Porosity Of Metal-organic Frameworks Research Articles

Exploitation of Pore Structure for Increased CO2 Selectivity in Type 3 Porous Liquids.

CO2 capture requires materials with high adsorption selectivity and an industrial ease of implementation. To address these needs, a new class of porous materials was recently developed that combines the fluidity of solvents with the porosity of solids. Type 3 porous liquids (PLs) composed of solvents and metal-organic frameworks (MOFs) offer a promising alternative to current liquid carbon capture methods due to the inherent tunability of the nanoporous MOFs. However, the effects of MOF structural features and solvent properties on CO2-MOF interactions within PLs are not well understood. Herein experimental and computational data of CO2 gas adsorption isotherms were used to elucidate both solvent and pore structure influences on ZIF-based PLs. The roles of the pore structure including solvent size exclusion, structural environment, and MOF porosity on PL CO2 uptake were examined. A comparison of the pore structure and pore aperture was performed using ZIF-8, ZIF-L, and amorphous-ZIF-8. Adsorption experiments here have verified our previously proposed solvent size design principle for ZIF-based PLs (1.8× ZIF pore aperture). Furthermore, the CO2 adsorption isotherms of the ZIF-based PLs indicated that judicious selection of the pore environment allows for an increase in CO2 selectivity greater than expected from the individual PL components or their combination. This nonlinear increase in the CO2 selectivity is an emergent behavior resulting from the complex mixture of components specific to the ZIF-L + 2'-hydroxyacetophenone-based PL.

Molecular-caged metal-organic frameworks for energy management.

Metal-organic frameworks (MOFs) hold great promise for diverse applications when combined with polymers. However, a persistent challenge lies in the susceptibility of exposed MOF pores to molecule and polymer penetration, compromising the porosity and overall performance. Here, we design a molecular-caged MOF (MC-MOF) to achieve contracted window without sacrificing the MOF porosity by torsional conjugated ligands. These molecular cages effectively shield against the undesired molecule penetration during polymerization, thereby preserving the pristine porosity of MC-MOF and providing outstanding light and thermal management to the composites. The polymer containing 0.5 wt % MC-MOF achieves an 83% transmittance and an exceptional haze of 93% at 550 nanometers, coupled with remarkable thermal insulation. These MC-MOF/polymer composites offer the potential for more uniform daylighting and reduced energy consumption in sustainable buildings when compared to traditional glass materials. This work delivers a general method to uphold MOF porosity in polymers through molecular cage design, advancing MOF-polymer applications in energy and sustainability.

Design of Mixed-Matrix MOF Membranes with Asymmetric Filler Density and Intrinsic MOF/Polymer Compatibility for Enhanced Molecular Sieving.

The separation of high-value-added chemicals from organic solvents is important for many industries. Membrane-based nanofiltration offers a more energy-efficient separation than the conventional thermal processes. Conceivably, mixed-matrix membranes (MMMs), encompassing metal-organic frameworks (MOFs) as fillers, are poised to promote selective separation via molecular sieving, synergistically combining polymers flexibility and fine-tuned porosity of MOFs. Nevertheless, conventional direct mixing of MOFs with polymer solutions results in underutilization of the MOF fillers owing to their uniform cross-sectional distribution. Therefore, in this work, a multizoning technique is proposed to produce MMMs with an asymmetric-filler density, in which the MOF fillers are distributed only on the surface of the membrane, and a seamless interface at the nanoscale. The design strategy demonstrates five times higher MOF surface coverage, which results in a solvent permeance five times higher than that of conventional MMMs while maintaining high selectivity. Practically, MOFs are paired with polymers of similar chemical nature to enhance their adhesion without the need for surface modification. The approach offers permanently accessible MOF porosity, which translates to effective molecular sieving, as exemplified by the polybenzimidazole and Zr-BI-fcu-MOF system. The findings pave the way for the development of composite materials with a seamless interface.

