Structural, thermal and functional characterization of metal-organic frameworks containing poly(pyrazolates)-based ligands for carbon dioxide adsorption

The dissertation proposes a comprehensive and systematic study of five new families of bis(pyrazolate) metal-organic frameworks (MOFs) for post-combustion CO2 capture and sequestration (CCS). Chapter I introduces the reader to the renowned problem of global warming, with a special focus on the role of CO2 and the different technologies for post-combustion CCS. MOFs state of the art in CO2 adsorption and the essential properties they should possess to be efficient in this application conclude the Chapter. Chapter II, after an overview on the use of pyrazolate-based MOFs, collects the syntheses of the studied compounds. The structural and thermal characterizations are reported in Chapter III. Chapter IV discusses the textural and adsorption properties, focusing on the influence of the different ligand functionalization. A comparison between the studied MOFs and the literature ones is then reported. Finally, starting from the most performing bis(pyrazolates) in terms of CO2 capacity and affinity, a series of mixed-ligand MOFs (MIXMOFs) is presented to further elucidate the role of linker functionalization in CO2 adsorption. MIXMOFs syntheses and full solid-state characterization are collected in Chapter V together with their CO2 adsorption capacity, affinity and selectivity. MIXMOFs performances are then compared to those of state-of-the-art materials developed for CO2 capture

Structural, thermal and functional characterization of metal-organic frameworks containing poly(pyrazolates)-based ligands for carbon dioxide adsorption

The dissertation proposes a comprehensive and systematic study of five new families of bis(pyrazolate) metal-organic frameworks (MOFs) for post-combustion CO2 capture and sequestration (CCS). Chapter I introduces the reader to the renowned problem of global warming, with a special focus on the role of CO2 and the different technologies for post-combustion CCS. MOFs state of the art in CO2 adsorption and the essential properties they should possess to be efficient in this application conclude the Chapter. Chapter II, after an overview on the use of pyrazolate-based MOFs, collects the syntheses of the studied compounds. The structural and thermal characterizations are reported in Chapter III. Chapter IV discusses the textural and adsorption properties, focusing on the influence of the different ligand functionalization. A comparison between the studied MOFs and the literature ones is then reported. Finally, starting from the most performing bis(pyrazolates) in terms of CO2 capacity and affinity, a series of mixed-ligand MOFs (MIXMOFs) is presented to further elucidate the role of linker functionalization in CO2 adsorption. MIXMOFs syntheses and full solid-state characterization are collected in Chapter V together with their CO2 adsorption capacity, affinity and selectivity. MIXMOFs performances are then compared to those of state-of-the-art materials developed for CO2 capture

CO2 Adsorption in a Robust Iron(III) Pyrazolate-Based MOF: Molecular-Level Details and Frameworks Dynamics From Powder X-ray Diffraction Adsorption Isotherms

This research is part of the project “One Health Action Hub: University Task Force for the resilience of territorial ecosystems” by Università degli Studi di Milano – PSR 2021 – GSA – Linea 6. V.C.The Italian MIUR for funding through the PRIN2017 program (project “Moscato” n° 2017KKP5ZR_004) and Università degli Studi di Milano for the Transition Grant (PSR2015-1721VCOLO_01). R.V.S.G. acknowledge Università dell’Insubria for partial funding. R.V. acknowledges Fondazione CRUI for a one-year post-doctoral grant (Go4IT, 2020)Programa Juan de la Cierva Formación (FJC2020-045043-I). J.A.R.N.MCIN/ AEI/10.13039/501100011033European Union NextGenerationEU/ PRTR (Grants PID2020-113608RB-I00; TED2021-129886B-C41)Junta de Andalucía-Conserjería de Economía y Conocimiento/EU ERDF (Project P18.RT.612)The European Synchrotron Radiation Facility for the beamtime (experiments CH-5337 and CH-6073, ID-22 High-Resolution Powder-Diffraction Beamline

Mercury Clathration-Driven Phase Transition in a Luminescent Bipyrazolate Metal−Organic Framework: A Multitechnique Investigation

