David H. Olson

Bio: David H. Olson is an academic researcher from Rutgers University. The author has contributed to research in topics: Adsorption & Microporous material. The author has an hindex of 29, co-authored 47 publications receiving 16323 citations. Previous affiliations of David H. Olson include Spanish National Research Council & National Institute of Standards and Technology.

Understanding the Unusual Adsorption Behavior in Hierarchical Zeolite Nanosheets

Abstract: Hierarchical zeolites are advanced materials possessing the catalytic and adsorption properties of conventional zeolites while eliminating their transport limitations through the introduction of mesopores. Recent experiments comparing the adsorption in hierarchical self-pillared pentasils (SPP) and silicalite-1 (MFI) revealed an interesting crossover in sorbate loading for branched or long-chain alkanes but not for shorter linear alkanes, but an explanation for this behavior is not readily available through experimental probes due to the complications arising from the presence of multiple adsorption sites. Here we present a molecular simulation study on the adsorption of alkane isomers and show that a multi-step mechanism, found here for all molecules, is responsible for the observed phenomena.

Flexible Zn-MOF with Rare Underlying scu Topology for Effective Separation of C6 Alkane Isomers.

Abstract: Adsorptive separation by porous solids provides an energy-efficient alternative for the purification of important chemical species compared to energy-intensive distillations. Particularly, the separation of linear hexane isomers from its branched counterparts is crucial to produce premium grade gasoline with high research octane number (RON). Herein, we report the synthesis of a new, flexible zinc-based metal-organic framework, [Zn5(μ3-OH)2(adtb)2(H2O)5·5 DMA] (Zn-adtb), constructed from a butterfly shaped carboxylate linker with underlying (4,8)-connected scu topology capable of separating the C6 isomers nHEX, 3MP, and 23DMB. The sorbate-sorbent interactions and separation mechanisms were investigated and analyzed through in situ FTIR, solid state NMR measurements and computational modeling. These studies reveal that Zn-adtb discriminates the nHEX/3MP isomer pair through a kinetic separation mechanism and the nHEX/23DMB isomer pair through a molecular sieving mechanism. Column breakthrough measurements further demonstrate the efficient separation of linear nHEX from the mono- and dibranched isomers.

Further Search for Hydroxyl Nests in Acid Dealuminated Zeolite Y

Abstract: The removal of Al with acid solution from a zeolite framework is customarily associated with formation of framework defects known as hydroxyl nests, but their existence has not been unambiguously confirmed thus far. In a recent study on acid dealuminated Y zeolite, pre-exchanged predominantly with Cs in order to ensure maximized elimination of molecular water that can conceal hydrogen bonded OH groups, no indication has been found for the presence of hydroxyl nests.9 We present here temperature-programmed desorption (TPD) and Fourier transform infra-red (FTIR) evidence that such hydroxyl nests cannot be identified in an approximately 20% acid dealuminated and solely sodium re-exchanged zeolite NaY(-Al) that has not been exposed to temperatures above 25 °C during and after dealumination. These experimental conclusions were matched by results of combined density functional theory (DFT)-based spectroscopic study and reactive-force field molecular dynamics calculations on full periodic model zeolites. They sh...

Triblock copolymer syntheses of mesoporous silica with periodic 50 to 300 angstrom pores

Abstract: Use of amphiphilic triblock copolymers to direct the organization of polymerizing silica species has resulted in the preparation of well-ordered hexagonal mesoporous silica structures (SBA-15) with uniform pore sizes up to approximately 300 angstroms. The SBA-15 materials are synthesized in acidic media to produce highly ordered, two-dimensional hexagonal (space group p6mm) silica-block copolymer mesophases. Calcination at 500°C gives porous structures with unusually large interlattice d spacings of 74.5 to 320 angstroms between the (100) planes, pore sizes from 46 to 300 angstroms, pore volume fractions up to 0.85, and silica wall thicknesses of 31 to 64 angstroms. SBA-15 can be readily prepared over a wide range of uniform pore sizes and pore wall thicknesses at low temperature (35° to 80°C), using a variety of poly(alkylene oxide) triblock copolymers and by the addition of cosolvent organic molecules. The block copolymer species can be recovered for reuse by solvent extraction with ethanol or removed by heating at 140°C for 3 hours, in both cases, yielding a product that is thermally stable in boiling water.