Revisiting Metal-Organic Frameworks Porosimetry by Positron Annihilation: Metal Ion States and Positronium Parameters.

Metal-organic frameworks (MOFs) stand as pivotal porous materials with exceptional surface areas, adaptability, and versatility. Positron Annihilation Lifetime Spectroscopy (PALS) is an indispensable tool for characterizing MOF porosity, especially micro- and mesopores in both open and closed phases. Notably, PALS offers porosity insights independent of probe molecules, which is vital for detailed characterization without structural transformations. This study explores how metal ion states in MOFs affect PALS results. We find significant differences in measured porosity due to paramagnetic or oxidized metal ions compared to simulated values. By analyzing CPO-27(M) (M = Mg, Co, Ni), with identical pore dimensions, we observe distinct PALS data alterations based on metal ions. Paramagnetic Co and Ni ions hinder and quench positronium (Ps) formation, resulting in smaller measured pore volumes and sizes. Mg only quenches Ps, leading to underestimated pore sizes without volume distortion. This underscores the metal ions' pivotal role in PALS outcomes, urging caution in interpreting MOF porosity.

Adsorption and Diffusion Properties of Functionalized MOFs for CO2 Capture: A Combination of Molecular Dynamics Simulation and Density Functional Theory Calculation.

The capture of carbon dioxide (CO2) from fuel gases is a significant method to solve the global warming problem. Metal-organic frameworks (MOFs) are considered to be promising porous materials and have shown great potential for CO2 adsorption and separation applications. However, the adsorption and diffusion mechanisms of CO2 in functionalized MOFs from the perspective of binding energies are still not clear. Actually, the adsorption and diffusion mechanisms can be revealed more intuitively by the binding energies of CO2 with the functionalized MOFs. In this work, a combination of molecular dynamics simulation and density functional theory calculation was performed to study CO2 adsorption and diffusion mechanisms in five different functionalized isoreticular MOFs (IRMOF-1 through -5), considering the influence of functionalized linkers on the adsorption capacity of functionalized MOFs. The results show that the CO2 uptake is determined by two elements: the binding energy and porosity of MOFs. The porosity of the MOFs plays a dominant role in IRMOF-5, resulting in the lowest level of CO2 uptake. The potential of mean force (PMF) of CO2 is strongest at the CO2/functionalized MOFs interface, which is consistent with the maximum CO2 density distribution at the interface. IRMOF-3 with the functionalized linker -NH2 shows the highest CO2 uptake due to the higher porosity and binding energy. Although IRMOF-5 with the functionalized linker -OC5H11 exhibits the lowest diffusivity of CO2 and the highest binding energy, it shows the lowest CO2 uptake. Accordingly, among the five simulated functionalized MOFs, IRMOF-3 is an excellent CO2 adsorbent and IRMOF-5 can be used to separate CO2 from other gases, which will be helpful for the designing of CO2 capture devices. This work will contribute to the design and screening of materials for CO2 adsorption and separation in practical applications.

Post-synthetic modifications of MOFs by different bolt ligands for controllable release of cargoes

Post-synthetic modifications (PSM) have drawn great attention as a vigoroso tool to tune or enhance the performance of metal-organic frameworks (MOFs). However, the current PSM method usually have to sacrifice the porosity of MOFs to enrich their functionality, such as pore space partition (PSP) and post-synthetic elimination and insertion (PSE&I), causing a trade-off in this aspect. To address this issue, we herein propose a new PSM strategy of using the size-matching ligands as the bolts to lock MOFs’ pores, which could be anchored onto open metal sites (OMSs) after guest loading through a stepwise manipulation. As a result, the loaded cargoes undergo a controlled releasing process with respect to different bolt ligands. Our proposed strategy provides a promising way to balance the functionality and porosity of MOFs.

