Open Sites Research Articles

Confined space of a nickel-triazole metal–organic framework responsible for high product selectivity and enantiospecific yield of lactic acid converted from sugar in a water-based system

Abstract Enantioselective production of lactic acid from xylose sugar in the constrained pore space of the Ni-triazole metal-organic framework (MOF) is demonstrated. A robust hydrophilic structure with a confined nano-pocket is constructed from the [Ni3(µ3-OH)(Tz)3(OH)2(H2O)4]n secondary building unit (SBU). At elevated temperature, the de-coordination of water and hydroxide species on the Ni node can generate accessible an open metal site (OMS) possessing Lewis acidicity, acting as catalytic center for the catalysis of xylose to lactic acid. Density functional theory (DFT) calculations suggests that an enantiospecific yield of lactic acid is realizable by a preferential interaction between any pair of SBUs and the interlocked trans-pyruvaldehyde intermediate. This work highlights the unique spatial and chemical environment of MOFs as an advantageous platform for specific processes in catalysis.

A phase II trial of cemiplimab alone or in combination with standard of care chemotherapy in locally advanced or metastatic penile carcinoma (EPIC trial).

TPS14 Background: Penile cancer is rare, <1% of male malignancies diagnosed each year, but its incidence is increasing with an 18% increase over the last decade projected to rise a further 9% in the next 10 years. Patients with locally advanced/metastatic penile cancer (la/mPC) have very few treatment options and there is a lack of clinical trial data to guide management. Cisplatin containing combination chemotherapy regimens are regarded as the standard of care (SOC) in this setting. However, with response rates of 50% or less there is a need to further improve treatment outcomes. PDL1 is upregulated in 40–60% of PC cases and is correlated with poor prognosis making a case for immunotherapy as a treatment for la/mPC. The PD-1 inhibitor cemiplimab is approved for patients with locally advanced or metastatic cutaneous squamous cell carcinoma (SCC) suggesting efficacy against penile SCC. The EPIC trial was set up to evaluate the benefit and safety of cemiplimab alone, or, in combination with SOC chemotherapy in patients with la/mPC. Methods: This is a non-randomised, 2 arm, phase II multi-centre trial. Arm 1 cemiplimab + SOC chemotherapy (local site choice of cisplatin/5FU, TPF or TIP regimes); Arm 2 single agent cemiplimab. The choice of arm decided by the investigator site based on chemotherapy eligibility. 47 patients will be recruited from 10 UK centres: 29 patients into ARM 1 who will receive 4 cycles of cemiplimab 350mg IV q3 weekly + SOC chemotherapy, followed by single agent cemiplimab x 30 cycles (24 months total). 18 patients into ARM 2 who will receive single agent cemiplimab 350mg IV q3 weekly x 34 cycles (24 months total). The primary endpoint is clinical benefit rate (CBR) of cemiplimab: objective response rate (ORR) plus stable disease as assessed radiologically (RECIST 1.1) at 12 weeks from first dose in patients with la/mPC. Secondary end-points include safety, tolerability, CBR at 1, 2 and 3 years, ORR, progression-free survival, overall survival and assessment of patient health status and quality of life using the patient reported outcome measures EQ-5D-5L and EORTC QLQ-C30. Each arm will be analysed separately as a Fleming A’Hern study α=0.05 + power (1-β)=0.8. Arm 1 assumes 25% meeting the clinical end point is a poor treatment (p0=0.25) and 50% is a good treatment (p1=0.5). Arm 2 assumes 5% meeting the clinical end point is a poor treatment (p0=0.05) and 25% is a good treatment (p1=0.25). Progress: By February 2023 10 UK sites had been opened to recruitment. The first patient entered the trial in November 2021 and to date 25 patients have been recruited into Arm 1 and 10 into Arm 2. Opening sites was slower than anticipated following emergence from the COVID pandemic. However, a recruitment rate of 1-2 patients per month has shown the feasibility of running a trial for this rare patient population. Clinical trial information: ISRCTN95561634 .

One Scalable and Stable Metal-Organic Framework for Efficient Separation of CH4/N2 Mixture.

