Three-axis attitude determination via Kalman filtering of magnetometer data

A three-axis Magnetometer/Kalman Filter attitude determination system for a spacecraft in low-altitude Earth orbit is developed, analyzed, and simulation tested. The motivation for developing this system is to achieve light weight and low cost for an attitude determination system. The extended Kalman filter estimates the attitude, attitude rates, and constant disturbance torques. Accuracy near that of the International Geomagnetic Reference Field model is achieved. Covariance computation and simulation testing demonstrate the filter's accuracy. One test case, a gravity-gradient stabilized spacecraft with a pitch momentum wheel and a magnetically-anchored damper, is a real satellite on which this attitude determination system will be used. The application to a nadir pointing satellite and the estimation of disturbance torques represent the significant extensions contributed by this paper. Beyond its usefulness purely for attitude determination, this system could be used as part of a low-cost three-axis attitude stabilization system

A Luminescent Terbium MOF Containing Hydroxyl Groups Exhibits Selective Sensing of Nitroaromatic Compounds and Fe(III) Ions

A new 3D porous Tb­(III)-ion based PMOF, {[Tb­(<i>L</i>)­(DMA)]·(DMA)·(0.5H₂O)} (<b>1</b>) (where <i>L</i> = L^3–, H₃L = 3′-hydroxybiphenyl-3,4′,5-tricarboxylic acid), with uncoordinated hydroxyl groups decorating the pores has been solvothermally synthesized in moderate yield. The hydroxyl groups act as potential interaction sites to sensitize the luminescence output of the Tb³⁺ ion. Luminescence studies reveal that the PMOF can selectively and reversibly sense nitroaromatic compounds and Fe­(III) ions in DMF suspension through fluorescence quenching observable under UV light. The probable mechanisms for such sensing processes are, for the nitroaromatic compounds, the host–guest interactions with the PMOF and, for Fe³⁺ ion, the competitive absorption of excitation energy

A Porous Cu(II)-MOF with Proline Embellished Cavity: Cooperative Catalysis for the Baylis-Hillman Reaction

l-Proline has been covalently attached in a rigid linear ligand, <b>H</b>_<b>4</b><b>L</b>, having an isophthalate moiety at each terminal to form the chiral ligand, <b>H</b>_<b>4</b><b>LPRO</b>. This linker has been used for the construction of a porous MOF, <b>L</b>_<b>Cu</b><b>PRO</b>. The free l-proline moiety in the cavity of the framework in the presence of imidazole as a cocatalyst functions synergistically to catalyze the Baylis–Hillman reaction between α,β-unsaturated carbonyl compounds and aromatic aldehydes. High porosity of the framework is proven by the nitrogen adsorption isotherm

A Porous Cu(II)-MOF with Proline Embellished Cavity: Cooperative Catalysis for the Baylis-Hillman Reaction

l-Proline has been covalently attached in a rigid linear ligand, <b>H</b>_<b>4</b><b>L</b>, having an isophthalate moiety at each terminal to form the chiral ligand, <b>H</b>_<b>4</b><b>LPRO</b>. This linker has been used for the construction of a porous MOF, <b>L</b>_<b>Cu</b><b>PRO</b>. The free l-proline moiety in the cavity of the framework in the presence of imidazole as a cocatalyst functions synergistically to catalyze the Baylis–Hillman reaction between α,β-unsaturated carbonyl compounds and aromatic aldehydes. High porosity of the framework is proven by the nitrogen adsorption isotherm

Linker-Induced Structural Diversity and Photophysical Property of MOFs for Selective and Sensitive Detection of Nitroaromatics

