Covalent organic frameworks (COFs) show great potential for many advanced applications on account of their structural uniqueness. To address the synthetic challenges, facile chemical routes to engineer porosity, crystallinity and functionality of COFs are highly sought after. Herein we report a synthetic approach that employs the Cadogan reaction to introduce nitrogen-containing heterocycles as the linkage in the framework. Irreversible indazole and benzimidazolylidene (BIY) linkages are introduced into COFs for the first time via phosphine-induced reductive cyclization of the common imine linkages following either stepwise or one-pot reaction protocols. The successful linkage transformation introduces new functionalities, as demonstrated in the case of BIY-COF, which displays excellent 2 intrinsic proton conductivity without the need of impregnation with external proton transfer reagents. Such a general strategy will open the window to a broader class of functional porous crystalline materials.

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The anionic complex [Ir(2-phenylpyridine)2(benzene-1,2-dithiolate)](-) ([IrSS](-)) is a nucleophile and metalloligand that reacts with methyl iodide and AuPR3(+) (R = Ph or Et) to form S-methylated complexes (thiother-thiolate and dithiother complexes) and S-aurated complexes, respectively. The reactions are completely diastereselective, producing only the enantiomers ΛS and ΔR or ΛSS and ΔRR. The diastereoselectivity is stereoelectronically controlled by the orientation of the highest occupied molecular orbital (HOMO) of [IrSS](-) arising from filled dπ-pπ antibonding interactions, and the chirality of the iridium ion. Methylation or auration removes the high-energy lone pair of the thiolate S atom, leading to low-lying HOMOs composed mainly of the Ir d-orbital and the 2-phenylpyridine π (ppyπ) orbital. The methylated and aurated complexes can be oxidized by H2O2 or peracid to give sulfinate-thiother, disulfoxide, and sulfinate-sulfoxide complexes, and the oxygenation further stabilizes the HOMO. All the complexes are luminescent, and their electronic spectra are interpreted with the aid of time-dependent density functional theory calculations. The thiother-thiolate complex exhibits ligand(S)-to-ligand(π* of ppy)-charge-transfer/metal-to-ligand-charge-transfer absorption (LLCT/MLCT) and a relatively low-energy (3)LLCT/MLCT emission, while the other complexes display (3)ππ*/MLCT emissions.

In the past decades, many attempts have been made to mimic the energy transfer (EnT) in photosynthesis, a key process occurring in nature that is of fundamental significance in solar fuels and sustainable energy. Metal–organic frameworks (MOFs), an emerging class of porous crystalline materials self-assembled from organic linkers and metal or metal cluster nodes, offer an ideal platform for the exploration of directional EnT phenomena. However, placing energy donor and acceptor moieties within the same framework with an atomistic precision appears to be a major synthesis challenge. In this work, we report the design and synthesis of a highly porous and photoactive N,N′-bicarbazole- and porphyrin-based mixed-ligand MOF, namely, NPF-500-H2TCPP (NPF = Nebraska porous framework; H2TCPP = meso-tetrakis­(4-carboxyphenyl)­porphyrin), where the secondary ligand H2TCPP is incorporated precisely through the open metal sites of the equatorial plane of the octahedron cage resulting from the underlying (4,8) connected network of NPF-500. The efficient EnT process from N,N′-bicarbazole to porphyrin in NPF-500-H2TCPP was captured by time-resolved spectroscopy and exemplified by photocatalytic oxidation of thioanisole. These results demonstrate not only the capability of NPF-500 as the scaffold to precisely arrange the donor–acceptor assembly for the EnT process but also the potential to directly utilize the EnT process for photocatalytic applications.

Separation of xylene isomers is one of the most important but most challenging and energy‐intensive separation processes in the petrochemical industry. Here, we report an adaptive hydrogen‐bonded organic framework (HOF‐29) constructed from a porphyrin based organic building block 4,4′,4′′,4′′′‐(porphyrin‐5,10,15,20‐tetrayl) tetrabenzonitrile (PTTBN), exhibiting the exclusive molecular recognition of p‐xylene (pX) over its isomers of o‐xylene (oX) and m‐xylene (mX), as clearly demonstrated in the single crystal structure transformation and 1H NMR studies. Single crystal structure studies show that single‐crystal‐to‐single‐crystal transformation from the as‐synthesized HOF‐29 to the pX exclusively included HOF‐29⊃pX is triggered by the encapsulation of pX molecules, accompanied by sliding of the 2D layers and local distortion of the ligand, which provides multiple C−H⋅⋅⋅π interactions.