Separating CH4 from coal bed methane is of great importance but challenging. Adsorption-based separation often suffers from low selectivity, poor stability, and difficulty to scale up. Herein, a stable and scalable metal-organic framework [MOF, CoNi(pyz-NH2)] with multiple CH4 binding sites was reported to efficiently separate the CH4/N2 mixture. Due to its suitable pore size and multiple CH4 binding sites, it exhibits excellent CH4/N2 selectivity (16.5) and CH4 uptake (35.9 cm3/g) at 273 K and 1 bar, which is comparable to that of the state-of-the-art MOFs. Theoretical calculations reveal that the high density of open metal sites and polar functional groups in the pores provide strong affinity to CH4 than to N2. Moreover, CoNi(pyz-NH2) displays excellent structural stability and can be scale-up synthesized (22.7 g). This work not only provides an excellent adsorbent but also provides important inspiration for the future design and preparation of porous adsorbents for separations.

Metal-organic Frameworks: Emerging Luminescent Sensors

Abstract: Metal-organic frameworks (MOFs), a crystalline material, are a new type of inorganicorganic hybrid material. MOFs are of great interest to researchers in chemistry and material science due to their various chemical and physical properties, and features include their remarkable surface area, high porosity, flexibility, structural variety, flexibility, extreme porosity, a large surface area, augmented adsorption/desorption kinetics, biocompatibility and functional tunability. MOFs are multi-dimensional crystals and have extended net-like frameworks from molecular building units such as inorganic metal nodes and organic linkers. The structurally diverse MOFs have found applications in chemical sensing and several other fields, such as energy applications, biomedicine, and catalysis. Numerous researchers from other fields have been drawn to this topic by the intrinsic potential to absorb gas molecules, which has led to the applications of gas storage and heterogeneous catalysis. Because of their low framework density, open metal sites for interaction, adjustable pore size, fast response with high sensitivity and selectivity, and real-time monitoring, luminescent metalorganic frameworks, or LMOFs, have piqued the interest of a large scientific community as a promising candidate for sensor applications. A number of characteristics, including non-toxicity, biodegradability, and reasonably priced, varied functionality, are important factors in the use of MOFs in chemo- and biosensing. MOFs can be very promising candidates as selective and sensitive chemosensors for the detection of cations, anions, small molecules, gases and explosives. In this manuscript, we address recent research advances in the use of metal-organic-framework-based luminescent sensors for detecting some small molecules and various metal ions in aqueous biological and environmental samples. A wide range of materials may be reached in the emerging field of synthetic and material chemistry, thanks to the capacity to change the pore size and chemically functionalize its nature without changing its architecture.

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.

Hydrogen Adsorption on PCN‐250(Fe) Metal Organic Framework: Temperature and Pressure Swings

AbstractThis manuscript is reporting hydrogen adsorption uptake of PCN‐250(Fe) metal organic framework (MOF) at temperature of 300, 126K, and pressure in between 6 and 10 bar. X‐ray diffraction spectrum of PCN‐250(Fe) confirms crystalline structure, however Fourier transform infrared (FT‐IR) spectrum showing dominant bonding structure of COOH, N = N, and Fe─O functional groups. SEM images confirm surface morphology as an octahedrons of average crystalline size upto 50 µm. Thermogravimetric analysis (TGA) confirms excellent thermal stability upto 450 °C. The hydrogen adsorption uptake of 0.80 wt% has been found at 126 K and pressure of 10 bar attributes adsorption occurs due to the structural and physical properties like topology, porosity, and presence of open metal sites as well as surface area. It is suggested that PCN‐250(Fe) as an adsorbent material offers as an intensive way of storing H2 at low temperature and at ambient pressure.

