Benzenepentacarboxylic Acid Research Articles

Using the benzenepolycarboxylic acid (BPCA) method to assess activated biochars and their PFAS sorption abilities

Activated carbon (AC) has important industrial and environmental applications as it has excellent abilities to sorb contaminants such as per- and polyfluoroalkyl substances (PFAS). Current research aims to develop activated biochars (AB) from renewable biomass to replace AC that is produced from fossil feedstock. Both AC and AB are primarily comprised of condensed aromatic carbon (ConAC), the component that is the focus of this study. ConAC is characterized to determine its relationship with biochar activation conditions and PFAS sorption, which are understudied at present.Benzenepolycarboxylic acid (BPCA) markers for ConAC were quantified in steam-activated biochars (AB-Steam) and carbon dioxide-activated biochars (AB-CO2) prepared from waste timber at different temperatures (800, 850, 900 °C) and molar ratios of feedstock-carbon:steam (0.50 – 1.25). A non-activated biochar was also included as a reference. ConAC relative to total organic carbon content was higher in AB-Steam than in AB-CO2 (92 ± 2 % vs. 81 ± 11%). The ratio of benzenehexa- (B6CA) to benzenepentacarboxylic (B5CA) acids revealed that AB-Steam also had larger ConAC clusters than AB-CO2. These findings provide novel evidence that steam activation is more effective than CO2 activation in creating ConAC.To assess how ConAC impacts AB sorption abilities, AB-Steam were used to remediate PFAS from contaminated soils. The observed strong correlations between ConAC content and sorption of long-chain PFAS suggest the importance of hydrophobic interactions between PFAS tails and ConAC. Poor correlations for short-chain PFAS, on the other hand, indicated the existence of electrostatic repulsion interactions between PFAS head groups and ConAC. Collectively, these results explain the great ability of AB-Steam to sorb PFAS from contaminated soils (up to 100% remediation). More broadly, this work demonstrates that the BPCA method can be a valuable tool to assess the quality of biochars and other carbonaceous sorbents in relation to their production conditions or contaminant sorption abilities.

Insight into structure features of coals with different metamorphic degrees via step-wise oxidation

A step-wise oxidation method, combining H2O2 oxidation and alkali-oxygen oxidation (AOO), was applied to study the structure features of coals with different metamorphic degrees. The results show that the conversion of Baiyinhua coal, Hongshaquan coal, Pingshuo coal and Hongliulin coal in 30 % H2O2 solution for 10 h at 60 °C are 89.8 wt%, 79.0 wt%, 29.5 wt%, and 14.8 wt%, respectively. The oxygen containing species retrieved from water-soluble product by ethyl acetate extraction are mainly concentrated in O4-O8 class species, including aliphatic carboxylic acids with a carboxylic range of 1–5 and carbon numbers from 3 to 11, and phenols or aromatic carboxylic acids of 1–3 ring. The residues from H2O2 oxidation of four coals can be completely depolymerized through AOO. The maximum benzene carboxylic acid (BCA) yield of RBYH is 7.66 wt%, while that of RHSQ, RPS, and RHLL are 18.24 wt%, 19.52 wt%, and 19.91 wt%, respectively. The AOO products of four residues show the similar BCA distributions, and mellitic acid, benzenepentacarboxylic acid, pyromellitic acid, trimellitic acid, hemimelitic acid, and phthalic acid are the main BCAs. Therefore, step-wise oxidation can be used as an effective method to understand the structural features of coal, including the small molecule structures obtained after breaking weak bonds and the aromatic substitution information in the residue.

Benzenepoly(carboxylic acid)s as Exclusive Intrinsic Markers to Assess Riverine Export of Dissolved Black Carbon.

Landscape fires annually generate large quantities of black carbon. The water-soluble fraction of black carbon (i.e., dissolved black carbon/DBC) is an important constituent of the dissolved organic carbon (DOC) pool, playing a crucial role in the global budget of refractory carbon and climate change. A key challenge in constraining the flux and fate of riverine DBC is to develop targeted and accurate quantification methods. Herein, we report that benzenepentacarboxylic acid (B5CA) intrinsically present in DBC can be used as an exclusive and holistic marker (representing both condensed aromatics and less-/nonaromatic fractions) for DBC quantification. B5CA was universally detected in water extractions of biochar and fire-affected soils with relatively large abundance but not produced by nonthermogenic processes. It has good mobility in the environment as it is not readily precipitated by cations or adsorbed by common geosorbents. B5CA also represents the recalcitrant components of DBC with excellent stability against photodegradation and biodegradation. Applying B5CA as the DBC marker in surface waters of the Changjiang River (i.e., the third largest river in the world), we calculate the DBC concentration in the downstream Changjiang River to be 4.8 ± 5.5% of the DOC flux. Our work provides a simple and reliable approach for the accurate quantification and source tracking of DBC in the soil and aquatic carbon pools.

