Facile synthesis of the DD3R zeolite: performance in the adsorptive separation of buta-1,3-diene and but-2-ene isomers

Small pore size and hydrophobic nature of DD3R make this material a unique zeolite with high potential in industrial separation applications. However, the reproducible rapid synthesis of this zeolite is still a problem. In this work, a thorough assessment of different synthetic methods revealed that synthesis reproducibility relies on two main pillars: the use of properly cleaned autoclave liners and the synthesis composition. High quality DD3R crystals are obtained when KOH is used as a cleaning agent, eliminating memory effects, and when KF is used in the synthesis as a mineralizing agent. The effect of fluoride addition is investigated by use of several characterization techniques (13C, 19F and 29Si MAS-NMR and (2D) 29Si–1H correlation spectra), while monitoring the temporal crystallization of DDR. 29Si–1H NMR reveals that template molecules accommodated within the cages are sticking to these 8-ring windows through their amine group. High quality DD3R crystals are applied in the adsorptive separation of buta-1,3-diene and but-2-ene isomers, one of the most energy intensive separations in chemical industry. Mixture separation experiments revealed that the 8-ring apertures of the DD3R cages are only accessible to trans-but-2-ene and buta-1,3-diene, while excluding but-1-ene and cis-but-2-ene molecules, resulting in shape-selective separation in the presence of C4 mixtures.status: publishe

Electrochemical Synthesis of Some Archetypical Zn²⁺, Cu²⁺, and Al³⁺ Metal Organic Frameworks

Several archetypical metal organic frameworks (MOFs), namely, HKUST-1, ZIF-8, MIL-100­(Al), MIL-53­(Al), and NH₂-MIL-53­(Al), were synthesized via anodic dissolution in an electrochemical cell. The influence of different reaction parameters such as solvent, electrolyte, voltage–current density, and temperature on the synthesis yield and textural properties of the MOFs obtained was investigated. The characterization of the samples involved X-ray diffraction, gas adsorption, atomic force microscopy, diffuse reflectance infrared Fourier transform spectroscopy, and scanning electron microscopy. In the present article, we demonstrate that electrochemical synthesis is a robust method offering additional degrees of freedom in the synthesis of these porous materials. The main advantages are the shorter synthesis time, the milder conditions, the facile synthesis of MOF nanoparticles, the morphology tuning and the high Faraday efficiencies. The synthesized MIL-53 and NH₂-MIL-53 samples exhibit suppressed framework flexibility compared to samples synthesized solvothermally

Micro-imaging of transient guest profiles in nanoporous host systems of cylindrical symmetry

Nanoporous host materials giving rise to transient guest profiles of cylindrical symmetry during molecular uptake and release are shown to provide particularly advantageous conditions for the study of guest diffusion by micro-imaging. Considering zeolites of structure type DDR (Deca-dodecasil 3R) as a host system and short-chain length hydrocarbons as guest molecules, the benefits thus attainable in micro-imaging studies using interference microscopy are shown to include the determination of transient concentration profiles with improved accuracy, the option to overcome the disturbing impact of surface imperfections, and easy access to concentration-dependent diffusivities.ChemE/Chemical EngineeringElectrical Engineering, Mathematics and Computer Scienc

Interplay of Metal Node and Amine Functionality in NH₂‑MIL-53: Modulating Breathing Behavior through Intra-framework Interactions

A series of amino-functionalized MIL-53 with different metals as nodes has been synthesized. By determining adsorption properties and spectroscopic characterization, we unequivocally show that the interaction between the amines of the organic linker and bridging μ₂-OH of the inorganic scaffold modulates metal organic framework (MOF) flexibility. The strength of the interaction has been found to correlate with the electropositivity of the metal