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Two complexes based on phosphorescent viologen ligands have been synthesized. Complexes 1 and 2 not only possess reversible photochromic and electrochromic properties, but also exhibit fluorescence and persistent luminescence. They have potential applications in inkless print, color-changing films, data encryption, and anti-counterfeiting. [Display omitted] • Complexes 1 and 2 exhibit reversible photochromic and electrochromic behaviors. • Complexes 1 and 2 exhibit long-lived persistent phosphorescence. • Complexes show great potential in data encryption and anticounterfeiting. • Complexes have potential applications in inkless printing, color-changing films. Viologen-based complexes have garnered significant attention due to their multifunctional stimuli-responsive properties and tunable persistent luminescence. However, achieving ultralong afterglow emission and color change in these complexes remains a challenge, limiting their application in the field of persistent luminescence. Herein, two novel viologen-based complexes were successfully designed and synthesized using N,N′-bis(2-carboxyethyl)-4,4′-bipyridinium dichloride (H 2 bybpy) ligands and trimesic acid (H 3 BTC) with the transition metals Zn(II)/Cd(II). Complexes 1 and 2 display reversible photochromic and electrochromic properties. Interestingly, complexes 1 and 2 in their crystal state exhibit dual fluorescence and persistent luminescence, emitting a green and cyan afterglow when the UV lamp is turned off at 77 K. Incorporating phosphorescent molecules and changing the metal significantly extended the duration of persistent luminescence and altered the hue. The complexes were also demonstrated to have potential applications in inkless printing, color-changing films, data encryption, and anti-counterfeiting. This work enhances the application of viologen-based complexes in light-controlled persistent fluorescence and provides ideas for achieving ultra-long afterglow emission. [ABSTRACT FROM AUTHOR]

An NDI-based compound (2-NDI) with 2-butyric acid attached at imide N atoms was intelligently constructed. 2-NDI exhibits 2-NDI − monomer (low concentration) and 2-NDI − excimer (high concentration) emission state in different solvents after 365 nm illumination, forming multi-color radical fluorescence. It shows dynamic free radical emission in DMF solvent with rare white light emission. Theoretical calculations show that the fluorescence is derived from the D n -D 0 vertical emission of 2-NDI − monomer and 2-NDI − excimer. Finally, 2-NDI is made into PMMA film, which is successfully applied to information anti-counterfeiting and dynamic information encryption systems. [Display omitted] • 2-NDI was synthesized and showed different free radical emission colors in different solvents. • The dynamic fluorescence of 2-NDI in DMF solution changed with the irradiation time. • 2-NDI shows different free radical fluorescence emission types at different concentrations. • DFT shows that the free radical fluorescence is the vertical emission of D n -D 0. • 2-NDI PMMA film can be used for dynamic information encryption and anti-counterfeiting. Developing innovative materials with environmentally stable 1,4,5,8-Naphthalene diimide radicals (NDI −) emissions is significant. In this work, we have successfully constructed an NDI-based material 2-NDI (N, N′-bis(2-butyric acid)-1,4,5,8-naphthalene diimide) that emits strong fluorescence in solvents and polymethyl methacrylate (PMMA) upon irradiation. The radical 2-NDI − exhibits multi-color emission in different solvent systems, and the fluorescence emission is concentration-dependent. It is worth noting that it exhibits a rare dynamic fluorescence in DMF solvent, with the fluorescence color changing from yellow-green to orange and finally to white. Theoretical calculations show that the fluorescence is derived from the D n -D 0 vertical emission of 2-NDI − monomer and excimer. Owing to the outstanding free radical fluorescence emission properties, various films (PMMA systems) based on 2-NDI in different solvents have been successfully made