Synthesis of Phase-Pure Interpenetrated MOF-5 and Its Gas Sorption Properties

For the first time, phase-pure interpenetrated MOF-5 (1) has been synthesized and its gas sorption properties have been investigated. The phase purity of the material was confirmed by both single-crystal and powder X-ray diffraction studies and TGA analysis. A systematic study revealed that controlling the pH of the reaction medium is critical to the synthesis of phase-pure 1, and the optimum apparent pH (pH*) for the formation of 1 is 4.0−4.5. At higher or lower pH*, [Zn2(BDC)2(DMF)2] (2) or [Zn5(OH)4(BDC)3] (3), respectively, was predominantly formed. The pore size distribution obtained from Ar sorption experiments at 87 K showed only one peak, at ∼6.7 Å, which is consistent with the average pore size of 1 revealed by single crystal X-ray crystallography. Compared to MOF-5, 1 exhibited higher stability toward heat and moisture. Although its surface area is much smaller than that of MOF-5 due to interpenetration, 1 showed a significantly higher hydrogen capacity (both gravimetric and volumetric) than MOF-5 at 77 K and 1 atm, presumably because of its higher enthalpy of adsorption, which may correlate with its higher volumetric hydrogen uptake compared to MOF-5 at room temperature, up to 100 bar. However, at high pressures and 77 K, where the saturated H2 uptake mostly depends on the surface area of a porous material, the total hydrogen uptake of 1 is notably lower than that of MOF-5

Synthesis of Phase-Pure Interpenetrated MOF-5 and Its Gas Sorption Properties

For the first time, phase-pure interpenetrated MOF-5 (1) has been synthesized and its gas sorption properties have been investigated. The phase purity of the material was confirmed by both single-crystal and powder X-ray diffraction studies and TGA analysis. A systematic study revealed that controlling the pH of the reaction medium is critical to the synthesis of phase-pure 1, and the optimum apparent pH (pH*) for the formation of 1 is 4.0−4.5. At higher or lower pH*, [Zn2(BDC)2(DMF)2] (2) or [Zn5(OH)4(BDC)3] (3), respectively, was predominantly formed. The pore size distribution obtained from Ar sorption experiments at 87 K showed only one peak, at ∼6.7 Å, which is consistent with the average pore size of 1 revealed by single crystal X-ray crystallography. Compared to MOF-5, 1 exhibited higher stability toward heat and moisture. Although its surface area is much smaller than that of MOF-5 due to interpenetration, 1 showed a significantly higher hydrogen capacity (both gravimetric and volumetric) than MOF-5 at 77 K and 1 atm, presumably because of its higher enthalpy of adsorption, which may correlate with its higher volumetric hydrogen uptake compared to MOF-5 at room temperature, up to 100 bar. However, at high pressures and 77 K, where the saturated H2 uptake mostly depends on the surface area of a porous material, the total hydrogen uptake of 1 is notably lower than that of MOF-5

Nonreciprocal Infrared Absorption via Resonant Magneto-optical Coupling to InAs

Nonreciprocal elements are a vital building block of electrical and optical systems. In the infrared regime, there is a particular interest in structures that break reciprocity because their thermal absorptive (and emissive) properties should not obey the Kirchhoff thermal radiation law. In this work, we break time-reversal symmetry and reciprocity in n-type doped magneto-optic InAs with a static magnetic field where light coupling is mediated by a guided-mode-resonator (GMR) structure whose resonant frequency coincides with the epsilon-near-zero (ENZ) resonance of the doped InAs. Using this structure, we observe the nonreciprocal absorptive behavior as a function of magnetic field and scattering angle in the infrared. Accounting for resonant and nonresonant optical scattering, we reliably model experimental results that break reciprocal absorption relations in the infrared. The ability to design such nonreciprocal absorbers opens an avenue to explore devices with unequal absorptivity and emissivity in specific channels

Highly Selective Carbon Dioxide Sorption in an Organic Molecular Porous Material

The organic molecular porous material 1 obtained by recrystallization of cucurbit[6]uril (CB[6]) from HCl shows a high CO2 sorption capacity at 298 K, 1 bar. Most interestingly, 1 showed the highest selectivity of CO2 over CO among the known porous materials so far. The remarkable selectivity of CO2 may be attributed to the exceptionally high enthalpy of adsorption (33.0 kJ/mol). X-ray crystal structure analysis of CO2 adsorbed 1 revealed three independent CO2 sorption sites: two in the 1D channels (A and B) and one in the molecular cavities (C). The CO2 molecules adsorbed at sorption site A near the wall of the 1D channels interact with 1 through hydrogen bonding and at the same time interact with those at site B mainly through quadrupole−quadrupole interaction in a T-shaped arrangement. Interestingly, two CO2 molecules are included in the CB[6] cavity (site C), interacting not only with the carbonyl groups of CB[6] but also with each other in a slipped-parallel geometry. The exceptionally selective CO2 sorption properties of 1 may find useful applications in the pressure swing adsorption (PSA) process for CO2 separation not only in the steel industry but also in other industries such as natural gas mining