Synthesis and Analysis of Titanium Based Metal Organic Frameworks for Photocatalysis

Metal-Organic Frameworks (MOFs) are porous inorganic networks that have recently shown potential in energy applications as photocatalysts. The porosity of MOFs make them excellent for guest-host interactions, however, most MOFs are slightly insulating due to metal oxide nodes, resulting in larger band gaps and poor conductivity. In order to combat these issues, post-synthetic modifications (PSM) can be used to slightly alter MOF properties. In this study, PSM’s were introduced to Titanium-based MOFs with MIL topology, such as MIL-125 and MIL-125-NH2, to improve their ability to photocatalytically degrade organic dyes through the addition of polyaniline nanofibers and additional metal interactions. The performance of these modified MOFs were tested and compared to the unmodified MOFs. In addition, titanium-based MOFs, were investigated because their nodes that are more semiconducting than other MOF types. Each MOF was characterized using BET surface area analysis, infrared spectroscopy, and powder X-ray diffraction. The conductivity of different MOFs were compared using cyclic voltammetry. The relative photocatalytic properties of each MOF was determined by monitoring their efficiency for photocatalytic degradation of rhodamine B and phenol red dyes in solution under controlled environments.

Nitrogen-Doped Carbon Cubosomes as an Efficient Electrocatalyst with High Accessibility of Internal Active Sites.

Porous carbon particles (PCPs) present considerable potential for applications across a wide range of fields, particularly within the realms of energy and catalysis. The control of their overall morphologies and pore structures has remained a big challenge. Here, using metal-organic frameworks (MOFs) as the precursor and polymer cubosomes (PCs) as the template, nitrogen-doped carbon cubosomes (SP-NCs) with a single primitive bicontinuous architecture are prepared. SP-NCs inherit the high porosity of MOFs, generating a high specific surface area of 825 m2 g-1 and uniformly distributed active sites with a 5.9 at % nitrogen content. Thanks to the presence of three-dimensional continuous mesochannels that enable much higher accessibility of internal active sites over those of their porous counterparts' lack of continuous channels, SP-NCs exhibit superior electrocatalytic performance for oxygen reduction reaction with a half-wave potential of 0.87 V, situating them in the leading level of the reported carbon electrocatalysts. Serving as an air cathode catalyst of the Zn-air battery, SP-NCs exhibit excellent performance, outperforming the commercial Pt/C catalysts.

Concomitant role of metal clusters and ligands in the synthesis and control of porosity in Metal-Organic Frameworks: A literature review

A clossal increase in the number of research articles on metal–organic frameworks (MOFs) have recently been anticipated as next-generation functional materials. The characteristic coordination behavior between metal ion and organic linker in MOFs provide them hydrid functional features of both the moieties. For the substantial improved performance of MOFs and to achieve widespread applications of MOFs in diverse fields, it is essential to develop effective synthetic strategies and understand the role of metal ion cluster or coordination sphere or secondary building units (SBU’s) and organic linker in detail. The augmentation in porosity and large surface area with multitude in diverse topologies provide a boost for the application of these materials in diverse allied fields. This review article provides a detailed introduction of the porous MOF materials; encompassing the role of secondary building units or metal cluster and organic linkers in defining the porosity of MOF materials. Detailed investigations about the role of metal ion clusters and expanded organic linkers that lead to MOFs with ultrahigh porosity have been done and portrayed carefully. The structural aspects of zirconium, zinc and copper cluster based porous MOFs and organic linkers (porphyrin and pyrene based) have been thoroughly portrayed owing to their various application in various fields. This review article will provide better understanding about the various factors involved in synthesis and controll of the porosity toward desired applications.

