Porous Monoliths Research Articles

Mesoporosity enhancement in carbon monoliths through incorporation of a nonpolar solvent with a templating source for fast adsorption of organic dyes

Obtaining hierarchical porous carbon monoliths with bigger and controlled pore sizes through soft templating and without macroscopic phase separation remains a challenge for the synthesis. In this study, we tried to introduce nonpolar solvents (benzene or toluene) together with a pluronic template in the sol-gel polycondensation route of polymer precursors to obtain carbons in the monolithic form without macroscopic phase separation during the polymerization stage. The porosity results show that carbon monoliths vary solely with mesopore features while retaining macropores, compared to carbon monoliths obtained with pluronic template alone. The mesopore volumes almost double with an increase in pore sizes by 1 nm at maxima, and the pore sizes extend to 30 nm from the addition of nonpolar solvent. This is possible due to the interaction of the nonpolar solvent with the hydrophobic core of the pluronic template, which causes swelling of micelles during the polymerization stage, and thus finally, retention of larger pore sizes and pore volumes within carbon monoliths. The structural and surface chemistry characterizations ensure a similar behaviour of the resulting carbon monoliths that are further investigated for the adsorption kinetics of different types of organic dyes (methylene blue, methyl orange, and congo red) to understand the sole role of mesoporosity. The adsorption kinetics follows the trend of mesopore volumes with fast adsorption vis-à-vis the sizes and molar masses of organic dyes.

Hierarchically Porous Ceramic and Metal‐Ceramic Hybrid Materials Structured by Vat Photopolymerization‐Induced Phase Separation

Additive manufacturing techniques such as vat photopolymerization have laid the foundation for impressive advances in the 3D structuring of ceramic materials. However, simultaneous structuring of these complex‐shaped ceramic objects on the sub‐µm scale, an essential feature for a wide range of applications in separation, energy conversion and storage, adsorption or sensing, has remained a tremendous challenge. This study demonstrates how complex‐shaped polymer‐derived SiOC ceramics exhibiting hierarchical porosity ranging from the sub‐µm‐ to the millimeter‐range can be generated by combining vat photopolymerization with photopolymerization‐induced phase separation using preceramic polymer‐based phase‐separating resins. In addition to allowing single‐step, multi‐level structural control, this new processing concept allows for the chemical modification of the 3D‐printable, phase‐separating preceramic polymer resins using organometallic compounds, including the possibility to generate functional metal nanoparticles in situ during the polymer‐to‐ceramic conversion. In this manner, a chemical toolbox is provided, facilitating the introduction of Ni, Co, Mo, or La into the hierarchically structured SiOC matrix. The versatile applicability of this new materials design approach is demonstrated by employing complex‐shaped, hierarchically porous monoliths containing in situ generated Ni nanoparticles as heterogeneous catalysts for CO2 methanation, with a profound increase in catalyst performance attained by oxidative post‐treatment of the metal‐ceramic hybrid material.

Fast and effective palladium adsorption from electronic waste using a highly macroporous monolith synthesized via rapid UV-irradiation

Recovering palladium rapidly and effectively from electronic waste materials presents a challenging and essential task, mainly due to the harsh acidic conditions. This study developed a highly porous and lightweight monolith to address this issue by enabling rapid and efficient palladium adsorption under acidic conditions. The monoliths were fabricated through a quick UV-irradiation cryopolymerization process. The resulting monoliths exhibited significantly enhanced palladium adsorption capacity, measuring at 155.5 mg g−1, surpassing most previously reported data. The adsorbed concentrations of Pd(II) and other coexisting ions were determined using an Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES, VISTA-MPX, Varian). Various parameters such as pH, contact time, temperature, concentration, and selectivity were investigated to assess their impact on palladium adsorption. The material demonstrated superior selectivity for palladium ions in the presence of coexisting metal ions. Furthermore, the material's thermal stability was evaluated within the 25–100 °C range, revealing sufficient adsorption capacity at temperatures up to 100 °C, indicating its potential for implementation in harsh conditions. The synthesized monolith exhibited a shelf life of up to six months without degrading its adsorption performance. Moreover, the material retained its adsorption efficiency after multiple cycles of use. The effectiveness of palladium adsorption was also demonstrated in actual wastewater samples, further validating the material's practical application. Overall, this designed system showcases excellent adsorption performance and stability, making a valuable contribution to polymer chemistry and environmental science for recovering precious metals from wastewater.

