Hot-Pressing Method To Prepare Imidazole-Based Zn(II) Metal-Organic Complexes Coatings for Highly Efficient Air Filtration

Hybrid Photochromic Lanthanide Phosphonate with Multiple Photoresponsive Functionalities

Hybrid photochromic materials (HPMs) with specific photoresponsive functionality have applications in many fields. The photoinduced electron-transfer (ET) strategy has been proved to be effective in the synthesis of HPMs with diverse photomodulated properties. The exploitation of new electron acceptors (EAs) is meaningful for promoting the development of HPMs. In this work, we introduced a rigid tetraimidazole derivative, 3,3,5,5-tetra(imidazol-1-yl)-1,1-biphenyl (TIBP) as a potential EA, into a metal-diphosphonate (1-hydroxyethylidene-1,1-diphosphonic acid, H₄-HEDP) system to explore HPMs and finally obtained a hybrid metal phosphonate (H₄-TIBP)_0.5·[Dy(H-HEDP) (H₂-HEDP)]·H₂O (1). 1 features anionic chains composed of diphosphonate and Dy³⁺ ions. The extra charge is balanced by protonated TIBP cations, which exist in the void of adjacent chains and form H-bonds with O_phosphonate (N-H···O). Upon photostimulation with a Xe lamp (300 W), the crystalline sample 1 exhibited coloration by changing from colorless to pale yellow because of the presence of photoinduced radicals that originated from the ET from O_phosphonate to N_TIBP. Along with the coloration, photomodulated fluorescence, magnetism, and proton conductivity were also detected in the photoactivated samples. Different from the reported HPMs based on polypyridine derivatives and photoactive species such as pyridinium and naphthalimide derivatives as EAs, our study provides a new category of EA units to yield HPMs with fascinating photoresponsive functionality via the assembly of polyimidazole derivatives and phosphonate-based supramolecular building blocks.

Inserting protonated phenanthroline derivatives to interchain voids of anionic halometallate units to generate hybrid materials with tunable photochromic performance

Hybrid photochromic materials (HPMs) have potential application in many fields like display, protection, information storage. The generation of HPMs with tunable photochromic performance is meaningful for the availability of smart...

Modulating the structure and photochromic performance of hybrid metal chlorides with nonphotochromic 1,10-phenanthroline and its derivative

Hybrid photochromic materias (HPMs), especially crystalline HPMs (CHPMs), have been widely investigated due to their feasibility in maintaining the advantages of each constituent and genearating captivating photomodulated functionality. Metal-organic complexes (MOCs), as promising candidates for fabricating CHPMs, have attracted the interest of researchers. The molecular predesign of ligands plays a crucial role in yielding MOC-based CHPMs with tunable photochromic functionality. Hitherto, a great majority of CHPMs are driven by photosensitive ligands. However, the complicated synthesis and high cost of photosensitive ligands obviously prevent the macro-synthesis and future application of these CHPMs. Thus, it is indispensable to explore novel branches of CHPMs. Herein, we report a series of photochromic solid materials bearing modulated photochromic properties by hybridizing metal chlorides with a nonphotosensitive coplanar dipyridine unit 1,10-phenanthroline (phen) and its derivative 5-chloro-1,10-phenanthroline (5-Cl-phen). The resulting hybrids, [ZnCl₂(phen)] (1), [CdCl₂(phen)] (2), [PbCl₂(phen)] (3), [ZnCl(H₂O)(5-Cl-phen)₂]Cl·2H₂O (4), [Cd₂Cl₄(5-Cl-phen)₂] (5) and [Pb₂Cl₄(5-Cl-phen)₂] (6), exhibit distinct structures from the isolated molecular complexes (1 and 4) to the hybrid chain (2, 3, 5 and 6) because of the distinct coordination mode of central metal ions and chloride ions. After photo-irradiation with a Xe-lamp, all complexes, as expected, exhibited apparent color change because of the photoinduced electron transfer (ET) between coordinated chloride ions (Cl^-) as electron donors (EDs) and the coordinated coplanar phen and 5-Cl-phen species as electron acceptors (EAs). More importantly, the photochromic performance of the title complexes could be modulated by phen and 5-Cl-phen. This study provides a general and facile way for modulating the structure and photochromic performance of hybrid metal chlorides with phen or phen-based derivatives under the synergy of crystalline engineering strategy and ET mechanism.