Effects of birch encroachment, water table and vegetation on methane emissions from peatland microforms in a rewetted bog

This study investigated the influence of vegetation and microforms on methane (CH4) balances of a rewetted bog in north-west Germany. The two study sites are in close proximity on the same former peat extraction area, one dominated by Sphagnum-mosses and the other one by a dense Betula pubescens stand with a high Eriophorum vaginatum cover. The contribution of microforms (hummocks/hollows) to CH4 emissions and the effect of Betula encroachment has been studied. Transparent and opaque chambers were used to measure CH4 fluxes every 3–4 weeks during daytime for one year. For the estimation of annual balances, three methods were compared and the method using water level and soil temperature as explanatory variables was selected. Fluxes were scaled to the site level. The annual emissions per site are and 7.1 ± 1.5 g CH4-C m−2 year−1 at the treed site and 36.1 ± 3.5 g CH4-C m−2 year−1 at the open site, mainly controlled by higher water levels. Highest annual emissions originated from hollows at the open site, but in the vegetation period, hummock emissions tend to be higher. At the tree site, emission differences between the microforms were less pronounced. There were no differences between fluxes from transparent and opaque chambers.

In Situ Single-crystal X-ray Diffraction Studies of Physisorption and Chemisorption of SO2 within a Metal-Organic Framework and Its Competitive Adsorption with Water.

Living on an increasingly polluted planet, the removal of toxic pollutants such as sulfur dioxide (SO2) from the troposphere and power station flue gas is becoming more and more important. The CPO-27/MOF-74 family of metal-organic frameworks (MOFs) with their high densities of open metal sites is well suited for the selective adsorption of gases that, like SO2, bind well to metals and have been extensively researched both practically and through computer simulations. However, until now, focus has centered upon the binding of SO2 to the open metal sites in this MOF (called chemisorption, where the adsorbent-adsorbate interaction is through a chemical bond). The possibility of physisorption (where the adsorbent-adsorbate interaction is only through weak intermolecular forces) has not been identified experimentally. This work presents an in situ single-crystal X-ray diffraction (scXRD) study that identifies discrete adsorption sites within Ni-MOF-74/Ni-CPO-27, where SO2 is both chemisorbed and physisorbed while also probing competitive adsorption of SO2 of these sites when water is present. Further features of this site have been confirmed by variable SO2 pressure scXRD studies, DFT calculations, and IR studies.

Selective Adsorption of Oxygen from Humid Air in a Metal-Organic Framework with Trigonal Pyramidal Copper(I) Sites.

High or enriched-purity O2 is used in numerous industries and is predominantly produced from the cryogenic distillation of air, an extremely capital- and energy-intensive process. There is significant interest in the development of new approaches for O2-selective air separations, including the use of metal-organic frameworks featuring coordinatively unsaturated metal sites that can selectively bind O2 over N2 via electron transfer. However, most of these materials exhibit appreciable and/or reversible O2 uptake only at low temperatures, and their open metal sites are also potential strong binding sites for the water present in air. Here, we study the framework CuI-MFU-4l (CuxZn5-xCl4-x(btdd)3; H2btdd = bis(1H-1,2,3-triazolo[4,5-b],[4',5'-i])dibenzo[1,4]dioxin), which binds O2 reversibly at ambient temperature. We develop an optimized synthesis for the material to access a high density of trigonal pyramidal CuI sites, and we show that this material reversibly captures O2 from air at 25 °C, even in the presence of water. When exposed to air up to 100% relative humidity, CuI-MFU-4l retains a constant O2 capacity over the course of repeated cycling under dynamic breakthrough conditions. While this material simultaneously adsorbs N2, differences in O2 and N2 desorption kinetics allow for the isolation of high-purity O2 (>99%) under relatively mild regeneration conditions. Spectroscopic, magnetic, and computational analyses reveal that O2 binds to the copper(I) sites to form copper(II)-superoxide moieties that exhibit temperature-dependent side-on and end-on binding modes. Overall, these results suggest that CuI-MFU-4l is a promising material for the separation of O2 from ambient air, even without dehumidification.

Solar-Driven Ammonia Production through Engineering of the Electronic Structure of a Zr-Based MOF.