to be applied in multiple dynamic information anti-counterfeiting and encryption. This work achieved simple and stable fluorescence emission based on NDI −, making it a potential candidate for practical applications and providing a new platform for the future design of NDI-based photochromic materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Complexes 1 , 2 and 3 exhibit reversible photochromic behavior. • Complexes 1 , 2 and 3 exhibit long-lived persistent phosphorescence. • Complex 2 exhibits excitation wavelength dependent fluorescence. • Three complexes show great potential in data encryption and anticounterfeiting. • 2 was fabricated in inkless printing performance and information transmission. Long persistent luminescence materials have wide application prospects in the fields of optical communication, sensors, and anticounterfeiting. Recently, some researchers have proved the feasibility of charge transfer effect in the construction of visible light excited room temperature phosphorescence (RTP) materials. However, materials with electronic effects require elaborate design to exhibit long-lived phosphorescence. Herein, a series of coordination compounds based on viologen ligand HL⋅Cl (4-carboxybenzyl)-4,4′-bipyridinium chloride) and Zn2+ with benzoic acid derivatives (o- , m- , p- phthalic acid) were reported. They exhibit not only reversible photochromic properties, but also long-lived persistent phosphorescence. Three complexes possess different structures through different auxiliary ligands with different optical physical properties. Complex 1 exhibits dynamic phosphorescence emission at low temperatures. Interestingly, we synthesized the first viologen complex (complex 2) with excitation wavelength dependent fluorescence, and the emission color gradually changed from blue to red with the increase of excitation wavelength. In addition, the applications of three complexes in data encryption and anticounterfeiting are further demonstrated. This work not only presents coordination compounds with dynamic afterglow materials, excitation wavelength- and time-dependent emission properties, but also provides a new strategy for the charge transfer effect in visible light-excited RTP materials. [ABSTRACT FROM AUTHOR]

A Naphthalenediimide-based photochromic 2D MOF was successfully synthesized. After irradiation and immersion in acetonitrile solution, the single-crystal-to-single-crystal transition occurred, and 1-P and 1@MeCN were obtained, respectively. 1-P is a rare example of structural visualization during the formation of free radicals after NDI-based photochromism. 1@MeCN improves the photochromic performance of the system by introducing solvent molecules. Finally, for the first time, 1@MeCN was combined with organic glass for practical applications in ink-free printing, purple light detection/filtering, and information anti-counterfeiting. [Display omitted] • A photochromic MOF (1) based on the NDI ligand was synthesized and characterized. • Captured a rare process of structural visualization of free radical formation in 1-P. • The effect of solvent on the photochromic properties (1@MeCN) was revealed. • 1 and 1@MeCN were first used to selectively detect and filter 395 nm purple light. • The 1@MeCN glass was prepared for the first time. It is still a great challenge to understand the structural variation during the photochromic process, to rationally regulate the photochromic performance, and to expand the practical application of NDI-based photochromic materials. Herein, we found a 2D NDI-type photochromic MOF (1). When illuminated by 395 nm purple light, 1 underwent a single-crystal-to-single-crystal (SCSC) transition, resulting in 1-P , which is a rare structural visualization phenomenon during the formation of free radicals. In addition, it was demonstrated for the first time that the introduction of solvent molecules into the system (1@MeCN) can modulate the photochromic ability caused by electron transfer. It was found that 1 and 1@MeCN have the most sensitive response to 395 nm purple light, and are ideal candidates for detecting and filtering purple light. Finally, a photochromic glass based on 1@MeCN was reported, which is first applied in ink-free printing, purple light detection/filtering, and information anti-counterfeiting. [ABSTRACT FROM AUTHOR]

