High hydrogen release catalytic activity by quasi-MOFs prepared via post-synthetic pore engineering

[EN] The catalytic activity of metal-organic frameworks (MOFs) depends largely on the presence of structural defects. In the present study, cobalt based metal-organic framework TMU-10, [Co-6(oba)(5)(OH)(2)(H2O)(2)(DMF)(4)](n)center dot 2DMF has been subjected to controlled thermolysis under air atmosphere at different temperatures in the range of 100-700 degrees C. This treatment results in the removal of ligands, and generation of structural defects and additional porosity in a controlled manner. The resulting materials, denoted as quasi MOFs according to the literature, were subsequently employed as catalysts for hydrogen release from NaBH4 by hydrolysis. The quasi TMU-10 framework obtained at 300 degrees C (QT-300) shows the highest turnover frequency of the series with a value of 13 333 mL min(-1) g(-1) at room temperature in the absence of a base, with an activation energy of 56.8 kJ mol(-1). The simultaneous presence of micro- and mesopores in QT-300 with unsaturated Lewis acid sites on cobalt nodes due to the conversion of a fraction of Co(ii) centers to Co(iii) as well as the presence of tetrahedral Co(ii) sites is responsible for this catalytic behavior. The influence of the catalyst dosage and BH4- concentration is in good agreement with the Langmuir-Hinshelwood model in which both reactants must be adsorbed onto the catalyst surface. Further investigation on the hydrolysis of the NaBH4 + D2O system presents a primary kinetic isotope effect indicating that water O-H bond cleavage occurs in the rate determining step.Support of this investigation by Arak University and Iran National Science Foundation (INSF) (grant No. 4000089) are gratefully acknowledged. Ministerio de Ciencia e Innovacion (Severo Ochoa and RTI2018-98237-CO2-1) and Generalitat Valenciana (Prometeo 2017/083) are also acknowledged.Bagheri, M.; Masoomi, MY.; Domínguez Torres, E.; García Gómez, H. (2021). High hydrogen release catalytic activity by quasi-MOFs prepared via post-synthetic pore engineering. Sustainable Energy & Fuels. 5(18):4587-4596. https://doi.org/10.1039/d1se00661dS4587459651

Cobalt-Based Quasi-Metal-Organic Framework as a Tandem Catalyst for Room-Temperature Open-Air One-Pot Synthesis of Imines

[EN] The catalytic activity of MOFs derives in a large extent from defects. To generate these defects, a cobalt-based metal-organic framework TMU 10, [Co-6(oba)(5)(OH)(2)(H2O)(2)(DMF)(4)](n). 2DMF has been subjected in the present study to controlled thermal treatment under air at different temperatures ranging from 100 to 700 degrees C. This treatment produces the removal of ligands, generation of structural defects, and additional porosity in an extent that depends on the conditions of the thermal treatment. The resulting defective materials, denoted according to the literature as quasi-MOFs, were subsequently employed as heterogeneous tandem catalysts in the one-pot synthesis of N-benzylideneaniline from aniline and benzyl alcohol in open air as a terminal oxidant at 60 degrees C under solvent-, base-, and dehydrating agent-free conditions. The quasi-TMU-10 framework obtained at 300 degrees C (QT-300) can efficiently promote imine synthesis within 2 h, forming water as the only byproduct. Unsaturated cobalt sites and the presence of micro- and mesopores in QT-300 are responsible for this excellent catalytic performance as tandem catalysts. The influence on QT-300 catalytic activity of catalyst amount, reactant ratio, and reaction temperature was investigated, as well as the stability and recyclability of the catalyst. The one-pot imine formation promoted by QT-300 follows alcohol aerobic oxidation and subsequent anaerobic condensation of the aldehyde intermediate with aniline.Support of this investigation by Arak University and Iran Science Elites Federation is gratefully acknowledged.Baheri, M.; Masoomi, MY.; Domínguez Torres, E.; García Gómez, H. (2021). Cobalt-Based Quasi-Metal-Organic Framework as a Tandem Catalyst for Room-Temperature Open-Air One-Pot Synthesis of Imines. ACS Sustainable Chemistry & Engineering. 9(31):10611-10619. https://doi.org/10.1021/acssuschemeng.1c02851S106111061993

Quasi-HKUST Prepared via Postsynthetic Defect Engineering for Highly Improved Catalytic Conversion of 4-Nitrophenol

