Quantum Monte Carlo Study of the Water Dimer Binding Energy and Halogen-?? Interactions

Halogen-?? systems are involved with competition between halogen bonding and ??-interaction. Using the diffusion quantum Monte Carlo (DMC) method, we compare the interaction of benzene with diatomic halogens (X2: Cl2/Br2) with the typical hydrogen bonding in the water dimer, taking into account explicit correlations of up to three bodies. The benzene-Cl2/Br2 binding energies (13.07 ?? 0.42/16.62 ?? 0.02 kJ/mol) attributed to both halogen bonding and dispersion are smaller than but comparable to the typical hydrogen bonding in the water dimer binding energy (20.88 ?? 0.27 kJ/mol). All of the above values are in good agreement with those from the coupled-cluster with single, double, and noniterative triple excitations (CCSD(T)) results at the complete basis set limit (benzene-Cl2/Br2: 12.78/16.17 kJ/mol; water dimer: 21.0 kJ/mol)

Impact of Zr6 Node in a Metal???Organic Framework for Adsorptive Removal of Antibiotics from Water

Quinolone-based antibiotics commonly detected in surface, ground, and drinking water are difficult to remove and therefore pose a threat as organic contaminants of aqueous environment. We performed adsorptive removal of quinolone antibiotics, nalidixic acid and ofloxacin, using a zirconium???porphyrin-based metal???organic framework (MOF), PCN-224. PCN-224 exhibits the highest adsorption capacities for both nalidixic acid and ofloxacin among those reported for MOFs to date. The accessible metal sites of Zr metal nodes are responsible for efficient adsorptive removal. This study offers a pragmatic approach to design MOFs optimized for adsorptive removal of antibiotics

Anisotropic and amphoteric characteristics of diverse carbenes

Despite its key importance in carbene chemistry, the amphoteric (i. e., both nucleophilic and electrophilic) behavior of the divalent carbon atom (: C) in carbenes is not well understood. The electrostatic potential (EP) around : C is often incorrectly described by simple isotropic atomic charges (particularly, as in singlet CF2); therefore, it should be described by the multipole model, which can illustrate both negative and positive EPs, favoring the positively and negatively charged species that are often present around : C. This amphotericity is much stronger in the singlet state, which has more conspicuous anisotropic charge distribution than the triplet state; this is validated by the complexation structures of carbenes interacting with Na+, Cl-, H2O, and Ag+. From the study of diverse carbenes [including CH2, CLi2/CNa2, CBe2/CMg2, CF2/CCl2, C(BH2) 2/C(AlH2) 2, C(CH3) 2/C(SiH3) 2, C(NH2) 2/C(PH2) 2, cyclic systems of C(CH2) 2/C(CH) 2, C(BHCH) 2, C(CH2CH) 2/C(CHCH) 2, and C(NHCH) 2/C(NCH) 2], we elucidate the relationships between the electron configurations, electron accepting/donating strengths of atoms attached to : C, p conjugation, singlet-triplet energy gaps, anisotropic hard wall radii, anisotropic electrostatic potentials, and amphotericities of carbenes, which are vital to carbene chemistry. The (s 2, p 2 or sp) electronic configuration associated with : C on the : CA2 plane (where A is an adjacent atom) in singlet and triplet carbenes largely governs the amphoteric behaviors along the : C tip and : C face-on directions. The : C tip and : C face-on sites of s 2 singlet carbenes tend to show negative and positive EPs, favoring nucleophiles and electrophiles, respectively; meanwhile, those of p 2 singlet carbenes, such as very highly p-conjugated 5-membered cyclic C(NCH) 2, tend to show the opposite behavior. Open-shell sp singlet (such as highly p-conjugated 5-membered cyclic C(CHCH) 2) and triplet carbenes show less anisotropic and amphoteric behaviors

Targeted Adsorptive Removal of Nonsteroidal Anti-inflammatory Drugs for Water Purification Using Nanoporous Zr-based Metal-Organic Framework Microcubes

Chemically synthesized drugs used in the industry are associated with potential environmental risks. Herein, we report the targeted adsorption of nonsteroidal anti-inflammatory drugs, with and without a carboxylic acid group, using a water-stable Zr-based porphyrinic metal???organic framework (MOF), PCN???224. Nanoporous PCN???224 contains interaction sites for drugs and thus enables the removal of organic pollutants. The removal efficiency of NPX and IBP was 96 and 94%, but PCN???224 removed only 37% of SMX from water. The apparent difference in the adsorption efficiency of PCN???224 indicates that the carboxylic acid functional groups in drugs strongly interacted with the open metal sites of the PCN???224 Zr6 node via coordination bonding, resulting in a high adsorption capacity. This discovery provided a practical approach for the selective adsorptive removal of various other drugs with carboxylate groups

Adsorptive Removal of Industrial Dye by Nanoporous Zr porphyrinic Metal-Organic Framework Microcubes

Increasing anthropogenic activities have adversely affected freshwater supply, making it an important global issue. Water resources are often contaminated by industrial dyes, which may harm both environment and human health even at low-level exposure. Herein, we report the adsorptive removal of a representative azo dye, methyl orange (MO) on PCN-224, a Zr porphyrinic metal-organic framework (MOF). Nanoporous PCN-224 has desirable structural characteristics such as an optimal pore aperture and a large pore volume optimized for trapping MO molecules, in addition to superior water stability. Significantly, through the combined investigation of experimental and theoretical studies, multiple adsorption sites such as the porphyrin linkers and Zr-6 nodes of the framework formed pi-pi interactions and hydrogen bonding with MO molecules, respectively, affording the highest adsorption capacity among the reported MOFs

Origamic metal-organic framework toward mechanical metamaterial

Abstract Origami, known as paper folding has become a fascinating research topic recently. Origami-inspired materials often establish mechanical properties that are difficult to achieve in conventional materials. However, the materials based on origami tessellation at the molecular level have been significantly underexplored. Herein, we report a two-dimensional (2D) porphyrinic metal-organic framework (MOF), self-assembled from Zn nodes and flexible porphyrin linkers, displaying folding motions based on origami tessellation. A combined experimental and theoretical investigation demonstrated the origami mechanism of the 2D porphyrinic MOF, whereby the flexible linker acts as a pivoting point. The discovery of the 2D tessellation hidden in the 2D MOF unveils origami mechanics at the molecular level

Targeted Adsorptive Removal of Nonsteroidal Anti-inflammatory Drugs for Water Purification Using Nanoporous Zr-Based Metal–Organic Framework Microcubes

Chemically synthesized drugs used in the industry are associated with potential environmental risks. Herein, we report the targeted adsorption of nonsteroidal anti-inflammatory drugs, with and without a carboxylic acid group, using a water-stable Zr-based porphyrinic metal–organic framework (MOF), PCN–224. Nanoporous PCN–224 contains interaction sites for drugs and thus enables the removal of organic pollutants. The removal efficiency of NPX and IBP was 96 and 94%, but PCN–224 removed only 37% of SMX from water. The apparent difference in the adsorption efficiency of PCN–224 indicates that the carboxylic acid functional groups in drugs strongly interacted with the open metal sites of the PCN–224 Zr6 node via coordination bonding, resulting in a high adsorption capacity. This discovery provided a practical approach for the selective adsorptive removal of various other drugs with carboxylate groups