Systematic separation of carboxylic acids from H8[PMo7V5O40]-catalyzed lignite oxidation products via deep eutectic solvent

To separate the valuable carboxylic acids (CAs) from the complicated oxidized products (OPs) of H8[PMo7V5O40]-catalyzed lignite, systematic processes including distillation, ether extraction, acetone dissolution and separation by deep eutectic solvent (DES) were first constructed and sequentially performed. First, formic acid and acetic acid are separated in vacuum at 56 °C with the separation efficiency of 95% and 82%, respectively. Subsequently, sequential treatments of OPs by ether extraction and acetone/water dissolution are implemented to reduce the low-polarity compounds contents and fully dissolve CAs from concentrated residue. Separation results indicate that choline chloride (ChCl) shows a better separation performance compared to acetylcholine chloride and gives optimal separation efficiencies of 78.19% and 94.45% for benzenepentacarboxylic acid (BPA) and mellitic acid (MLA) within 2 h at ambient temperature, respectively. The hydrogen-bonded binding energies (BEs) formed in DES are calculated based on density functional theory, and results show that total BEs of MLA and ChCl is as high as −31.09 kcal/mol, and the next is −26.79 kcal/mol for BPA, leading to their quick and high separation efficiencies within 2 h. As a result, only MLA and BPA show the high correlation with pseudo-second-order kinetic model, and the rate constant of MLA is as high as 0.3367 g/(mg·h), which is far more than that of BPA. Additionally, the effect of hydrogen bonds on the separation of CAs follows the order of Cl∙∙∙H-O > O-H∙∙∙O-C > O-H∙∙∙O = C. Overall, this attractive strategy provides ideas for efficient separation of CAs, which will pave the way for utilization of lignite.

Structural evolution characteristics of lignite during pyrolysis based on alkaline-oxygen oxidation, NMR and FTIR

Pyrolysis is a crucial conversion process for lignite to improve its quality and produce chemicals. Here, the evolution characteristics and pathways of lignite during pyrolysis were investigated by the combination of oxidation product distribution and physical structural parameters, which reflected the correlations between the size of aromatic clusters and pyrolysis temperature. The results showed that with increasing the pyrolysis temperature up to 500 ℃, the aromatic structures were enriched, and the average size of aromatic clusters increased with pyrolysis temperature. A little variation of interlayer spacing (d002) was observed, while the stacking height (Lc) and the average lateral size (La) increased gradually. Before 400 ℃, double-aromatic clusters were dominant in chars, and the corresponding chars were abundant with precursor structures of the alkaline-oxygen oxidation products benzene tricarboxylic acid (BCA3), benzene tetracarboxylic acid (BCA4) and benzene pentacarboxylic acid (BCA5). Above 400 ℃, more triple- or quadruple-ring aromatic clusters were present, and the precursor structures of benzene dicarboxylic acid (BCA2), benzene tricarboxylic acid (BCA3), and benzene tetracarboxylic acid (BCA4) increased considerably. The results indicate that the benzene carboxylic acids (BCAs) from oxidation are an effective evaluation method to reflect the abundance of aromatic rings in the parent structure of coals.

Effect of preoxidation treatment with H2O2 on ruthenium ion-catalyzed oxidation of Yima long flame coal

Environmental concerns have led researches to investigate carbon neutral and sustainable strategies to satisfy well-being of present and future generations, in which coal oxidation becomes a promising approach to achieve this goal. In this study, Yima long flame coal (YLFC) was subjected to ruthenium-ion-catalyzed oxidation (RICO) after peroxidation with H2O2 (PO). The results indicate that the organic matter in YLFC is mainly oxidized into benzenecarboxylic acids, accounting for 70.36% of all the oxidation products, and the yields of the valuable resulting carboxylic acids are significantly elevated by PO from 12.99 wt% to 35.06 wt%, leading to a higher utilization of carbon and lower CO2 emission. Moreover, PO can enhance remarkably the reactivity of the macromolecular precursors of coals, especially highly condensed aromatic species to produce benzenepentacarboxylic acid and mellitic acid more efficiently with a 20-fold increase and 200-fold increase, which is ascribed to the formation of carboxyl groups from other oxygen-containing groups or bonds in coals via PO. The reactive intermediates OH and OOH generated from H2O2 decomposition can attack the carbon atom of alkyl side chains, ether bonds, C=O bonds, and the bridged linkages to undergo a preliminary degradation of macromolecular networks in coals and produce more active sites for the subsequent RICO, leading to the yield and species number increase of carboxylic acids via PO.

