The synthesis of fully conjugated sp 2 -carbon covalent organic frameworks (COF) is extremely challenging given the difficulty of the formation of very stable carbon-carbon double bonds (-C=C-). Here,w er eport the successful preparation of a2 DC OF (TP-COF) based on triazine as central planar units bridged by sp 2 -carbon linkers through the -C = Ccondensation reaction. High-resolution-transmission electron microscopy( HRTEM) clearly confirmed the tessellated hexagonal pore structure with ap ore center-to-center distance of 2nm. Powder X-rayd iffraction (PXRD) together with structural simulations revealed an AA stacking mode of the obtained layered structure.T P-COF turned out to be an excellent semiconductor material with aL UMO energy of À3.23 eV and aband gap of 2.36 eV.Excitingly,this novel sp 2carbon conjugated TP-COF exhibited unprecedented coenzyme regeneration efficiency and can significantly boost the coenzyme-assisted synthesis of l-glutamate to arecord-breaking 97 %yield within 12 minutes.Long-range p-conjugated two-dimensional (2D) materials have received considerable attention in recent years and present ar ange of unique advantages over traditional polymeric materials. [1][2][3][4][5][6][7] In particular, the topological arrangement of aromatic units propagating in two spatial directions equips them with superior (photo-)electronic and magnetic properties. [8][9][10] However,t he delicate control over specific arrangements of functional units to obtain highly ordered 2D materials is still ag reat challenge. [11][12][13][14] Covalent organic frameworks (COFs) take advantage of the structural selfhealing properties stemming from dynamic covalent bond formation. [15][16][17][18][19][20][21] This advancement has made it possible to synthesize well-defined 2D structures with diverse functionalities.A mong all synthetic strategies of COFs,t he most frequently used dynamic covalent-bond-formations trategies are the Schiff base condensation reaction and the boronate ester bond formation. Despite the fact that the extended pconjugation can propagate through the -N = C-double bonds in the Schiff base structure,t he imine-linkage displays relatively poor stability and weak electron delocalization. To overcome this limitation, researchers have been actively exploring new reactions to construct fully conjugated COFs with an optimal electron delocalization. [22][23][24][25][26][27][28] However,examples of fully conjugated imine-free COFs with sp 2 -carbon double bond structures are still rare because it is extremely difficult to form -C = C-bonds via reversible coupling reactions and simultaneously gain the desired conjugation as well as the refined crystallinity within the COF structure.Recently, Jiang et al. and Feng et al. successfully constructed conjugated 2D COFs bearing -C = C-linkage by using Knoevenagel polycondensation. [29][30][31][32] Ther eported sp 2 -carbon linked 2D COFs were demonstrated to have excellent electrochemical and charge-transfer properties.Thee nhanced electron delocalization of sp 2...

The influence of top electrode material on the resistive switching properties of ZrO 2 -based memory film using Pt as a bottom electrode was investigated in this letter. In comparison with Pt/ZrO 2 /Pt and Al/ZrO 2 /Pt devices, the Ti/ZrO 2 /Pt device exhibits different resistive switching current-voltage (I-V ) curve, which can be traced and reproduced by a dc voltage more than 1000 times only showing a little decrease of resistance ratio between high and low resistance states. Furthermore, the broad dispersions of resistive switching characteristics in the Pt/ZrO 2 /Pt and Al/ZrO 2 /Pt devices are generally observed during successive resistive switching, but those dispersions are suppressed by the device using Ti as a top electrode. The reliability results, such as cycling endurance and continuous readout test, are also presented. The write-read-erase-read operations can be over 10 4 cycles without degradation. No data loss is found upon successive readout after performing various endurance cycles.Index Terms-Nonvolatile memory, resistive random access memory (RRAM), resistive switching, ZrO 2 .

By examining structurally similar halogenated xanthene dyes, this study establishes a guiding principle for resolving structure−property− performance relationships in the photocontrolled PET-RAFT polymerization system (PET-RAFT: photoinduced electron/energy transfer−reversible addition−fragmentation chain transfer). We investigated the effect of the halogen substituents on the photophysical and electrochemical properties of the xanthene dyes acting as photocatalysts and their resultant effect on the performance of PET-RAFT polymerization. Consideration of the structure− property−performance relationships allowed design of a new xanthene photocatalyst, where its photocatalytic activity (oxygen tolerance and polymerization rate) was successfully optimized for PET-RAFT polymerization. We expect that this study will serve as a theoretical framework in broadly guiding the design of high performance photocatalysts for organic photocatalysis.

