Three-dimensional Porous Materials Research Articles

Enhancing Kinetics in Sodium Super Ion Conductor Na3MnTi(PO4)3 through Microbe-Assisted and Structural Optimization.

Sodium (Na) super ion conductor (NASICON) structure Na3MnTi(PO4)3 (NMTP) is considered a promising cathode for sodium-ion batteries due to its reversible three-electron reaction. However, the inferior electronic conductivity and sluggish reaction kinetics limit its practical applications. Herein, we successfully constructed a three-dimensional cross-linked porous architecture NMTP material (AsN@NMTP/C) by a natural microbe of Aspergillus niger (AsN), and the structure of different NMTP cathodes was optimized by adjusting different transition metal Mn/Ti ratios. Both approaches effectively altered the three-dimensional NMTP structure, not only improving electronic conductivity and controlling Na+ diffusion pathways but also enhancing the electrochemical kinetics of the material. The resultant AsN@NMTP/C-650, sintered at 650 °C, exhibits better electrochemical performance with higher reversible three-electron reactions corresponding to the voltage platforms of Ti4+/3+, Mn3+/2+, and Mn4+/3+ around 2.1, 3.6, and 4.1 V (vs Na+/Na), respectively. The capacity retention rate is up to 89.3% after 1000 cycles at a 2C rate. Moreover, a series of results confirms that the Na3.4Mn1.2Ti0.8(PO4)3 cathode has the most excellent electrochemical performance when the Mn/Ti ratio is 1.2/0.8, with a high capacity of 96.59 mAh g-1 and 97.1% capacity retention after 500 cycles.

Bio-carbon coil aerogels from tea waste: A sustainable solution for efficient oil-water separation

Discharging wastewater containing oils, fats, and organic solvents into water bodies poses a significant threat to the already limited freshwater resources. In recent years, three-dimensional (3D) porous adsorbent materials, such as aerogel materials, have gained attention for their high separation effectiveness in adsorption technology. However, the poor mechanical strength of existing aerogel materials limits their application in oil–water separation. To address this challenge, this study proposes to use carbon coils obtained from tea waste as a template for producing low-cost, ultra-light, elastic, and highly recyclable bio-carbon coil aerogels (BCCA). The BCCA, featuring high porosity and a hierarchical porous structure, demonstrated exceptional performance in oil–water separation applications. Specifically, it exhibited a high adsorption capacity for organic solutions (39 ∼ 117 g/g) and oils (32 ∼ 41 g/g), respectively, along with excellent selectivity, rapid adsorption time of approximately 30s, and good reuse capability, maintaining an adsorption efficiency of 85 %. These remarkable properties can be attributed to the exceptional hydrophobicity of the BCCA, with a contact angle of 134°, and the rapid capillary action facilitated by the helical network structure. The use of tea waste-derived carbon coils as a precursor for producing efficient and sustainable carbon coil aerogels presents a promising solution for environmental remediation, particularly in oil–water separation applications. This research addresses the issue of wastewater contamination and contributes to the utilization of tea waste, a readily available and abundant biomass resource, in the development of value-added materials for environmental sustainability.

Three-dimensional Ti3C2 structure design and in-situ growth of nano-TiO2 crystals to realize high performance lithium-sulfur battery

