Monodispersed covalent organic framework nanocrystals in aqueous solution for DNA inclusion

Covalent organic framework(COF)nanocrystals are useful in biological applications;however,their hydrophobic nature makes them aggregate into clusters in aqueous media.In this work,we show that by modifying the crystal surface with hydrophilic functional groups,these nanocrystals can maintain in the monodispersed form in aqueous solution.Specifically,three COFs,TPB-DMTP COF,TAPB-PDA COF and TAPB-BPDA COF were synthesized using organic Lewis acid as the catalyst,to generate nanoparticles with the size ranging from 180 nm to 1μm.2-Aminoethanesulfonic acid(AESA)was applied to react with the terminal aldehyde functional groups exposed at the surface of COF nanocrystals.The resulting negatively charged surface keeps these nanocrystals apart from each other in aqueous solution for at least 48 h.The mesopore of these COF nanocrystals allows the entering of single-strand DNA molecules and the release in the presence of complementary DNA.

Covalent organic frameworks for optical applications

Linking molecules into extended crystalline networks to construct covalent organic frameworks(COFs)added in variety to the readily thriving research on moleculebased solid-state materials,featured by classic polymers and molecular crystals.Compared to the development of COFs for gas separation,energy storage,and conversion,where the porosity feature of COFs is utilized,the optical applications,such as fluorescence,white light emission,and photodynamic therapy,involving the molecular and crystalline feature of COFs,are much less explored.In this review,we focused on the optical properties of COFs,and how do these macroscopic properties correlate with the microscopic structure of COFs.Other than the influence from organic functional groups in previous reviews on COFs,here,three critical structure factors,the connection,orientation,and alignment of the molecular building blocks,are outlined and associated with the optical properties of COFs.We also analyze the properties of COFs from both energy and dynamic aspects in an attempt to provide further insight into the possible underlying mechanism.At the end of this review,we also discuss the remaining challenges and future directions for the design of COFs for optical applications,and unveil the potential of COFs toward this direction.

Covalent organic frameworks catalyzed by organic Lewis acid

We report the synthesis of covalent organic framework(COF)crystals with organic Lewis acid instead of the conventional use of Br?nsted acid or inorganic Lewis acid.Specifically,tris(pentafluorophenyl)borane was applied for the growth of seven imine COFs:TAPB-PDA-,TAPB-2,5-DMTA-,TAPB-2,3-DMTA-,TAPT-PDA-,TAPT-2,5-DMTA-,TAPT-2,3-DMTA-COF with hcb topology and varied in functional groups,as well as a new one,COF-820,with sql topology.All these COFs were obtained at room temperature.Their high crystallinity and porosity demonstrate the versatility of the organic Lewis acid as a catalyst.Bulky organic Lewis acid was found critical for the production of COF-820,while its absence resulted in the formation of a different COF,4PE-1P-COF,with kgm topology using the same building blocks.Such steric effect,typical for organic catalysts,provides a new way to regulate the topology of COFs and their future design.