Highly conjugated three-dimensional covalent organic frameworks (3D COFs) were constructed based on spirobifluorene cores linked via imine bonds (SP-3D-COFs) with novel interlacing conjugation systems. The crystalline structures were confirmed by powder X-ray diffraction and detailed structural simulation. A 6-or 7-fold interpenetration was formed depending on the structure of the linking units. The obtained SP-3D-COFs showed permanent porosity and high thermal stability. In application for solar cells, simple bulk doping of SP-3D-COFs to the perovskite solar cells (PSCs) substantially improved the average power conversion efficiency by 15.9% for SP-3D-COF 1 and 18.0% for SP-3D-COF 2 as compared to the reference undoped PSC, while offering excellent leakage prevention in the meantime. By aid of both experimental and computational studies, a possible photoresponsive perovskite−SP-3D-COFs interaction mechanism was proposed to explain the improvement of PSC performance after SP-3D-COFs doping.

Over the past decade, the use of photocatalysts (PCs) in controlled polymerization has brought new opportunities in sophisticated macromolecular synthesis. However, the selection of PCs in these systems has been typically based on laborious trialand-error strategies. To tackle this limitation, computer-guided rational design of PCs based on knowledge of structure-property-performance relationships has emerged. These rational strategies provide rapid and economic methodologies for tuning the performance and functionality of a polymerization system, thus providing further opportunities for polymer science. This review provides an overview of PCs employed in photocontrolled polymerization systems and summarizes their progression from early systems to the current state-of-the-art. Background theories on electronic transitions are also introduced to establish the structure-property-performance relationships from a perspective of quantum chemistry. Typical examples for each type of structure-property relationships are then presented to enlighten future design of PCs for photocontrolled polymerization. CONTENTS Glossary 5512 References 5513

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.

In this work, we adopted a fully computer-guided strategy in discovering an efficient pH-switchable organic photocatalyst (OPC), unprecedentedly turning colorless at pH 5 and recovering strong visiblelight absorption and photoactivity at pH 7. This is the first example of an OPC design fully guided by comprehensive density functional theory (DFT) studies covering electrostatic, electrochemical, and photophysical predictions. Characterization of the designed OPC after synthesis confirmed the computational predictions. We applied this OPC to mediate an aqueous photoinduced electron/energy transfer-reversible addition−fragmentation chain transfer (PET-RAFT) polymerization under green LED light (nominal emission wavelength: 530 nm, 5 mW/ cm 2 ). We demonstrated that the polymerization can be reversibly ceased by a slight change of pH (pH ≤ 5.0) or in the absence of light. Furthermore, we demonstrated that the polymerization rate could be significantly retarded by bubbling carbon dioxide into the reaction solution under visible light. Conversely, the rate could be fully recovered via exposure to nitrogen gas. This is the first example of a pH and light dual-gated polymerization system with complete and reversible inhibition.

Photomediated-reversible-deactivation radical polymerisation (photo-RDRP) has a limited scope of available photocatalysts (PCs) due to multiple stringent requirements for PC properties, limiting options for performing efficient polymerisations under long wavelengths. Here we report an oxygen-mediated reductive quenching pathway (O-RQP) for photoinduced electron transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerisation. The highly efficient polymerisations that are performed in the presence of ambient air enable an expanded scope of available PCs covering a much-broadened absorption spectrum, where the oxygen tolerance of PET-RAFT allows high-quality polymerisation by preventing the existence of O2 in large amounts and efficient O-RQP is permitted due to its requirement for only catalytic amounts of O2. Initially, four different porphyrin dyes are investigated for their ability to catalyse PET-RAFT polymerisation via an oxidative quenching pathway (OQP), reductive quenching pathway (RQP) and O-RQP. Thermodynamic studies with the aid of (time-dependent) density functional theory calculations in combination with experimental studies, enable the identification of the thermodynamic constraints within the OQP, RQP and O-RQP frameworks. This knowledge enables the identification of four phthalocyanine photocatalysts, that were previously thought to be inert for PET-RAFT, to be successfully used for photopolymerisations via O-RQP. Well-controlled polymerisations displaying excellent livingness are performed at wavelengths in the red to near-infrared regions. The existence of this third pathway O-RQP provides an attractive pathway to further expand the scope of photocatalysts compatible with the PET-RAFT process and facile access to photopolymerisations under long wavelengths.