Lithium–sulfur (Li–S) batteries represent a promising energy storage system with the potential to replace traditional lithium-ion batteries. Recent research has explored the practical applications of Li–S batteries. However, due to the insulation properties of the sulfur components and the shuttle effect of polysulfides, the practical application of Li–S batteries is hindered by poor cycle stability and short life. In this study, we developed a controllable three-dimensional Ti3C2 structure design process, and through in situ growth of TiO2 nanocrystals, we prepared three-dimensional porous materials with TiO2@Ti3C2 heterostructures. These materials constructed using two-dimensional lamellar Ti3C2 function as a conductive skeleton to improve the conductivity of the sulfur cathodes, and through the in-situ growth of nano-TiO2 to introduce more binding sites and provide more chemisorption sites to limit the dissolution and shuttle of polysulfides. In addition, the TiO2@Ti3C2 heterointerface generated in situ on the surface of the lamellar structure can induce an internal electric field and increase active reaction sites, which promotes reaction kinetics, accelerates charge diffusion/transport, and promotes LiPS transformation. The materials designed in this study can effectively restrain the shuttle effect by realising the association process of adsorption, capture, and transformation of polysulfides. Thus, when applied as the sulfur cathode frame, it shows a high specific capacity of 1261.41 mAh g−1 at a rate of 0.1 C. In addition, a specific capacity of 66.5 % is maintained over 500 cycles at a rate of 1 C. This strategy supports the development of Li–S batteries with extraordinary performance and opens up a promising way to design next-generation electrochemical energy storage devices.

Investigation on the Microstructural Diversity of a Three-Dimensional Porous Hydroxyapatite/Wollastonite Skeleton via Biomineralization in Simulated Body Fluids

The occurrence of fractures has emerged as one of the most prevalent injuries in the human body. In bone reconstruction surgery, after the implantation of porous hydroxyapatite materials, there is an initial infiltration of body fluids into the porous implant, followed by biomineralization-mediated apatite crystal formation and the subsequent ingrowth of bone cells. Despite extensive research efforts in this field, previous investigations have primarily focused on the formation of apatite crystals on exposed surfaces, with limited literature available regarding the formation of apatite crystals within the internal microstructures of bone implants. Herein, we demonstrate the occurrence of dynamic biomineralization within a three-dimensional porous hydroxyapatite/wollastonite (HA/WS) skeleton, leading to the abundant formation of nano-sized apatite crystals across diverse internal environments. Our findings reveal that these apatite nanocrystals demonstrate distinct rates of nucleation, packing densities, and crystal forms in comparison to those formed on the surface. Therefore, the objective of this study was to elucidate the temporal evolution of biomineralization processes by investigating the microstructures of nanocrystals on the internal surfaces of HA/WS three-dimensional porous materials at distinct stages of biomineralization and subsequently explore the biological activity exhibited by HA/WS when combined with cell investigation into apatite crystal biomineralization mechanisms at the nanoscale, aiming to comprehend natural bone formation processes and develop efficacious biomimetic implants for tissue engineering applications. The simultaneous examination of bone cell attachment and its interaction with ongoing internal nanocrystal formation will provide valuable insights for designing optimal scaffolds conducive to bone cell growth, which is imperative in tissue engineering endeavors.

Framework reinforced orderly-woven superhydrophobic metal–carbon composites for efficient emulsion separation in harsh environments

The primary barrier to the widespread use of super-wetting materials is the surface's limited resistance to physical damage, which leads to poor mechanical qualities. In this study, framework-reinforced orderly-woven superhydrophobic metal spiral coil-carbon fibers composites (SMSC-CFsC) with a durable uniform micro-structure were prepared by nested carbon fibers into metal spiral coils cleverly and woven them into a three-dimensional porous material innovatively. The separation purity of the prepared metal–carbon composites on several commonly used industrial lubricating oil emulsions was better than 99.90 % and the flux was greater than 1000 L/m2h. More significantly, computational fluid dynamics was used to establish a simulation model for emulsion separation that revealed the real-time dynamic motion trajectory and volume changes of water droplets. Additionally, even after high-temperature, compression, wear, and corrosion experiments, it still showed dependable separation purity and stable flux. As a result, it has been demonstrated that the proposed metal–carbon composite has a long oil–water separation service life in harsh environments and has great potential for developing efficient and durable emulsion separation materials.