[EN] HKUST-1 [Cu-3(BTC)(2)(H2O)(3)](n)center dot nH(2)OMeOH was submitted to thermolysis under controlled conditions at temperatures between 100 and 300 degrees C. This treatment resulted in partial ligand decarboxylation, generating coordinatively unsaturated Cu2+ sites with extra porosity on the way to the transformation of the initial HKUST-1 framework to CuO. The obtained materials retaining in part the HKUST-1 original crystal structure (quasi-MOFs) were used to promote 4-nitrophenol conversion to 4-aminophenol. Because of the partial linker decomposition, the quasi-MOF treated at 240 degrees C contains coordinatively unsaturated Cu2+ ions distributed throughout the Q-HKUST lattice together with micro- and mesopores. These defects explain the excellent catalytic performance of QH-240 with an apparent rate constant of 1.02 X 10(-2) s(-1) in excess of NaBH4 and an activity factor and half-life time of 51 s(-1)g(-1) and 68 s, respectively, which is much better than that of the HKUST parent. Also, the induction period decreases from the order of minutes to seconds in the presence of the HKUST and QH-240 catalysts, respectively. Kinetic studies fit with the Langmuir-Hinshelwood theory in which both 4-nitrophenol and BH4- should be adsorbed onto the catalyst surface. The values of the true rate constant (k), the adsorption constants of 4-nitrophenol and BH4- (K4-NP and K-BH4(-)), as well as the activation energy are in agreement with a rate-determining step involving the reduction of 4-nitrophenol by the surface-bound hydrogen species.This work is based upon research funded by the Iran National Science Foundation (INSF) under project no. 4000089. Also, support of this investigation by Arak University is gratefully acknowledged. The Spanish Ministry of Science and Innovation (Severo Ochoa and RTI2018-89237-CO2-R1) and Generalitat Valenciana (Prometeo 2021-038) are gratefully acknowledged.Bagheri, M.; Melillo, A.; Ferrer Ribera, RB.; Masoomi, MY.; García Gómez, H. (2022). Quasi-HKUST Prepared via Postsynthetic Defect Engineering for Highly Improved Catalytic Conversion of 4-Nitrophenol. ACS Applied Materials & Interfaces. 14(1):978-989. https://doi.org/10.1021/acsami.1c1986297898914

Enhanced Catalytic Performance of Quasi-HKUST-1 for the Tandem Imine Formation

[EN] Copper-based metal-organic framework (Cu3 (BTC)2 (H2 O)3 ]n ¿nH2 OMeOH (HKUST-1) has been subjected to thermolysis under air atmosphere at different temperatures ranging from 100 to 300 °C. This treatment produces the partial removal of ligands, the generation of structural defects and additional porosity in a controlled way. The resulting defective materials denoted according to the literature as quasi-MOFs, were subsequently employed as heterogeneous catalysts in the one pot synthesis of N-benzylideneaniline from aniline and benzyl alcohol in open air as terminal oxidant at 70 °C under base- and dehydrating agent-free conditions. The Q-HKUST catalysts calcined at 240 °C (QH-240) was the most efficient in the series, promoting imine synthesis. Data from Knoevenagel condensation of malononitrile shows that in QH-240 the distances of Cu ions in HKUST-1 cavities are preserved, increasing the Knoevenagel activity, but a strong rearrangement takes place at 300 °C or above. The unsaturated copper active sites with simultaneous presence of micro- and mesopores in QH-240 are responsible for this excellent catalytic performance. The effective parameters on catalytic activity of QH-240 including deligandation temperature, the amount of catalyst, the ratio of reactants, and reaction temperature as well as the stability and recyclability of the catalyst were also investigated. The possible mechanism used by QH-240 follows alcohol aerobic oxidation and subsequent anaerobic condensation of aldehyde intermediate with aniline.Support of this investigation by Arak University and Iran Science Elites Federation are gratefully acknowledged.Bagheri, M.; Melillo, A.; Ferrer Ribera, RB.; Masoomi, MY.; García Gómez, H. (2021). Enhanced Catalytic Performance of Quasi-HKUST-1 for the Tandem Imine Formation. Chemistry - A European Journal. 27(57):14273-14281. https://doi.org/10.1002/chem.2021024051427314281275

Improved catalytic hydrogen release of quasi HKUST-1 compared to HKUST-1

[EN] On-demand hydrogen release could be an important process for the transportation of fuel in the near future. Herein it is reported that the controlled thermolysis of HKUST-1 under optimal conditions generates structural defects resulting in a quasi-HKUST-1 material showing a 20-fold enhancement of the H-2 release turnover frequency at room temperature in the absence of a baseThis work is based upon research funded by the Iran National Science Foundation (INSF) under project no. 4000089 and Spanish Ministry of Science and Innovation (Severo Ochoa and RTI201898237-CO2-1). Also, support for this investigation from Arak University is gratefully acknowledged.Bagheri, M.; Melillo, A.; Ferrer Ribera, RB.; Masoomi, MY.; García Gómez, H. (2021). Improved catalytic hydrogen release of quasi HKUST-1 compared to HKUST-1. Chemical Communications. 57(90):11964-11967. https://doi.org/10.1039/d1cc05182b1196411967579