Mercury is one of the most toxic heavy metals. By virtue of its triple bond, the novel ligand 1,2-bis(1H-pyrazol-4- yl)ethyne (H2BPE) was expressly designed and synthesized to devise metal−organic frameworks (MOFs) exhibiting high chemical affinity for mercury. Two MOFs, Zn(BPE) and Zn(BPE)·nDMF [interpenetrated i-Zn and noninterpenetrated ni-Zn·S, respectively; DMF = dimethylformamide], were isolated as microcrystalline powders. While i-Zn is stable in water for at least 15 days, its suspension in HgCl2 aqueous solutions prompts its conversion into HgCl2@ni-Zn. A multitechnique approach allowed us to shed light onto the observed HgCl2-triggered i-Zn-to- HgCl2@ni-Zn transformation at the molecular level. Density functional theory calculations on model systems suggested that HgCl2 interacts via the mercury atom with the carbon−carbon triple bond exclusively in ni-Zn. Powder X-ray diffraction enabled us to quantify the extent of the i-Zn-to-HgCl2@ni-Zn transition in 100−5000 ppm HgCl2 (aq) solutions, while X-ray fluorescence and inductively coupled plasma-mass spectrometry allowed us to demonstrate that HgCl2 is quantitatively sequestered from the aqueous phase. Irradiating at 365 nm, an intense fluorescence is observed at 470 nm for ni-Zn·S, which is partially quenched for i-Zn. This spectral benchmark was exploited to monitor in real time the i-Zn-to-HgCl2@ni-Zn conversion kinetics at different HgCl2 (aq) concentrations. A sizeable fluorescence increase was observed, within a 1 h time lapse, even at a concentration of 5 ppb. Overall, this comprehensive investigation unraveled an intriguing molecular mechanism, featuring the disaggregation of a water-stable MOF in the presence of HgCl2 and the self-assembly of a different crystalline phase around the pollutant, which is sequestered and simultaneously quantified by means of a luminescence change. Such a case study might open the way to new-conception strategies to achieve real-time sensing of mercury-containing pollutants in wastewaters and, eventually, pursue their straightforward and costeffective purification.University of Insubria for partial fundingPrograma Juan de la Cierva Formación (FJC2020-045043-I)MCIN/AEI/10.13039/501100011033European Union NextGenerationEU/PRTR (Grants PID2020- 113608RB-I00 and TED2021-129886B-C41

CO2 Adsorption in a Robust Iron(III) Pyrazolate-Based MOF: Molecular-Level Details and Frameworks Dynamics From Powder X-ray Diffraction Adsorption Isotherms

Understanding adsorption processes at the molecular level, with multi-technique approaches, is nowadays at the frontier of porous materials research. In this work it is shown that with a proper data treatment, in situ high-resolution powder X-ray diffraction (HR-PXRD) at variable temperature and gas pressure can reveal atomic details of the accommodation sites, the framework dynamics as well as thermodynamic information (isosteric heat of adsorption) of the CO2 adsorption process in the robust iron(III) pyrazolate-based MOF Fe2(BDP)3 [H2BDP = 1,4-bis(1H-pyrazol-4-yl)benzene]. Highly reliable "HR-PXRD adsorption isotherms" can be constructed from occupancy values of CO2 molecules. The "HR-PXRD adsorption isotherms" accurately match the results of conventional static and dynamic gas sorption experiments and Monte Carlo simulations. These results are indicative of the impact of the molecular-level behavior on the bulk properties of the system under study and of the potential of the presented multi-technique approach to understand adsorption processes in metal-organic frameworks

Zirconium Metal−Organic Polyhedra with Dual Behavior for Organophosphate Poisoning Treatment

Organophosphate nerve agents and pesticides are extremely toxic compounds because they result in acetylcholinesterase (AChE) inhibition and concomitant nerve system damage. Herein, we report the synthesis, structural characterization, and proof-of-concept utility of zirconium metal−organic polyhedra (Zr-MOPs) for organophosphate poisoning treatment. The results show the formation of robust tetrahedral cages [((n-butylCpZr)3(OH)3O)4L6]Cl6 (Zr-MOP-1; L = benzene-1,4- dicarboxylate, n-butylCp = n-butylcyclopentadienyl, Zr-MOP-10, and L = 4,4′-biphenyldicarboxylate) decorated with lipophilic alkyl residues and possessing accessible cavities of ∼9.8 and ∼10.7 Å inner diameters, respectively. These systems are able to both capture the organophosphate model compound diisopropylfluorophosphate (DIFP) and host and release the AChE reactivator drug pralidoxime (2-PAM). The resulting 2-PAM@ Zr-MOP-1(0) host−guest assemblies feature a sustained delivery of 2-PAM under simulated biological conditions, with a concomitant reactivation of DIFP-inhibited AChE. Finally, 2-PAM@Zr-MOP systems have been incorporated into biocompatible phosphatidylcholine liposomes with the resulting assemblies being non-neurotoxic, as proven using neuroblastoma cell viability assays.Spanish MCIN/AEI PID2020-113608RB-I00FEDER/Junta de Andalucia-Conserjeria de Economia y Conocimiento B-FQM-364-UGR18 B-FQM-006-UGR18FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades P18-RT-612 P20_00672Fondazione CRUIprograma Juan de la Cierva FormacionSpanish Government PID2020-118117RB-I00Center for Forestry Research & Experimentation (CIEF)European Commission SEJIGENT/2021/059 PROMETEU/2021/054La Caixa Foundation 100010434 LCF/BQ/PR20/11770014"Maria de Maeztu" Program for Centers of Excellence in RD CEX2019-000919-MH2020-MSCA-IF2019-888972-PSust-MO