An eco-friendly approach to low-temperature and near-neutral bleaching of cotton knitted fabrics using glycerol triacetate as an activator

Near-neutral bleaching of cotton fabrics at low temperature is of great importance for saving energy and ecological friendliness in textile industry. In this work, glycerol triacetate (GT) was investigated as an activator of hydrogen peroxide (H2O2) for low temperature bleaching of cotton knitted fabrics, and satisfactory whiteness was obtained. The bleaching properties of H2O2/GT system for cotton was assessed by the CIE whiteness index (WI), H2O2 decomposition rate, concentration of generated peracetic acid and bursting strength. Possible factors affecting the properties of cotton bleached by H2O2/GT bleaching system were discussed in detail. At 60 °C, adding only 10 mmol/L GT to the hydrogen peroxide solution (60 mmol/L) to bleach cotton knitted fabrics for 60 min, the WI was significantly increased from 52.09 to 68.92. By using benzenepentacarboxylic acid as a fluorescent probe for hydroxyl radical (HO·) detection, it was found that GT could clearly promote HO· generation and its concentration closely related to the WI of cotton fabric. Furthermore, the bleaching mechanism of H2O2/GT system was proposed by exploring the relationship between WI and HO· concentration. GT as a bleach activator has more economical benefits and better water solubility than tetraacetylethylenediamine. The H2O2/GT system may provide a cost-effective and environmentally friendly bleaching approach of cotton as alternative to conventional alkaline high-temperature bleaching.

Mechanism of H2O2/bleach activators and related factors

A mechanism of H2O2/bleach activator bleaching systems was proposed by using H2O2/tetraacetylethylenediamine (TAED) system as a model. HO· concentrations of the system under different pH conditions was measured by using benzenepentacarboxylic acid as a fluorescent probe. Computational analysis of bond enthalpies of H2O2 and peracids revealed that HO· should be the most effective agent in bleaching process, and peracids formed in H2O2/bleach activator bleaching systems could more easily produce HO·. The formation of peracids in H2O2/TAED system depends on the pH values of bleaching solutions and a nucleophilic substitution of the acid derivative by peroxide anion (HOO−). Charge density on carbonyl carbons of bleach activators affects the formation of peracids as well, which was proven from these compounds of TAED, tetraacetylhydrazine, N-[4-(triethylammoniomethyl)-benzoyl]-caprolactam chloride, phthalimide, N-acetylphthalimide and nonanoyloxybenzene sulphonate. It is likely that the charge densities on carbonyl carbon of amide bleach activators should be larger than 0.185. For ester bleach activators, the results were also investigated by activation energy, Gibbs free energy and Hansen solubility parameters. In addition, the ecotoxicity of bleach activators has been evaluated by ECOSAR program. Potential bleach activators can be designed and explored according to these results instead of large amounts of experimental data.

Formation of benzene polycarboxylic acids using alkali‑oxygen oxidation of coal-tar pitch pre-treated by extraction and air-blowing

Benzene polycarboxylic acids (BPCAs) could be produced from oxidation of a coal-tar pitch (CTP) by oxygen in NaOH solution. In this work, CTP was extracted by methanol and subsequently air-blown prior to oxidation by oxygen at 260 °C for 1 h, during which the amount and condensed degree of aromatic portion obviously increased, while the oxygen-containing groups were successfully introduced into CTP. The pre-treatment of CTP not only increased the yield of BPCAs in the resulting oxidation products, but also improved the distribution of BPCAs, especially selectively increasing the content of mellitic acid and benzenepentacarboxylic acid in the BPCAs. This investigation provides a promising approach for obtaining BPCAs especially high value-added mellitic acid and benzenepentacarboxylic acid using inexpensive and underutilized CTP.