All-in-one self-floating porous foams as robust heat-blocking layers for efficient photothermal conversion and solar desalination

Solar-driven interfacial evaporation is a highly efficient and ecofriendly technology for producing freshwater. Herein, self-floating plasmon Ag/black TiO2/carbon porous layered foams (Ag-BTCFs) were demonstrated as efficient solar-thermal convectors using freeze-drying cast-molding and high-temperature surface hydrogenation strategies. This all-in-one three-dimensional (3D) cross-linked self-floating porous layered foam material with full-spectrum absorption can fully harvest sunlight (∼95.45%) and effectively block heat transfer to its sublayer. The synergy of sufficient utilization of absorbed ultraviolet radiation by black TiO2 (b-TiO2), visible light absorption by Ag nanoparticles (Ag NPs) via localized surface plasmon resonance, and near-infrared absorption by layered-amorphous carbon can achieve full-solar-spectrum absorption to concentrate thermal energy. In addition to their synergistic effect, they are conducive to the relaxation of hot electrons when utilizing photogenerated holes to degrade pollutants in domestic wastewater. The steam generation efficiency of Ag-BTCFs is up to 1.79 kg m−2h−1 due to their solar energy conversion efficiency of 81.74% under 1 sun irradiation, which is five times higher than the evaporation rate of pure water. Notably, the material’s efficient ion removal rate of 99.80% for solar desalination indicates its high potential for various applications. This strategy provides new insights for fabricating recyclable heat-blocking layer systems against thermal loss to enhance solar steam generation.

Synthesis and formation mechanism of pitch-based carbon foam for three-dimensional structural applications

Carbon foam is a three-dimensional porous, rigid, and permeable material with applications in many fields owing to its excellent electrical and thermal properties. Pitch is a promising carbon source for carbon foam production, and its modification with nitric and sulfuric acids has been widely investigated. However, the foaming phenomenon resulting from the acid treatment of pitch and the resultant formation of porous structures remain poorly understood. Herein, we clarified the mechanism by which the porous structure of pitch-derived carbon foam is formed by analyzing the components of pitch modified by nitric acid treatment and identifying essential conditions for foam production. Carbon foam was obtained by pitch modification at a high concentration of nitric acid (60 wt%), whereas no carbon foam was formed at low nitric acid concentrations (<60 wt%). Furthermore, at high nitric acid concentrations, carbon foam formation proceeded at a relatively low temperature (280 °C). The formation of carbon foam from modified pitch was attributed to the synergistic effect of the functional groups introduced onto pitch and the low-molecular-weight components resulting from cracking. This work provides new insights into pitch as a precursor and provides a straightforward method for producing carbon foam.

An integrated approach for soluble and insoluble pollutants: Surface performance regulation of Co2CO3(OH)2@Ni foam for effective ciprofloxacin removal and oil/water separation

Effectively removing both soluble antibiotics and insoluble oils from wastewater is a significant challenge. To address both the problems, we synthesized a three-dimensional (3D) porous water treatment material. It can be converted from antibiotic removal mode to oil removal mode by simple surface performance regulation. This approach achieved a high removal rate for ciprofloxacin (CIP) and good separation efficiency for oil/water mixtures. Initially, Co2CO3(OH)2 nano-needles were fixed on Ni foam to synthesize Co2CO3(OH)2@Ni foam-1, which had a high CIP removal rate (93.59 % at pH 7.0) and a certain anti-interference ability. To assess the CIP removal performance, the environmental impact, economic benefit and energy consumption (3E) triangle model was established and the optimal operating point was selected. Characterization experiments demonstrated that the removal of CIP was attributed to the mechanisms of surface complexation, electrostatic attraction, cation bridging, precipitation and flocculation. Subsequently, Co2CO3(OH)2@Ni foam-2 was obtained by hydrophobic modification, which exhibited separation efficiencies above 93.5 % for a series of different oil/water mixtures. Co2CO3(OH)2@Ni foam series materials are easy to prepare and possess effective pollutants treatment efficiency, thus providing a new strategy for developing multi-functional water treatment materials and a novel approach for the treatment of soluble antibiotics and insoluble oils in wastewater.