Scalable Synthesis and Electrocatalytic Performance of Highly Fluorinated Covalent Organic Frameworks for Oxygen Reduction

In this study, we present a novel approach for the synthesis of covalent organic frameworks (COFs) that overcomes the common limitations of non-scalable solvothermal procedures. Our method allows for the room-temperature and scalable synthesis of a highly fluorinated DFTAPB-TFTA-COF, which exhibits intrinsic hydrophobicity. We used DFT-based calculations to elucidate the role of the fluorine atoms in enhancing the crystallinity of the material through corrugation effects, resulting in maximized interlayer interactions, as disclosed both from PXRD structural resolution and theoretical simulations. We further investigated the electrocatalytic properties of this material towards the oxygen reduction reaction (ORR). Our results show that the fluorinated COF produces hydrogen peroxide selectively with low overpotential (0.062 V) and high turnover frequency (0.0757 s−1) without the addition of any conductive additives. These values are among the best reported for non-pyrolyzed and metal-free electrocatalysts. Finally, we employed DFT-based calculations to analyse the reaction mechanism, highlighting the crucial role of the fluorine atom in the active site assembly. Our findings shed light on the potential of fluorinated COFs as promising electrocatalysts for the ORR, as well as their potential applications in other fieldsThis work was financially supported by Ministerio de Ciencia e Innovación of Spain MICINN (TED2021-129886B-C41, TED2021-129886BC42; TED2021-129886BC43; PID2019-106268GB-C32; PID2019-106268GB C33, PID2020-113608RB-I00; PID2022-138908NB-C33, PID2022-138470NB-100, RED2018-102412-T; PID2020-116728RB-I00). Comunidad de Madrid (P2018/NMT-4349 TRANSNANOAVANSENS Program; SI3/PJI/2021-0034). F.Z. acknowledge financial support from the Spanish Ministry of Science and Innovation, through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805-M). R.V. acknowledges “Programa Juan de la Cierva Formación” (FJC2020-045043-I). R.V. and J.A.R.N. acknowledge MCIN/AEI/10.13039/501100011033 and European Union NextGenerationEU/PRTR

One class classification as a practical approach for accelerating π–π co-crystal discovery

Machine learning using one class classification on a database of existing co-crystals enables the identification of co-formers which are likely to form stable co-crystals, resulting in the synthesis of two co-crystals of polyaromatic hydrocarbons.</p

Structural, thermal and functional characterization of metal-organic frameworks containing poly(pyrazolates)-based ligands for carbon dioxide adsorption

The dissertation proposes a comprehensive and systematic study of five new families of bis(pyrazolate) metal-organic frameworks (MOFs) for post-combustion CO2 capture and sequestration (CCS). Chapter I introduces the reader to the renowned problem of global warming, with a special focus on the role of CO2 and the different technologies for post-combustion CCS. MOFs state of the art in CO2 adsorption and the essential properties they should possess to be efficient in this application conclude the Chapter. Chapter II, after an overview on the use of pyrazolate-based MOFs, collects the syntheses of the studied compounds. The structural and thermal characterizations are reported in Chapter III. Chapter IV discusses the textural and adsorption properties, focusing on the influence of the different ligand functionalization. A comparison between the studied MOFs and the literature ones is then reported. Finally, starting from the most performing bis(pyrazolates) in terms of CO2 capacity and affinity, a series of mixed-ligand MOFs (MIXMOFs) is presented to further elucidate the role of linker functionalization in CO2 adsorption. MIXMOFs syntheses and full solid-state characterization are collected in Chapter V together with their CO2 adsorption capacity, affinity and selectivity. MIXMOFs performances are then compared to those of state-of-the-art materials developed for CO2 capture

The Hg(3,3'-dimethyl-1H,1H'-4,4'-bipyrazolate) coordination polymer: Synthesis, crystal structure and thermal behavior

The novel coordination polymer Hg(Me2BPZ) (H2Me2BPZ=3,3'-dimethyl-1H,1'H-4,4'-bipyrazole) was prepared by reacting the H2Me2BPZ ligand and mercury(II) acetate. The crystal structure of Hg(Me2BPZ), determined by powder X-ray diffraction with laboratory instrumentation, is characterized by a (4,4)-connected 3-D polymeric network, in which the metal ions show a see-saw stereochemistry. Investigating the thermal behavior by thermogravimetric analysis and variable-temperature powder X-ray diffraction revealed that the material is stable up to 340\uc2\ub0C, both under nitrogen and in air, and undergoes a volumetric thermal expansion amounting to \ue2\u88\ubc2% before losing crystallinity