Selective production and characterization of aromatic carboxylic acids from Xianfeng lignite-derived residue by mild oxidation in aqueous H2O2 solution

Lignites show great potential as feedstock for the production of valuable carboxylic acids by mild oxidation. In this study, valuable aromatic polycarboxylic acids were produced from Xianfeng lignite-derived residue (XLDR) through mild oxidation in green aqueous H2O2 solution. The results show that XLDR oxidation can produce benzene carboxylic acids (BCAs) and polycyclic aromatic carboxylic acids (PCACAs) in high selectivity. The BCAs are dominated by mellitic acid and benzenepentacarboxylic acid with 55.5% and 13.3% in the total yield of all group components based on the analysis with gas chromatography/mass spectrometer. Moreover, three series of PCACAs with an aliphatic ring were identified by direct analysis in a real-time ionization source coupled to a time-of-flight mass spectrometer. The BCAs and PCACAs could be generated from different kinds of aromatic structures via oxidation by OH produced from H2O2.

Bleaching of cotton fabric with tetraacetylhydrazine as bleach activator for H2O2

Tetraacetylhydrazine (TH) as bleach activator for H2O2 cotton bleaching was synthesized and characterized by 1H NMR, 13C NMR and MS spectra. TH has better solubility than that of TAED. The CIE whiteness index (WI), H2O2 decomposition rate and bursting strength were employed to investigate the performance of H2O2/TH bleaching system. By addition of TH, WI and H2O2 decomposition rate increased significantly at 70 °C. Bleaching temperature, NaHCO3 concentration and bleaching time were also discussed in detail and the loss of bursting strength is not clear. By using benzenepentacarboxylic acid (BA) as a fluorescent probe for hydroxyl radical detection, the bleaching process of H2O2/TH system was investigated. Acetylhydrazine and diacetylhydrazine were also utilized to further confirm the process. In addition, bimolecular decomposition was investigated by using 9,10-dimethylanthracene (DMA) as fluorescent probe of 1O2. Based on these experimental results, the bleaching mechanism of H2O2/TH system was proposed.

Development of o-phthalic anhydride as a low-temperature activator in H2O2 bleaching system for cotton fabric

O-phthalic anhydride (PA) was developed as a low-temperature activator in the H2O2 bleaching system for cotton fabric. The performance of the H2O2/PA bleaching system was investigated by measuring the CIE whiteness index (WI) of the bleached cotton fabric, H2O2 decomposition rate and bursting strength, respectively. The effects of experimental conditions, including PA dosage, bleaching time, bleaching temperature and NaOH concentration, were discussed in the H2O2/PA bleaching system. Upon addition of PA, the WI and H2O2 decomposition rate increased significantly at 70 °C. The results showed that the bleaching system had a promising application prospect. Compared with the H2O2 system, the H2O2/PA system significantly promoted 1O2 generation under the same alkali condition by using 9,10-dimethylanthracene as a fluorescent probe for 1O2. And the generation of large amount of 1O2 did not obviously affect the bleaching performance in the H2O2/PA system. By using benzenepentacarboxylic acid as a fluorescent probe for HO· detection, it was found that the fluorescence intensity was enhanced 14 folds in the presence of PA, indicating that PA could strongly promote HO· generation. By using dimethyl sulfoxide as a scavenger to control HO· concentration, it was found that the WI of the fabric was closely related to the HO· concentration, revealing that the HO· could play an important role in the bleaching process. Phthalic acid was also added to the H2O2 bleaching system to investigate potential bleaching route of the H2O2/PA system. Based on these experimental results, a possible bleaching mechanism of the H2O2/PA system was proposed.

Online quantification and compound‐specific stable isotopic analysis of black carbon in environmental matrices via liquid chromatography‐isotope ratio mass spectrometry

AbstractBlack carbon (BC) is derived from the burning of biomass, a considerable portion of organic matter across terrestrial and marine ecosystems, and a major contributor to global carbon cycles. The benzenepolycarboxylic acid method, which converts condensed aromatic BC structures to molecular markers (BPCAs), has been widely adopted for environmental BC assessments. We present a novel analytical method for the online separation, quantification, and determination of compound‐specific stable carbon isotopes of individual BPCAs via high performance liquid chromatography‐stable carbon isotope ratio mass spectrometry (HPLC‐C‐IRMS). To assess δ13C values of environmental BC, the HPLC‐C‐IRMS method was applied to a variety of samples (soil, char, aerosol, and dissolved organic matter). The method reliably measured amounts and δ13C values of benzenepentacarboxylic acid (B5CA) and mellitic acid (B6CA) over a range of 8.3–130 μmol‐C of organic matter oxidized. BPCA‐specific δ13C values deviated from bulk OC δ13C values for different sample types. However, the stable carbon isotopic composition of B5CA and B6CA was found to be generally correlated with that of bulk organic carbon. The stable isotopic compositions of environmental samples covered a wide dynamic range, indicating BC‐specific δ13C values will be useful for tracking BC sources and processing. For instance, the BPCAs derived from marine dissolved organic matter (DOM) were enriched in 13C relative to BPCAs from riverine DOM, suggesting rivers are not the only source of dissolved black carbon to the oceans.