Progress in antibacterial/osteogenesis dual-functional surface modification strategy of titanium-based implants

To review antibacterial/osteogenesis dual-functional surface modification strategy of titanium-based implants, so as to provide reference for subsequent research. The related research literature on antibacterial/osteogenesis dual-functional surface modification strategy of titanium-based implants in recent years was reviewed, and the research progress was summarized based on different kinds of antibacterial substances and osteogenic active substances. At present, the antibacterial/osteogenesis dual-functional surface modification strategy of titanium-based implants includes: ① Combined coating strategy of antibiotics and osteogenic active substances. It is characterized in that antibiotics can be directly released around titanium-based implants, which can improve the bioavailability of drugs and reduce systemic toxicity. ② Combined coating strategy of antimicrobial peptides and osteogenic active substances. The antibacterial peptides have a wide antibacterial spectrum, and bacteria are not easy to produce drug resistance to them. ③ Combined coating strategy of inorganic antibacterial agent and osteogenic active substances. Metal ions or metal nanoparticles antibacterial agents have broad-spectrum antibacterial properties and various antibacterial mechanisms, but their high-dose application usually has cytotoxicity, so they are often combined with substances that osteogenic activity to reduce or eliminate cytotoxicity. In addition, inorganic coatings such as silicon nitride, calcium silicate, and graphene also have good antibacterial and osteogenic properties. ④ Combined coating strategy of metal organic frameworks/osteogenic active substances. The high specific surface area and porosity of metal organic frameworks can effectively package and transport antibacterial substances and bioactive molecules. ⑤ Combined coating strategy of organic substances/osteogenic active substancecs. Quaternary ammonium compounds, polyethylene glycol, N-haloamine, and other organic compounds have good antibacterial properties, and are often combined with hydroxyapatite and other substances that osteogenic activity. The factors that affect the antibacterial and osteogenesis properties of titanium-based implants mainly include the structure and types of antibacterial substances, the structure and types of osteogenesis substances, and the coating process. At present, there is a lack of clinical verification of various strategies for antibacterial/osteogenesis dual-functional surface modification of titanium-based implants. The optimal combination, ratio, dose-effect mechanism, and corresponding coating preparation process of antibacterial substances and bone-active substances are needed to be constantly studied and improved.

Functional material “Ionic liquid-supported MIL-101(Fe)” to enhance composite solid electrolyte for lithium metal batteries

Because of poor ionic conductivity, insufficient interfacial compatibility and other issues, all-solid-state lithium metal batteries (ASSLMBs) are difficult to commercialize. Here, a sort of composite solid-state polymer electrolytes (CSPEs) is prepared by compounding multifunctional fillers with polyethylene oxide (PEO), and the multifunctional filler is obtained by absorbing the ionic liquids (ILs) into the iron-containing metal-organic frameworks (MOFs). The porosity of MOFs can improve the path for Li+ transport and accelerate the Li+ transport after adsorbing ILs. This strategy endows the prepared CSPEs with high ionic conductivity of 8.46 × 10−4 S cm−1 at 60 °C and wide electrochemical window (5.2 V). In addition, the transference number of the CSPEs is increased to 0.54. After 250 cycles, the assembled LiFePO4/CSPE/Li battery has a discharge-specific capacity of 139.1 mAh g−1 and a capacity retention of 93.3% at 0.5 C under 60 °C. This work reveals a feasible strategy in constructing high-performance solid-state LMBs, as well as an important complement for material and structure development in the field of energy storage.

Defect-induced confinement in zirconium metal-organic frameworks for enhanced hydrogen adsorption

Hydrogen is an essential gas to multiple industrial processes, and due to its high gravimetric density, it promises a large potential as a clean energy source. The risks of hydrogen at low pressures, however, have deterred substantial progress in improving hydrogen storage technology. Metal-organic frameworks (MOFs) are crystalline porous materials that have emerged as excellent gas adsorbents, and their gas storage properties can be tuned using a variety of synthetic methods. Herein, we leveraged the tunability and porosity of MOFs to introduce defect engineering as a method to improve hydrogen storage technology at low pressure regimes in two zirconium-based MOFs (Zr-MOFs), UiO-66 and NU-403, which feature ideal pore apertures (7 Å) for studying the confinement effect and ease of defect engineering. By reducing the number of defects in these Zr-MOFs, and thereby decreasing the quantity of larger pores, we can induce a structural confinement effect that increases the selectivity of hydrogen adsorption. A combination of thermogravimetric analysis (TGA) and nuclear magnetic resonance (NMR) spectroscopic analysis enabled quantification of the defect levels, confirming that each sample exhibits a distinct level of defectiveness. Gas adsorption measurements revealed that the adsorption of hydrogen is greatly enhanced in samples with fewer defects, while the calculated isosteric heats of enthalpy (Qst) indicate that there are no open metal sites in these MOFs that could be the cause. Overall, we can conclude that defect engineering for pore tailoring is a viable strategy to enhance hydrogen adsorption at low-pressure regimes.