The linker [1,1′:3′,1″-terphenyl]-4,4′,4″,6′-tetracarboxylic acid (<b>H</b>_<b>4</b><b>L</b>) was used to construct two three-dimensional (3D) metal–organic frameworks (MOFs), namely, {[Cd₂(L)­(L₁)­(DMF)­(H₂O)]­(2DMF)­(3H₂O)}_<i>n</i> (<b>1</b>) and {[Cd₄(L)₂(L₂)₃(H₂O)₂]­(8DMF)­(8H₂O)}_<i>n</i> (<b>2</b>) (DMF = <i>N</i>,<i>N</i>′-dimethylformamide) in the presence of colinkers 4,4′-bipyridine (<b>L</b>_<b>1</b>) and 2-amino-4,4′-bipyridine (<b>L</b>_<b>2</b>), respectively, under solvothermal condition. A small change in the colinker leads to significant differences in the overall structure of the MOFs. Topological analysis reveals that the framework <b>1</b> exhibits 6,4-connected forbidden sub-configuration (FSC) topology, while the framework <b>2</b> exhibits twofold interpenetrated and (3,4,4)-connected new network topology with Schläfli point symbol {4.6²}­{4.6⁴.8}­{4².6².8²}. The crystallographic investigation reveals the framework <b>2</b> having single helix structure, which is further coiled through noncovalent interaction, afforded a double-helix structure similar to DNA. These double helices are further connected through the colinker <b>L</b>_<b>2</b> to form an overall 3D structure. Besides framework <b>2</b> exhibits remarkable fluorescence intensity compared to <b>1</b>. Framework <b>2</b> displayed a strong emission at 457 nm when a sample of <b>2</b> was dispersed in ethanol and excited at 334 nm. This emission is selectively and completely quenched in the presence of 2,4,6-trinitrophenol (TNP) allowing its detection in the presence of other nitroaromatic compounds. The quenching constant for TNP was found to be 3.89 × 10⁴ M^–1, which is 26 times higher than that of TNT demonstrating greater and selective quenching ability. The emission is restored to its original value when the sample after collected by filtration is dispersed in fresh ethanol for 1 d. Interestingly, when solid <b>2</b> is exposed to different nitroaromatic compounds, its emission is quenched selectively in the presence of nitrobenzene. In this case, the emission is restored upon heating the sample to 150 °C for 2 h

A Porous Cu(II)-MOF with Proline Embellished Cavity: Cooperative Catalysis for the Baylis-Hillman Reaction

l-Proline has been covalently attached in a rigid linear ligand, <b>H</b>_<b>4</b><b>L</b>, having an isophthalate moiety at each terminal to form the chiral ligand, <b>H</b>_<b>4</b><b>LPRO</b>. This linker has been used for the construction of a porous MOF, <b>L</b>_<b>Cu</b><b>PRO</b>. The free l-proline moiety in the cavity of the framework in the presence of imidazole as a cocatalyst functions synergistically to catalyze the Baylis–Hillman reaction between α,β-unsaturated carbonyl compounds and aromatic aldehydes. High porosity of the framework is proven by the nitrogen adsorption isotherm

Linker-Induced Structural Diversity and Photophysical Property of MOFs for Selective and Sensitive Detection of Nitroaromatics