Customised Microporous Carbon 3D Structures with Good Mechanical Properties and High Nitrogen Content Obtained from Whey Powders

Novel customised carbon monoliths with a high specific surface area were synthesised by carbonisation plus activation of dehydrated whey powders, a biomass byproduct of the dairy industry. The whey powders were casted directly by pouring them into a desired mould. After a pseudo-sintering process promoted by the self-reaction of the whey components (mostly lactose and whey proteins) at moderate temperatures (ca. 250 °C), 3D porous carbons were obtained. The process did not require any binder or external overpressure to prepare the 3D porous carbons. Upon thermal activation with CO2 or chemical activation with H3PO4 and KOH, the shape of the monolithic structure was preserved after the development of a microporous network (SBET up to 2400 m2/g). Both thermal and chemical activation had little effect on the macroporosity of the monoliths. Activation of these 3D carbons had to be performed with care to avoid heterogeneous skin/core activation and/or overactivation. Highly porous monoliths (SBET of 980 m2/g; open porosity of 70%) with outstanding compressive strength (10 MPa) could be obtained by thermal activation (CO2) of whey monoliths at 850 °C for 1.5 h. Additionally, the use of whey as a precursor provided the carbon monolith with a relatively high nitrogen content (ca. 3 wt.%).

Utilization of an aqueous two-phase emulsification to prepare bimodal porous cellulose monolith for efficient adsorption of bovine serum albumin

Cellulose monolith has garnered significant interest in the field of biochromatography, which lies in its interconnected porous structure, large surface area and biocompatibility. In this context, we propose a novel approach for preparing cellulose monoliths using an aqueous two-phase system devoid of any organic solvents and surfactants. In this strategy, emulsifying cellulose solution into PEG 20,000 solution gives bicontinuous aqueous phases and further porous cellulose monolith after regeneration of dissolved cellulose. And the macroporous channels are derived from the removal of the PEG 20,000 aqueous phase while the micropores are from the phase separation of the cellulose phase. Physical characterizations reveal the obtained cellulose monolith exhibits exceptional column permeability of 1.36 × 10−11 m2 and a substantial surface area of 39.34 m2/g. Furthermore, cellulose monolith is functionalized with diethyl ethylamine hydrochloride (DEAE-HCl) to evaluate its potential as an anion adsorbent. Experimental results reveal that the DEAE-modified cellulose monolith possesses of adsorptive capacity of 316.58 mg/g of bovine serum albumin, along with fast adsorption kinetic. This study introduces an innovative strategy for fabricating porous cellulose monoliths tailored for biochromatography applications.

Cocontinuous Nanostructures by Microphase Separation of Statistically Cross-Linked Polystyrene/Poly(2-vinylpyridine) Networks.

Cocontinuous polymeric nanostructures have drawn considerable attention due to their ability to combine distinct, percolation-dependent properties of two different polymer domains. Randomly end-linked copolymer networks (RECNs) have previously been shown to support the formation of disordered cocontinuous nanostructures across wide composition windows in a robust way. However, achieving highly efficient linking of telechelic polymers with excellent end-group fidelity often requires complex synthetic routes. As an alternative, we study here statistically cross-linked copolymer networks (SCCNs) composed of polystyrene and poly(2-vinylpyridine) (PS and P2VP) with cross-linkable allyl pendent groups that are conveniently synthesized by controlled radical copolymerization. Via selective extraction of P2VP, coupled with gravimetry, small-angle X-ray scattering, and electron microscopy, we find disordered cocontinuous phases across wide composition ranges (up to ≈ 35 wt %), approaching values previously determined for RECNs. Remarkably, even for samples that appear to exhibit full percolation, a substantial fraction of P2VP (≈ 20-30 wt %) cannot be removed, which we ascribe to short strands between nearby cross-linkers that are physically embedded within PS domains. The resulting PS porous monoliths with residual surface P2VP layers enable facile surface modification to resist protein adsorption and templating of porous gold nanostructures.