As a hydrogen carrier and a vital component in fertilizer production, ammonia (NH3) is set to play a crucial role in the planet's future. While its industrial production feeds half of the global population, it uses fossil fuels and emits greenhouse gases. To tackle this issue, photocatalytic nitrogen fixation using visible light is emerging as an effective alternative method. This strategy avoids carbon dioxide (CO2) emissions and harnesses the largest share of sunlight. In this work, we successfully incorporated a 5-nitro isophthalic acid linker into MOF-808 to introduce structural defects and open metal sites. This has allowed modulation of the electronic structure of the MOF and effectively reduced the band gap energy from 3.8 to 2.6 eV. Combination with g-C3N4 enhanced further NH3 production, as these two materials possess similar band gap energies, and g-C3N4 has shown excellent performance for this reaction. The nitro groups serve as acceptors, and their integration into the MOF structure allowed effective interaction with the free electron pairs on N-(C)3 in the g-C3N4 network nodes. Based on DFT calculations, it was concluded that the adsorption of N2 molecules on open metal sites caused a decrease in their triple bond energy. The modified MOF-808 showed superior performance compared with the other MOFs studied in terms of N2 photoreduction under visible light. This design concept offers valuable information about how to engineer band gap energy in MOF structures and their combination with appropriate semiconductors for solar-powered photocatalytic reactions, such as N2 or CO2 photoreduction.

Structure-based insights into the mechanism of [4Fe-4S]-dependent sulfur insertase LarE.

Several essential cellular metabolites, such as enzyme cofactors, contain sulfur atoms and their biosynthesis requires specific thiolation enzymes. LarE is an ATP-dependent sulfur insertase, which catalyzes the sequential conversion of the two carboxylate groups of the precursor of the lactate racemase cofactor into thiocarboxylates. Two types of LarE enzymes are known, one that uses a catalytic cysteine as a sacrificial sulfur donor, and the other one that uses a [4Fe-4S] cluster as a cofactor. Only the crystal structure of LarE from Lactobacillus plantarum (LpLarE) from the first class has been solved. We report here the crystal structure of LarE from Methanococcus maripaludis (MmLarE), belonging to the second class, in the cluster-free (apo-) and cluster-bound (holo-) forms. The structure of holo-MmLarE shows that the [4Fe-4S] cluster is chelated by three cysteines only, leaving an open coordination site on one Fe atom. Moreover, the fourth nonprotein-bonded iron atom was able to bind an anionic ligand such as a phosphate group or a chloride ion. Together with the spectroscopic analysis of holo-MmLarE and the previously reported biochemical investigations of holo-LarE from Thermotoga maritima, these crystal structures support the hypothesis of a reaction mechanism, in which the [4Fe-4S] cluster binds a hydrogenosulfide ligand in place of the chloride anion, thus generating a [4Fe-5S] intermediate, and transfers it to the substrate, as in the case of [4Fe-4S]-dependent tRNA thiolation enzymes.

Single Cobalt Ion-Immobilized Covalent Organic Framework for Lithium-Sulfur Batteries with Enhanced Rate Capabilities.

Covalent organic frameworks (COFs) are notable for their remarkable structure, function designability, and tailorability, as well as stability, and the introduction of "open metal sites" ensures the efficient binding of small molecules and activation of substrates for heterogeneous catalysis and energy storage. Herein, we use the postsynthetic metal sites to catalyze polysulfide conversion and to boost the binding affinity to active matter for lithium-sulfur batteries (LSBs). A dual-pore COF, USTB-27, with hxl topology has been successfully assembled from the imine chemical reaction between 2,3,8,9,14,15-hexa(4-formylphenyl)diquinoxalino [2,3-a:2',3'-c]phenazine and [2,2'-bipyridine]-5,5'-diamine. The chelating nitrogen sites of both modules are able to postsynthetically functionalize with single cobalt sites to generate USTB-27-Co. The discharge capacity of the sulfur-loaded S@USTB-27-Co composite in a LSB is 1063, 945, 836, 765, 696, and 644 mA h g-1 at current densities of 0.1, 0.2, 0.5, 1.0, 2.0, and 5.0 C, respectively, much superior to that of non-cobalt-functionalized species S@USTB-27. Following the increased current densities, the rate performance of S@USTB-27-Co is much better than that of S@USTB-27. In particular, the capacity retention at 5.0 C has a magnificent increase from 19% for the latter species to 61% for the former one. Moreover, S@USTB-27-Co exhibits a higher specific capacity of 543 mA h g-1 than that of S@USTB-27 (402 mA h g-1) at a current density of 1.0 C after electrochemical cycling for 500 runs. This work illustrates the "open metal sites" strategy to engineer the active chemical component conversion in COF channels as well as their binding strength for specific applications.