• A complex gradient passivation strategy was first proposed for inverted PSCs. • In(SCN 2 H 4) 3 Cl 3 effectively passivates defect states in bulk perovskite layer. • In(SCN 2 H 4) 3 Cl 3 facilitates hole extraction by modulating interface energy level alignment. • The efficiency and stability of inverted PSCs are significantly improved. To address the interfacial and bulk defects and mismatched energy band alignment at perovskite/hole transport layr (HTL) interface in inverted perovskite solar cells (PSCs), here a novel In(SCN 2 H 4) 3 Cl 3 complex diffusion doping strategy was proposed to construct CH 3 NH 3 PbI 3 :In(SCN 2 H 4) 3 Cl 3 composite layer for poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine (PTAA)-based inverted PSCs. The In(tu) 3 Cl 3 effectively promotes the quality of perovskite films with larger perovskite crystal grains and flatter and denser surfaces. Both theoretical and experimental results reveal that the In(SCN 2 H 4) 3 Cl 3 can not only passivate interfacial and bulk defects in perovskite layer, but also form a spatial separation of photogenerated charges through CH 3 NH 3 PbI 3 :In(SCN 2 H 4) 3 Cl 3 heterojunction interface, which effectively decreases the charge recombination and enhances charge separation and transport property in PSCs. Moreover, the In(SCN 2 H 4) 3 Cl 3 optimizes energy band alignment at perovskite/PTAA interface and creates a polarization electric field at the PTAA/In(SCN 2 H 4) 3 Cl 3 interface directing toward PTAA layer, which promotes the hole transfer from the CH 3 NH 3 PbI 3 to the PTAA and increases the open-circuit voltage (V oc). As a consequence, optimized inverted PSCs with CH 3 NH 3 PbI 3 :In(SCN 2 H 4) 3 Cl 3 layer achieve high efficiency of 21.25 % and also show a significantly improved long-term stability under different aging test conditions. Our work provides a valuable guide for designing efficient and stable inverted PSCs. [ABSTRACT FROM AUTHOR]

C@Fe 2 C/TiO photocatalytic CO 2 realizes C–C coupling to produce C2 fuel mainly due to the formation of a Z-scheme heterojunction between Fe 2 C and TiO, which changes the electron transmission path, and the CO* generated by TiO induces the production of C2. [Display omitted] • A novel C@Fe 2 C/TiO ternary composite catalyst is prepared. • The catalyst exhibits high activity under simulated sunlight with main-product of C 2 H 4. • The catalyst could be excited by NIR lights. CO 2 conversion is of great industrial importance in reducing green-house effect and reusing carbon-resource. Most studies are focused on the thermocataltic CO 2 conversion, which usually performs over noble metal catalysts at high temperature and pressure. Recently, photocatalytic CO 2 conversion has caused increasing attention owing to the energy save, low-cost and clean reaction route. The key problem is to design photocatalysts high activity and strong durability. Here, we choose to prepare a novel C@Fe 2 C/TiO ternary composite catalyst by reducing organic compounds under an ammonia atmosphere. During CO 2 reduction reaction in aqueous solution, the catalyst exhibits high activity under simulated sunlight with main-product of C 2 H 4 (35.483 μmol g-1h−1). Even irradiating with near-infrared lights, the catalytic conversion still proceeds successfully, but the main-product turns to be CH 4 (18.315 μmol g-1h−1). Based on the chanracterizations and DFT calculation, the high activity could be attributed to the cooperation between the Fe 2 C catalyst toward C 2 H 4 and the TiO 2 photocatalyst. Specially, C@Fe 2 C/TiO could be excited by NIR lights owing to the narrow-energy band gap. More importantly, the photoelectrons could be easily separated from holes owing to the presence of the Z-scheme heterojunctions, leading to the enhanced photocatalytic activity. This work provides new insights to understand the CO 2 reduction reaction mechanism to develop photocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tuning