Chelating Co-reduction Strategy for the Synthesis of High-Entropy Alloy Aerogels.

Aerogels, as three-dimensional porous materials, have attracted much attention in almost every field owing to their unique structural properties. Designing high-entropy alloy aerogels (HEAAs) to quinary and above remains an enormous challenge due to the different reduction potentials and nucleation/growth kinetics of different constituent metals. Herein, a novel and universal chelating co-reduction strategy to prepare HEAAs at room temperature in the water phase is proposed. The addition of chelators (ethylenediaminetetraacetic acid tetrasodium salt, sodium citrate, salicylic acid, and 4,4'-bipyridine) with a certain strong coordination capacity can adjust the reduction potential of different metal components, which is the key to synthesize single-phase solid solution alloys successfully. The optimized AgRuPdAuPt HEAA can be an excellent electrocatalyst for hydrogen evolution reaction (HER) with an ultrasmall overpotential of 22 mV at 10 mA cm-2 and excellent stability for 24 h in an alkaline solution. In situ Raman spectroscopy unveils the enhanced hydrogen evolution reaction mechanism of HEAAs. Overall, this work provides a novel chelating co-reduction strategy for the facile and versatile synthesis and design of advanced HEAAs and broadens the development and utilization of multi-elemental alloy electrocatalysts.

Biomass-derived foams with three-dimensional hierarchical structure for efficient p-arsanilic acid removal

As an emerging micro-pollutant, p-arsanilic acid (p-ASA) exist widely in the environment, and it can form highly toxic arsenate and arsenite during the migration and transformation process, which greatly increases the risk of arsenic pollution in the ecosystem. Additionally, three-dimensional (3D) porous block materials have the advantage of stronger adsorption performance, faster adsorption rate and easy recovery, showing broad application prospects in water pollution control. Hence, the aminozed collagen fibers foam (ACFF) with 3D porous block structure was synthesized. The maximum adsorption capacity of ACFF for p-ASA was 476.19 mg·g−1 due to the rich honeycomb porous structure and the synergistic effect of electrostatic attraction, hydrogen bonding effect and amphiphilicity. Moreover, ACFF is not only easy to recycle, but also has good elastic recovery and regeneration performance. The pore size of ACFF was concentrated in the range of 25–5000 nm, and the porosity was 71.66%. ACFF may be an adsorbent with great potential for the removal of organoarsenic contaminants in water.

Self-standing tridimensional structures from crumpling techniques made with composite films of polylactic acid and exfoliated graphite

Obtaining three-dimensional porous materials for different applications, has required complex methods to achieve the desired structure. Crumpling is an alternative to develop three-dimensional structures by randomly folding a sheet of material and offering a simple yet effective method to generate a unique, stiff and lightweight three-dimensional structure with minimal processing. Here, composite films made from polylactic acid (PLA), and exfoliated graphite (EG) were elaborated using solvent casting method. Additional pore formation is achieved adding calcium carbonate (CaCO3) particles as porogen. Films were characterized to corroborate the integration of exfoliated graphite to the PLA matrix as well as crystallinity changes due to EG and CaCO3 particles. Microscopy help to identify pore formation after CaCO3 remotion. Tensile tests, after increasing EG concentration in PLA, corroborate the formation of stiffer films with lower tensile strength, while pore formation decreased tensile strength and Young's modulus. After adding 0.5% wt. of EG, tensile strength partially recovered while Young's modulus was maintained. Composite films allowed to obtain 3D crumpled structures. Tests under compression help finding that 0.5% wt. of EG in PLA matrix resulted in a yield strength (26.6 MPa) and Younǵs modulus (32.5 MPa) increase, making necessary the application of considerable force to deform them.

