Imidazolium Ionic Liquids,Imidazolylidene Heterocyclic Carbenes,and Zeolitic Imidazolate Frameworks for CO2 Capture and Photochemical Reduction

Imidazolium ionic liquids (ILs), imidazolylidene N‐heterocyclic carbenes (NHCs), and zeolitic imidazolate frameworks (ZIFs) are imidazolate motifs which have been extensively investigated for CO₂ adsorption and conversion applications. Summarized in this minireview is the recent progress in the capture, activation, and photochemical reduction of CO₂ with these three imidazolate building blocks, from homogeneous molecular entities (ILs and NHCs) to heterogeneous crystalline scaffolds (ZIFs). The developments and existing shortcomings of the imidazolate motifs for their use in CO₂ utilizations is assessed, with more of focus on CO₂ photoredox catalysis. The opportunities and challenges of imidazolate scaffolds for future advancement of CO₂ photochemical conversion for artificial photosynthesis are discussed.     

Synthesis and Characterization of Two Pb(II) Complexes of 2,2′-dihydroxy,Dimethoxy-1,1′-binaphthyl-3,3′-dicarboxylic Acid

Two new complexes {[Pb(L¹)(DMSO)₂(H₂O)]·DMF}_n (1, L¹ = 2,2′-dihydroxy-l,l′-dinaphthyl-3,3′-dicarboxylate) and {[Pb(L²)(DMS O)·DMSO}_n (2, L² = 2,2′-dimethoxy-l,l′-dinaphthyl-3,3′-dicarboxylate) have been synthesized under mild conditions and structurally characterized. Crystal structural analysis reveals that complex 1 adopts a 1D infinite chain structure which forms 2D sheet by hydrogen bonds interactions. Complex 2 possesses a 2D sheet structure, which was further assembled into a 3D supramolecular network through the π-π weak interactions. IR spectra indicates the carboxyl group coordinates with the Pb²⁺ ion. TGA shows that complex 2 is highly thermally stable up to 120°C.     

Protamine‐Capped Mesoporous Silica Nanoparticles for Biologically Triggered Drug Release

The fabrication of a mesoporous silica nanoparticle (MSN)?protamine hybrid system (MSN?PRM) is reported that selectively releases drugs in the presence of specific enzyme triggers present in the proximity of cancer cells. The enzyme trigger involved is a protease called trypsin, which is overexpressed in certain specific pathological conditions, such as inflammation and cancer. Overexpression of trypsin is known to be associated with invasion, metastasis, and growth in several cancers, such as leukemia, colon cancer, and colorectal cancer. The current system (MSN–PRM) consists of an MSN support in which mesopores are capped with an FDA‐approved peptide drug protamine, which effectively blocks the outward diffusion of the drug molecules from the mesopores of the MSNs. On exposure to the enzyme trigger, the protamine cap disintegrates, opening up the molecular gates and releasing the entrapped drug molecules. The system exhibits minimal premature release in the absence of the trigger and selectively releases the encapsulated drugs in the presence of the proteases secreted by colorectal cancer cells. The ability of the MSN–PRM particles to deliver anticancer drugs to colorectal cancer cells has also been demonstrated. The hydrophobic drug is released into cancer cells subsequent to disintegration of the protamine cap, resulting in cell death. Drug‐induced cell death in colorectal cancer cells is significantly enhanced when the hydrophobic drug that is known to degrade in aqueous environments is encapsulated in the MSN–PRM system in comparison to the free drug (P < 0.05). The system, which shows good biocompatibility and selective drug release, is a promising platform for cancer specific drug delivery.     

不对称卟啉共价固载于硅基介孔薄膜材料模拟RS触发器的研究

合成了5-(4-氨基苯基)-10,15,20-三苯基卟啉(ATPP),并成功将其以共价嫁接的形式固载于介孔二氧化硅薄膜。基于卟啉化合物对酸碱的特异性响应,实现了对RS触发器逻辑功能的模拟。卟啉化合物被共价固载于介孔薄膜材料使得该分子逻辑器件具有相对较大的表面积、周期性排布的均一孔道结构以及高的光透过性等介孔薄膜材料的优异性质。这种混合多孔结构不但有利于嫁接于介孔材料中的卟啉与酸碱的更有效相互作用,而且还使酸碱输入能够被更加彻底地清除。     

