Acid-functionalized Metal-organic Framework Research Articles

Stimuli-responsive nucleic acid-functionalized metal-organic framework nanoparticles using pH- and metal-ion-dependent DNAzymes as locks.

A versatile approach to modify metal-organic framework nanoparticles (NMOFs) with nucleic acid tethers, using the "click chemistry" method is introduced. The nucleic acid-functionalized NMOFs are used to prepare stimuli-responsive carriers of loads (fluorescence probes or anti-cancer drugs). Two different stimuli-responsive nucleic acid-based NMOFs are presented. One system involves the preparation of pH-responsive NMOFs. The NMOFs are loaded with fluorophores or doxorubicin anti-cancer drug and locked in the NMOFs by pH-responsive DNA duplex capping units. At pH = 5.0 the capping units are unlocked, leading to the release of the loads. The AS1411 aptamer is conjugated to the locking units as the targeting unit for the nucleolin biomarker present in cancer cells. The pH-responsive doxorubicin-loaded NMOFs and, in particular, the AS1411 aptamer-modified pH-responsive NMOFs reveal selective, targeted, cytotoxicity toward MDA-MB-231 breast cancer cells. A second system involves the synthesis of NMOFs that are loaded with fluorophores or doxorubicin and capped with metal-ion-dependent DNAzyme/substrate complexes as locking units (metal ion = Mg2+ or Pb2+ ions). In the presence of the respective metal ions, the nucleic acid locking units are cleaved off, resulting in the release of the loads. Also, "smart" Mg2+-ion-dependent DNAzyme capped doxorubicin-loaded NMOFs are synthesized via the integration of the ATP aptamer sequence in the loop domain of the Mg2+-dependent DNAzyme. The unlocking of these NMOFs proceeds effectively only in the presence of ATP and Mg2+ ions, acting as cooperative triggers. As ATP is over-expressed in cancer cells, the "smart" carrier provides sense-and-treat functions. The "smart" ATP/Mg2+-triggered doxorubicin-loaded NMOFs reveal selective cytotoxicity toward MDA-MB-231 cancer cells. Beyond the use of the metal-ion-dependent DNAzymes as ion-responsive locks of drug-loaded NMOF carriers, the DNAzyme-capped fluorophore-loaded NMOFs are successfully applied as functional units for multiplexed ion-sensing and for the design of logic-gate systems.

Stimuli-Responsive DNA-Functionalized Metal-Organic Frameworks (MOFs).

The synthesis of nucleic acid-functionalized metal-organic frameworks (MOFs) is described. The metal-organic frameworks are loaded with a dye being locked in the structures by means of stimuli-responsive nucleic acid caps. The pH and K+ -ion-triggered release, and switchable release, are demonstrated.

Computational exploration of H2S/CH4 mixture separation using acid-functionalized UiO-66(Zr) membrane and composites

A computational study was firstly performed in this work to examine the applicability of an acid-functionalized metal-organic framework (MOF), UiO-66(Zr)-(COOH)2, in membrane-based H2S/CH4 separation. The results show that this MOF could be potentially interesting when being used as the pure membrane material for the separation of the mixture with low H2S concentration. Further, the performance of 10 different mixed matrix membranes (MMMs) on the basis of the MOF was predicted by combing the molecular simulation data and the Maxwell permeation model. The results indicate that using this MOF as filler particles in MMMs can significantly enhance the permeation performance of pure polymers. The findings obtained in this work may be helpful in facilitating the application of this promising MOF for practical desulfurization process of fuel gas.

Conversion of fructose into 5-hydroxymethylfurfural catalyzed by recyclable sulfonic acid-functionalized metal–organic frameworks

Sulfonic acid-functionalized metal–organic frameworks are efficiently used as recyclable solid acid catalysts for the fructose-to-HMF transformation.

Amino acid functionalized metal–organic frameworks by a soft coupling–deprotection sequence

Covalent post-synthetic modification of a MOF, (In) MIL-68-NH(2), is carried out in a novel fashion to immobilize amino acids within the structure. Solid-phase peptide coupling methodology opens new perspectives for anchoring chiral bio- and catalytically active species. This could facilitate the immobilization of highly active and/or coordinating moieties inside MOF cavities.