Semiconducting MOFs on ultraviolet laser-induced graphene with a hierarchical pore architecture for NO2 monitoring

Due to rapid urbanization worldwide, monitoring the concentration of nitrogen dioxide (NO2), which causes cardiovascular and respiratory diseases, has attracted considerable attention. Developing real-time sensors to detect parts-per-billion (ppb)-level NO2 remains challenging due to limited sensitivity, response, and recovery characteristics. Herein, we report a hybrid structure of Cu3HHTP2, 2D semiconducting metal-organic frameworks (MOFs), and laser-induced graphene (LIG) for high-performance NO2 sensing. The unique hierarchical pore architecture of LIG@Cu3HHTP2 promotes mass transport of gas molecules and takes full advantage of the large surface area and porosity of MOFs, enabling highly rapid and sensitive responses to NO2. Consequently, LIG@Cu3HHTP2 shows one of the fastest responses and lowest limit of detection at room temperature compared with state-of-the-art NO2 sensors. Additionally, by employing LIG as a growth platform, flexibility and patterning strategies are achieved, which are the main challenges for MOF-based electronic devices. These results provide key insight into applying MOFtronics as high-performance healthcare devices.

Tailoring chirality and porosity in metal-organic frameworks for efficient enantioselective recognition

•Defect-engineering approach to constructing chiral metal-organic frameworks (CMOFs) •One-pot scalable synthesis of CMOFs with high stability and enlarged pore size •Chiral-defect MOFs for high-performance enantioselective sensing The porosity and stability of chiral metal-organic frameworks (CMOFs) are crucial for enantioselective applications. However, coupling these properties by directly assembling metal nodes and chiral linkers is highly challenging. Post-synthetic chiralization provides a facile way to construct CMOFs, but it can decrease pore sizes, which presents a barrier for chiral molecule accommodation. Herein, we have developed a defect-engineering approach to introducing chiral centers and enlarged pores. In contrast to other strategies for synthesizing CMOFs containing large pores, this approach maintains framework stability without additional templates, as demonstrated by the successful preparation of chiral UiO-66, MIL-125-NH2, and MIL-53. Notably, the CMOFs feature high selectivity, record-breaking efficiency, and a broad substrate scope for enantioselective recognition. This study provides a facile and scalable synthetic method for constructing CMOFs with enlarged pores and high stability. The porosity and stability of chiral metal-organic frameworks (CMOFs) are crucial for enantioselective applications. However, coupling these properties by directly assembling metal nodes and chiral linkers is highly challenging. Post-synthetic chiralization provides a facile way to construct CMOFs, but it can decrease pore sizes, which presents a barrier for chiral molecule accommodation. Herein, we have developed a defect-engineering approach to introducing chiral centers and enlarged pores. In contrast to other strategies for synthesizing CMOFs containing large pores, this approach maintains framework stability without additional templates, as demonstrated by the successful preparation of chiral UiO-66, MIL-125-NH2, and MIL-53. Notably, the CMOFs feature high selectivity, record-breaking efficiency, and a broad substrate scope for enantioselective recognition. This study provides a facile and scalable synthetic method for constructing CMOFs with enlarged pores and high stability.

MOFs Containing Solid-State Electrolytes for Batteries.