phases of MIL-100, MIL-110 and MIL-96 by applying formic acid as modulator. • Demonstrating the diversity of various ligands on node sites of MIL-110 and MIL-96. • Illustrating a highly flexible formate bonding site on Al 3 (OH) 3 unit of MIL-96. • Elucidating only a small fraction of node sites contributes to catalysis. Metal oxide cluster MOF nodes are a good platform to understand the reactivities and catalysis. MIL-96, MIL-100 and MIL-110 are drastically different in their node structures. Following our previous reported results for MIL-100, we report the modified synthesis and characterization of the node sites of MIL-110 and MIL-96 and their catalytic sites by using methanol dehydration as probe reaction. We show that these MOFs can be synthesized from the same solution by adding various amounts of formic acid as modulator. Herein, the chemistry of hydroxyl, formate and methoxy groups were used to probe the three MOFs' node sites. IR data show the bonding structures of these ligands are highly diverse, with reactivities and flexibilities depending on node sites. We identified terminal OH group and various µ 2 -OH groups in single, paired or hydrogen bonded modes on the MOF nodes. Formate ligands were introduced to the node sites during the synthesis or by a post treatment in formic acid/DMF solution. Surprisingly, the bonding modes of formate ligands on Al 3 (OH) 3 node structure of MIL-96 can be reversibly switched between monodentate and bidentate through a process induced by water molecules. Further, methoxy ligands—likely to be the intermediate for catalytic reaction—were also observed on the node sites under methanol dehydration conditions at 250 ℃. The activities of MIL-100 and MIL-96 for methanol dehydration determined by TOF per node were similar, both approximately 3-fold higher than that of MIL-110. The data suggests that catalytic sites incorporate adjacent vacancy and defect node sites, which constitute a minority among all observed MOF node sites. We foresee the opportunities in expanding the chemistry and understanding into other MOFs with metal oxide cluster nodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A multi-ligand strategy was proposed to design high-efficient MOF photocatalysts. • The three-ligand MOFs, EY/NH 2 /H-MIL-125, were synthesized to verify our strategy. • The optimal three-ligand MOF can yield H 2 of 2.15 mmol g−1 h−1 under visible light. • Electron transfer is enhanced by a push–pull effect induced by the NH 2 -H 2 BDC and H 2 BDC ligands. • The third ligand EY facilitates the electron photoexcitation under visible light. The design and construction of high-performance photocatalysts with both strong visible light harvesting and effective electron transfer are highly desired in the photocatalysis field. Herein, a multi-ligand strategy based on the MOF materials is proposed. A three-ligand Ti-MOF EY/NH 2 /H-MIL-125 (ENHM) was prepared via a facile hydrothermal method, in which 2-aminoterephthalic acid (NH 2 -H 2 BDC), terephthalic acid (H 2 BDC) and Eosin Y (EY) were employed as three ligands. The push–pull effect induced by different substituent groups (–NH 2 and –H) on the skeleton of NH 2 -H 2 BDC and H 2 BDC promotes the efficient transfer of photogenerated electrons from organic ligands to metal nodes; while the third ligand EY increases the number of photoexcited electrons by enhancing the visible light absorption ability. Among the three-ligand MOF photocatalytic materials, ENHM-2 performs the optimal H 2 production activity of 2.15 mmol g−1 h−1, much higher than dual-ligand NH 2 /H-MIL-125 and EY/NH 2 -MIL-125 and single-ligand NH 2 -MIL-125. A probable mechanism was also proposed for the three-ligand MOFs. This multi-ligand strategy may open up a new direction toward the preparation of MOF-based photocatalytic materials with excellent photocatalytic performances. [ABSTRACT FROM AUTHOR]