Optical Characterization of Silicon Nitride Metagrating-Based Lightsails for Self-Stabilization

We report ultrathin photonic metagratings where anisotropic scattering is designed to achieve self-stabilizing dynamics in a collimated beam of laser light. Stability necessitates a delicate balance between all scattered orders of light, which we demonstrate in a monolithic material platform suited for efficient propulsion in space. Our suspended structures are fabricated in silicon nitride membranes, which is a promising lightsail material candidate due to its wafer-level scalability and favorable mechanical and optical properties. Lightsail prototype designs are optically characterized by angle-resolved photocurrent measurements of the intensities and angles of the asymmetric ±1 diffraction orders. We infer the optically induced forces and torques from refracted and reflected light measurements and show that these are restoring along one axis by providing them as input functions to numerical simulations of lightsail dynamics. Our experimental results represent a first step toward full dynamical verification of realistic lightsail designs and pave the way for realization of stable beam-riding lightsails composed of ultrathin dielectric membranes

Highly Selective Carbon Dioxide Sorption in an Organic Molecular Porous Material

The organic molecular porous material 1 obtained by recrystallization of cucurbit[6]uril (CB[6]) from HCl shows a high CO2 sorption capacity at 298 K, 1 bar. Most interestingly, 1 showed the highest selectivity of CO2 over CO among the known porous materials so far. The remarkable selectivity of CO2 may be attributed to the exceptionally high enthalpy of adsorption (33.0 kJ/mol). X-ray crystal structure analysis of CO2 adsorbed 1 revealed three independent CO2 sorption sites: two in the 1D channels (A and B) and one in the molecular cavities (C). The CO2 molecules adsorbed at sorption site A near the wall of the 1D channels interact with 1 through hydrogen bonding and at the same time interact with those at site B mainly through quadrupole−quadrupole interaction in a T-shaped arrangement. Interestingly, two CO2 molecules are included in the CB[6] cavity (site C), interacting not only with the carbonyl groups of CB[6] but also with each other in a slipped-parallel geometry. The exceptionally selective CO2 sorption properties of 1 may find useful applications in the pressure swing adsorption (PSA) process for CO2 separation not only in the steel industry but also in other industries such as natural gas mining

Light-Induced Acid Generation on a Gatekeeper for Smart Nitric Oxide Delivery

We report herein the design of a light-responsive gatekeeper for smart nitric oxide (NO) delivery. The gatekeeper is composed of a pH-jump reagent as an intermediary of stimulus and a calcium phosphate (CaP) coating as a shielding layer for NO release. The light irradiation and subsequent acid generation are used as triggers for uncapping the gatekeeper and releasing NO. The acids generated from a light-activated pH-jump agent loaded in the mesoporous nanoparticles accelerated the degradation of the CaP-coating layers on the nanoparticles, facilitating the light-responsive NO release from diazeniumdiolate by exposing a NO donor to physiological conditions. Using the combination of the pH-jump reagent and CaP coating, we successfully developed a light-responsive gatekeeper system for spatiotemporal-controlled NO delivery

Systematic Study on the Sensitivity Enhancement in Graphene Plasmonic Sensors Based on Layer-by-Layer Self-Assembled Graphene Oxide Multilayers and Their Reduced Analogues

The use of graphene in conventional plasmonic devices was suggested by several theoretic research studies. However, the existing theoretic studies are not consistent with one another and the experimental studies are still at the initial stage. To reveal the role of graphenes on the plasmonic sensors, we deposited graphene oxide (GO) and reduced graphene oxide (rGO) thin films on Au films and their refractive index (RI) sensitivity was compared for the first time in SPR-based sensors. The deposition of GO bilayers with number of deposition L from 1 to 5 was carried out by alternative dipping of Au substrate in positively- and negatively charged GO solutions. The fabrication of layer-by-layer self-assembly of the graphene films was monitored in terms of the SPR angle shift. GO-deposited Au film was treated with hydrazine to reduce the GO. For the rGO-Au sample, 1 bilayer sample showed a higher RI sensitivity than bare Au film, whereas increasing the rGO film from 2 to 5 layers reduced the RI sensitivity. In the case of GO-deposited Au film, the 3 bilayer sample showed the highest sensitivity. The biomolecular sensing was also performed for the graphene multilayer systems using BSA and anti-BSA antibody

<i>N</i>‑Heterocyclic Carbene Nitric Oxide Radicals

<i>N</i>-Heterocyclic carbene-stabilized nitric oxide radicals were prepared by direct addition of nitric oxide to two <i>N</i>-heterocyclic carbenes in solution phase. The compounds were fully characterized by X-ray crystallography and EPR. The nitric oxide moiety in the solid compounds obtained can be thermally transferred to another <i>N</i>-heterocyclic carbene, suggesting potential applications to NO delivery