CO Coordination Research Articles

Coordination and Homologation of CO at Al(I): Mechanism and Chain Growth, Branching, Isomerization, and Reduction.

Homologation of carbon monoxide is central to the heterogeneous Fischer–Tropsch process for the production of hydrocarbon fuels. C–C bond formation has been modeled by homogeneous systems, with [CnOn]2– fragments (n = 2–6) formed by two-electron reduction being commonly encountered. Here, we show that four- or six-electron reduction of CO can be accomplished by the use of anionic aluminum(I) (“aluminyl”) compounds to give both topologically linear and branched C4/C6 chains. We show that the mechanism for homologation relies on the highly electron-rich nature of the aluminyl reagent and on an unusual mode of interaction of the CO molecule, which behaves primarily as a Z-type ligand in initial adduct formation. The formation of [C6O6]4– from [C4O4]4– shows for the first time a solution-phase CO homologation process that brings about chain branching via complete C–O bond cleavage, while a comparison of the linear [C4O4]4– system with the [C4O4]6– congener formed under more reducing conditions models the net conversion of C–O bonds to C–C bonds in the presence of additional reductants.

Identifying Key Descriptors for the Single-Atom Catalyzed CO Oxidation

Identifying Key Descriptors for the Single-Atom Catalyzed CO Oxidation

Surface engineering of MOFs as a route to cobalt phosphide electrocatalysts for efficient oxygen evolution reaction

Exploring efficient routes for the fabrication of promising transition metal phosphides electrocatalysts towards oxygen evolution reaction (OER) has become a top priority in the field of water-splitting technology. Herein, a cobalt phosphide (CoxP) electrocatalyst composed of high-density small Co2P/CoP nanoparticles homogeneously embedded in one-dimensional (1-D) carbon has been synthesized by using surface-engineered cobalt benzimidazole zeolitic imidazolate framework (ZIF-9) rods as a precursor. The surface engineering strategy employs melamine to modify ZIF-9 by constructing robust Co coordination sites on ZIF-9 surface through the coordination of Co with nitrogen donor sites in melamine. DFT calculations indicate that the surface engineering of ZIF-9 triggered by melamine occurs not only at coordinatively unsaturated Co sites but also at coordinatively saturated Co sites via a thermodynamically favored ligand exchange process between benzimidazole in ZIF-9 and melamine. Subsequent reaction with red phosphorus at high temperature affords a 1-D material having high-density of CoxP reactive sites and facilitated charge/mass transport, leading to an outstanding electrocatalytic activity for OER—even comparable to commercial RuO2—and excellent electrochemical durability. This scalable strategy involving surface engineering of MOFs represents a breakthrough in the synthesis of efficient OER electrocatalysts in water electrolyzer application.

A universal ionic liquid solvent for non-halide lead sources in perovskite solar cells

Replacing lead iodide (PbI2) with suitable non-halides lead source has been found to be an effective method to control crystallization and fabricate high-performance perovskite solar cells (PSCs). However, the solubility of non-halide lead sources is highly limited by traditional solvents due to the chemical interaction limitation. Here, we report a series of non-halide lead sources (e.g., lead acetate (PbAc2), lead sulfate (PbSO4), lead carbonate (PbCO3), lead nitrate (Pb(NO3)2), lead formate (Pb(HCOO)2) and lead oxalate (PbC2O4)) can be well dissolved in an ionic liquid solvent methylammonium acetate (MAAc). We found that the universal strong coordination of CO with lead ion (Pb2+) and the formation of hydrogen bonds were observed in perovskite precursor solution. This allows the dissolution of non-halide lead salts and is able to produce perovskite film with smooth, compact, and full coverage crystal grain. The power conversion efficiency (PCE) of 14.48%, 19.21%, and 20.13% in PSCs based on PbSO4, PbAc2, and PbCO3 was achieved, respectively, in the absence of any additives and passivation agents. This study demonstrates the universality of ionic liquid for the preparation of PSCs based on non-halides lead sources.