Preparation and characterization of highly conductive lignin aerogel based on tunicate nanocellulose framework

The highly conductive and elastic three-dimensional mesh porous material is an ideal platform for the fabrication of high electrical conductivity conductive aerogels. Herein, a multifunctional aerogel that is lightweight, highly conductive and stable sensing properties is reported. Tunicate nanocellulose (TCNCs) with a high aspect ratio, high Young's modulus, high crystallinity, good biocompatibility and biodegradability was used as the basic skeleton to prepare aerogel by freeze-drying technique. Alkali lignin (AL) was used as the raw material, polyethylene glycol diglycidyl ether (PEGDGE) was used as the cross-linking agent, and polyaniline (PANI) was used as the conductive polymer. Preparation of aerogels by freeze-drying technique, in situ synthesis of PANI, and construction of highly conductive aerogel from lignin/TCNCs. The structure, morphology and crystallinity of the aerogel were characterized by FT-IR, SEM, and XRD. The results show that the aerogel has good conductivity (as high as 5.41 S/m) and excellent sensing performance. When the aerogel was assembled as a supercapacitor, the maximum specific capacitance can reach 772 mF/cm2 at 1 mA/cm2 current density, and maximum power and energy density can reach 59.4 μWh/cm2 and 3600 μW/cm2, respectively. It is expected the aerogel can be applied in the field of wearable devices and electronic skin.

Controllable synthesis of nitrogen-doped porous Fe3C@C nanocomposites for efficient microwave absorption

Three-dimensional (3D) porous carbon-based materials are commonly considered to be a hopeful microwave absorbing materials owing to their lightweight and broadband absorption. However, the structure between dissipation mechanism is still not clear. Therefore, in this work, the nitrogen-doped porous Fe3C@C nanocomposites derived from Fe(NO3)3·9 H2O and polyvinyl pyrrolidone (PVP) were fabricated through pre-blowing followed by in situ carbonization method with various temperatures. The obtained material treated at 600 °C, which the content of N was 4.07 %, exhibits the most excellent microwave absorption (MA) property with the minimal reflection loss of − 63.1 dB at 5.0 GHz while the matching thickness is 4.6 mm. The MA performance of the composite is originated from the synergy of magnetic-dielectric loss and improved interfacial polarization. This research provides a way to prepare high-property MA absorbers.

In Situ Probing the Mass Transport Property Inside an Imitated Three-Dimensional Porous Bioelectrode.

Three-dimensional porous materials have been demonstrated as the most successful bioelectrodes in bioelectrochemical systems due to their high specific surface area and abundant adhesion regions for electroactive bacteria. However, the pore clogging potentially limits the mass transfer process inside the electrode due to the unreasonable structure design and long-term operation. The investigation of mass transport behavior in the porous scaffolds is of great significance for designing the electrode structure and optimizing bioelectrochemical system performance. To in situ characterize the mass transport behavior in the orderly pore structure, model electrodes with 100 copper wires (10 × 10) are constructed to imitate a three-dimensional porous structure (pore size: ∼150 μm) commonly employed in bioelectrodes. The poor proton effective diffusion coefficient solidly demonstrates that the mass transport inside the three-dimensional porous electrode is critically inhibited, leading not only to a progressive change and sparse biomass in the biofilm development process but also to biofilm acidification due to serious proton accumulation. It finally results in sluggish bacterial metabolic activity and a decreased electrocatalytic capacity. The interior space of porous electrodes cannot be adequately utilized, resulting in the inability to fully exploit the advantages of their abundant surface area. Consequently, the construction of gradient porous electrodes with small inner and large outer pores to enhance mass transport is a feasible proposal for enhancing performance. The proposed methodology of establishing model electrodes combined with the in situ detection technique within porous electrodes is crucial for acquiring various types of physicochemical information inside the bioelectrode, such as biofilm growth situation, biochemical reaction conditions, as well as mass transfer characteristics. More importantly, the work provides a fundamental basis for designing highly efficient bioelectrodes.