Synergistic Boosting Capture Ability of Thiophene Sulfur with a Novel Dual-Amino-Functionalized MOF-on-MOF Adsorbent.

A single metal-organic framework (MOF) exhibits some drawbacks in deep adsorptive desulfurization such as insufficient functional active sites, water instability, low surface area, etc. Herein, a dual-amino-functionalized (ZIF-8-NH2)-PVP-(Cu-BTC-NH2) core-shell dual MOF adsorbent was first synthesized by the hydrothermal growth method. The adsorption performance of thiophene sulfur (ThS) is systematically investigated and evaluated at mild temperatures through batch tests. The (ZIF-8-NH2)-PVP-(Cu-BTC-NH2) exhibits good adsorption ability toward ThS, which is attributed to the associative effects of dual MOFs with structure features such as hydrogen bond, open metal active sites, suitable pore sizes and π-π conjugation, etc. Meanwhile, the (ZIF-8-NH2)-PVP-(Cu-BTC-NH2) embedded 25 wt % water still remains crystal intact and good adsorption desulfurization performance, which is attributed to the NH2- functional groups. After five recycles, more than 90% ThS uptake onto (ZIF-8-NH2)-PVP-(Cu-BTC-NH2) could be recovered, exhibiting good reuse performance. This study presents a new strategy for grafting MOF-on-MOF with specific functional groups to improve the abilities of desulfurization and water resistance.

Multi-layered physical factors govern mercury release from soil: Implications for predicting the environmental fate of mercury

Despite the recognised risks of human exposure to mercury (Hg), the drivers of gaseous elemental mercury (GEM) emissions from the soil remain understudied. In this study, we aimed to identify the environmental parameters that affect the GEM flux from soil and derive the correlations between environmental parameters and GEM flux. Principal component analysis (PCA), factor analysis (FA), and structural equation modelling (SEM) were performed on samples from forest and non-forest sites. The associated results revealed the impact of each environmental parameter on GEM flux, either due to the interaction between the parameters or as a coherent set of parameters. An introductory correlation matrix examining the relationship between two components showed a negative correlation between GEM flux and atmospheric pressure at the two sites, as well as strong correlations between atmospheric pressure and soil temperature. In cases of non-forest open sites with no trees, the PCA and FA results were consistent, indicating that atmospheric pressure, solar irradiance, and soil moisture—defined as primary causality—are largely independent drivers of GEM flux. In contrast, the PCA and FA results for the forest areas with high humidity, tree coverage, and shade were inconsistent, confirming the hypothesis that primary causality affects GEM flux rather than consequent parameters driven by primary causality, such as air and soil temperature and atmospheric humidity. The SEM results provided further evidence for primary and consequent causality as crucial drivers of the GEM flux. This study demonstrates the importance of key primary parameters, such as atmospheric pressure, solar irradiance, and soil moisture content, that can be used to predict mercury release from soils, as well as the importance of consequent parameters, such as air and soil temperature and atmospheric humidity. Monitoring the magnitude of these environmental parameters alone may facilitate the estimation of mercury release from soils and be useful for detailed modelling of soil–air Hg exchange.

A Study on Physical Characterization of Municipal Solid Waste of Jammu City on the basis of Socioeconomic Status of the Population