Two ZnII Metal‐Organic Frameworks with Coordinatively Unsaturated Metal Sites: Structures,Adsorption, and Catalysis

Assembly of Zn(NO₃)₂ with the tripodal ligand H₃TCPB (1,3,5‐tri(4‐carboxyphenoxy)benzene) affords two porous isoreticular metal‐organic frameworks, [Zn₃(TCPB)₂?2DEF]? 3DEF ( 1 ) and [Zn₃(TCPB)₂?2H₂O]? 2H₂O?4DMF ( 2 ). Single‐crystal X‐ray diffraction analyses reveal that 1 crystallizes in the monoclinic space group P2₁/c and possesses a 2D network containing 1D microporous opening channels with an effective size of 3.0×2.9 Ų, whereas 2 crystallizes in the trigonal space group c1 and also possesses a 2D network containing 1D channels, with an effective aperture of 4.0×4.0 Ų. TOPOS analysis reveals that both 1 and 2 have a (3,6)‐connected network topology with the Schläfli symbol of (4³?6¹²) (4³)₂. According to the variable‐temperature powder X‐ray diffraction patterns, the solid phase of 1 can be converted into that of 2 during a temperature‐induced dynamic structural transformation, thus indicating that the framework of 2 represents the most thermally stable polymorph. Desolvated 2 exhibits highly selective adsorption behaviors toward H₂/N₂, CO₂/N₂, and CO₂/CH₄; furthermore, it displays size‐selective catalytic activity towards carbonyl cyanosilylation and Henry (nitroaldol) reactions.     

Reversible interpenetration in a metal-organic framework triggered by ligand removal and addition

Caging cages: Crystals of a metal-organic framework, MOF-123 [Zn(7) O(2) (NBD)(5) (DMF)(2) ] have a three-dimensional porous structure in which DMF ligands (see picture, pink) protrude into small channels. Removal of these ligands triggers the transformation of this MOF to the doubly interpenetrating form, MOF-246 [Zn(7) O(2) (NBD)(5) ]. Moreover, addition of DMF into MOF-246 triggers reverse transformation to give MOF-123. NBD=2-nitrobenzene-1,4-dicarboxylate.     

How Can a Hydrophobic MOF be Water‐Unstable? Insight into the Hydration Mechanism of IRMOFs

We report an ab initio molecular dynamics study of the hydration process in a model IRMOF material. At low water content (one molecule per unit cell), water physisorption is observed on the zinc cation but the free?bound equilibrium strongly favors the free state. This is consistent with the hydrophobic nature of the host matrix and its type‐V isotherm observed in a classical Monte Carlo simulation. At higher loading, a water cluster can be formed at the Zn₄O site and this is shown to stabilize the water‐bound state. This structure rapidly transforms into a linker‐displaced state, where water has fully displaced one arm of a linker and which corresponds to the loss of the material’s fully ordered structure. Thus an overall hydrophobic MOF material can also become water unstable, a feature that has not been fully understood until now.     

Formaldehyde encapsulated in lithium-decorated metal-organic frameworks: a density functional theory study

The stability of monomeric formaldehyde encapsulated in the lithium-decorated metal-organic framework Li-MOF-5 was investigated by means of density functional calculations with the M06-L functional and the 6-31G(d,p) basis set. To assess the efficiency of Li-MOF-5 for formaldehyde preservation, we consider the reaction kinetics and the thermodynamic equilibrium between formaldehyde and its trimerized product, 1,3,5-trioxane. We propose that trimerization of encapsulated formaldehyde takes place in a single reaction step with an activation energy of 34.5 kcal mol(-1). This is 17.2 kcal mol(-1) higher than the corresponding activation energy in the bare system. In addition, the reaction energy of the system studied herein is endothermic by 6.1 kcal mol(-1) and the Gibbs free energy (ΔG) of the reaction becomes positive (11.0 kcal mol(-1)). Consequently, the predicted reverse rate for the trimerization reaction in the Li-MOF-5 is significantly faster than the forward rate. The calculations show that the oligomerization of formaldehyde in Li-MOF-5 is a reversible reaction, suggesting that such a zeolite might be a good candidate material for preserving formaldehyde in its monomeric form.