The linker [1,1′:3′,1″-terphenyl]-4,4′,4″,6′-tetracarboxylic acid (<b>H</b>_<b>4</b><b>L</b>) was used to construct two three-dimensional (3D) metal–organic frameworks (MOFs), namely, {[Cd₂(L)­(L₁)­(DMF)­(H₂O)]­(2DMF)­(3H₂O)}_<i>n</i> (<b>1</b>) and {[Cd₄(L)₂(L₂)₃(H₂O)₂]­(8DMF)­(8H₂O)}_<i>n</i> (<b>2</b>) (DMF = <i>N</i>,<i>N</i>′-dimethylformamide) in the presence of colinkers 4,4′-bipyridine (<b>L</b>_<b>1</b>) and 2-amino-4,4′-bipyridine (<b>L</b>_<b>2</b>), respectively, under solvothermal condition. A small change in the colinker leads to significant differences in the overall structure of the MOFs. Topological analysis reveals that the framework <b>1</b> exhibits 6,4-connected forbidden sub-configuration (FSC) topology, while the framework <b>2</b> exhibits twofold interpenetrated and (3,4,4)-connected new network topology with Schläfli point symbol {4.6²}­{4.6⁴.8}­{4².6².8²}. The crystallographic investigation reveals the framework <b>2</b> having single helix structure, which is further coiled through noncovalent interaction, afforded a double-helix structure similar to DNA. These double helices are further connected through the colinker <b>L</b>_<b>2</b> to form an overall 3D structure. Besides framework <b>2</b> exhibits remarkable fluorescence intensity compared to <b>1</b>. Framework <b>2</b> displayed a strong emission at 457 nm when a sample of <b>2</b> was dispersed in ethanol and excited at 334 nm. This emission is selectively and completely quenched in the presence of 2,4,6-trinitrophenol (TNP) allowing its detection in the presence of other nitroaromatic compounds. The quenching constant for TNP was found to be 3.89 × 10⁴ M^–1, which is 26 times higher than that of TNT demonstrating greater and selective quenching ability. The emission is restored to its original value when the sample after collected by filtration is dispersed in fresh ethanol for 1 d. Interestingly, when solid <b>2</b> is exposed to different nitroaromatic compounds, its emission is quenched selectively in the presence of nitrobenzene. In this case, the emission is restored upon heating the sample to 150 °C for 2 h

Metal–Organic Frameworks Built from a Linear Rigid Dicarboxylate and Different Colinkers: Trap of the Keto Form of Ethylacetoacetate, Luminescence and Ferroelectric Studies

The ligand 2,6,2′,6′-tetranitro-biphenyl-4,4′-dicarboxylic acid (<b>H</b>_<b>2</b><b>L</b>) has been used alone or with a coligand to construct a number of metal organic frameworks (MOFs) with different metal ions that are X-ray crystallographically characterized. The porous three-dimensional (3D) MOF {[Gd₂(L)₃­(DMF)₄]­·(4DMF)­·(3H₂O)}<i>_n</i> (<b>1</b>) (DMF = <i>N,N</i>′-dimethylformamide) is found to be an excellent host to the keto form of ethylacetoacetate to produce {[Gd­(L)_1.5­(DMF)₂­(H₂O)₂]­(S)­(H₂O)}_<i>n</i> (<b>1a</b>) (S = ethyl 3-oxobutanoate) in single crystal to single crystal (SC–SC) transformation. This involves drastic rearrangement of the channels including several carboxylate shifts and concomitant movement of water molecules from the cavity to the metal center. Interestingly, the daughter framework <b>1a</b> reverts back to the mother framework <b>1</b> upon keeping it in DMF for 3 days at room temperature, suggesting that the framework <b>1</b> can be used as a container. The linker <b>H</b>_<b>2</b><b>L</b> also forms the MOFs {[(Cd)₄(L)₃­(H_lL₁)₂­(DMF)­(H₂O)₂]­(DMF)₃­(H₂O)₂}<i>_n</i> (<b>2</b>), {[Cd­(L)­(L₂)]}_<i>n</i> (<b>3</b>), {[(Cd)_1.5­(L)_1.5­(L₃)]}<i>_n</i> (<b>4</b>), and {[Cd­(L)­(L₄)­(H₂O)]}<i>_n</i> (<b>5</b>) in the presence of different colinkers. Solid-state photoluminescence studies performed on MOFs <b>2</b>–<b>5</b> at room temperature showed intraligand (π–π*) emission. The MOF <b>2</b> being a chiral compound has been subjected to ferroelectric measurements. All the compounds (<b>1</b>–<b>5</b>) have been characterized by X-ray crystallography, elemental analysis, powder X-ray diffraction patterns, thermogravimetry, and infrared spectroscopy