Generation of waste has been associated with humans since dawn of civilization. But in recent decades due to factors like ever increasing population, urbanization and industrialization, the amount of waste generated has spiked to enormous proportions. The composition of waste has significantly changed since plastic was first used in the middle of the 19th century. MSW management is a significant environmental concern in India. Jammu City generates an immense amount of solid waste, approximately 350–400 metric tons (MT) daily, with an individual generation rate of around 0.55 kg per day. MSW management in Jammu City is handled by the Jammu Municipal Corporation (JMC). In the city, MSW collection, transportation, and disposal are all handled by JMC. MSW of Jammu city is disposed at Kot Bhalwal which is an open landfill site. As of now no prior treatment of MSW is being done. Present study attempts to assess the current state of MSW management in Jammu city. Sampling was done in the month of July, 2022 from 15 different wards classified in the basis of socioeconomic status and physical characterization of MSW was conducted. This paper analyzes the results obtained from physical characteristics of MSW from three diverse socioeconomic groups HIG, MIG and LIG. This would help in understanding the waste generation pattern of different socioeconomic groups. MSW from MIG contains large proportion of organic matter (55%) and is thus suitable for composting and bio-methanation, however MSW collected from HIG locality contain high proportion of inorganic materials like paper/cardboard, plastic, polythene and textile waste and therefore it is suitable for Refuse Derived Fuel (RDF) facility. MSW from Jammu city also contain high fraction of inert waste (20% to 45%). Inert waste can be easily disposed but when it is mixed with MSW it increases the volume and weight of total MSW and therefore increase the difficulty if MSW management. This study also explores the alternative approaches to MSWM in Jammu city. Data generated by present study will be beneficial to JMC for designing future course of action for management of MSW of Jammu City.

A Highly Chemically Robust 3D Interpenetrated MOF Heterogeneous Catalyst for the Synthesis of Hantzsch 1,4-Dihydropyridines and Drug Molecules.

Metal-organic frameworks (MOFs) have attracted immense attention as efficient heterogeneous catalysts over other solid catalysts, however, their chemical environment instability often limits their catalytic potential. Herein, utilizing a flexible unexplored tetra-acid ligand and employing the mixed ligand approach, a 3D interpenetrated robust framework is strategically developed, IITKGP-51 (IITKGP stands for Indian Institute of Technology Kharagpur), which retained its crystallinity over a wide range of pH solution (4-12). Having ample open metal sites (OMSs), IITKGP-51 is explored as a heterogeneous catalyst in one-pot Hantzsch condensation reaction, with low catalyst loading for a broad range of substrates. The synthesis of drug molecules remains one of the most significant and emergent areas of organic and medicinal chemistry. Considering such practical utility, biologically important Nemadipine B and Nifedipine drug molecules (calcium channel protein inhibitor) are synthesized for the first time by using this catalyst and fully characterized via SC-XRD and other spectroscopic methods. This report inaugurates the usage of a MOF material as a catalyst for the synthesis of drug molecules.

Analisis Sanitasi Lingkungan Berdasarkan Tempat Pembuangan Sementara (TPS) Sampah pada Rumah Kos Wilayah Kota Semarang

Sanitation of public places is one of the efforts that can be made to maintain cleanliness. The minimum requirements for TTU sanitation are solid waste management, dirty water, and human excrement. Based on these sanitation requirements, there are still problems, namely many boarding houses whose garbage containers do not meet the requirements. Open disposal of waste has the potential to pollute the environment and will have a negative impact on public health. The purpose of this research is to analyze the health impacts that will arise as a result of an open waste temporary disposal site. The method in this research is observation by collecting data. Sampling was carried out purposively which was in accordance with the research objectives, namely a sample of five boarding house in the city of Semarang. The observation results show that the boarding house environment has a problem with garbage. This is evident from the observation results which show that there are 4 out of 5 that do not have trash covers and 4 out of 5 boarding houses whose trash cans are breeding grounds for insects. Conclusion: Seeing these results, problems can arise in the surrounding environment and cause disease for residents who live in the boarding house. Therefore, the trash can and lid must be located together in every place. Suggestion: It is better if the owner can provide garbage facilities and trash covers at the boarding house so that the environment is clean, comfortable, and protected from animals that can cause disease.

