Xiao-Jun Sun

A dye-like ligand-based metal–organic framework for efficient photocatalytic hydrogen production from aqueous solution

A dye-like azo-carboxylic acid was chosen as an organic linker to construct a Gd3+ based metal–organic framework: [Gd2(abtc)(H2O)2(OH)2]·2H2O (Gd-MOF) (H4abtc = 3,3′,5,5′-azobenzene tetracarboxylic acid). The ultra-stable Gd-MOF possesses a HOMO–LUMO gap of 2.35 eV determined by UV-vis spectroscopy with an absorption edge at 530 nm, which presents effective photocatalytic activity for hydrogen evolution under UV-vis light illumination due to the porous structure and excellent light absorption of the dye-like ligand. To further enhance the photocatalytic activity, different amounts of Ag (1.0–2.0%) were deposited on Gd-MOF as a co-catalyst. The results of electrochemical impedance spectroscopy (EIS) and photoluminescence spectroscopy (PL) clearly indicate that the reaction proceeds through the electron transfer from Gd-MOF to the deposited Ag. Especially, Ag(1.5)/Gd-MOF exhibits significant improvement in the hydrogen evolution rate, which is about 1.5 times greater compared to that of bare Gd-MOF.

Postsynthetic Modification of ZIF-90 for Potential Targeted Codelivery of Two Anticancer Drugs

Combination therapy has been regarded as a promising strategy for cancer treatment due to the enhanced anticancer efficacy achieved by blocking multiple drug resistance pathways. In this work, a drug carrier based on nanoscale ZIF-90 for the codelivery of two anticancer drugs has been synthesized by covalently attaching doxorubicin (DOX) to the surface of ZIF-90 via Schiff base reaction of amino group in DOX and aldehyde group of imidazole-2-carboxaldehyde (ICA) ligand and encapsulating 5-fluorouracil (5-FU) into the pores of the framework. The results of drug loading measurements show that the loading amount of drugs was estimated as high as 36.35 and 11-13.5 wt % for 5-FU and DOX, respectively. Moreover, we demonstrated that the carrier had the potential of cancer-targeted delivery of drugs for the collapse of framework under the pH environment around cancer cells and subsequently releasing drugs. Drug release at pH 5.5, imitating the environment of tumor, can reach over 95%, and the release time is less 16 h, meaning a more effective and faster release of drugs around tumoral cells than that in a normal environment. This is the first report for cancer-targeted codelivery of two different chemical drugs based on nanoscale metal-organic frameworks (NMOFs).

ZIF-derived CoP as a cocatalyst for enhanced photocatalytic H2 production activity of g-C3N4

The graphitic carbon nitride (g-C3N4) photocatalyst has drawn widespread attention owing to its excellent photocatalytic hydrogen production activity. For the first time, an efficient g-C3N4-based non-precious-metal photocatalyst, CoP/g-C3N4, with ZIF-67-derived CoP nanoparticles as cocatalysts was prepared by a two-step calcination under different atmospheres. It demonstrates that CoP nanoparticles derived from ZIF-67 can extensively improve the photocatalytic activity of g-C3N4. When the amount of CoP in the photocatalyst was calculated to be 1.42 wt%, a high photocatalytic hydrogen production rate of 201.5 μmol g−1 h−1 was obtained, which was almost 23 times higher than that of bulk g-C3N4 and also surpassed that of bulk g-C3N4 with Pt as the cocatalyst. In addition, electrochemical experiments and photoluminescence spectra indicate that the CoP/g-C3N4 photocatalysts exhibit the advantage of a low recombination rate of photogenerated electrons and holes, resulting in a high rate of electron transport.

Rapid and Large-Scale Synthesis of IRMOF-3 by Electrochemistry Method with Enhanced Fluorescence Detection Performance for TNP

Rapid and large-scale synthesis of metal-organic frameworks (MOFs) materials is of great significance for their practical applications. For the first time, we have electrochemically synthesized IRMOF-3 at room temperature by applying a voltage to a zinc electrode immersed in electrolyte containing 2-aminoterephthalic acid (NH2-H2BDC). The reaction conditions, including the ratio of solvent (electrolyte), the applied voltage, and different reaction times, were investigated and optimized. The degree of crystallinity and nanomorphology of the synthesized IRMOF-3 can be controlled by changing the reaction conditions. More importantly, we demonstrated that the electrochemical synthesis strategy can rapidly obtain nanoscale IRMOF-3 with high crystallinity on a gram scale. In addition, in comparison with the product of solvothermal synthesis, the electrochemically synthesized nanoscale IRMOF-3 exhibits improved fluorescent detection ability to 2,4,6-trinitrophenol (TNP) with a detection limit of about 0.1 ppm.