The use of metal-organic frameworks (MOFs) in solid-state electrolytes (SSEs) has been a very attractive research area that has received widespread attention in the modern world. SSEs can be divided into different types, some of which can be combined with MOFs to improve the electrochemical performance of the batteries by taking advantage of the high surface area and high porosity of MOFs. However, it also faces many serious problems and challenges. In this review, different types of SSEs are classified and the changes in these electrolytes after the addition of MOFs are described. Afterward, these SSEs with MOFs attached are introduced for different types of battery applications and the effects of these SSEs combined with MOFs on the electrochemical performance of the cells are described. Finally, some challenges faced by MOFs materials in batteries applications are presented, then some solutions to the problems and development expectations of MOFs are given.

Unravelling the influence of interfacial tailoring in metal-organic framework-derived ultrathin sheets of Co2P/Cu3P for high-performance hybrid supercapacitor

Metal-organic frameworks (MOFs) with porous and diverse structures have created to devote research for MOF based materials for energy storage application, but their inadequate conductivity and sturdiness impede their realistic progress. MOF-derived transition metal phosphides (TMPs) materials could maintain the architectural diversity and porosity of MOFs, as well as, boost their electrical conductivity and durability. Herein, for the first time, we unravel the influence of interfacial tailoring in MOF templated cobalt copper phosphide (CoCuP) composite as electrode material for supercapacitor with battery-type behavior. The as-synthesized MOF-derived cobalt copper phosphide electrode (CoCuP@400) prepared at optimum 400 °C phosphorization temperature exhibits outstanding electrochemical performance by delivering a specific capacity (Csp) of 549 C/g (152.5-mAh/g) at a specific current of 1 A/g in aqueous electrolyte (6 M KOH). Additionally, by applying CoCuP@400 as a positive electrode (energy source) and lima bean shell-derived oxygen, nitrogen, and sulfur-enriched porous carbon (O, N, S@AC) as a negative electrode (power source), a hybrid supercapacitor device fabricated, which unveiled a widespread working potential window of 1.5 V. In addition, the hybrid supercapacitor device revealed a specific capacity of 38-mAh/g with a maximum specific energy (Esp) of 37.3 Wh/kg and a maximum specific power (Psp) of 12308.8 W/kg as well as exceptional cyclic stability over 10,000 uninterrupted galvanostatic charge/discharge cycles with 89% of initial capacity retention. As a result, after synthetic phosphorization technique for synthesizing electrode materials offers a new avenue for using battery-type supercapacitors.

Defective Metal‐Organic Frameworks with Tunable Porosity and Metal Active Sites for Significantly Improved Performance in Styrene Oxidation

Metal active sites and sufficient porosity in metal-organic frameworks (MOFs) are crucial parameters determining the performances of catalysis, guest molecule adsorption, etc. Herein, through in situ introduction of Ru sites with different levels to Cu-BTC structure together with post-synthetic activation at 180 °C, a series of hierarchically porous CuRu-BTC (HP-CuRu-BTC) MOFs were obtained. Besides, selective thermal decomposition (STD) treatment was carried out at 240 °C to further tune the hierarchical pores and metal sites, yielding rare case of metal nanoparticles (NPs)@HP-CuRu-BTC composites. After full characterization by XRD, N2 physisorption, SEM, ICP and XPS, these HP-CuRu-BTC and NPs@HP-CuRu-BTC samples possess high surface area (682-1199 m2 g-1 ), hierarchical pores and highly distributed metal sites with reduced oxidation states (Cu+ and Ru2+ ), indicating regulation of both metal sites and hierarchical pores. The HP-CuRu-BTC and NPs@HP-CuRu-BTC were further employed as catalysts for the heterogeneous styrene oxidation reaction under mild condition. Compared to microporous Cu-BTC with unary metal component, HP-CuRu-BTC-3 and NPs@HP-CuRu-BTC-3 exhibited more than 2 times higher styrene conversion after 7 hours reaction under same condition.

Diagnosing, Typing, and Staging of Renal Cell Carcinoma by Designer Matrix-Based Urinary Metabolic Analysis.

