Developing cost-effective and highly efficient photocathodes toward polysulfide redox reduction is highly desirable for advanced quantum dot (QD) photovoltaics. Herein, we demonstrate nitrogen doped carbon (N-C) shell-supported iron single atom catalysts (Fe-SACs) capable of catalyzing polysulfide reduction in QD photovoltaics for the first time. Specifically, Fe-SACs with FeN4 active sites feature a power conversion efficiency of 13.7% for ZnCuInSe-QD photovoltaics (AM1.5G, 100 mW/cm2), which is the highest value for ZnCuInSe QD-based photovoltaics, outperforming those of Cu-SACs and N-C catalysts. Compared with N-C, Fe-SACs exhibit suitable energy level matching with polysulfide redox couples, revealed by the Kelvin probe force microscope, which accelerates the charge transferring at the interfaces of catalyst/polysulfide redox couple. Density functional theory calculations demonstrate that the outstanding catalytic activity of Fe-SACs originates from the preferable adsorption of S4 2– on the FeN4 active sites and the high activation degree of the S–S bonds in S4 2– initiated by the FeN4 active sites.

Rational construction of strong electron-transfer materials remains a challenging task. Herein, we show a fundamental design rule for construction of strong electron-transfer materials through covalently integrating electron-donoring Cu(I) clusters and electron-withdrawing triazine monomers together. As expected, the two resultant Cu(I)-triazine frameworks (Cu-CTFs) showed strong electron transfer up to 0.46|e| from each Cu(I) metal center to each adjacent triazine fragment, and the size of triazine monomer was found to give tunable ability for electron transfer. Accompanied to the stronger electron transfer is the observation of more narrow bang gap and good spatial separation of HOMO and LUMO level. This finally leads to good spatial separation of photo-generated electron-hole pairs and function units for boosting photocatalytic reduction of uranium under ambience and no sacrificial agent with ultrahigh removal efficiency up to 99.7%, and good charge separation of [I+][I5-] for boosting I2 immobilization under extremely rigorous conditions with benchmark I2 uptake of 0.32 g/g. The results not only have opened up a structural design principle to access electron-transfer materials, but also solved several challenging tasks in the field of radionuclide capture and CTFs.

nuclear energy. [1][2] Generally, selective adsorption of UO 2 2+ was viewed to be one of the best effective methods to achieve UO 2 2+ separation, due to the complicated environment in both spent fuel or seawater that contains a large number of other metal ions except for UO 2 2+ ion. [3] Accordingly, there have paid a long-term and big effort to enhance the selectivity of uranyl over other metal ions (S U/M ) selectivity by designing various adsorption sites via tuning their affinity towards UO 2 2+ such as amidoxime, phosphonic, sulfonic, and carboxylate units. [4][5][6][7][8][9][10][11][12][13][14][15] Although there have obtained a great achievement in this route, however, this two-step route still suffers two inherently scientific and industrial problems. One is coadsorption, viz. while it captures UO 2 2+ ions, it also adsorbs other metal ions. Inevitably, this not only reduces the S U/M selectivity, but also requires further purification. The other is the regeneration of UO 2 2+ from adsorbents by means of desorption, where we commonly use of acid or base as eluent; however, this could not only damage the adsorbent, leading to sharp decrease in adsorption performance and subsequent reusability, but also bring secondary pollution and high cost. [13d] Alternative to this two-step S U/M method, we proposed a direct separation approach by means of coordination sieve effect (CSE) with reverse selectivity (S M/U ), which could theoretically avoid further purification and the use of eluent, representing a more simple, low-cost, and facile counterpart. Although direct separation through MSE has been shown promising potential in gas separation such as C 2 H 2 and C 2 H 4 purification, [16] however, to the best of our knowledge, there is still unknown about direct separation of metal ions through CSE.CSE with S M/U means highly capturing other metal ions, but excluding UO 2 2+ ion. This could be theoretically accessed if designing a unique coordination surrounding to fix other metal ions, except for UO 2 2+ ion. As we know, UO 2 2+ ion owns the unique planar coordination feature, [17] due to the presence of two uranyl oxygen atoms, where the location of adsorption sites is co-plane; by contrast, other metal ions such as monovalent Cs + , divalent Sr 2+ , trivalent Eu 3+ , and tetravalent Th 4+ ions (usually existed in spent fuel or seawater) generally take the spherical coordination character, [18] where the adsorption sites are arranged in a surrounding way. In this regard, Molecule sieve effect (MSE) can enable direct separation of target, thus overcoming two major scientific and industrial separation problems in traditional separation, coadsorption, and desorption. Inspired by this, herein, the concept of coordination sieve effect (CSE) for direct separation of UO 2 2+, different from the previously established two-step separation method, adsorption plus desorption is reported. The used adsorbent, polyhedron-based hydrogenbond framework (P-HOF-1), made from a metal-organic framework (MOF) precursor through a...

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