Highly Improved Performance of Cotton Air Filters in Particulate Matter Removal by the Incorporation of Metal-Organic Frameworks with Functional Groups Capable of Large Charge Separation

Currently, air contamination, especially with particulate matters (PMs), is severe in several countries. To increase the efficiency of air filters in PM removal, metal-organic frameworks (MOFs, here, Zr-MOFs, especially with functional groups (FGs) such as -NO₂) were coated, after synthesis, onto cotton using covalent bonding for the first time. The removal efficiencies (REs) and quality factors (QFs) of cottons with or without MOFs were in the order: cotton < Zr-MOF/cotton < Zr-MOF-NH₂/cotton < Zr-MOF-NH-SO₃H/cotton < Zr-MOF-NH₃⁺Cl^-/cotton < Zr-MOF-NO₂/cotton. This monotonic increase in the PM removal efficiency or QF could be explained with the order of charge separation or developed charges (total, in absolute value: ∼0 to 2.0) on FGs of MOFs. Importantly, Zr-MOF-NO₂ coating on cotton showed a very high increase in the performance of cotton in PM removal. QF and RE of Zr-MOF-NO₂/cotton were 4.6 times and 6.2 times of the bare cotton, respectively, for PM2.5 removal, even with a very small increase in pressure drop (3 Pa or less) with MOF coating. Based on the research, it can be suggested that coating MOFs on substrates is a promising way to improve the performances of air filters for PM removal, especially when MOFs have FGs that can have large charge separation such as -NO₂. This work may pave a way to utilize a functionalized MOF in the effective removal of PMs from air.

Personal strategies to minimise effects of air pollution on respiratory health: advice for providers, patients and the public

As global awareness of air pollution rises, so does the imperative to provide evidence-based recommendations for strategies to mitigate its impact. While public policy has a central role in reducing air pollution, exposure can also be reduced by personal choices. Qualified evidence supports limiting physical exertion outdoors on high air pollution days and near air pollution sources, reducing near-roadway exposure while commuting, utilising air quality alert systems to plan activities, and wearing facemasks in prescribed circumstances. Other strategies include avoiding cooking with solid fuels, ventilating and isolating cooking areas, and using portable air cleaners fitted with high-efficiency particulate air filters. We detail recommendations to assist providers and public health officials when advising patients and the public regarding personal-level strategies to mitigate risk imposed by air pollution, while recognising that well-designed prospective studies are urgently needed to better establish and validate interventions that benefit respiratory health in this context.

Metal-Organic Complexes@Melamine Foam Template Strategy to Prepare Three-Dimensional Porous Carbon with Hollow Spheres Structures for Efficient Organic Vapor and Small Molecule Gas Adsorption

Three-dimensional (3D) porous carbon materials have received substantial attention owing to their unique structural features. However, the synthesis of 3D porous carbon, especially 3D porous carbon with hollow spheres structures at the connection points, still pose challenges. Herein, we first develop a metal-organic complexes@melamine foam (MOC@MF) template strategy, by using hot-pressing and carbonization method to synthesize 3D porous carbon with hollow spheres structures (denoted as NOPCs). The formation mechanism of NOPCs can be attributed to the difference in Laplace pressure and surface energy gradient between the carbonized MOC and carbonized MF. These rare 3D porous carbons exhibit high BET surface area (2453.8 m² g^-1), N contents (10.5%), and O contents (16.3%). Moreover, NOPCs show significant amounts of toluene and methanol at room temperature, reaching as high as 1360 and 1140 mg g^-1. The adsorption amounts of SO₂ and CO₂ for NOPCs are up to 93.1 and 445 mg g^-1. Theoretical calculation indicates surfaces of porous carbon with N and O coexistence could strongly enhance adsorption with high adsorption energy of -65.83 kJ mol g^-1.