One-pot synthesis of ion-imprinted three-dimensional porous material based on graphene oxide for the selective adsorption of copper(II)

Molecularly imprinted polymers (MIPs) are synthetic polymers with predetermined selectivity for a given analyte. One major problem associated with MIPs is the inaccessibility of a large fraction of the recognition sites that remain buried within the polymeric matrix. To address this problem, the high selectivity imparted by the imprinting technique and the porosity of three-dimensional (3D) graphene oxide (GO)-based porous materials were utilized in this work to prepare a 3D GO-based Cu(II)-ion-imprinted material (hereafter denoted as IIM) via one-pot reactions of GO, chitosan (CS), and glutaraldehyde in the presence of Cu(II). Results of equilibrium binding experiments show that IIM has a high template-ion binding capacity (1.75 mmol g−1) and good imprinting factor (2.19). Further, results of selectivity tests indicate that IIM has a high Cu(II)-recognition ability. IIM also has a fast binding rate and satisfactory reusability. In addition, the Langmuir isotherm model was well fitted with the experimental data, indicating the monolayer adsorption of Cu(II) ions. The present work provided a convenient approach to prepare 3D GO-based imprinted materials that are promising for enrichment or recycling of target compounds from wastewater.

Non-enzymatic electrochemical malathion sensor based on bimetallic Cu-Co metal-organic gels modified glassy carbon electrode

A non-enzymatic electrochemical sensor based on bimetallic Cu-Co metal-organic gel (MOG) modified glassy carbon electrode (GCE) was reported to achieve super-sensitive malathion detection. Phytic acid-based Cu-Co bimetallic MOG (PA-Cu-Co composite) is a kind of three-dimensional porous material and has a large surface area and superior conductivity due to crosslinked network structure and bimetal composition. The obtained PA-Cu-Co/GCE sensor can easily bond malathion due to the good affinity between Cu element and sulfur groups of malathion, leading to an inhibited redox signal of Cu element in presence of malathion. The electrode reaction was a typical adsorption controlled process. The introduction of Co element not only greatly improves the electron transfer ability but increases surface area and active sites of sensor interface for high affinity of malathion, thus endowing PA-Cu-Co composite with outstanding sensitivity and selectivity. Under optimized operating conditions, the enzyme-free PA-Cu-Co/GCE malathion sensor exhibits good stability and excellent detection performance, with a wide linear range to malathion of 0.5 pM to 5 μM and low detection limit of 0.3 pM. Furthermore, the PA-Cu-Co/GCE sensor showed good recovery in real samples detection, implicating the potential applicability of PA-Cu-Co/GCE sensor in sensitive and selective detection of organophosphorus pesticides (OPs).

Design of three-dimensional hexagonal petal-like nickel-copper cobaltite // luffa sponge-derived activated carbon electrode materials for high-performance solid-state supercapattery

Three-dimensional porous nanostructured materials are considered superior materials for energy storage applications due to their high storage capability. A nickel copper-cobalt oxide (NCC) composite with a uniform 3-D porous nanostructure (positive electrode materials) and luffa sponge-derived activated carbon (LPAC) with honeycomb-like structure (negative electrode materials) were synthesized by a simple hydrothermal and chemical method. A sample of the nickel-copper cobalt oxide-5 (NCC-5) nanocomposite reached a high specific capacitance of 1048 F/g at the current density of 0.5 A/g. The NCC-5 nanocomposite sample shows a retention capacity of 93 % after 10,000 charge and discharge cycles with 95 % of Coulombic efficiency (CE). The LPAC illustrates a remarkable specific capacitance of 909 F/g at 1 A/g of current density, compared to the best literature value of 400 F/g. The full-cell NCC-5//LPAC delivered an energy density of 65 Wh/kg, corresponding to a power density of 500 W/kg. The supercapacitor devices connected in series could glow 55 red LEDs for 5 min.

