Robust Biological Hydrogen‐Bonded Organic Framework with Post‐Functionalized Rhenium(I) Sites for Efficient Heterogeneous Visible‐Light‐Driven CO 2 Reduction

Stimuli-Responsive Porous Molecular Crystal with Reversible Modulation of Porosity

Responsive materials have received much attention due to modulated properties under stimuli such as light, heat, and electricity. A photoresponsive porous molecular crystal (1) has been assembled from a racemic dithienylethene-cage (L) by multiple C-F···H-C hydrogen bonds and van der Waals forces according to crystallographic investigation. Electronic absorption spectroscopy reveals reversible photochromic behaviors of the solution and film forms of enantiomeric L upon UV and visible light irradiation due to photoisomerization of dithienylethene units. X-ray photoelectron spectroscopy (XPS), in combination with NMR, discloses the quantitative photoisomerization of photochromic dithienylethene moieties. Moreover, the porosity of 1 is modulated by UV irradiation based on gas sorption data. Interestingly, heating the irradiated sample of 1 in 1,4-dioxane leads to recovered porosity due to the recovered cage molecular structure and maintained periodic frameworks.

Chemical conversion of metal–organic frameworks into hemi-covalent organic frameworks

A hemi-covalent organic framework, P-Ni3(TAA)3, with the different conversion efficiency (P) of 34–72% for bis(diimine) nickel units has been obtained. The 40%-Ni3(TAA)3 exhibits the improved chemical stability and significantly catalytic property.

Facile Construction of Covalent Organic Framework Nanozyme for Colorimetric Detection of Uranium

2D covalent organic frameworks (2D COFs) have been recognized as a novel class of photoactive materials owing to their extended π-electron conjugation and high chemical stabilities. Herein, a new covalent organic framework (Tph-BDP) is facilely synthesized by using a porphyrin derivative and an organic dye BODIPY derivative (5,5-difluoro-2,8-diformyl-1,3,7,9-tetramethyl-10-phenyl-5H-dipyrrolo[1,2-c:2',1'-f][1,3,2]diazabori-nin-4-ium-5-uide) as monomers for the first time, and their unique photosensitive properties endow them excellent simulated oxidase activity under 635 nm laser irradiation that can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). Further findings demonstrate that the presence of uranium (UO₂²⁺ ) can coordinate with imines of the oxidation products of TMB, thus modulating the charge transfer process of the colored products accompanied with intensive aggregation and remarkable color fading. This research provides a preparation strategy for COFs with excellent photocatalytic properties and nanozyme activity, and broadens the applications of the simple colorimetric methods for sensitive and selective radionuclide detection.

A Solid Transformation into Carboxyl Dimers Based on a Robust Hydrogen-Bonded Organic Framework for Propyne/Propylene Separation

Self-assembly of N,N,N',N'-tetrakis(4-carboxyphenyl)-1,4-phenylenediamine with the help of different solvents provides isostructural hydrogen-bonded organic frameworks (HOF-30). Single-crystal X-ray diffraction (SCXRD) analysis reveals HOF-30 possesses 3D ten-fold interpenetrated dia nets connected by two kinds of hydrogen bonds, namely solvent-bridged carboxyl dimers and carboxyl⋅⋅⋅carboxyl dimers. Degassing treatment for HOF-30 yields HOF-30a with 3D ten-fold interpenetrated dia nets but linked with sole carboxyl⋅⋅⋅carboxyl dimers. Reversible hydrogen-bond-to-hydrogen-bond transformation between solvent-bridged carboxyl dimers in HOF-30 and carboxyl⋅⋅⋅carboxyl dimers in HOF-30a has been unveiled by single-crystal and powder X-ray diffraction. In addition, HOF-30a enables the selective adsorption of propyne over propylene according to single-component sorption and breakthrough experiments. The preferred propyne location in HOF has also been identified by SCXRD test.