Cobalt-intercalated one-dimensional nanocrystals of urea perylene imide polymer for enhanced visible-light photocatalytic water oxidation

Urea perylene imide polymer (UPDI) is successfully recombined with Co(NO3)2 molecules into one-dimensional nanocrystals (Co−UPDI) for enhanced photocatalytic oxygen evolution (POE) under visible light. Co−UPDI as photocatalyst exhibits more an order of magnitude of POE rate than UPDI at pH = 4.8 (8.00 vs. 0.58 mmol h−1g−1), which is the highest among reported POE tests in aqueous colloid system with AgNO3 as sacrificial agent. The apparent quantum yield (AQY) reaches 4.39 % at 450 nm. The systematical experiments reveals that the heterojunction formation between UPDI line and Co(NO3)2 molecules is crucial through the coordination of Co with N atoms. Consequently, the rigidity of UPDI line enhances, H−type stacking of PDI moiety becomes closer, and CoOOH as cocatalyst in-situ forms during POE. Meanwhile, more excitons with longer lifetime generate and more quickly transfer in Co−UPDI than UPDI nanocrystals. This work provides an efficient strategy for photocatalytic water oxidation.

Enhanced stability and rate performance of zinc-doped cobalt hexacyanoferrate (CoZnHCF) by the limited crystal growth and reduced distortion

Cobalt hexacyanoferrate (CoHCF) is a potential cathode for aqueous Na-ion batteries due to its high theoretical specific capacity (170 mAh g−1); however, its lower rate capability and cyclability limit its applications. Structural distortion at a weak N-coordinated crystal field during cycling disintegrates Co, yielding an irreversible reaction. Different Zn amounts ranging 0–1 were added to the Co site to suppress the structural irreversibility of CoHCF, yielding Co1-xZnxHCF powder; this Zn (x ≤ 0.09) addition reduced the powder’s dimension because the lower four coordination of Zn–N, not the six coordination of Co–N, limits the powder growth. Simultaneously, a small lattice parameter and interaxial angle (∼90°) are obtained, implying that a narrower Co1−xZnxHCF inner structure is formed to accommodate Na ions. Moreover, the electronic conductivity of Co1−xZnxHCF gradually increased within 0–0.09 range. A smaller particle size with a high surface area leads to a near-surface-limited redox process, similar to a capacitive reaction. Both the surface-limited reaction and electronic conductivity enhances the reversibility due to the smaller charge transfer resistance at the electrode/electrolyte interface caused by Zn addition. Replacing redox-active Co with non-active Zn amount of 0.07 (Co0.93Zn0.07HCF) slightly reduces the specific capacity from 127 to 119 mAh g−1 at 0.1 A g−1 due to the shrunken Co charging sites. Rate performance is enhanced by compromising the capacity and reduced distortion, resulting in 81% retention at a 20-times-faster charging rate. Notably, the Co0.93Zn0.07HCF sample exhibited the good stability while preserving 74% of the initial capacity at 0.5 A g−1 after 200 cycles.

Interaction of Divalent Metals with Struvite: Sorption, Reversibility, and Implications for Mineral Recovery from Wastes

Phosphorus (P) recovered from wastewater as struvite (MgNH4PO4·6H2O) can meet high P demands in the agricultural sector by reuse as a P fertilizer. Heavy metals are prevalent in wastewaters and are common fertilizer contaminants, therefore struvite as a sorbent for metals requires evaluation. Struvite sorption experiments were conducted in model solutions with cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) at 1-5 μM concentrations from pH 7-10. The struvite metal loading increased with dissolved metal concentration and pH, ranging from 2-493 mg kg-1. Highest loadings were observed for 5 μM Pb, which exceeded the 120 mg kg-1 European Union (EU) struvite fertilizer limit at all pH values. At 5 μM concentrations, Ni and Cd loadings exceeded EU limits of 100 mg kg-1 at pH 10, and 60 mg kg-1 at pH 8-10, respectively. In desorption experiments, 10-85% metal was released after resuspension in metal-free solutions, with a positive correlation between initial loading and amount desorbed. Distortions of the struvite phosphate band, by Fourier transformation infrared (FTIR) spectroscopy, indicated lowered symmetry of phosphate vibrations with metal sorption. X-ray absorption fine structure spectroscopy (XAFS) analysis of pH 9 solids indicated tetrahedral coordination for Cu and Zn, octahedral coordination for Co and Ni, and Pb in 9-fold coordination. Precipitation of Pb-phosphate minerals was a primary mechanism for Pb sorption. The results provide insight into metal contaminant sorption with struvite in wastewaters, and the potential for metal desorption after recovery.

Heterogeneous Structure Regulated by Selection Pressure on Bacterial Adhesion Optimized the Viability Stratification Structure of Electroactive Biofilms.