• By inhibiting SLC7A11/xCT with the inhibitor sulfasalazine and nanoreactors with tetrasulfide bond (-s-s-s-s-)- as the backbone, tumor cell glutathione synthesis is suppressed and its consumption is promoted. • Decreased glutathione content inhibits GPX4 synthesis, promotes intracellular lipid peroxide accumulation, and induces ferroptosis in tumor cells. • The photosensitizer DVDMS produces ROS under ultrasound, which, together with Fe3+, promotes lipid peroxide generation. • Targeted delivery of USP39 shRNA can efficiently silence USP39 gene expression under ultrasound stimulation, inhibiting cell proliferation and selectively inducing autophagy-dependent ferroptosis. The promotion of cellular ferroptosis through ultrasound (US)-assisted Fenton chemistry has emerged as a promising strategy for tumor therapy. To enhance the therapeutic effect, we designed a GSH-responsive ultrasound-driven nanoreactor for RNA interference (RNAi)-intensified ferroptosis in synergistic sono-chemodynamic therapy. Our nanoreactor comprises Fe3+/tetrasulfide bond (-s-s-s-s-) enriched dendritic organosilica encapsulating USP39 shRNA, along with co-loading of sinophoryrin sodium (DVDMS) and sulfasalazine (SAS). Hyaluronic acid surface functionalization ensures high tumor accumulation for active targeting of tumor cells. Upon internalization into tumor cells, the nanoreactor degrades upon the triggering of intracellular overproduced GSH. Ultrasound-triggered release of DVDMS generates large amounts of ROS, synergizing with Fe-catalyzed Fenton chemistry. The simultaneous depletion of glutathione peroxidase 4 and GSH by SAS and Fe3+ weakens the ROS-scavenging system, leading to tumoral redox dyshomeostasis via oxidative stress amplification. This results in the accumulation of lipid peroxide in tumor cells, efficiently inducing ferroptosis. Additionally, USP39 shRNA effectively silences the expression of the USP39 gene in cells, inhibiting tumor cell proliferation, while promoting ATG5 gene expression to intensify ferroptosis. Our work provides a promising nanoreactor for high-efficiency synergistic tumor therapy via RNAi-intensified ferroptosis, highlighting the potential of sono-chemodynamic therapy in cancer treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ML-Pd@Au NRs catalyst shows super-high HER activity and ultra-low overpotential under irradiation. • Au NRs not only adjust the electronic structure and lattice strain of Pd but also offer plasmonic hot charge carriers. • The method to synthesize the single atomic layer Pd@Au NRs catalyst is simple, gentle, and accurate. The development of efficient catalysts with low energy consumption has always been a key issue for sustainable hydrogen energy. Here, we report a catalyst comprising a single atomic Pd layer deposited on Au nanorods (ML-Pd@Au NRs) that shows a super-high HER activity and ultra-low overpotential under localized surface plasmon resonance condition. The Au NR plays triple determining roles in HER performance via adjusting the electronic structure and lattice strain of Pd that effectively reduces the adsorption energy of H-adatoms, eliminating the penetration of H adatoms in multilayer Pd crystal that decreases the H adatoms diffusion kinetics, and providing high energetic hot charge carriers under near-IR light irradiation that decreases the activation energy and onset potential of HER. The single atomic Pd layer on Au NRs ensures the hot electron transfer as the main dissipation pathway of the plasmonic hot charge carriers for HER. Thus, under near-IR light irradiation, HER on ML-Pd@Au NRs occurs with a high mass activity of 17.47 mA mg−1 at 100 mV and a very low overpotential of 13 mV at 10 mA cm−2, which are superior to the commercial Pd/C and commercial Pt/C catalysts under the same conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • A metal doping strategy is proposed for N 2 activation. • Ca2+-doped UiO-66 is synthesized. • The Ca2+ doping fortifies the electron transfer from active sites to N 2. • The diamino ligand incorporating fortifies the electron generation and separation. • Photocatalytic NH 3 yield reaches 759.3 μmol h−1 g−1 under full spectrum. Photocatalytic NH 3 synthesis from N 2 is a clean and sustainable approach, however, the efficiency of this process is low due to the difficult activation of N N triple bonds. Herein, we