Porous metal–organic gel assisted by L-tartaric acid ligand for efficient and controllable drug delivery

A novel Al-based metal–organic gel (Al-MOG), as a stable and controllable drug carrier, is assembled from bridging L-tartaric and Al3+ ions using a simple solvothermal method. The reaction temperature and the ratio of metal ions and ligands are vital for the formation of the gel. Transmission electron microscopy (TEM) and N2 adsorption measurements demonstrate the porous structure of Al-MOG, which exhibits Brunauer–Emmett–Teller (BET) surface area of 427.9 m2 g−1. The coordination between Al3+ and L-tartaric acid as well as non-covalent interactions could play a vital role in the formation of Al-MOG. Considering its large BET and excellent biocompatibility derived from low toxicity of the metal ions and the natural acid ligand, we further investigate the behaviors of Al-MOG for the controlled release of methyl salicylate (MS), an antimicrobial drug. The results of drug loading experiments show that the largest drug loading amount of MS reaches 31.8 wt%, whereas the release time of MS is over 600 min. In addition, the mouldability of Al-MOG further demonstrates its promising potential to act as a drug carrier.

Novel stable metal–organic framework photocatalyst for light-driven hydrogen production

A novel MOF formulated as [Dy2(abtc)(H2O)2(OH)2]·2H2O (H4abtc = 3,3′,5,5′-azobenzene tetracarboxylic acid) was successfully synthesized, in which a dye-like ligand was integrated as a photosensitizer into MOFs by the reaction with Dy3+ ions (dye-based Dy-MOF). The ultra-stable dye-based Dy-MOF possesses a HOMO–LUMO gap of 2.17 eV as determined by UV-vis spectrum with absorbed edge at 570 nm. The dye-based Dy-MOF shows high catalytic activity for the UV-vis light driven hydrogen production, attributed to the porous structure and light harvesting from the dye-like ligand. The band-edge positions of the crystals of the dye-based Dy-MOF were studied via cyclic voltammetry (CV) to further verify the principle of photocatalytic hydrogen production. Furthermore, the exceptional thermal and pH stability of the dye-based Dy-MOF makes it possible to use them as photocatalysts in water. On using Pt cocatalyst, the UV-vis light photocatalytic hydrogen evolution rate of the dye-based Dy-MOF reaches 21.53 μmol h−1 g−1. In addition, the as-prepared dye-based Dy-MOF materials also exhibited good stability and recycling performance.

Folic Acid Functionalized Zirconium‐Based Metal–Organic Frameworks as Drug Carriers for Active Tumor‐Targeted Drug Delivery

Nanoscale metal-organic frameworks (NMOFs) have proven to be a class of promising drug carriers as a result of their high porosity, crystalline nature with definite structure information, and potential for further functionality. However, MOF-based drug carriers with active tumor-targeting function have not been extensively researched until now. Here we show a strategy for constructing active tumor-targeted NMOF drug carriers by anchoring functional folic acid (FA) molecules onto the metal clusters of NMOFs. Two zirconium-based MOFs, MOF-808 and NH2 -UiO-66, were chosen as models to reduce to the nanoscale for application as drug carriers, and then the terminal carboxylates of FA molecules were coordinated to Zr6 clusters on the surfaces of the nanoparticles by substitution of the original formate or terminal -OH ligands. The successful modification with FA was confirmed by solid-state 13 C MAS NMR and UV/Vis spectroscopy and other characterization methods. Drug loading and controlled release behavior at different pH were determined by utilizing the anticancer drug 5-fluorouracil (5-FU) as the model drug. Confocal laser scanning microscopy measurements further demonstrated that 5-FU-loaded FA-NMOFs have excellent targeting ability through the efficient cellular uptake of FA-NMOFs. This work opens up a new avenue to the construction of active tumor-targeted NMOF-based drug carriers with potential for cancer therapies.

Luminescent Functionalised Supramolecular Coordination Polymers Based on an Aromatic Carboxylic Acid Ligand for Sensing Hg2+ Ions

Two luminescent functionalised supramolecular coordination polymers, namely, [Zn(TPDC-2CH3)(H2O)2]·H2O (1) and [Cd(TPDC-2CH3)(H2O)4]·H2O (2), were successfully synthesised by the reaction of 2′,5′-dimethyl-[1,1′:4′,1″-terphenyl]-4,4″-dicarboxylic acid (H2TPDC-2CH3) with Zn2+ and Cd2+ ions, respectively. X-Ray crystallographic analysis reveals that both compounds 1 and 2 exhibit fascinating 3D supramolecular networks, in which metal ions are linked by ligands to form a 1D chain which further extends to a 3D structure through the interaction of hydrogen bonding. The use of 1 and 2 as luminescent sensors for the optical detection of metal ions: Na+, K+, Hg2+, Ag+, Ca2+, Co2+, Ni2+, Mn2+, Cu2+, Zn2+, Cd2+, Pb2+, Mg2+, Al3+, Fe3+, Fe2+, In3+, Bi3+, and Cr3+ was carried out in aqueous solution, and the results indicated that compound 1 could effectively detect Hg2+ ions among various cations at room temperature, with a detection limit of 3.6u2009×u200910−15 M.