A systematic theoretical investigation on a series of dimeric complexes formed between some halocarbon molecules and electron donors has been carried out by employing both ab initio and density functional methods. Full geometry optimizations are performed at the Moller-Plesset second-order perturbation (MP2) level of theory with the Dunning's correlation-consistent basis set, aug-cc-pVDZ. Binding energies are extrapolated to the complete basis set (CBS) limit by means of two most commonly used extrapolation methods and the aug-cc-pVXZ (X = D, T, Q) basis sets series. The coupled cluster with single, double, and noniterative triple excitations [CCSD(T)] correction term, determined as a difference between CCSD(T) and MP2 binding energies, is estimated with the aug-cc-pVDZ basis set. In general, the inclusion of higher-order electron correlation effects leads to a repulsive correction with respect to those predicted at the MP2 level. The calculations described herein have shown that the CCSD(T) CBS limits yield binding energies with a range of -0.89 to -4.38 kcal/mol for the halogen-bonded complexes under study. The performance of several density functional theory (DFT) methods has been evaluated comparing the results with those obtained from MP2 and CCSD(T). It is shown that PBEKCIS, B97-1, and MPWLYP functionals provide accuracies close to the computationally very expensive ab initio methods.

A multifunctional metal-organic framework, NBU-3, has been explored as a 2D three-connected network based on a naphthalenediimide-based ligand. The NBU-3 crystals display photochromic properties, and NBU-3 thin films on FTO substrates exhibit electrochromic properties. NBU-3 is the first example of MOF materials containing both photochromic and electrochromic properties, which can be desirable for thin film devices.

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Metal-organic frameworks (MOFs) are considered as suitable materials for various applications in the area of photocatalysis. On the other hand, 2D BiOBr materials are efficient for the photodegradation of organic dyes under visible light illumination. In this work, BiOBr/NH-MIL-125(Ti) composite photocatalysts with different NH-MIL-125(Ti) content were prepared by incorporating NH-MIL-125(Ti) with BiOBr using a co-precipitation method. A series of characterizations confirmed the strong synergistic effect between BiOBr and NH-MIL-125(Ti). In rhodamine B (RhB) degradation experiments, the composite photocatalyst with a mass percent of 7 wt% NH-MIL-125(Ti) exhibited an improved photocatalytic activity compared to pristine BiOBr and NH-MIL-125(Ti). Furthermore, the enhanced photocatalytic performance under visible light illumination could be attributed to the Ti-Ti intervalence electron transfer and synergistic effect between NH-MIL-125(Ti) and BiOBr, and also resulted in a separation efficiency of photo-generated electron-hole pairs during the photocatalytic reaction. This study can open up numerous opportunities for the development of various MOF-based visible light photocatalysts when combined with 2D bismuth oxyhalide materials for applications in environmental cleaning.

The development of photocatalysts based on covalent organic frameworks (COFs) is intriguing research due to their structural flexibility and tremendous catalytic sites. Herein we demonstrate a facile strategy to prepare composite materials of combined COFs and inorganic semiconductors with enhanced photocatalytic performances. A new composite photocatalyst (BiOBr/CTF-3D) integrated three-dimensional (3D) covalent triazine framework (CTF-3D) with two-dimensional BiOBr nanoflake was prepared via a simple coprecipitation method. The structural characterizations demonstrated that the amorphous CTF-3D was well modified on the surfaces of BiOBr. The photocatalytic activity of the BiOBr/CTF-3D composite was evaluated by the degradation of colorless antibiotic agents, tetracycline hydrochloride (TC) and ciprofloxacin (CIP), under visible light irradiation. When the mass percent of CTF-3D was 2%, the BiOBr/CTF-3D composite displayed the highest photocatalytic activity. The enhancement of photocatalytic performance was mainly derived from the enlarged optical adsorption range, the efficiently separated photogenerated electron−hole pairs, and the accelerated adsorption and transfer of antibiotic molecules, in the synergistically facilitating photocatalytic process. In addition, a possible photocatalytic mechanism for degrading TC by BiOBr/ CTF-3D-2% was tentatively proposed. This work opens up a new strategy to improve the photocatalytic activity of traditional inorganic photocatalysts by modification with COFs materials for solving the pollution of living ecosystems.