Molecular diagnosing, typing, and staging have been considered to be the ideal alternatives of imaging-based detection methods in clinics. Designer matrix-based analytical tools, with high speed, throughout, efficiency and low/noninvasiveness, have attracted much attention recently for in vitro metabolite detection. Herein, we develop an advanced metabolic analysis tool based on highly porous metal oxides derived from available metal-organic frameworks (MOFs), which elaborately inherit the morphology and porosity of MOFs and newly incorporate laser adsorption capacity of metal oxides. Through optimized conditions, direct high-quality fingerprinting spectra in 0.5 μL of urine are acquired. Using these fingerprinting spectra, we can discriminate the renal cell carcinoma (RCC) from healthy controls with higher than 0.99 of area under the curve (AUC) values (R2Y(cum) = 0.744, Q2 (cum) = 0.880), as well, from patients with other tumors (R2Y(cum) = 0.748, Q2(cum) = 0.871). We also realize the typing of three RCC subtypes, including clear cell RCC, chromophobe RCC (R2Y(cum) = 0.620, Q2(cum) = 0.656), and the staging of RCC (R2Y(cum) = 0.755, Q2(cum) = 0.857). Moreover, the tumor sizes (threshold value is 3 cm) can be remarkably recognized by this advanced metabolic analysis tool (R2Y(cum) = 0.710, Q2(cum) = 0.787). Our work brings a bright prospect for designer matrix-based analytical tools in disease diagnosis, typing and staging.

Metal-organic aerogels based on titanium(IV) for visible-light conducted CO2 photoreduction to alcohols

Metal-organic frameworks (MOFs) imply an appealing source of photocatalysts as they combine porosity with tailorable electronic properties and surface chemistry. Herein, we report a series of unprecedented metal-organic aerogels (MOAs) comprised by Ti(IV) oxo-clusters and aromatic dicarboxylic linkers as an alternative to microporous MIL-125 and MIL-125-NH2 MOFs. Discrete titanium oxo-clusters polymerized upon the addition of the dicarboxylic linkers to give rise to a metal-organic gel. Their supercritical drying led to aerogels comprised by nanoscopic particles (ca. 5–10 nm) cross-linked into a meso/macroporous microstructure with surface area ranging from 453 to 617 m2·g−1, which are comparatively lower than the surface area of the microporous counterparts (1336 and 1145 m2·g−1, respectively). However, the meso/macroporous microstructure of MOAs can provide a more fluent diffusion of reagents and products than the intrinsic porosity of MOFs, whose narrower channels are expected to imply a more sluggish mass transport. In fact, the assessment of the continuous visible-light-driven photocatalytic CO2 reduction into methanol shows that MOAs (221–786 μmol·g−1·h−1) far exceed not only the performance of their microporous counterparts (49–65 μmol·g−1·h−1) but also surpass the production rates provided by up-to-date reported photocatalysts.

Water-based synthesis of nanoscale hierarchical metal-organic frameworks: Boosting adsorption and catalytic performance

The combination of nano sizes, large pore sizes and green synthesis is recognized as one of the most crucial and challenging problems in constructing metal-organic frameworks (MOFs). Herein, a water-based strategy is proposed for the synthesis of nanoscale hierarchical MOFs (NH-MOFs) with high crystallinity and excellent stability. This approach allows the morphology and porosity of MOFs to be fine tuned, thereby enabling the nanoscale crystal generation and a well-defined hierarchical system. The aqueous solution facilitates rapid nucleation kinetics, and the introduced modulator acts as a deprotonation agent to accelerate the deprotonation of the organic ligand as well as a structure-directing agent (SDA) to guide the formation of hierarchical networks. The as-synthesized NH-MOFs (NH-ZIF-67) were assessed as efficient adsorbents and heterogeneous catalysts to facilitate the diffusion of guest molecules, outperforming the parent microZIF-67. This study focuses on understanding the NH-MOF growth rules, which could allow tailor-designing NH-MOFs for various functions.