Spherical Attapulgite/Silica Aerogels Fabricated via Different Drying Methods with Excellent Adsorption Performance.

Dye wastewater has caused great harm to the environment, which is an urgent problem to be solved. As typical three-dimensional porous materials, aerogels have attracted great interest in dye wastewater treatment. In this work, spherical attapulgite/silica (ATP/SiO2) gels were initially prepared by easily scalable sol-gel dripping methods and then dried to aerogels with three drying techniques, namely, supercritical CO2 drying (SCD), freeze-drying (FD), and ambient pressure drying (APD). The effect of the drying techniques and heat-treated temperature on the physical characteristic, morphological properties, microstructure, and chemical structure of the spherical ATP/SiO2 aerogels were investigated. The macroscopic morphology of the spherical ATP/SiO2 aerogels was homogeneous and integrated without local cracking. The average pore diameter and specific surface area of the spherical ATP/SiO2 aerogels prepared by the three drying techniques were in the range of 6.8-8.6 nm and 218.5-267.4 m2/g, respectively. The heat treatment temperature had a significant effect on the pore structure and the wetting properties of the aerogels. The 600 °C heat-treated aerogels were subjected to adsorption tests in methylene blue (MB) solution (60 mg/g, 100 mL), which exhibited a great adsorption capacity of 102.50 mg/g. Therefore, the resulting spherical ATP/SiO2 aerogels possessed multipath preparation and exhibited an efficient adsorption performance, with the potential to be applied as an adsorbent for dye wastewater.

Atomic layer deposition of TiO2 on porous polysulfone hollow fibers membranes for water treatment

Numerous membranes devoted to water treatment are made of Polysulfone (PSF) and can suffer from performance deterioration because of the intrinsic hydrophobicity of this material. Modifying membrane surface allows the engineering of its physicochemical properties and can achieve improved permeability and anti-fouling efficiency by tuning the membrane hydrophilicity or porosity. Atomic layer deposition (ALD) is a unique technology that provides highly conformal and uniform coatings layers such as oxides over surfaces of three-dimensional (3D) parts, porous materials and particles. In this work, titanium dioxide (TiO2) was deposited on polysulfone hollow fibers (HF) membranes via ALD using TiCl4 and H2O as precursors. Membranes obtained with increasing number of deposition ALD cycles were tested until the pores were totally blocked. The morphology, structure and mechanical properties of membranes were not altered. The deposition was confirmed by scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS) analyses. The deposition of TiO2 enhanced by 50% the water permeability and by 20% the fouling resistance of the PSF HF membranes until only 20 ALD cycles. This is accompanied by an increase of hydrophilicity and a pores size reduction.

Biomedically-relevant metal organic framework-hydrogel composites.

Metal organic frameworks (MOFs) are incredibly versatile three-dimensional porous materials with a wide range of applications that arise from their well-defined coordination structures, high surface areas and porosities, as well as ease of structural tunability due to diverse compositions achievable. In recent years, following advances in synthetic strategies, development of water-stable MOFs and surface functionalisation techniques, these porous materials have found increasing biomedical applications. In particular, the combination of MOFs with polymeric hydrogels creates a class of new composite materials that marries the high water content, tissue mimicry and biocompatibility of hydrogels with the inherent structural tunability of MOFs in various biomedical contexts. Additionally, the MOF-hydrogel composites can transcend each individual component such as by providing added stimuli-responsiveness, enhancing mechanical properties and improving the release profile of loaded drugs. In this review, we discuss the recent key advances in the design and applications of MOF-hydrogel composite materials. Following a summary of their synthetic methodologies and characterisation, we discuss the state-of-the-art in MOF-hydrogels for biomedical use - cases including drug delivery, sensing, wound treatment and biocatalysis. Through these examples, we aim to demonstrate the immense potential of MOF-hydrogel composites for biomedical applications, whilst inspiring further innovations in this exciting field.