Chromogenic probe adhered porous polymer monolith as real-time solid-state sensor for the detection of ultra-trace toxic mercury ions

The escalating predicament of water pollution has spurred the development of new chromogenic materials for the efficient detection/screening of toxic mercuric (Hg2+) ions. In this study, we report a simple and efficient detection stratagem by infusing a chromogenic ion-receptor (BTDA), i.e., 4-(benzothiazol-2-yl)-N, N-dimethylaniline onto a structurally intertwined meso-/macro-pore polymer template for the target-specific sensing of ultra-trace Hg2+. The structural/surface features of the monolithic polymer template, prepared from glycidyl methacrylate (GMA) monomer crosslinked with ethylene glycol dimethacrylate (EGDMA), facilitate voluminous infusion and uniform decoration of ion-receptor molecules across the continuous porous poly(GMA-co-EGDMA) framework, resulting in a solid-state colorimetric sensory system. The bimodal polymer network's intriguing surface and structural morphology of the chromogenic sensor material are interpreted using scanning/transmission electron microscopy, X-ray diffraction, photoelectron spectroscopy, energy dispersive X-ray spectrometry, optical spectroscopy, surface area, porosity and thermal analysis. The proposed Hg2+ sensor offers a linear response range of 1–150 μg/L, with a detection and quantification limit of 0.29 and 0.97 μg/L, respectively. The poly(GMA-co-EGDMA)-BTDA sensor exhibits a quick ion-sensing response (40 s) with distinct color transitions from pastel yellow to olive as a function of increasing Hg2+ concentration. The matrix tolerance studies for the proposed sensory system reveal high selectivity for Hg2+, with a recovery of ≥99.2% in on-site environmental samples. The sensor material exhibits excellent data reproducibility and reliability up to seven cycles of reusability.

Powdered Hierarchically Porous Silica Monoliths for the Selective Extraction of Scandium.

Scandium (Sc) is a high value Critical Material that is most commonly used in advanced alloys. Due to current and potential supply limitations, there has been an international effort to find new and improved ways to extract Sc from existing and novel resources. Solid-phase extraction (SPE) is one promising approach for Sc recovery, particularly for use with low-grade feedstocks. Here, unfunctionalized, powdered hierarchically porous silica monoliths from DPS Inc. (DPS) are used for Sc extraction in batch and semicontinuous flow systems at model conditions. The sorbent exhibits excellent mass transfer properties, much like the whole monoliths, which should permit Sc to be rapidly recovered from large volumes of feedstock. The Sc adsorption capacity of the material is ∼142.7 mg/g at pH 6, dropping to ∼12.0 mg/g at pH 3, and adsorption is furthermore highly selective for Sc compared with the other rare earth elements (REEs). Under semicontinuous flow conditions, recovery efficiency is limited by a kinetic process. The primary mechanism responsible for the system's slow approach to equilibrium is the Sc adsorption reaction kinetics rather than inter- or intraparticle diffusion. Overall, this unmodified hierarchically porous silica powder from DPS shows great promise for the selective extraction of Sc from various feedstocks.

Monolithic-structured nickel silicide electrocatalyst for bifunctionally efficient overall water splitting

The rational design and synthesis of cost-effective and efficient bifunctional electrocatalysts are crucial for developing hydrogen energy yet challenging. Here we report porous monolith electrocatalysts (PMECs) comprising transition metal silicide (e.g., nickel silicide) with high activity and durability. These PMECs offer strong synergetic effects and high exposure of active sites, resulting in excellent kinetics in catalyzing both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), which surpass the benchmark catalysts RuO2 and Pt/C. The doping strategy is demonstrated to further enhance electrocatalytic performance by constructing Mo-doped Ni2Si PMEC, which requires only a cell voltage of 1.60 V at 100 mA cm−2. Density functional theory calculations display that the synergistic effect of Ni and Si can reduce the energy barriers of intermediate adsorption, and the introduction of Mo into Ni2Si can further decrease the energy barrier of determining step and optimize the H* adsorption energy, thus enhancing the electrochemical kinetics for OER and HER. Our work paves the way for designing high-efficiency and low-cost porous monolith catalysts through a facile and scalable method, showing great prospects for industrialization.

From natural clinoptilolite to hierarchical designed porous geopolymer-zeolite monoliths: Synthesis, characterization and formation mechanism

This work reports a novel approach to tailored design of clinoptilolite based hierarchically porous geopolymer-zeolite foams (CFs) by concurrent use H2O2 solution and montmorillonite as pore formers. Natural clinoptilolite, calcined clinoptilolite and aluminate activator were used as starting mix to produce the hybrid foams. The resultant products possess multiscale distributed pores – micropores (<2 nm), meso-macropores (50–175 nm) and macropores (0.1–0.2 μm, 100 μm-2 mm). The formation of macropores in micron-millimeter range is due to the decomposition of H2O2. Montmorillonite act as another pore-forming agent and construct macropores in submicron range. Hierarchical porous geopolymer-zeolite monoliths can be produced by varying the composition. The dissolution of clinoptilolite, montmorillonite, illite, metazeolite and anorthite contribute to the formation of geopolymer gel, while quartz and albite remains inert. The characters of CFs are highly depended on the clinoptilolite/metazeolite mass ratio. The porosities, bulk densities and BET surface areas range from 35.2 to 70.3 %, 0.808–1.325 g/cm3 and 2.557–23.330 m2/g, respectively. In addition, mechanisms for the formation of hierarchical porous geopolymer-clinoptilolite monoliths was proposed. These porous materials with tailored porosity are favored applied as building materials (thermal insulation). In contrast to the traditional foaming techniques, our work presents the possibility of directing the tailored synthesis of geopolymer-zeolite foams with at least three level of pores.

