and sodium vanadium(III) hydrogenphosphate β‐NaV(HPO4)2 were prepared in mild hydrothermal conditions. The crystal structures of NaV(HPO4)2(H2O)0.5 [space group Cc, Z = 4, a = 8.46174(19) Å, b = 9.52583(19) Å, c = 8.69376(15) Å, β = 110.9553(11) °, V = 654.41(2) Å3] and β‐NaV(HPO4)2 [space group C2/c, Z = 4, a = 7.8681(3) Å, b = 9.8451(3) Å, c = 8.5180(2) Å, β = 107.626(2) °, V = 628.85(3) Å3] were solved and refined from X‐ray powder diffraction data. Both compounds were used as precursors in a new route for the preparation of attractive cathode material β‐NaVP2O7. The formation of the structure motive providing fast sodium ion diffusion at the first synthesis stage and its further conservation upon stepwise dehydration was revealed. The oversized Na+‐embedding channels are stabilized by site‐coordinated water in NaV(HPO4)2(H2O)0.5 structure. The topology resemblance and difference in known sodium vanadium(III) complex phosphates are discussed.

Thermal degradation kinetics of sepiolite

AbstractThe kinetic parameters of the thermal degradation of sepiolite were evaluated with a new method based on thermal analysis data. Thermogravimetric/differential thermal analysis curves were recorded for the natural and preheated sepiolite samples in the temperature range 25–800°C for 4 h. The temperature-dependent height of the exothermic heat flow peak for the thermal decomposition of sepiolite located at ~850°C on the differential thermal analysis curve was taken as a kinetic variable for the thermal degradation. A thermal change coefficient was defined depending on this variable because this coefficient fit to the Arrhenius equation was assumed as a rate constant for the thermal degradation. The Arrhenius plot showed that the degradation occurs in three steps. Two of these are due to stepwise dehydration and the third originated from dehydroxylation of sepiolite. Three activation energies were obtained that increase with the increasing temperature interval of the steps.

Kinetic and thermodynamic approaches on thermal degradation of sepiolite crystal using XRD-analysis

A method was proposed to use XRD-data for thermal analyses of crystalline solids. Therefore, the XRD-pattern was recorded for natural and preheated sepiolite samples at the different temperatures in the interval of 25–800 °C for 4 h. The temperature-dependent intensity (I) of the most characteristic 001 reflection was used as a crystallite variable. The assumed parameters $$k = - (\partial I/\partial T)_{\text{p}} / I$$ and $$K = \left( {1 - x} \right)/ x$$ were calculated for each heating temperature, where I0 is the intensity for the natural sample and $$x = I/I_{0}$$ is the relative crystallite of the heated ones, since the k and K supply Arrhenius equation and van’t Hoff equation behave as reaction rate constant and equilibrium constant for a chemical reaction, respectively. Arrhenius plot showed that the degradation has three kinetic steps. Two of these are due to the stepwise (1, 2) dehydration and third (3) originated from dehydroxylation of sepiolite crystal. Three activation energies were obtained such as $$E_{1}^{\# } = 8.6$$ kJ mol−1, $$E_{2}^{\# } = 28.5$$ kJ mol−1, and $$E_{3}^{\# } = 124.8$$ kJ mol−1 from the slope of three intersected straight lines which are plotted according to the Arrhenius equation. Otherwise, van’t Hoff plot indicated that the degradation has two thermodynamic steps which are due to the dehydration (1, 2) and dehydroxylation (3). The basic thermodynamic relationship, $$\Delta G^{0} = \Delta H^{0} - T\Delta S^{0} ,$$ for these steps are $$\Delta G_{1,2}^{0} = 46{,}933 - 65.7T$$ and $$\Delta G_{3}^{0} = 143{,}491 - 177.1T$$, respectively. Finally, the spontaneous tendency for the thermal degradation was discussed.

Synthesis of HfO2 from hafnium hydroxide hydrate

A comprehensive study of processes taking place during synthesis and subsequent thermal treatment of hafnium oxide was performed. Synthesis of HfO2 involves following stages: stepwise dehydration of hydrated hafnium hydroxide, crystallization of metastable tetragonal phase of HfO2 and subsequent irreversible transition to the stable monoclinic modification. Preliminary heat treatment lowered temperature of crystallization of HfO2 and resulted in changing process mechanism.

