On the basis of high stability of phosphorus–oxygen linkage, we constructed two microporous covalent phosphazene-based frameworks (CPFs), for the first time, by choosing hexachlorocyclotriphosphazene as a core unit and polyhydroxy aromatic compounds (hydroquinone or phloroglucinol) as monomers, named CPF-D and CPF-T, respectively. Characterization studies by using Fourier transform infrared, nuclear magnetic resonance, thermal gravimetric analysis, 60Co γ-ray irradiation, and so forth, demonstrated that both of the CPF materials have excellent acid and radiation stability and relatively higher thermal stability. The results of batch adsorption experiments show that CPF-T is significantly more capable of sorbing uranium than CPF-D. In a pure uranium system with higher acidity (pH 1), the uranium sorption amount of CPF-T can reach up to 140 mg g–1. Distinctively, in mixed-metal solution with 12 coexisting cations, CPF-T shows relatively stable and excellent uranium adsorption capability over a wide range of acidity (pH 4 to 3 M HNO3), and the difference in uranium sorption amounts is less than 30% with the maximum of 0.26 mmol g–1 at pH 4 and the minimum of 0.20 mmol g–1 at 3 M HNO3, which is far superior to that of the conventional solid-phase extractant (SPE) materials previously reported. The research results suggested that the sorption model based on the speculated mechanism of size-matching plus hydrogen bond network has played a dominant role in the process of uranium adsorption. The proposed strategy for the one-pot fabrication of an acid-resistant microporous framework materials by bridging the aromatic monomers via P–O bonds provides an alternative approach for the design and synthesis of new SPE materials with size-matching function desired for effective separation of uranium or other valuable metals from highly acidic environments.
PbS colloidal quantum dots (CQDs) have been widely applied in infrared (IR) solar cells, as they can broaden the photon conversion region beyond 1100 nm, which can help promote an extra 6% of power conversion efficiency (PCE) as bottom subcells for silicon solar cell. Although halide liquid exchange is the dominant passivation strategy for CQDs, it is difficult to passivate all the surface defects , especially for IR CQD, which leaves the main limitation for improving PCE. Here, a facile in-situ solution-processed patch-passivation strategy was first proposed for developing efficient PbS CQD IR solar cells. A typical Lewis base triphenylphosphine oxide (TPPO) was added to I − /Br − capped PbS CQDs, aiming at passivation with uncoordinated Pb 2+ as a “patch-ligand”. As a result, the phosphorus oxygen bond coordination could help suppress the non-radiative recombination in CQD films. The TPPO-passivated devices delivered an IR PCE as high as 1.36% under silicon-filtered AM 1.5G, along with a promising open-circuit voltage ( V OC ) of 0.44 V, both of which are the highest among other single-junction solar cells with a band gap of ∼0.95 eV. The significant VOC and fill factor (FF) enhancement can be attributed to the decrease in defect density and faster charge transport in TPPO-passivated devices.
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