An official website of the United States government
Abstract The recovery and separation of organic solvents is highly important for the chemical industry and environmental protection. In this context, porous organic polymers (POPs) have significant potential owing to the possibility of integrating shape‐persistent macrocyclic units with high guest selectivity. Here, we report the synthesis of a macrocyclic porous organic polymer (np‐POP) and the corresponding model compound by reacting the cyclotetrabenzil naphthalene octaketone macrocycle with 1,2,4,5‐tetraaminobenzene and 1,2‐diaminobenzene, respectively, under solvothermal conditions. Co‐crystallization of the macrocycle and the model compound with various solvent molecules revealed their size‐selective inclusion within the macrocycle. Building on this finding, thenp‐POP with a hierarchical pore structure and a surface area of 579 m2 g−1showed solvent uptake strongly correlated with their kinetic diameters. Solvents with kinetic diameters below 0.6 nm – such as acetonitrile and dichloromethane – showed high uptake capacities exceeding 7 mmol g−1. Xylene separation tests revealed a high overall uptake (~34 wt %), witho‐xylene displaying a significantly lower uptake (~10 wt % less than other isomers), demonstrating the possibility of size and shape selective separation of organic solvents.
more »
« less
This content will become publicly available on June 16, 2026
Cyclotetrabenzil Oxime Derivatives
Abstract Cyclotetrabenzil, a shape‐persistent macrocyclic octaketone, is found to undergo eightfold condensation with hydroxylamine hydrochloride to yield its octaoxime. Subsequent acetylation of this macrocyclic oxime afforded the corresponding octaoxime acetate. Single‐crystal X‐ray diffraction reveals that both new derivatives assemble into nanotubular structures. However, their packing differs: the oxime forms hydrogen‐bonded tubes that bundle via included dimethyl sulfoxide (DMSO) molecules, whereas the acetate—lacking hydrogen‐bond donors—forms more loosely packed tubes with molecules tilted ∼54.5° relative to the tube axis. Gas sorption studies (CO2, C2, and C3hydrocarbons) show that cyclotetrabenzil is nonporous, whereas the oxime and acetate exhibit modest microporosity with BET surface areas of ∼200 m2g−1. Both derivatives display preferential uptake of propyne over propene and propane, and the acetate also adsorbs more acetylene than ethylene or ethane. Nonetheless, these capacities and selectivities are suboptimal for dynamic separation of C2and C3hydrocarbons. This study illustrates how oxime functionalization can modulate macrocyclic assembly and gas uptake behavior, providing insights for the design of future porous organic macrocycles.
more »
« less
- Award ID(s):
- 2204236
- PAR ID:
- 10600917
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Asian Journal of Organic Chemistry
- Volume:
- 14
- Issue:
- 8
- ISSN:
- 2193-5807
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The nature of the processes at the origin of life that selected specific classes of molecules for broad incorporation into cells is controversial. Among those classes selected were polyisoprenoids and their derivatives. This paper tests the hypothesis that polyisoprenoids were early contributors to membranes in part because they (or their derivatives) could facilitate charge transport by quantum tunneling. It measures charge transport across self‐assembled monolayers (SAMs) of carboxyl‐terminated monoterpenoids (O2C(C9HX)) and alkanoates (O2C(C7HX)) with different degrees of unsaturation, supported on silver (AgTS) bottom electrodes, with Ga2O3/EGaIn top electrodes. Measurements of current density of SAMs of linear length‐matched hydrocarbons—both saturated and unsaturated—show that completely unsaturated molecules transport charge faster than those that are completely saturated by approximately a factor of ten. This increase in relative rates of charge transport correlates with the number of carbon–carbon double bonds, but not with the extent of conjugation. These results suggest that polyisoprenoids—even fully unsaturated—are not sufficiently good tunneling conductors for their conductivity to have favored them as building blocks in the prebiotic world.more » « less
-
Abstract Magnetic resonance imaging of [1‐13C]hyperpolarized carboxylates (most notably, [1‐13C]pyruvate) allows one to visualize abnormal metabolism in tumors and other pathologies. Herein, we investigate the efficiency of1H and13C hyperpolarization of acetate and pyruvate esters with ethyl, propyl and allyl alcoholic moieties using heterogeneous hydrogenation of corresponding vinyl, allyl and propargyl precursors in isotopically unlabeled and 1‐13C‐enriched forms with parahydrogen over Rh/TiO2catalysts in methanol‐d4and in D2O. The maximum obtained1H polarization was 0.6±0.2 % (for propyl acetate in CD3OD), while the highest13C polarization was 0.10±0.03 % (for ethyl acetate in CD3OD). Hyperpolarization of acetate esters surpassed that of pyruvates, while esters with a triple carbon‐carbon bond in unsaturated alcoholic moiety were less efficient as parahydrogen‐induced polarization precursors than esters with a double bond. Among the compounds studied, the maximum1H and13C NMR signal intensities were observed for propyl acetate. Ethyl acetate yielded slightly less intense NMR signals which were dramatically greater than those of other esters under study.more » « less
-
Abstract A porous molecular crystal (PMC) assembled by macrocyclic cyclotetrabenzoin acetate is an efficient adsorbent for CO2separations. The 7.1×7.1 Å square pore of PMC and its ester C=O groups play important roles in improving its affinity for CO2molecules. The benzene walls of macrocycle engage in an apparent [π⋅⋅⋅π] interaction with the molecule of CO2at low pressure. In addition, the polar carbonyl groups pointing inward the square channels reduce the size of aperture to a 5.0×5.0 Å square, which offers kinetic selectivity for CO2capture. The PMC features water tolerance and high structural stability under vacuum and various gas adsorption conditions, which are rare among intrinsically porous organic molecules. Most importantly, the moderate adsorbate‐adsorbent interaction allows the PMC to be readily regenerated, and therefore applied to pressure swing adsorption processes. The eluted N2and CH4are obtained with over 99.9 % and 99.8 % purity, respectively, and the separation performance is stable for 30 cycles. Coupled with its easy synthesis, cyclotetrabenzoin acetate is a promising adsorbent for CO2separations from flue and natural gases.more » « less
-
Abstract We have studied the fragmentation of the brominated cyclic hydrocarbons bromocyclo-propane, bromocyclo-butane, and bromocyclo-pentane upon Br(3d) and C(1s) inner-shell ionization using coincidence ion momentum imaging. We observe a substantial yield of CH3+fragments, whose formation requires intramolecular hydrogen (or proton) migration, that increases with molecular size, which contrasts with prior observations of hydrogen migration in linear hydrocarbon molecules. Furthermore, by inspecting the fragment ion momentum correlations of three-body fragmentation channels, we conclude that CHx+fragments (withx = 0, …, 3) with an increasing number of hydrogens are more likely to be produced via sequential fragmentation pathways. Overall trends in the molecular-size-dependence of the experimentally observed kinetic energy releases and fragment kinetic energies are explained with the help of classical Coulomb explosion simulations.more » « less