Effect of Functional Groups of Metal-Organic Frameworks, Coated on Cotton, on Removal of Particulate Matters via Selective Interactions

Currently, the contamination of air with particulate matters (PMs such as PM2.5 and PM10) is very severe, especially in Asian countries. Metal-organic frameworks (MOFs), with or without extra functional groups such as -NH₂ and -NH-SO₃H, were coated on conventional cotton to improve the efficiency of filters (composed of cotton fabric) in the removal of PMs from air. More importantly, the effect of the functional group of MOFs on the effective PM removal was analyzed quantitatively for the first time and could be interpreted via selective interactions. The removal efficiency was increased on the order: cotton < UiO-66/cotton < UiO-66-NH₂/cotton < UiO-66-NH-SO₃H/cotton, and the efficiency of the UiO-66-NH-SO₃H-coated cotton was more than three times that of the pristine cotton. Moreover, the quality factor of cotton was more than doubled (or, 2.5-3 times) by UiO-66-NH-SO₃H (only 20%) coating. The plausible mechanism for PM removal could be suggested based on the characterization of captured PM and introduced functional groups on MOFs. Based on the removal efficiency, pressure drop, and quality factor, coating of MOFs with functional groups, especially that are effective for charge separations (such as -SO₃H), is one of the promising ways to improve the performance of PM filters. Moreover, the suggested strategy might be applied in capturing most of PMs composed of oxides, ammonium species, and carbons with polar outside.

Polyphenylene Sulfide Ultrafine Fibrous Membrane Modified by Nanoscale ZIF-8 for Highly Effective Adsorption, Interception, and Recycling of Iodine Vapor

In this study, two novel composite membranes containing nanoscale ZIF-8 and polyphenylene sulfide (PPS) nonwoven fabric were prepared via hydrothermal (PPS-ZIF-8) and biomimetic mineralization (PPS-ZIF-8-BSA; BSA, bovine serum albumin) approaches. The biomimetic mineralization approach in particular was extremely rapid and mild, and crystalline ZIF-8 was coated on the PPS substrate in only a few seconds at room temperature. The maximum iodine adsorption capacities of the PPS-ZIF-8 and PPS-ZIF-8-BSA membranes were 2.51 and 2.07 g/g, respectively. The composite fibrous membranes were able to capture trace iodine vapor under differential pressures ranging from 0 to 1000 Pa without almost any iodine vapor leakage. The composite membranes can be applied in harsh environments because of the excellent stability of ZIF-8 and the PPS high-performance fibers. This study provides a promising strategy to fabricate novel adsorption materials for the collection of radioactive iodine during nuclear waste disposal.

Textiles/Metal-Organic Frameworks Composites as Flexible Air Filters for Efficient Particulate Matter Removal

The health-threatening air pollution, especially from particulate matter (PM), has triggered increasing demands for developing low-cost and long-service-life air-cleaning technologies. In the present contribution, a range of high-efficiency textiles/metal-organic framework (MOF) composites (MOFs@textiles) air filters with excellent washable reusability is presented. By processing MOFs onto textile substrates via an eco-friendly solvent-free method to enable the microporous feature and also strong PM adhesion, we develop flexible, highly effective air filters with >95.00% PM removal efficiency (e.g., MiL-53(Al)@Aramid, PM_2.5: 95.30%, PM₁₀: 96.11%) under harmful air quality conditions (average PM_2.5 mass concentration > 280 μg m^-3 and PM₁₀ > 360 μg m^-3). Therefore, these MOFs@textiles are promising composites for producing efficient and recyclable out-/indoor air purifiers.