Reversible hydration/dehydration and thermal expansion of euchlorine, ideally KNaCu3O(SO4)3

Anhydrous alkali copper sulfates constitute the most abundant group of mineral species from the Second Scoria Cone of the Great Tolbachik Fissure Eruption (1975–1976), a location being renowned for its great mineral diversity. Euchlorine, ideally KNaCu3O(SO4)3, is the prevalent mineral in the hot sulfate-rich zones of the fumaroles. In this work, its thermal expansion and hydration/dehydration behavior have been studied. The results of a structure refinement from new single-crystal diffraction data are also reported, and a description of the structure based on anion-centered coordination polyhedra is given. The strongly anisotropic character of the thermal expansion of euchlorine remains essentially unchanged up to its decomposition. The strongest α11 expansion is observed approximately perpendicular to the alkali interlayer of the structure, whereas the minimal α22 and α33 thermal expansion coefficients are parallel to the plane of {Cu3O(SO4)3}2− layers. Hydration experiments controlled by X-ray powder diffraction reveal a very complex behavior with multicomponent phase formation. Remarkably, upon heating stepwise dehydration occurs, whereby the complex mixture of hydrated sulfates gradually reverses and becomes again essentially single-phased anhydrous euchlorine.

Thermal treatment of a mixture for the NaP zeolite synthesis based on sodium metasilicate and alumina: Effect of ultrasound

The thermal behavior of a mixture of sodium metasilicate, aluminum hydroxide and silicagel has been studied. The mixture was intended for the NaP zeolite synthesis; the atomic ratio of Si:Al was 2:1. To intensify heterophase processes in suspensions, the ultrasonic treatment with a frequency of 22 kHz was used. Suspensions were evaporated, molded into pellets and dried. X-ray diffraction, scanning electron microscopy, and synchronous thermal analysis have been used for testing. After calcination of the samples at 700 °C, α-Na2Si2O5 and β-Na2Si2O5 as well as the X-ray amorphous phase were detected. It was shown that preliminary ultrasonic treatment allows obtaining particles with smaller particle size and coherent scattering region dimension, as well as a greater value of microdeformations for above-mentioned crystalline phases. It was demonstrated that stepwise dehydration was observed during the heating of the specimens. It was shown that preliminary ultrasonic treatment allows reducing dehydration temperatures from 3 to 10 °C. The values of the apparent activation energy and the preexponential factor have been calculated by differential method (Friedman analysis) and integral methods (Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose analyzes). It was demonstrated that these analyzes yielded close values. It was established that the values of the apparent activation energy of the dehydration processes for the specimen after ultrasonic treatment are 50–100 kJ mol−1 less than for the specimen without ultrasound. All mentioned effects have been explained by the increase in the defectiveness of a solid as a result of the impact of shock waves which are produced during cavitation at the ultrasonic treatment of the suspension.

Comparative Investigation of the Thermoresponsive Behavior of Two Diblock Copolymers Comprising PNIPAM and PMDEGA Blocks.