A Partially Fluorinated, Water-Stable Cu(II)–MOF Derived via Transmetalation: Significant Gas Adsorption with High CO₂ Selectivity and Catalysis of Biginelli Reactions

A partially fluorinated, angular tetracarboxylic acid linker (<b>H</b>_<b>4</b><b>L</b>) incorporating a pendant amine moiety forms a three-dimensional Zn­(II) framework, <b>1</b>. The structure consists of paddle-wheel Zn₂(CO₂)₄ secondary building units (SBUs) and Zn₁₂(CO₂)₂₄ supramolecular building blocks (SBBs). Thermal stability of <b>1</b> is found to be low. However, it undergoes transmetalation reaction with Cu­(II) at room temperature without losing crystallinity affording an isostructural framework, <b>1</b>_<b>Cu</b>. Framework <b>1</b>_<b>Cu</b> is thermally robust and allows generation of the solvent-free porous framework <b>1</b>_<b>Cu</b><b>′</b> upon activation with coordinatively unsaturated metal centers. Framework <b>1</b>_<b>Cu</b><b>′</b> exhibits water stability and at 77 K, adsorbs 2.56 wt % of H₂ up to 1 bar that significantly increases to 4.01 wt % at 13 bar. Also, this framework gives a high adsorption of 164.70 cc/g of CH₄ (11.7 wt %) at 303 K and 60 bar. The channel surfaces decorated with −NH₂ group and unsaturated metal centers in <b>1</b>_<b>Cu</b><b>′</b> allow a promising 36.4 wt % of CO₂ adsorption at 1 bar and 273 K. Moreover, it exhibits pronounced selectivity of CO₂ adsorption over N₂ and H₂ at 273 K. Finally, the versatility of <b>1</b>_<b>Cu</b><b>′</b> is shown by its excellent heterogeneous catalytic activity in the Biginelli coupling reactions involving an aldehyde, urea, and ethylacetoacetate to afford dihydroprimidinones

A Partially Fluorinated, Water-Stable Cu(II)–MOF Derived via Transmetalation: Significant Gas Adsorption with High CO₂ Selectivity and Catalysis of Biginelli Reactions

A partially fluorinated, angular tetracarboxylic acid linker (<b>H</b>_<b>4</b><b>L</b>) incorporating a pendant amine moiety forms a three-dimensional Zn­(II) framework, <b>1</b>. The structure consists of paddle-wheel Zn₂(CO₂)₄ secondary building units (SBUs) and Zn₁₂(CO₂)₂₄ supramolecular building blocks (SBBs). Thermal stability of <b>1</b> is found to be low. However, it undergoes transmetalation reaction with Cu­(II) at room temperature without losing crystallinity affording an isostructural framework, <b>1</b>_<b>Cu</b>. Framework <b>1</b>_<b>Cu</b> is thermally robust and allows generation of the solvent-free porous framework <b>1</b>_<b>Cu</b><b>′</b> upon activation with coordinatively unsaturated metal centers. Framework <b>1</b>_<b>Cu</b><b>′</b> exhibits water stability and at 77 K, adsorbs 2.56 wt % of H₂ up to 1 bar that significantly increases to 4.01 wt % at 13 bar. Also, this framework gives a high adsorption of 164.70 cc/g of CH₄ (11.7 wt %) at 303 K and 60 bar. The channel surfaces decorated with −NH₂ group and unsaturated metal centers in <b>1</b>_<b>Cu</b><b>′</b> allow a promising 36.4 wt % of CO₂ adsorption at 1 bar and 273 K. Moreover, it exhibits pronounced selectivity of CO₂ adsorption over N₂ and H₂ at 273 K. Finally, the versatility of <b>1</b>_<b>Cu</b><b>′</b> is shown by its excellent heterogeneous catalytic activity in the Biginelli coupling reactions involving an aldehyde, urea, and ethylacetoacetate to afford dihydroprimidinones