Selective gas adsorption and separation in metal–organic frameworks

Abstract: Adsorptive separation is very important in industry. Generally, the process uses porous solid materials such as zeolites, activated carbons, or silica gels as adsorbents. With an ever increasing need for a more efficient, energy-saving, and environmentally benign procedure for gas separation, adsorbents with tailored structures and tunable surface properties must be found. Metal–organic frameworks (MOFs), constructed by metal-containing nodes connected by organic bridges, are such a new type of porous materials. They are promising candidates as adsorbents for gas separations due to their large surface areas, adjustable pore sizes and controllable properties, as well as acceptable thermal stability. This critical review starts with a brief introduction to gas separation and purification based on selective adsorption, followed by a review of gas selective adsorption in rigid and flexible MOFs. Based on possible mechanisms, selective adsorptions observed in MOFs are classified, and primary relationships between adsorption properties and framework features are analyzed. As a specific example of tailor-made MOFs, mesh-adjustable molecular sieves are emphasized and the underlying working mechanism elucidated. In addition to the experimental aspect, theoretical investigations from adsorption equilibrium to diffusion dynamics via molecular simulations are also briefly reviewed. Furthermore, gas separations in MOFs, including the molecular sieving effect, kinetic separation, the quantum sieving effect for H2/D2 separation, and MOF-based membranes are also summarized (227 references).

Nonionic Triblock and Star Diblock Copolymer and Oligomeric Surfactant Syntheses of Highly Ordered, Hydrothermally Stable, Mesoporous Silica Structures

Abstract: A family of highly ordered mesoporous (20−300 A) silica structures have been synthesized by the use of commercially available nonionic alkyl poly(ethylene oxide) (PEO) oligomeric surfactants and poly(alkylene oxide) block copolymers in acid media. Periodic arrangements of mescoscopically ordered pores with cubic Im3m, cubic Pm3m (or others), 3-d hexagonal (P63/mmc), 2-d hexagonal (p6mm), and lamellar (Lα) symmetries have been prepared. Under acidic conditions at room temperature, the nonionic oligomeric surfactants frequently form cubic or 3-d hexagonal mesoporous silica structures, while the nonionic triblock copolymers tend to form hexagonal (p6mm) mesoporous silica structures. A cubic mesoporous silica structure (SBA-11) with Pm3m diffraction symmetry has been synthesized in the presence of C16H33(OCH2CH2)10OH (C16EO10) surfactant species, while a 3-d hexagonal (P63/mmc) mesoporous silica structure (SBA-12) results when C18EO10 is used. Surfactants with short EO segments tend to form lamellar mesost...

Metal–Organic Framework Materials as Chemical Sensors

Abstract: 1. INTRODUCTION Among the classes of highly porous materials, metalÀorganic frameworks (MOFs) are unparalleled in their degree of tunability and structural diversity as well as their range of chemical and physical properties. MOFs are extended crystalline structures wherein metal cations or clusters of cations (\" nodes \") are connected by multitopic organic \" strut \" or \" linker \" ions or molecules. The variety of metal ions, organic linkers, and structural motifs affords an essentially infinite number of possible combinations. 1 Furthermore, the possibility for postsynthetic modification adds an additional dimension to the synthetic variability. 2 Coupled with the growing library of experimentally determined structures, the potential to computationally predict, with good accuracy, affinities of guests for host frameworks points to the prospect of routinely predesigning frameworks to deliver desired properties. 3,4 MOFs are often compared to zeolites for their large internal surface areas, extensive porosity, and high degree of crystallinity. Correspondingly, MOFs and zeolites have been utilized for many of the same applications