Metal-organic framework and porous polymer monolith as ion-receptor carrier templates for the solid-state naked-eye sensing of ultra-trace Cr(III) from aqueous medium

We report on an effective onsite optical sensor strategy using probe-decorated porous polymer monolith (PPM) and aluminum-based metal-organic framework (MIL-53 (Al) MOF) as a reliable colorimetric sensor for the detection of ultra-trace levels of Cr3+. MOFs and PPMs have attracted considerable interest in environmental applications due to their high surface area, perpetual porosity, and tunable structural network. Here, Al-MOF and PPM materials were used as porous templates for the uniform infusion of a chromoionophoric probe, i.e., (Z)-1,2-diphenyl-2-((4-(E)-phenyldiazenyl)phenyl)imino)ethan-1-ol (DPPE), for the solid-state colorimetric recognition and capturing of Cr3+ from aqueous medium. The structural morphology and surface topography of the sensor materials have been characterized using the transmission/scanning electron microscopy, optical spectroscopy, X-ray/electron diffraction, elemental mapping, surface area/pore volume and thermal analysis to understand the surface properties and stability features of the long-range ordered porous framework. The sensor's superior structural and surface features tender faster ion diffusion to the anchored probe sites within 60 s. The sensor induces a selective ligand-to-metal charge transfer (LMCT) chelation with Cr3+, resulting in a sequence of color transition from pale orange to sepia-brown, with incremental levels of Cr3+. The significance of physicochemical factors, such as pH, probe content, sensor dose, kinetics, temperature, reusability, selectivity, sensitivity, and stability, has been optimized to maximize the ion-sensing performance. The sensors' reusability has been tested by replicating the ion-sensing performance up to eight cycles. The solid-state sensor exhibited a linear range of 1.0–200 ppb for Cr3+, with a detection limit of 0.44 and 0.53 ppb and a quantification limit of 1.39 and 2.22 ppb for DPPE-loaded PPM and Al-MOF sensors, respectively. The practical utility of the sensor materials with industrial/environmental water samples reveals excellent data reliability/reproducibility (recovery ≥99.1 %; RSD ≤2.5 %) for real-time monitoring.

Sulfonated Hydrogel Formed via CO2-in-Water Emulsion: Potential in Antibiotic Removal.

Herein, a green, carbon dioxide-in-water high-internal-phase emulsion (C/W HIPEs) was developed and stabilized with polyvinyl alcohol (PVA) for the formation of chitosan oligosaccharide/poly(acrylamide-co-sodium 4-styrene sulfonate) [COS/P(AM-co-SSS)] monolithic porous hydrogel. The obtained monolith was characterized via FT-IR and SEM. The SEM patterns depicted that the monoliths were interconnected, the void sizes were 78.5 µm, and the interconnected pore throats were 28 μm approximately. Mechanical measurement results indicated that the maximum compress stress of the monolith could reach 334.4 kPa at 90% strain, and it exhibited good mechanical stability. After 200 cycles of compression, it could still recover its original shape without cracking. The obtained COS-based monolith was selected to remove tetracycline (TC) for evaluating the adsorptive features of the interpenetrating pore-containing monolith. The monolithic COS/P(AM-co-SSS) hydrogel behaved with strong antibiotic adsorption capacity (1600.4 mg/g for TC). The adsorption process agreed well with the pseudo-second-order kinetic and Langmuir isothermal models. In addition, the porous monolith had a strong electrostatic force on TC according to the thermodynamic study. This work provides a green route for the development of novel monolithic hydrogels and highlights its potential application in the treatment of antibiotic-containing wastewater.

Sheltering Mono-P-Ligated Metal Complexes in Porous Polystyrene Monolith: Effect of Aryl Pendant Stabilizers on Catalytic Durability.