As the core of microbial fuel cells (MFCs), the components and structure of electroactive biofilms (EABs) are essential for MFC performance. Bacterial adhesion plays a vital role in shaping the structure of EABs, but the effect of bacterial adhesion under selection pressure on EABs has not been systematically studied. Here, the response of the composition, structure, and electrochemical performance of EABs to the selective adhesion pressure due to the selective coordination of Fe(III) and Co(II) with thiol and the different affinities for bacteria on hybrid electrodes (Fe1Co, Fe4Co, and Fe10Co) were comprehensively investigated. Compared with carbon cloth (CC), the appropriate selective adhesion pressure of Fe4Co activated the dead inner core of EABs and optimized their viability stratification structure. Both the total viability and the viability of the inner core layer in the Fe4Co EAB (0.67, 0.70 ± 0.01) were higher than those of the CC (0.46, 0.54 ± 0.01), Fe1Co (0.50, 0.48 ± 0.03), and Fe10Co (0.51, 0.51 ± 0.03). Moreover, a higher proportion of proteins was detected in the Fe4Co EAB, enhancing the redox activity of extracellular polymeric substances. Fe4Co enriched Geobacter and stimulated microbial metabolism. Electrochemical analysis revealed that the Fe4Co EAB was the most electroactive EAB, with a maximum power density of 2032.4 mW m-2, which was 1.7, 1.3, and 1.1 times that of the CC (1202.6 mW m-2), Fe1Co (1610.3 mW m-2), and Fe10Co (1824.4 mW m-2) EABs, respectively. Our findings confirmed that highly active EABs could be formed by imposing selection pressure on bacterial adhesion.

Water-stable and hydrophobicity tunable organolead halide materials with Pb–N coordination for electrochemical CO2 reduction

Water-stable and hydrophobicity tunable organolead halide crystalline materials with Pb–N coordination were designed and employed in the electrocatalytic CO2 reduction with high performance in water solution.

Backbonding in Thorium(IV) and Uranium(IV) Diarsenido Complexes with tBuNC and CO.

The coordination of tBuNC and CO with the diarsenido complexes (C5 Me5 )2 An(η2 -As2 Mes2 ), An=Th, U, has been investigated. For the first time, a comparison between isostructural complexes of ThIV and UIV has been possible with CO; density functional calculations indicated an appreciable amount of π backbonding that originates from charge transfer from an actinide-arsenic sigma bond. The calculated CO stretching frequencies in the ThIV and UIV diarsenido complexes are consistent with the experimental measurements, both show large shifts to lower frequency. We demonstrate that the π backbonding is crucial to explaining the red shifts of CO frequency upon AnIV complex formation. Interestingly, this interaction essentially correlates to the parallel orientation of π*(C-O) orbitals relative to the An-As bond.

Small Transition-Metal Mixed Clusters as Activators of the C-O Bond. FenCum-CO (n + m = 6): A Theoretical Approach.

Binding of carbon monoxide, CO, and its activation on the surface of the FenCumCO (n + m = 6) clusters are studied in this work. Using the BPW91/6-311 + G(2d) method, we have found that adsorption of the CO molecule on the surface of FenCum (n + m = 6) clusters is thermochemically favorable. Atop and bridge CO cluster coordinations appear for pure, Fe6 and Cu6, and mixed, Fe2Cu4 and Fe4Cu2, clusters. Threefold coordination takes place for Fe3Cu3-CO where the CO bond length, dCO, suffers a largest increase from 1.128 ± 0.014 Å for bare CO up to 1.21 Å. The CO stretching, νCO, as an indicator for the CO bond weakening is redshifted, from 2099 ± 4 cm-1 for isolated CO up to 1690 cm-1 for Fe3Cu3CO and 1678 cm-1 for Fe6CO. In addition, in Cu6CO, the strongest CO bond is slightly weakened as it has a bond length of 1.15 Å and a νCO of 2029 cm-1. There is a correlation between the CO bond weakening and the increase of CO coordination in FenCumCO, which in turns promotes the transference of charges from the metal core into the antibonding orbitals of CO. Substitution of up to three Cu atoms in Fe6 increases the adsorption energies and the activation of CO. Indeed, FenCum (n + m = 6) are promising clusters to catalyze CO dissociation, particularly Fe3Cu3, Fe5Cu, and Fe6, which have large CO bond lengths and CO adsorption energies. The Bader analysis of the electronic density indicates that FenCumCO species with threefold coordination show a rise in the C-O covalent character due to the less electronic polarization. They also show important M → CO charge transfer, which favors the weakening of the CO bond.

