Amine-linked covalent organic frameworks (COFs) were synthesized by the reduction of parent imine-linked COFs by crystal-to-crystal transformation. The excellent chemical stability of these COFs in combination with the presence of a large amount of amine functional groups led to a robust and molecularly defined interface at the silver metal surface as an electrode for the electrochemical reduction of CO 2. The concerted operation of COF and the metal surface resulted in high conversion efficiency and excellent selectivity against the reduction of water.

A thin-film solar cell based on Cu2ZnSn(S,Se)4 (CZTSSe) alloy was recently found to exhibit a light to electricity conversion efficiency of 10%, making it competitive with the more mature Cu(In,Ga)Se2 based technologies. We study the compositional dependence of the physical properties of CZTSSe alloys through first-principles calculations and find that, these mixed-anion alloys are highly miscible with low enthalpies of formation, and the cations maintain the same ordering preferences as the parent compounds Cu2ZnSnS4 and Cu2ZnSnSe4. The band gap of the CZTSSe alloy decreases with the Se content almost linearly, and the band alignment between Cu2ZnSnS4 and Cu2ZnSnSe4 is of type-I, which allows for more facile n-type and p-type doping for alloys with high Se content. Based on these results we analyze the influence of composition on the efficiency of CZTSSe solar cells and explain the high efficiency of the cells with high Se content.

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We report the control of guest release profiles by dialing-in desirable interactions between guest molecules and pores in metal-organic frameworks (MOFs). The interactions can be derived by the rate constants that were quantitatively correlated with the type of functional group and its proportion in the porous structure; thus the release of guest molecules can be predicted and programmed. Specifically, three probe molecules (ibuprofen, rhodamine B, and doxorubicin) were studied in a series of robust and mesoporous MOFs with multiple functional groups [MIL-101(Fe)-(NH), MIL-101(Fe)-(CH), and MIL-101(Fe)-(CH)(NH)]. The release rate can be adjusted by 32-fold [rhodamine from MIL-101(Fe)-(NH)], and the time of release peak can be shifted by up to 12 days over a 40-day release period [doxorubicin from MIL-101(Fe)-(CH)(NH)], which was not obtained in the physical mixture of the single component MOF counterparts nor in other porous materials. The corelease of two pro-drug molecules (ibuprofen and doxorubicin) was also achieved.

Angle resolved photoemission spectroscopy study on TlBiTe2 and TlBiSe2 from a thallium-based ternary chalcogenides family revealed a single surface Dirac cone at the center of the Brillouin zone for both compounds. For TlBiSe2, the large bulk gap (∼200 meV) makes it a topological insulator with better mechanical properties than the previous binary 3D topological insualtor family. For TlBiTe2, the observed negative bulk gap indicates it as a semimetal, instead of a narrow-gap semiconductor as conventionally believed; this semimetality naturally explains its mysteriously small thermoelectric figure of merit comparing to other compounds in the family. Finally, the unique band structures of TlBiTe2 also suggest it as a candidate for topological superconductors.