Selective CO₂ capture in metal-organic frameworks with azine-functionalized pores generated by mechanosynthesis

Two new three-dimensional porous Zn(II)-based metal-organic frameworks, containing azine-functionalized pores, have been readily and quickly isolated via mechanosynthesis, by using a nonlinear dicarboxylate and linear N-donor ligands. The use of nonfunctionalized and methyl-functionalized N-donor ligands has led to the formation of frameworks with different topologies and metal-ligand connectivities and therefore different pore sizes and accessible volumes. Despite this, both metal-organic frameworks (MOFs) possess comparable BET surface areas and CO₂ uptakes at 273 and 298 K at 1 bar. The network with narrow and interconnected pores in three dimensions shows greater affinity for CO compared to the network with one-dimensional and relatively large pores-attributable to the more effective interactions with the azine groups

Ultrasound assisted synthesis of a Zn(II) metal–organic framework with nano-plate morphology using non-linear dicarboxylate and linear N-donor ligands

A 3D, porous Zn(II)-based metal–organic framework {[Zn2(oba)2(4-bpdb)]·2DMF}n (TMU-4) with double interpenetration was prepared by using a non-linear dicarboxylate (H2oba = 4,4'-oxybisbenzoic acid) and a linear N-donor (4-bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene) ligand. Also micro- and nano-plates of this MOF were synthesized by a sonochemical process and characterized by scanning electron microscopy, X-ray powder diffraction and IR spectroscopy. The thermal stability was studied by thermogravimetric analysis (TGA). Sonication time and concentration of initial reagents effects on the size and morphology of nano-structured MOFs, were studied. Calcination of TMU-4 at 500 °C under air atmosphere yields ZnO nanoparticles

Rapid mechanochemical synthesis of two new Cd(II)-based metal–organic frameworks with high removal efficiency of Congo red

Two new three-dimensional porous Cd(II)-based metal–organic frameworks, [Cd2(oba)2(4-bpdb)2]n·(DMF)x (TMU-8) and [Cd(oba)(4,4'-bipy)]n·(DMF)y (TMU-9), have been synthesized via mechanosynthesis by using nonlinear dicarboxylate and linear N-donor ligands and then characterized by single-crystal X-ray crystallography. The effect of using different N-donor ligands 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (4-bpdb) and 4,4'-bipyridine (4,4'-bipy) as pillars on the final structure has been studied. Also, the removal efficiency and order reaction kinetics of these MOFs in the presence of Congo red were investigated

Ultrasonic assisted synthesis of two new coordination polymers and their applications as precursors for preparation of nano-materials

Two new isostructural coordination polymers, [Zn-3(Oba)(4)][Me2NH2)(2)]center dot 6DMF center dot 3H(2)O (1) and [Cd-3(Oba)(4)][Me2NH2)(2)]center dot 2DMF center dot 2H(2)O (2), were synthesized using the nonlinear dicarboxylate ligand, 4,4'-oxybis(benzoic acid) (H(2)oba) and characterized by IR spectroscopy and single-crystal X-ray crystallography. Single-crystal X-ray data show that 1 and 2 are two-dimensional coordination polymers that can be extended to three-dimensional supramolecular networks by CH...O interactions. These two new coordination polymers were also sonochemically synthesized while sonication time and power of irradiation influencing size and morphology of nano-structured compounds were also studied. Moreover, calcination of these coordination polymers creates ZnO and CdO nanostructures

Chemical Hydrogen Generation by Hierarchically Structured Quasi-ZIF-67 Catalysts with Unsaturated Metal Centers

Preparing quasi-metal–organic frameworks (Q-MOFs) with unsaturated metal sites is an effective approach for developing highly active MOF-based catalysts. In this study, we synthesized quasi-ZIF-67 (Q-ZIF-67) with large-scale structural defects via controlled thermal partial deligandation at 310 °C under an air atmosphere. This process created additional open cobalt sites and hierarchical pores within the ZIF-67 framework. The resulting Q-ZIF-67 exhibited enhanced catalytic activity for the hydrolysis of NaBH4, compared to pristine ZIF-67 and related cobalt oxide, due to a cooperative effect of Lewis acid centers and the coexistence of micro- and meso/macropores. Hydrogen was successfully generated at a rate of 18500 mL·min–1 g–1 over Q-ZIF-67 at room temperature without the need for a base and with an activation energy of 53 kJ·mol–1 under mild conditions. In addition to the catalytic performance, we investigated the kinetics and thermodynamic parameters of the hydrogen generation reaction. Our mechanistic study revealed that strong acidity is critical for efficient chemohydrogen generation of NaBH4. We confirmed this by studying the isotope effect in a D2O system, which indicated that cleavage of the O–H bond of water occurs in the rate-determining step