Metal centers that can generate coordinatively unsaturated metals in accessible and stable states have been developed using synthetic polymers with sophisticated ligand and scaffold designs, which required synthetic efforts. Herein, we report a simple and direct strategy for producing polymer-supported phosphine-metal complexes, which stabilizes mono-P-ligated metals by modulating the electronic properties of the aryl pendant groups in the polymer platform. A three-fold vinylated PPh3 was copolymerized with a styrene derivative and a cross-linker to produce a porous polystyrene-phosphine hybrid monolith. Based on the Hammett substituent constants, the electronic properties of styrene derivatives were modulated and incorporated into the polystyrene backbone to stabilize the mono-P-ligated Pd complex via Pd-arene interactions. Through NMR, TEM, and comparative catalytic studies, the polystyrene-phosphine hybrid, which induces selective mono-P-ligation and moderate Pd-arene interactions, demonstrated high catalytic durability for the cross-coupling of chloroarenes under continuous-flow conditions.

3D porous alumina/graphene hybrids prepared by atomic layer deposition and their performance for water treatment

Metal / carbon hybrids have impressive potential of applications in many fields: catalysis, energy conversion and storage, environmental. However, further efforts are needed to achieve a better control of homogeneity of the metal oxide deposit on the carbon surface to provide reliable synthesis approaches of metal / carbon hybrids. In this work, atomic layer deposition is used to prepare 3D porous alumina / reduced graphene oxide hybrid monoliths. We show that atomic layer deposition, even though rarely reported to prepare metal oxide / carbon hybrids, allows a conformal coating onto the graphene nanosheet surface. In-depth advanced characterization have been performed thanks to a coupled approach consisting of the preparation of lamellas of the porous hybrid by means of focused ion beam and their analysis by transmission electron microscopy. A good accessibility of the alumina precursors to the internal surface of the prepared 3D porous carbon monoliths was evidenced. The alumina / graphene hybrid prepared with 50 cycles of ALD deposit has a surface as high as 284 m2/g. As a proof-of-concept for the interest of the designed hybrids, they are tested for the removal of Congo red, a standard organic dye pollutant. 87 and 98 % of Congo red removal were reached at the first and the second step of adsorption proving the good adsorption performance and reusability ability of the de designed hybrid adsorbents. We believe that such multi-porous 3D alumina / graphene macrostructures that offers a favorable accessibility to the adsorption sites open interesting potentialities for pollution remediation applications.

Enhanced electro-Fenton activity with Fe/Sm2O3 monoliths as novel and efficient heterojunction for glyphosate degradation

Excessive utilization of herbicide has posed irreversible effect on aquatic organisms and human being. FexSmy@PCMs have been synthesized as efficient heterogeneous electro-Fenton catalysts for herbicide degradation, in which H2O2 is in situ generated by the porous carbon monolith (PCM) ground and then H2O2 is activated into •OH by the anchored Fe/Sm2O3. Fe nanocrystals are intimately embedded into the Sm2O3 nanoblocks in Fe0.3Sm0.7@PCM, which can promote the electron transfer and induce synergistic redox cycle. Fe0.3Sm0.7@PCM achieves over 95% glyphosate (GLP) degradation within one hour in neutral condition, which is 30% better than Fe@PCM. Thanks to high efficiency and exceptional stability, Fe0.3Sm0.7@PCM maintains over 94% GLP removal after six consecutive batches.

Porous polymer monoliths with complementary retention mechanisms for online solid-phase extraction liquid chromatography to determine lysozyme in egg white

Porous polymer monoliths with complementary retention mechanisms for online solid-phase extraction liquid chromatography to determine lysozyme in egg white

Separation of alkane isomers in a hierarchically structured 3D-printed porous carbon monolith

Hierarchically structured 3D printed porous carbons monoliths, exhibiting cylinder structures composed of tetragonal cubic centered unit cells, were studied for their applicability in adsorptive pentane (C5) and hexane (C6) alkane isomers separation (linear/branched). Three materials of the same macroscopic shape were employed in the study, which varied in the micro- and mesoporosity by changing the final CO2 activation step: non-activated and activated at 1133 K for 6 and 12 h, respectively. Fixed bed breakthrough experiments were conducted for C5/C6 isomer feed mixtures, covering 373, 423, and 473 K temperatures and total alkane partial pressure up to 50.0 kPa. Results demonstrated that the initial porosity for the non-activated monolith enables the complete separation of linear from their respective branched isomers (slightly adsorbed) via a near molecular sieving effect, showing the following sorption hierarchy order (nC6 > nC5) ≫>≫ (2MP > 3MP > 23DMB ≈ iC5 > 22DMB). Regarding the CO2-activated monoliths, both showed a completely different picture, being all the alkane isomers adsorbed (much higher loadings) following the sorption hierarchy order: nC6 > 3MP > 2MP > 23DMB > 22DMB > nC5 > iC5. These results indicate that besides enhancing the microporosity and available specific surface area, the pore sieving effect of branched alkanes is lost due to the pore widening during the CO2 activation. The breakthrough data for the non-activated monolith is also numerically fitted with a convenient, dynamic adsorption model.