propose a metal-doping strategy to facilitate the interfacial charge transfer for promoting the photocatalytic NH 3 yield. Ca2+ with low electronegativity was doped in UiO-66-NH 2 , a kind of Zr-based MOFs, to increase the electron donor capacity of Zr active sites. The X-ray photoelectron spectroscopy (XPS) spectra and density functional theory (DFT) calculations show that the Ca2+ doping enhances the electron density of Zr active sites. Moreover, the diamino ligand is incorporated to tune the bandgap structure of MOFs to expand its light absorption range. By adjusting the ratio of metals and organic ligands, the optimal photocatalyst UN(Zr-0.30Ca)-4 reaches a high NH 3 evolution rate of 759.3 μmol g−1 h−1 under full spectrum. This study may provide some inspiration for the design of advanced photocatalysts for diverse chemical reduction reactions. [ABSTRACT FROM AUTHOR]

• The virus-like surface-assisted active targeting enhanced cellular internalization. • Tetra-sulfide-bridged nanocaspule with effective GSH-depletion to adjust the ROS. • ATO can significantly reduce the O 2 consumption to improve the efficiency of SDT. • The nanocaspule presented multi-mode imaging and PTT-augmented SDT on tumor. Compared to photodynamic therapy, sonodynamic therapy (SDT) has received increased attention due to higher tissue penetrative depth and low side effects. However, the hypoxia tumor microenvironment and monotherapy limitation still severely hindered its therapeutic effect. Herein, a biodegradable glutathione-depletion virus-inspired nanocapsule is prepared to achieve O 2 -economizing photothermal-augmented sonodynamic therapy. The nanocapsule is constructed by polydopamine (PDA) core and tetra-sulfide-bridged virus-like mesoporous silica/cyclic RGD shell, which could efficiently encapsulate both "chlorin e6-C-15-ethyl ester" (HB, a new photosensitizer) and atovaquone (ATO, a mitochondrial electron-transport-chain inhibitor). Owing to virus-like surface-assisted active targeting, the nanocapsule could efficiently accumulate within tumor tissues and rapidly invade the tumor cells. Afterwards, the silica shell would be decomposed under intracellular overproduced glutathione (GSH) via tetra-sulfide-thiol exchange to sustainedly release both ATO and HB while depleting GSH to weaken the antioxidant self-defense mechanism of tumor cells. Upon ultrasound (US) irradiation, the HB could efficiently generate singlet oxygen (1O 2) for SDT, while the previously elevated temperature from the PDA core upon 808 nm laser irradiation could promote 1O 2 generation efficiency for enhanced SDT. Furthermore, the released ATO could significantly reduce O 2 consumption by restraining the mitochondrial respiration to alleviate the hypoxic microenvironment to amplify oxidative stress. Therefore, the designed nanocapsule for O 2 -economized photothermal-augmented sonodynamic therapy could provide a promising strategy for tumor eradication. [ABSTRACT FROM AUTHOR]

[Display omitted] • Active site engineering in MOFs is first explored for photocatalytic N 2 fixation. • Acetic acid is added to expose and regulate the (1 0 0) facet with more active sites. • The FeIII/FeII ratio is controlled to improve active site reduction ability. • The photocatalytic NH 3 production rate of optimal MOFs reaches 164 μmol h−1 g−1. Photocatalytic ammonia synthesis from N 2 is a carbon neutral approach, its efficiency is yet impeded by the lack of abundant and efficient active sites on catalyst surface. Herein, we explore active site engineering strategy via employing MOF-235-based heterovalent metal organic frameworks (HMOFs) with FeIII/FeII clusters to break this dilemma. Acetic acid was added in solvothermal process, which was adsorbed on (1 0 1) facet of HMOF(FeIII/FeII) to restrain its further growth. The (1 0 0)/(1 0 1) facet ratio of HMOFs was regulated by the acetic acid content. Meanwhile, the FeIII/FeII ratio was regulated by the Fe3+/Fe2+ feeding ratio. It is found that the (1 0 0) facet of HMOFs exists more abundant Fe active sites, exposing (1 0 0) facet can increase the amount of active sites. On the other hand, the FeIII active site is favourable of N 2 adsorption, while the FeII active site is favourable for N 2 activation. The excellent balance between N 2 adsorption and N 2 activation can promote the reduction ability of active sites. At the optimal FeIII/FeII ratio of 1:1 and (1 0 0)/(1 0 1) facet ratio of 4.84, the photocatalytic activity of HMOF(FeIII/FeII)-10 reached 164 μmol g−1 h−1, more than 20 times compared to HMOF(FeIII/FeII)-0 without exposing the (1 0 0) facet. Our strategy may provide a reference in exploiting advanced photocatalysts based on organic framework-based materials. [ABSTRACT FROM AUTHOR]