Carbon monoxide adsorption on cobalt overlayers on a Si(1 1 1) surface studied by STM and XPS

We report on the structure and reactivity of the Co-Si polycrystalline surfaces that form at room temperature (RT). Scanning tunneling microscopy (STM) was used to examine the surface morphology while X-ray photoelectron spectroscopy (XPS) was used to detect the chemical states of cobalt and silicon as a function of cobalt coverage. Moreover, XPS measurements after exposing the Co-Si(111) samples to CO gas provide information about CO adsorption and dissociation. When <5 ML Co is deposited on Si(111) at RT, most Co atoms diffuse into Si lattice and no CO adsorption is found at RT. This shows that coordination of Co to Si suppresses CO adsorption. Neither Co-induced Si(111)-ring cluster nor CoSi2 crystalline film adsorb CO at RT. In contrast, CO adsorption was found at RT for cobalt doses >5 ML, an indication that Co-rich silicides and metallic Co present. The CO adsorption capacity increases with cobalt dose up to 30 ML after which it levels off, an indication that metallic cobalt sites are dominantly exposed on the surface. Furthermore, a closed metal film is formed for 200 ML dose. Some dissociation of CO was observed during heating of the CO-covered samples for Co doses ≥30 ML.

Broad magnetic anisotropy regulation in as-deposited Pt/Co/MgO multilayers by tuning electronic coordination

The regulation in the magnetic anisotropy of magnetic films is crucial for developing the magnetic storage and logic devices. The traditional work achieved an effective tunability of the magnetic anisotropy by a subsequent processing of the as-deposited film, such as a post-annealing treatment or electric field application. Here, we proposed an effective method to achieve a direct and broad tunability of the magnetic anisotropy in the as-prepared film by adjusting electronic coordination. Nitrogen (N) atoms were doped in the Co layer of Pt/Co/MgO multilayers to effectively control the electronic coordination of Co and enhance the 3dz2–r2 orbital occupancy of Co for modulating the Co–O orbital hybridization. Consequently, the magnetic anisotropy of the as-deposited film changed from in-plane to perpendicular direction with the N doping, resulting in a significant increment in the magnetic anisotropy energy by 2.48 × 106 erg/cm3. Furthermore, the critical Co thickness with maintaining the perpendicular magnetic anisotropy was enlarged from 1 to 3 nm, which is beneficial for enhancing the stability of nanodevices. These findings provide an effective strategy to tune the magnetic anisotropy of magnetic films toward the applications of various magnetic storage and logic devices.

Defective Metal-Organic Frameworks As Unpyrolyzed Electrocatalysts for Oxygen Reduction and Oxygen Evolution Reactions

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) represent core electrocatalytic processes in unitized regenerative fuel cells and rechargeable metal-air batteries catalyzed by the costly platinum group metals (PGMs) materials. Finding highly efficient yet durable ORR/OER catalysts using earth-abundant, low-cost materials represents a critical path in lowering cost barrier for widespread commercialization of the devices. We herein report two approaches to construct defective metal-organic frameworks (MOFs) to remove PGM usage for oxygen electrocatalysis.In approach 1, we prepared a coordinately unsaturated Co-MOF as a bifunctional ORR/OER electrocatalyst in an alkaline electrolyte. The Co-MOF possessed great π-π stacking and hydrogen bonding interactions, giving rise to excellent structural and catalytic stabilities. Structure characterizations demonstrated that the coordination of Co(II) was largely unsaturated. Modeling simulations further confirmed that the unsaturated coordination significantly promoted the interactions with molecular water and oxygen and improved the electronic conductivity, leading to enhanced mass and charge transfer properties.In approach 2, we developed a partial ligand removal (or ligand-defect) approach to create mesopores and unsaturated coordination in a Cu-MOF. Since the micropores typically limit the mass-transfer properties (and the capability to store insoluble discharge product for aprotic metal-air battery), the mesopores of the as-prepared MOF showed less steric hindrance, and the unsaturated Cu coordination also boosted electronic conductivity and auxiliary reactant affinity, leading to high Li-air battery capacity.The defective MOFs may open up a new venue for developing effective electrocatalysts with enhanced intrinsic activity towards oxygen electrocatalysis.

Is fighting against pollutants possible with critical raw material free perovskites?

