Postsynthetic Modification of Metal-Organic Frameworks through Click Chemistry

The postsynthetic modification （PSM） of metal-organic frameworks （MOFs） has emerged as a powerful tool to chemically tailor the interior of MOFs. In this review, we summarize the research progress of PSM of MOFs through click chemistry, including azide-alkyne click reaction and thiol-ene reaction.

Recent advance in porous coordination polymers from the viewpoint of crystalline-state transformation

Recently,research of crystalline-state transformation involving the removal/inclusion of guest molecules in porous coordination polymers(PCPs) was underway.Crystalline-state transformation,especially,single-crystal to single-crystal(SC-SC) transformation as new method for the direct observation of host-guest chemistry,can reveal the intrinsic relevance and interaction between the framework and guest molecules.This review describes our work concerning PCPs and recent investigations of others,within the last four years,from the viewpoint of crystalline-state transformations of PCPs on guest removal or inclusion processes.Ligand substitution reaction and postsynthetic modification of PCPs in SC-SC fashion which were distinguished from conventional crystalline-state transformation triggered by guest removal or exchange were highlighted in this review.The research status of crystalline-state transformation in China was briefly introduced as well.Series of structure analysis techniques including single-crystal X-ray diffraction,powder X-ray diffraction,neutron diffraction,inelastic neutron scattering as well as the application of synchrotron radiation light source will inevitably promote the advance of study of crystalline-state transformation.And as a hotspot,deep investigations of crystalline-state transformation also help us to overcome the challenge of achieving multifunction and the correlation among them,such as sorption,magnetism,optical or electrical properties simultaneously in PCPs and contribute to design stimulate-oriented porous intelligent materials in the future.

Selenium-functionalized metal-organic frameworks as enzyme mimics

The development of artificial enzyme mimics has been rapidly growing in recent years, and it is attracting increasing attention owing to their remarkable advantages over natural enzymes. Herein, we developed a general and facile method to fabricate efficient glutathione peroxidase （GPx） mimics by grafting selenium-containing molecules （phenylselenylbromide, PhSeBr） to a Zr（W）-based UiO-66-NH2 framework. In the presence of glutathione （GSH） serving as substrate, the fabricated UiO-66-Se catalysts can catalyze the reduction of hydroperoxides. The as-prepared UiO-66-Se systems show good catalytic activity over three cycles. These high-efficiency GPx mimic metal-organic frameworks （MOFs） are endowed with excellent thermal and structural stability, providing a promising avenue for the development of artificial enzyme mimics.

Highly catalytic metal–organic framework coating enabled by liquid superwetting and confinement

In this work,we report that high catalytic performance of metal–organic frameworks(MOFs)can be obtained through a synergistic effect of postsynthetic modification of MOF nanoparticles and liquid superwetting and confinement in the MOF coating.Specifically,2-ureido-4[1H]pyrimidinone(UPy)functionalized polysiloxanes were covalently appended onto the UiO-66 nanoparticles via a postsynthetic approach,which were further anchored onto different porous films through multivalent hydrogen bonding of the UPy motifs.The hydrophobic MOF coating can preserve the porosity of the solid substrates,enable rapid liquid superwetting and confinement within the porous substrates.Using the Knoevenagel condensation as a modeled system,robust and highly catalytic performances of the MOF coating were observed on a range of aldehyde substrates.Gram-scale production of chromene,a pharmaceutical which is typically synthesized via expensive catalysis,was successfully demonstrated on the MOF coating with high yielding rates,demonstrating the great potential of the MOF coating in pharmaceutical synthesis.

Tuning the release rate of volatile molecules by pore surface engineering in metal-organic frameworks

Encapsulation and controlled release of volatile molecules such as fragrances in a designed manner is important but challenging for the flavor and fragrance industry.Here,we report the tuning release of volatile molecules by postsynthetic modification of an amine-terminated metal-organic framework(MOF)MIL-101-NH_(2).By amidation,we obtained three MIL-101 MOFs,the trimethylacetamideterminated TC-MIL-101,the benzamide-terminated BC-MIL-101,and the oxalic acid monoamideterminated OC-MIL-101.All the MOFs can efficiently encapsulate volatile molecules.Moreover,we demonstrate that the release profile of volatiles can be widely tuned to sustain the release in several days to months and even over a year using different modified MIL-101 MOFs.We show that the release profiles are correlated with the binding energies between the guest volatiles and pores in MOFs.The pore diffusion and the synergistic transport are the rate-limiting step of the guest molecules from the modified MOFs.