Ionic porous organic polymers with high surface area and desirable ionic density are obtained by crosslinking strategy and these polymers have shown remarkable catalytic performance for the cycloaddition reaction of CO 2 with epoxides under mild conditions. [Display omitted] • Crosslinking strategy is proposed to improve the specific surface area of IPOPs. • IPOP1-XL and IPOP2-XL are successfully synthesized by crosslinking strategy. • IPOP1-XL and IPOP2-XL both possess excellent porosity and preferable ionic density. • IPOP1-XL shows remarkable catalytic performance in CO 2 chemical fixation. Ionic porous organic polymers (IPOPs) emerge as porous networks with charged characteristics for versatile applications. However, most of the reported IPOPs have suffered from poor porosity due to the presence of electric charges in the synthesis process. Until now, it is a challenge to obtain IPOPs with both great porosity and high ionic density. Herein, we demonstrate a simple crosslinking strategy to integrate large specific surface area and abundant ionic sites in IPOPs (named as IPOPs-XL). Especially, IPOP1-XL synthesized via crosslinking strategy exhibits a large Brunauer–Emmett–Teller (BET) specific surface area of 1830 m2 g−1, which is 18 times higher than that of the pyridine-based polymer before crosslinking (IPOP-1, 96 m2 g−1). The uptake capacity for carbon dioxide (CO 2) of IPOP1-XL (11.7 wt%) is also much higher than that of IPOP-1 (4.5 wt%) at 273 K due to the enhanced porosity. Meanwhile, IPOP1-XL also possesses an improved ionic density (3.5 mmol g−1), which plays a pivotal role in CO 2 chemical fixation. This work provides a feasible method to improve the porosity of IPOPs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The stable α-phase pure FAPbI 3 is prepared by imidazolium-based ionic liquid. • The efficiency enhances to 20.76% due to the high properties of pure FAPbI 3. • The unencapsulated pure FAPbI 3 devices show the excellent stability. The stable black α-phase is the key to attaining high-efficiency formamidinium lead triiodide (FAPbI 3) perovskite solar cells (PSCs). There have been some reports using different sizes of ions to stabilize α-phase FAPbI 3 ; unfortunately, they often affect the bandgap, stability and carrier dynamics, in addition to increasing the number of carrier trap sites. Herein, we present 1-allyl-3-methylimidazolium-chloride (AMICl) ionic liquid to stabilize the α-phase of pure FAPbI 3 perovskite without encountering the above adversities. It is found that the thermodynamic temperature of α-FAPbI 3 is significantly reduced from 150 °C to 145 °C by using AMICl, and the absorption edge of FAPbI 3 remains at 850 nm. The efficiency of a FAPbI 3 device with AMICl is increased from 18.47% for the control device to 20.76%, one of the highest values among pure FAPbI 3 solar cells. The high efficiency is attributed to the low trap density, long carrier lifetime and suppressed carrier recombination, thanks to the large grain size and good crystallinity of FAPbI 3 generated by the formation of intermediate products from PbI 2 and AMICl, demonstrating by density functional theory (DFT) calculation. Meanwhile, FAPbI 3 solar cells with AMICl exhibit the excellent environmental stability. The bare device without any encapsulation maintains about 87% of its initial value after being exposed to ambient for 24 days, significantly improved over the control device, which retains about 53% of its initial efficiency under the same conditions. [ABSTRACT FROM AUTHOR]