Perovskites free of critical raw materials (noble metals and rare earths) of the type Ba1-ySryMn1−0.2-xMg0.2CuxO3 (y = 0.1, 0.5; x = 0.1, 0.2, 0.3) are developed for the abatement of pollutants in automotive exhaust, both gaseous (CO, NOx and HCs) and solid (carbon soot). The reactivity in oxidation and reduction is tuned through ad-hoc induced surface segregation phenomena and the promotion of specific Mn(III)/Mn(IV) and Cu/Mn atomic ratios. The insertion of Cu into the perovskitic cell, moves the crystalline structure from 2H-type toward a Mn-deficient one, in which Mn(III) is prevalent. The catalytic capability in abatement of pollutants was studied comparing the activity in the following reactions: CO oxidation, CO assisted NO reduction, and with a complex mixture simulating the composition of automotive exhausts in stoichiometric and rich conditions. CO oxidation is favored by surface segregation of Mn, Mg may play a role in CO coordination. Copper enhances the NO reduction activity of the catalysts in the CO + NO reaction and Ba0.9Sr0.1Mn0.5Mg0.2Cu0.3O3 is the more active, whereas in the complex mixture Ba0.9Sr0.1Mn0.7Mg0.2Cu0.1O3 and Ba0.9Sr0.1Mn0.6Mg0.2Cu0.2O3 are the more active suggesting a less relevant role of surface composition and a more active contribution of bulk ion mobility.

Co-MOF as a highly efficient catalyst for contaminants degradation via sulfite activation

Activation of sulfite (SO32−) by heterogeneous catalysts draws increasing attention due to their promising performance and environmental benignity. In this work, Co-based metal organic framework (Co-MOF) was synthesized and directly used as a catalyst to activate SO32− for contaminants degradation. The Co-MOF catalyst exhibited high catalytic activity for Methyl Orange (MO) degradation in alkaline aqueous solution. Impressively, the catalytic performance of Co-MOF was more efficient than Co2+ and cobalt oxides of Co3O4, CoFe2O4 and Co nanoparticles embedded in carbon tubes. Radical quenching experiments and electron paramagnetic resonance suggested that special coordination and redox of Co(II) and Co(III) in the pristine of Co-MOF initiated a series of chain reaction of SO32− oxidation, with the formation of several oxysulfur radicals such as SO3−• and SO4−•. This work provides new insights into the stereoscopic cobalt based catalysts of sulfite catalysis and can guide new insights in future catalyst development in advanced oxidation process.

Surface Tuning to Promote the Electrocatalysis for Oxygen Evolution Reaction: From Metal-Free to Cobalt-Based Carbon Electrocatalysts.

Heterogeneous electrocatalytic reactions only occur at the interface between the electrocatalyst and reactant. Therefore, the active sites are only necessary to be distributed on the surface of the electrocatalyst. Based on this motivation, here, we demonstrate a systematic study on surface tuning for a carbon-based electrocatalyst from metal-free (with the heteroatoms N and S, NS/C) to metal-containing surfaces (with Co, N, and S, CoNS/C). The CoNS/C electrocatalyst was obtained by pyrolyzing the Co precoordinated and p-toluenesulfonate-doped polypyrrole (PPy). It was found that the coordination of Co on the PPy ring tuned the final carbon electrocatalyst into a catalyst with a CoNx moiety-rich surface. In addition, the as-synthesized CoNS/C was determined to have a very high loading of cobalt up to 2.02 wt %. The pyrolysis of the cobalt-containing precursor tends to proceed toward a characteristic of a higher sp2 carbon content, a higher surface area, and more nitrogen as well as active nitrogen sites than its metal-free counterpart. The most distinguished feature for such a catalyst is that the truly most active component is only distributed on the surface, in contrast with that of the conventional metal-N-based catalyst present throughout the bulky structure. Especially, the electrocatalytic activity toward oxygen evolution reaction (OER) has been investigated experimentally and theoretically. The results showed that the OER performance of the carbon-based electrocatalyst was remarkably boosted after the introduction of Co with an overpotential decrease from 678 to 345 mV at 10 mA cm-2. Furthermore, CoNS/C displayed an excellent durability upon a long-term measurement. The apparent activation energy measurements revealed that the metal-rich surface contributed to overcome the energy barrier for OER. In addition, density functional theory calculations have been conducted to explain the correlated OER mechanism. This study is expected to provide an effective strategy for the design and the synthesis of highly active metal-nitrogen-type electrocatalysts with a high metal loading for various electrocatalytic reactions.