The thermoresponsive behavior of two diblock copolymers PS- b-PNIPAM and PS- b-PMDEGA, which both comprise a hydrophobic polystyrene (PS) block but different thermoresponsive blocks, also differing in length, poly( N-isopropylacrylamide) (PNIPAM) and poly(methoxy diethylene glycol acrylate) (PMDEGA), respectively, was comparatively investigated in a wide temperature range. Concentrated aqueous solutions containing 25 wt % polymer were studied by small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and broadband dielectric spectroscopy (BDS). DSC measurements show that, during the demixing phase transition, the hydration number per oligo(ethylene glycol) side chain in the PS- b-PMDEGA solution decreases rather gradually, even up to 20 °C above the onset of the transition, i.e., the cloud point (CP). In contrast, the PS- b-PNIPAM solution exhibits an abrupt, stepwise dehydration behavior at its CP, indicated by the sharp, narrow endothermic peak. BDS measurements suggest that the organization of the expelled water during the phase transition and the subsequent evolution of the micellar aggregates are different for the two copolymers. In the PS- b-PMDEGA solution, the long-range charge transport process changes significantly at its CP and strong interfacial polarization processes appear, probably due to charge accumulation at the interfaces between the micellar aggregates and the aqueous medium. On the contrary, in the PS- b-PNIPAM solution, the phase transition has only a marginal effect on the long-range conduction process and is accompanied by a reduction in the high-frequency (1 MHz) dielectric permittivity, ε'. The latter effect is attributed to the reduced polarization strength of local chain modes due to an enhancement of intra- and interchain hydrogen bonds (HBs) in the polymer-rich phase during the water detaching process. Surprisingly, our BDS measurements indicate that prior to both the demixing and remixing processes the local chain mobility increases temporally. Our dielectric studies suggest that for PS- b-PNIPAM the water detaching process initiates a few degrees below CP and that the local chain mobility and intra- and/or interchain HBs of the PNIPAM blocks may control its thermoresponsive behavior. Dielectric "jump" experiments show that the kinetics of micellar aggregation in the PS- b-PMDEGA solution is slower than that in the PS- b-PNIPAM solution and is independent of the target temperature within the two-phase region. From the experimental point of view, it is shown that the dielectric susceptibility, especially, the dielectric permittivity, ε', is a well-suited probe for monitoring both the reversible changes in the molecular dipolar bond polarizability and the long-range interfacial polarization at the phase transition.

Copper(II) Dihalotetracyanoplatinate(IV) Coordination Polymers and Their Vapochromic Behavior

The coordination polymers [Cu(H2O)2(μ2-NC)4PtX2] (X = Cl, Br) form networks of square grid sheets that align in a staggered manner with one another via weak X···X interactions. Upon stepwise dehydration, the layers fuse, forming a 3-D network of distorted cubes. The materials were tested for visible vapochromic, Raman, and IR response to dimethyl sulfoxide, N,N-dimethylformamide, and pyridine. Analyte-bound coordination polymers of the form Cu(analyte)2[PtX2(CN)4] were structurally characterized by PXRD and found to form layers of square grids that align through X···X interactions. The reaction of [Cu(H2O)2(μ2-NC)4PtX2] with concentrated aqueous NH3 generated [PtBr(CN)4(NH3)]- and [PtCl(CN)4(OH)]2- anions that were incorporated into 1-D chain structures. UV-visible reflectance data show that a combination of shifting d-d transitions and the visible Br-Pt LMCT absorption band in [Cu(H2O)2(μ2-NC)4PtBr2] results in a greater vapochromic effect in comparison to that in chlorine-containing analogues.

Tunability in Metal Coordination Sphere, Ligand Coordination Mode, Network Topology, and Magnetism via Stepwise Dehydration Induced Single-Crystal to Single-Crystal Transformation

Stimuli-responsive solid-state crystal dynamics or flexibility in metal–organic frameworks (MOFs) showing multiple structure changes is an arising interest for understanding the structure–property relationship and designing functional materials. In this article, dehydration-induced stepwise single-crystal to single-crystal (SC–SC) transformations are observed in two-dimensional 63-topological coordination polymer [Co(H2L)(H2O)2]·H2O (1), where H4L is 3,5-bis(3′,5′-dicarboxylphenyl)-1H-1,2,4-triazole. Upon thermal dehydration at 130 °C for 2 h, half lattice water in 1 can be released to form [Co(H2L)(H2O)2]·0.5H2O (2). By increasing dehydration temperature to 150 °C for 3 h, the third phase [Co(H2L)(H2O)2] (3) that is free of lattice water molecule is gained. Further increasing the dehydration temperature to 160 °C for 6 h, one of coordination water molecule can be released, giving rise to dicobalt-based 2D (3,6)-connected kgd double layer [Co(H2L)(H2O)] (4). During stepwise dehydration SC–SC transformation courses, coordination sphere of Co(II) changes from penta-coordinate trigonal bipyramid to hexa-coordinate octahedra; H2L2– ligates from (κ1)–(κ1)–(κ1)−μ3–H2L2–, (κ1)–(κ1)–(κ2)−μ3–H2L2– to (κ1–μ2)–(κ1)–(κ2)−μ4–H2L2–; network topology ranges from 3-connected 63-hcb to (3,6)-connected kgd; magnetism changes from single-ion behavior of Co(II) to intradicobalt ferromagnetism.