High-strength, multifunctional and 3D printable mullite-based porous ceramics with a controllable shell-pore structure

The quest for lightweight and functional materials poses stringent requirements on mechanical performance of porous materials. However, the contradiction between high strength and elevated porosity of porous materials severely limits their application scenarios in emerging fields. Herein, high-strength multifunctional mullite-based porous ceramic monoliths were fabricated utilizing waste fly ash hollow microspheres (FAHMs) by the protein gelling technique. Owing to their unique shell-pore structure inspired by shell-protected biomaterials, the monoliths with porosity of 54.69%–70.02% exhibited a high compressive strength (32.3–42.9 ​MPa) which was 2–5 times that of mullite-based porous ceramics with similar density reported elsewhere. Moreover, their pore structure and properties could be tuned by regulation of the particle size and content of the FAHMs, and the resultant monoliths demonstrated superior integrated performances for multifunctional applications, such as broadband sound insulation, efficient thermal insulation, and high-temperature fire resistance (>1300 ​°C). On this basis, mullite-based porous ceramic lattices (porosity 68.28%–84.79%) with a hierarchical porous structure were successfully assembled by direct ink writing (DIW), which exhibited significantly higher compressive strength (3.02–10.77 ​MPa) than most other ceramic lattices with comparable densities. This unique shell-pore structure can be extended to other porous materials, and our strategy paves a new way for cost-effective, scalable and green production of multifunctional materials with well-defined microstructure.

Development of a novel biochar-made porous monolith for enhanced C1 and H2 fermentation

Biochar is a carbonaceous porous material that is produced through the thermal processing of biomass under oxygen-limited environment. Nevertheless, biochar is known to be an inexpensive and sustainable raw material with a wide range of possible applications. Recently, biochar has been discovered as an efficient biological catalyst for anaerobic conversion, mainly due to its highly porous structure with micro and macro channels, which procures a viable living area for attached-grown microorganisms. Whereas it is never applied to improve the biological conversion of gas substances such as C1 (e.g., CO, CO2) and H2, which is a promising research area with increasing commercial interest. However, considering that biological reaction is limited by the target water solubility of gas substrates, special attention is required when combining biochar for gas fermentation. The goal was to create a novel gas sparger where the biofilm grows on biochar, thus improving the interaction with the gaseous substrate. For this purpose, polystyrene foam and powdered biochar were compounded to form a mouldable composite, which was then cast as a porous monolith.•Biochar-made sparger (BS) was investigated for the homoacetogenic conversion of H2 gas via microbial mixed cultures as opposed to a control test equipped with a stone sparger.•BS showed a significantly better performance in terms of biological gas fixation rate (36% more than control) and productivity (8.5 gCOD L−1 d−1).

Self-assembly of MOF-801 into robust hierarchically porous monoliths for scale-up atmospheric water harvesting

MOFs are becoming one of the most promising sorbents for atmospheric water harvesting (AWH), but their powder form limits the scale-up application. Conventional shaping methods tend to deteriorate the sorption performance or weaken the mechanical strength of the sorbents. Here, monolithic MOF-801 was constructed by coupling sol–gel phase separation and acid-heat post-treatment method. The porosity can be optimized up to 59.7% by regulating the phase separation progress and gelation time, and the specific surface area and micropore volume can be optimized up to 977.8 m2 g−1 and 0.234 cm3 g−1 by the acid-heat post-treatment. The special properties ensured the monolithic MOF-801 with an excellent moisture sorption capacity of 1.2 times higher than that of the conventional MOF-801 powder in small batches and 1.4 times higher than that of the conventional compressed tablet in large batches at 30% RH. The monolithic MOF-801 had centimeter-scale morphology and good mechanical strength with compressive Young's modulus up to 61.3 MPa. This study provides a feasible strategy for achieving the monolithic shaping of MOFs for industrial-scale AWH.