The generation of benzene carboxylic acids from lignite and the change in structural characteristics of the lignite during oxidation

Production of carboxylic acids (including 12 types of benzene carboxylic acids (BCAs) and small-molecule fatty acids) from lignite via oxidation has been widely studied, but few studies addressed the relationship between distribution of BCAs and structure of lignite. This work studies alkali-oxygen oxidation of Xiaolongtan lignite and distributions of BCAs with 13C NMR as well as the relationship between the distributions of BCAs and the lignite structures. The results indicate that the dominant aromatic structures in the lignite are naphthalene and benzene with a mole ratio of around 3, and an alkyl-substituted degree of aromatic rings of 0.359. These structure characters determine that the yields of benzene tricarboxylic acids, benzene tetracarboxylic acids, benzene pentacarboxylic acid and mellitic acid are more than those of other BCAs. In the oxidation process, the organic matter of lignite is first converted to humic acids (HAs), then to water soluble acids, and last to carboxylic acids. The last conversion step is the rate-controlling step. Analyses of the residues and HAs indicate that C–O bond of lignite is easily cleaved. The aromatic structures (except condensed aromatic rings) are easily depolymerized from lignite, but the condensed aromatic rings and long alkyl chains are difficult to be oxidized. With an increase in oxidation time, in the residues, the contents of aromatic structures decrease, but the contents of condensed aromatic rings and long alkyl chains both increase. While in HAs, the contents of condensed aromatic rings increase, but the average methylene chain length (Cn) decreases.

Low-temperature bleaching of cotton knitting fabric with H2O2/PAG system

Pentaacetyl glucose (PAG) is a common and cheap intermediate and has biocompatible, nontoxic, and renewable features. PAG was investigated as a bleach activator for H2O2 in the pretreatment of gray knitting cotton fabric. The bleaching performance of the H2O2/PAG bleaching system was investigated by measuring the CIE whiteness index (WI), H2O2 decomposition rate and bursting strength. By addition of PAG, the WI and H2O2 decomposition rate increased significantly at 70 °C with little damage to the strength. The effects of temperature and pH value on WI were also considered. Due to its environmental advantages, the H2O2/PAG system showed a good applied prospect. By using benzenepentacarboxylic acid as a fluorescent probe for HO· detection, it was found that PAG could strongly promote HO· generation and that the concentration of HO· was closely related to the WI of the fabric. On this basis, a bleaching mechanism of the H2O2/PAG system was proposed.

Synthesis and structural evaluation of five coordination complexes of benzenepentacarboxylic acid with aza-donor ligands

Synthesis and structural features of five new coordination assemblies, [Co(bpyH)(H2O)5](BPCH)·(bpyH2)0.5·(H2O) (1a), [{Cu(H2O)3}·{Cu0.5(bpy)0.5(H2O)0.5}2(μ-BPCH)] (1b), [{Cd0.5(BPCH)}2·{Cd0.5(bpy)(H2O)2}2]·6(H2O) (1c), [Cu(BPCH2)(bpyeaH)]·2(H2O) (1d) and [Cd2 (bpyea)0.5(oxalate)0.5(μ-BPC) (H2O)]·(bpyeaH2)·2(H2O) (1e), have been reported. All the assemblies were prepared by co-crystallization of benzenepentacarboxylic acid (BPCH5) either with 4,4′-bipyridine (bpy) or 1,2-bis(4-pyridyl)ethane (bpyea) in the presence of a transition metal ion (either Co(II), Cu(II) or Cd(II)) as the case may be. All the five compounds were synthesized by hydrothermal method and structures were determined by single crystal X-ray diffraction. All the obtained compounds, 1a–1e, exhibit distinct 3-D polymeric architectures either in the form of stacked layers or host-guest networks in which water molecules play a pivotal role providing additional stabilization by coordinate bonds as well as hydrogen bonds. Other non-covalent interactions such as C–H … π and π … π stacking also participate in the formation of exotic 3-D structures of these complexes.