Micromesoporous Nitrogen-Doped Carbon Materials Derived from Direct Carbonization of Metal-Organic Complexes for Efficient CO2 Adsorption and Separation

Metal-organic complexes (MOCs) are considered as excellent precursors to prepare carbon materials, due to the fact that heteroatoms and functional groups can be naturally reserved in the resulting carbon materials through the carbonization. Herein, micromesoporous nitrogen-doped carbons MPNC-1 and MPNC-2 are successfully obtained by direct carbonization (800 °C, KOH activation) of metal-organic complexes DQA-1 and DQA-2. MPNC-1 and MPNC-2 exhibit high BET surface area (2368.9 and 2327.6 m² g^-1), pore volume (1.95 and 1.89 cm³ g^-1), and N contents (17.2% and 12.3%). At 25 °C and 1 bar, MPNC-1 and MPNC-2 show high CO₂ adsorption of 7.53 and 6.58 mmol g^-1, the estimated CO₂/N₂ selectivity are 20.5 and 22.6, indicating excellent promise for practical CO₂ adsorption and separation applications. Theoretical calculation indicates carbon surfaces with pyridinic-N, pyrrolic-N, and graphitic-N coexistence could strongly change the local electronic distribution and electrostatic surface potential, enhancing the CO₂ adsorption with adsorption energy of -58.96 kJ mol g^-1. Theoretical calculation also highlights that CO₂ adsorption mechanism is electrostatic interaction with a large green isosurface between CO₂ molecules and the carbon surface.

Nitrogen-Doped Microporous Carbons Derived from Pyridine Ligand-Based Metal-Organic Complexes as High-Performance SO2 Adsorption Sorbents

Heteroatom-doped porous carbons are emerging as platforms for gas adsorption. Herein, N-doped microporous carbon (NPC) materials have been synthesized by carbonization of two pyridine ligand-based metal-organic complexes (MOCs) at high temperatures (800, 900, 1000, and 1100 °C). For NPCs (termed NPC-1- T and NPC-2- T, where T represents the carbonization temperature), the micropore is dominant, pyridinic-N and other N atoms of MOC precursors are mostly retained, and the N content reaches as high as 16.61%. They all show high Brunauer-Emmett-Teller surface area and pore volume, in particular, NPC-1-900 exhibits the highest surface areas and pore volumes, up to 1656.2 m² g^-1 and 1.29 cm³ g^-1, respectively, a high content of pyridinic-N (7.3%), and a considerable amount of SO₂ capture (118.1 mg g^-1). Theoretical calculation (int = ultrafine m062x) indicates that pyridinic-N acts as the leading active sites contributing to high SO₂ adsorption and that the higher content of pyridinic-N doping into the graphite carbon layer structure could change the electrostatic surface potential, as well as the local electronic density, which enhanced SO₂ absorption on carbon edge positions. The results show great potential for the preparation of microporous carbon materials from pyridine ligand-based MOCs for effective SO₂ adsorption.

Synthesis, X-ray structure, in silico calculation, and carbonic anhydrase inhibitory properties of benzylimidazole metal complexes

Three coordination compounds of formula {M(bmim)₂Cl₂} were synthetised (M = Co, Zn, and Hg) and fully characterised. Each complex incorporates 1-benzyl-2-methylimidazole (bmim) as ligand. The coordination polyhedron around the metal center for all complexes has a quasi-regular tetragonal geometry. Density functional theory calculations were carried out on the title compounds and as well on hypothetical complexes (Cu, Ni), in order to elucidate their electronic and molecular structure. The calculations reproduced the Co, Zn, and Hg experimental structures and could predict stable complexes in the case of Ni(II) and Cu(II) ions. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory effects of the three complexes were investigated. Only compound {Hg(bmim)₂Cl₂} (3) exhibited a modest inhibitory effect against hCA I, probably due to the affinity of Hg(II) for His residues at the entrance of the active site cavity.