The significance of the local structure of cobalt-based catalysts on the photoelectrochemical water oxidation activity of BiVO4

The local structures of the water oxidation catalysts play an important role in reaction kinetics and the performance of the photoanodes. In this study, we deposited cobalt-based catalysts on nanoporous BiVO4 with controlled thicknesses by atomic layer deposition (ALD). Despite the similar oxidation states of cobalt in all depositions, different water oxidation activities in neutral pH conditions were observed. A dramatic photocurrent raise, lowered kinetic overpotential, and smaller charge transfer resistance across the photoanode/electrolyte interface were achieved when a uniform ultrathin Co(OH)2 layer was formed on BiVO4. Photocurrent density for water oxidation showed a 95% enhancement at 0.6 V vs. RHE when the catalyst was in the form of Co(OH)2, while an 80% increase was obtained for CoO. Ideal coordination of Co(OH)2 on hydroxylated BiVO4 surface assists the charge transfer between the electrolyte and BiVO4 without increasing surface recombination. The results of this study emphasize the importance of controlling the local structure of the catalysts in the performance of the water splitting photoanodes.

Precise Spin Manipulation of Single Molecule Positioning on Graphene by Coordination Chemistry.

Precise spin manipulation of single molecules is crucial for future molecular spintronics. However, it has been a formidable challenge due to the complexities of the strong molecule-substrate coupling as well as the response of the molecule to external stimulus. Here we demonstrate by density functional theory calculations that precise spin manipulation can be achieved by extra CO and NO molecules coordination to transition metal phthalocyanine (TMPc) (TM = Co, Fe, Mn) molecules deposited on metal-supported graphene; the spins of TMPc molecules are switched from S to S - 1/2 (|S - 1|) after NO (CO) coordination. With the aid of a combination of molecular orbitals (MO) theory and recently developed principal interacting spin-orbital (PISO) analysis, the impacts of NO and CO coordinations on both adsorption configuration and spin polarization of TMPc are well elucidated. We reveal the different coordination geometries that CO always coordinates axially to the TM center with a linear geometry, while NO prefers a bent geometry, which can be attributed to the competition between the σ- and π-type interactions according to the PISO analysis. Particularly, the NO-MnPc complex adopts a bent geometry deviating from the prediction by the existing Enemark-Feltham formalism. In addition, MO analysis suggests that during the CO coordination, the simultaneous existence of σ-donation and π-back-donation promotes electrons flowing from the dz2 to partially occupied dπ (dxz and dxz) orbitals with subsequent reordering of the TM d-orbitals, resulting in the spin transition of S → |S - 1|. In comparison, given that NO is regarded as NO- when it adopts a bent geometry coordinating to the TM center, the complete (CoPc) or partial (FePc and MnPc) quenching of the molecular spins caused by NO coordination is attributed to the electron transfer from TM to NO. These theoretical findings provide important insights into relevant experiments and offer an effective design strategy to realize underlying single-molecular spintronics devices integrated with two-dimensional materials.

Fibrous chitosan/cellulose composite as an efficient adsorbent for Co(Ⅱ) removal

With the rapid development of industries, the heavy metal-containing wastewater has become one of the most serious environmental problems. Adsorption is a key approach in treating heavy metal-containing wastewater. The performance of adsorbents is determined by the effective exposure of its adsorptive sites, which determines its adsorption capacity. In this study, fibrous chitosan/cellulose composite was prepared using the wet-spinning method to increase its specific surface area, thus enhancing the adsorption capacity. The as-prepared fibrous composite showed a homogeneous fiber structure (diameter: 88 ± 16 μm) and high specific surface area (2.5 m2 g−1). Furthermore, the adsorption capacity towards Co(Ⅱ) was greatly enhanced, more than three times higher than that of the pure chitosan beads (diameter: 2–3 mm). The maximum adsorption capacity was calculated to be 23.6 ± 2.5 mg-Co(Ⅱ) per g-chitosan by the Langmuir isotherm model, an order of magnitude higher than that of pure chitosan beads. In addition, the adsorption kinetic behavior of chitosan/cellulose fibers on Co(Ⅱ) followed the pseudo second-order kinetic model. The optimal pH for Co(Ⅱ) removal was approximately 6.0. Furthermore, FT-IR and XPS analyses indicated the amino groups played a dominant role, with the aid of hydroxyl groups, in the coordination and adsorptive removal of Co(II). Possible interaction configurations were also proposed in this study. In conclusion, the proposed physical modification of chitosan greatly improved its adsorption capacity and mechanical strength, making it a promising biosorbent for Co(II) removal.