Aminobenzoate-defected UiO-66(Zr)–NH2 frameworks: Scalable synthesis and characterizations for adsorptive denitrogenation from model fuel

In this work, imperfection UiO-66-NH2 frameworks (AUiO-66-NH2) were engineered and scalably produced by a continuous flow method with the assistance of 4-aminobenzoate (ABA) modulators. ABA modulators competed with MOF ligands to bond to Zr4+ clusters under continuous flow conditions, producing AUiO-66-NH2 frameworks containing aminobenzoate linkers and ligand-missing defects. The average ligand deficiency per Zr6 unit of defective AUiO-66(Zr)–NH2 framework ranged from 0.75 ∼ 2.36 upon changing ABA/H2N-BDC molar ratio and reaction temperature, thereby adjusting their porosity and exposing more metal open sites of Zr4+. The batch removal of N-containing compounds (NCCs), including quinoline (QUN) and 2-methyl pyrrole (MPR) in n-octane indicated that the ABA-modulated UiO-66-NH2 samples had improved adsorption capability compared to the perfect MOF. Noticeably, the adsorption performances were further enhanced by protonating 2.5AUiO-66-NH2 to 2.5AUiO-66-NH3+ owing to the synergetic effects of acid-base interaction, H-bonds, cation-π interactions, and π-π stacking interactions between adsorbent and adsorbate. Density functional theory (DFT) calculations further revealed that the NCCs preferably accumulated onto the protonated AUiO-66-NH3+ rather than AUiO-66-NH2. The AUiO-66-NH3+ exhibited adsorbing capacities of ∼204 mg/g and ∼275 mg/g for MPR and QUN, respectively, and obeyed the pseudo-second-order kinetic model. Finally, the continuous fixed-bed adsorptions of these NCCs in model fuel over the AUiO-66-NH3+ pellets (3 mm × 6 mm) showed that 1.0 g of adsorbent can purify with ∼28 L and ∼49 L liquid fuel containing MPR and QUN with a concentration of 1 mg L−1. These state that combining continuous-flow synthesis and defect engineering of the UiO-66-NH2 could be a promising strategy to produce efficient adsorbent materials for upgrading liquid fuel.

Machine learning potential for modelling H2 adsorption/diffusion in MOFs with open metal sites.

Metal-organic frameworks (MOFs) incorporating open metal sites (OMS) have been identified as promising sorbents for many societally relevant-adsorption applications including CO2 capture, natural gas purification and H2 storage. This has been ascribed to strong specific interactions between OMS and the guest molecules that enable the MOF to achieve an effective capture even under low gas pressure conditions. In particular, the presence of OMS in MOFs was demonstrated to substantially boost the H2 binding energy for achieving high adsorbed hydrogen densities and large usable hydrogen capacities. So far, there is a critical bottleneck to computationally attain a full understanding of the thermodynamics and dynamics of H2 in this sub-class of MOFs since the generic classical force fields (FFs) are known to fail to accurately describe the interactions between OMS and any guest molecules, in particular H2. This clearly hampers the computational-assisted identification of MOFs containing OMS for a target adsorption-related application since the standard high-throughput screening approach based on these generic FFs is not applicable. Therefore, there is a need to derive novel FFs to achieve accurate and effective evaluation of MOFs for H2 adsorption. On this path, as a proof-of-concept, the soc-MOF-1d containing OMS, previously envisaged as a potential platform for H2 adsorption, was selected as a benchmark material and a machine learning potential (MLP) was derived for the Al-soc-MOF-1d from a dataset initially generated by ab initio molecular dynamics (AIMD) simulations. This MLP was further implemented in MD simulations to explore the H2 binding modes as well as the temperature dependence distribution of H2 in the MOF pores from 10 K to 80 K. MLP-Grand Canonical Monte Carlo (GCMC) simulations were then performed to predict the H2 sorption isotherm of Al-soc-MOF-1d at 77 K that was further confirmed using sorption data we collected on this sample. As a further step, MLP-based molecular dynamics (MD) simulations were conducted to anticipate the kinetics of H2 in this MOF. This work delivers the first MLP able to describe accurately the interactions between the challenging H2 guest molecule and MOFs containing OMS. This innovative strategy applied to one of the most complex molecules owing to its highly polarizable nature, paves the way towards a more systematic accurate and efficient in silico assessment of MOFs containing OMS for H2 adsorption and beyond to the low-pressure capture of diverse molecules.

Simulation studies of water adsorption on MIL-101(Cr) revealing the role of inhomogeneous potential field composed of open metal sites and organic linkers

Simulation studies reveal that the capillary condensation of water on MIL-101(Cr) occurs due to the formation of a liquid film that covers the hydrophobic pore surface, driven by the presence of open metal sites.