Uranium carbide dissolution in nitric acid: speciation of organic compounds

The direct dissolution of UC, a potential fuel for generation-IV nuclear reactors, in nitric acid can produce organic complexants that may interfere with the consumed fuel reprocessing based on liquid–liquid extraction. This study shows the presence of 17 % of carboxylic and polycarboxylic acids (e.g. benzenepentacarboxylic acid). 25 % of the carbon mass balance seemed to correspond to unfunctionalized polyaromatic compounds with more than 3–4 aromatic rings. Under an active oxidation process, these compounds become smaller and very functionalized polyaromatic compounds. Structures have been proposed for 8 % of the carbon mass balance.

Study on H2O2/TAED and H2O2/TBCC bleaching mechanism related to hydroxyl radical with a fluorescent probe

The generation of hydroxyl radical (HO) in H2O2/TAED and H2O2/TBCC systems for cotton fabric bleaching was proved and detected with a novel fluorescent probe benzenepentacarboxylic acid (BA). Effect of HO generation on the cotton fabric bleaching performances was further discussed. The results show that HO yield in H2O2/TAED and H2O2/TBCC systems was respectively about 11 and 15 times higher than that in H2O2 system without activators under the same alkali condition. Meanwhile, TAED and TBCC apparently promoted fabric whiteness and H2O2 decomposition rate. As the addition of HO scavenger dimethylsulfoxide (DMSO), fabric whiteness decreased while tensile strength increased. It proves that HO played a significant role in H2O2/TAED and H2O2/TBCC bleaching. Two main bleaching routes were suggested. The present work brought new insight into H2O2/TAED and H2O2/TBCC bleaching mechanism. It is quite instructive to develop efficient and ecological bleaching processes.

The quantitative detection of HO˙ generated in a high temperature H2O2 bleaching system with a novel fluorescent probe benzenepentacarboxylic acid

A novel fluorescent probe, benzenepentacarboxylic acid (BA), was developed for the quantitative detection of hydroxyl radicals (HO˙) in a simulated hydrogen peroxide (H2O2) bleaching system. Compared to terephthalic acid (TA), a commonly-used fluorescent probe of HO˙ with four possible reaction sites, the present probe has only one reaction site for HO˙ addition that results in the formation of a single fluorescent product, hydroxybenzenepentacarboxylic acid (HBA). The generation of the single pure fluorescent product by BA, rather than mixtures by TA, made the present probe more sensitive, accurate and reproducible in the quantitative detection of HO˙. Based on the working curve obtained from the fluorescence intensity and HBA concentration, a fluorimetric method for the quantitative detection of HO˙ was developed. The present probe BA was successfully used for the quantitative detection of HO˙ under alkaline and high temperature (80 °C) conditions, in a simulated H2O2 bleaching system. The method was highly sensitive, reproducible, and applicable in a wide temperature range of 20–98 °C. The present novel fluorescent probe will be potential tool for evaluating the generation and function kinetics of HO˙ generated in biological and environmental fields.

Hydrated and anhydrous molecular complexes of benzenepentacarboxylic acid and 4,4′-bipyridine

Supramolecular assemblies of benzenepentacarboxylic acid (BPC) and 4,4′-bipyridine (bpy) as hepta- and di-hydrates in a 2:1 and 1:1 ratios of the respective co-crystal formers, as well as an anhydrous complex of 1:2 ratio have been reported. The three supramolecular complexes [(BPC−)2(bpy2+)(H2O)7], 1a, [(BPC−)(bpy+)(bpy)], 1b and [(BPC2−)(bpy2+)(H2O)2], 1c, were obtained by carrying out co-crystallization experiments at varied conditions. 1a and 1b were obtained at ambient and hydrothermal conditions, respectively, while 1c also was obtained at hydrothermal conditions but only in the presence of Ni(NO3)2. All the molecular complexes were characterized by single-crystal X-ray diffraction method. Molecules in all the complexes are packed in the form of stacked layers with the realization of host–guest network in 1a and 1c along a crystallographic axis, wherein the host network is formed by BPC and water molecules through different types of hydrogen bonding patterns and bpy molecules remain as guests in the voids, while in 1b, a ladder type network is observed.