Covalent organic frameworks (COFs)
with improved stability and
extended π-conjugation structure are highly desirable. Here,
two imine-linked COFs were converted into ultrastable and π-conjugated
fused-aromatic thieno[3,2-c]pyridine-linked COFs
(B-COF-2 and T-COF-2). The successful conversion
was confirmed by infrared and solid-state 13C NMR spectroscopies.
Furthermore, the structures of thieno[3,2-c]pyridine-linked
COFs were evaluated by TEM and PXRD. It is noted that a slight difference
in the structure leads to totally different photoactivity. The fully
π-conjugated T-COF-2 containing triazine as the
core exhibited an excellent photocatalytic NADH regeneration yield
of 74% in 10 min.
Developing a facile strategy for the construction of vinylene-linked fully π-conjugated covalent organic frameworks (COFs) remains a huge challenge. Here, a versatile condition of Knoevenagel polycondensation for constructing vinylene-linked 2D COFs was explored. Three new examples of vinylene-linked 2D COFs (BTH-1, 2, 3) containing benzobisthiazoles units as functional groups were successfully prepared under this versatile and mild condition. The electron-deficient benzobisthiazole units and cyano-vinylene linkages were both integrated into the π conjugated COFs skeleton and acted as acceptor moieties. Interestingly, we found the construction of a highly ordered and conjugated D-A system is favorable for photocatalytic activity. BTH-3 with benzotrithiophene as the donor with a strong D-A effect exhibited an attractive photocatalytic HER of 15.1 mmol h−1g−1 under visible light irradiation.
Singlet fission (SF), in which one singlet exciton (S ) splits into two triplets (T ) on adjacent molecules through a correlated triplet-pair (TT) state, requires precise but difficult tuning of exciton energetics and intermolecular electronic couplings in the solid state. Antiaromatic 4nπ dibenzopentalenes (DPs) are demonstrated as a new class of single-chromophore-based intramolecular SF materials that exhibit an optically allowed S state with E(S )>2×E(T ) and an optically forbidden S state. Ultrafast population transfer from a high-lying S state to a (TT) state was observed in monomeric solution of styryl-substituted DP (SDP) on a sub-picosecond timescale. There is evidence of exciton diffusion (ED) of the (TT) state to yield two individual long-lived triplets in SDP thin film. The overall triplet yield via intramolecular SF and subsequent triplet-pair diffusion can be as high as 142±10 % in thin film.
Since the discovery of the aggregation-induced emission (AIE) phenomenon in 2001, research on AIE molecules has drawn much attention, and this area has been expanding tremendously. This brief review will focus on recent advances in the science and application of AIE molecules, including new mechanistic understanding, new AIE molecules for sensing and imaging, stimuli-responsive AIE molecules and applications of AIE molecules for OLEDs. Moreover, this review will give a perspective on the possible opportunities and challenges that exist in the future for this area.
The efficient conversion of CO 2 to chemical fuels driven by solar energy is still a challenging research area in photosynthesis, in which the conversion efficiency greatly relies on photocatalytic coenzyme NADH regeneration. Herein, a photocatalyst/biocatalyst synergetic system based on a conjugated microporous polymer (CMP) was prepared for sustainable and highly selective photocatalytic reduction of CO 2 to methanol. Two thiazolo [5,4-d]thiazole-linked CMPs (TZTZ-TA and TZTZ-TP) were designed and synthesized as photocatalysts. Slight skeleton modification led to a great difference in their photocatalytic performance. Triazine-based TZTZ-TA exhibited an unprecedentedly high NADH regeneration efficiency of 82.0% yield within 5 min. Furthermore, the in situ photocatalytic NADH regeneration system could integrate with three consecutive enzymes for efficient conversion of CO 2 into methanol. This CMP−enzyme hybrid system provides a new avenue for accomplishing the liquid sunshine from CO 2 .
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