Photocatalytic water splitting requires separation of the mixed H2 and O2 products and is often hampered by the sluggish O2‐producing half reaction. An approach is now reported to address these ...issues by coupling the H2‐producing half reaction with value‐added benzylamine oxidation reaction using metal–organic framework (MOF) composites. Upon MOF photoexcitation, the electrons rapidly reduce the protons to generate H2 and the holes promote considerable benzylamine oxidation to N‐benzylbenzaldimine with high selectivity. Further experimental characterizations and theoretical calculation reveal that the highly conjugated s‐triazine strut in the MOF structure is crucial to the efficient charge separation and excellent photocatalytic activity.
A metal–organic framework (MOF) composite (Pt/PCN‐777) has been prepared to achieve efficient proton reduction and selective benzylamine oxidation simultaneously under light irradiation. The enlarged π‐conjugation in the MOF ligand has been demonstrated to be crucial for improving the separation of charge carriers and thus greatly enhanced catalytic efficiency.
Metal‐organic frameworks (MOFs) have been shown to be an excellent platform in photocatalysis. However, to suppress electron–hole recombination, a Pt cocatalyst is usually inevitable, especially in ...photocatalytic H2 production, which greatly limits practical application. Herein, for the first time, monodisperse, small‐size, and noble‐metal‐free transitional‐metal phosphides (TMPs; for example, Ni2P, Ni12P5), are incorporated into a representative MOF, UiO‐66‐NH2, for photocatalytic H2 production. Compared with the parent MOF and their physical mixture, both TMPs@MOF composites display significantly improved H2 production rates. Thermodynamic and kinetic studies reveal that TMPs, behaving similar ability to Pt, greatly accelerate the linker‐to‐cluster charge transfer, promote charge separation, and reduce the activation energy of H2 production. Significantly, the results indicate that Pt is thermodynamically favorable, yet Ni2P is kinetically preferred for H2 production, accounting for the higher activity of Ni2P@UiO‐66‐NH2 than Pt@UiO‐66‐NH2.
Monodisperse, small‐size, and noble‐metal‐free cocatalysts of transition‐metal phosphides, such as Ni2P and Ni12P5, have been incorporated into metal‐organic frameworks. Thermodynamic and kinetic studies demonstrate that Pt as a cocatalyst is thermodynamically favorable, yet Ni2P is kinetically preferred in photocatalytic H2 production. Taking all factors into account, Ni2P exhibits an even better photocatalytic H2‐production activity than Pt.
Considering the rapid increase of CO
emission, especially from power plants, there is a constant need for materials which can effectively eliminate post-combustion CO
(the main component: CO
/N
= ...15/85). Here, we show the design and synthesis of a Cu(II) metal-organic framework (FJI-H14) with a high density of active sites, which displays unusual acid and base stability and high volumetric uptake (171 cm
cm
) of CO
under ambient conditions (298 K, 1 atm), making it a potential adsorbing agent for post-combustion CO
. Moreover, CO
from simulated post-combustion flue gas can be smoothly converted into corresponding cyclic carbonates by the FJI-H14 catalyst. Such high CO
adsorption capacity and moderate catalytic activity may result from the synergistic effect of multiple active sites.
Achieving white‐light emission, especially white circularly polarized luminescence (CPL) from a single‐phase material is challenging. Herein, a pair of chiral CuI coordination polymers (1‐M and 1‐P) ...have been prepared by the asymmetrical assembly of achiral ligands and Cu2I2 clusters. The compounds display dual emission bands and can be used as single‐phase white‐light phosphors, achieving a “warm”‐white‐light‐emitting diode with an ultra‐high color rendering index (CRI) of 93.4 and an appropriate correlated color temperature (CCT) of 3632 K. Meanwhile, corresponding CPL signals with maximum dissymmetry factor |glum|=8×10−3 have been observed. Hence, intrinsic white‐light emission and CPL have been realized simultaneously in coordination polymers for the first time. This work gains insight into the nature of chiral assembly from achiral units and offers a prospect for the development of single‐phase white‐CPL materials.
A pair of chiral CuI coordination polymers (1‐P/M) were produced from achiral precursors by crystallization‐driven symmetry‐breaking assembly. The enantiomers feature unique helical layered structures and tunable dual‐emission photoluminescence, achieving intrinsic “warm”‐white emitting with an ultra‐high color rendering index (93.4) and circularly polarized luminescence with a remarkable dissymmetry factor (8×10−3) simultaneously.
Single‐atom catalysts (SACs) are witnessing rapid development due to their high activity and selectivity toward diverse reactions. However, it remains a grand challenge in the general synthesis of ...SACs, particularly featuring an identical chemical microenvironment and on the same support. Herein, a universal synthetic protocol is developed to immobilize SACs in metal–organic frameworks (MOFs). Significantly, by means of SnO2 as a mediator or adaptor, not only different single‐atom metal sites, such as Pt, Cu, and Ni, etc., can be installed, but also the MOF supports can be changed (for example, UiO‐66‐NH2, PCN‐222, and DUT‐67) to afford M1/SnO2/MOF architecture. Taking UiO‐66‐NH2 as a representative, the Pt1/SnO2/MOF exhibits approximately five times higher activity toward photocatalytic H2 production than the corresponding Pt nanoparticles (≈2.5 nm) stabilized by SnO2/UiO‐66‐NH2. Remarkably, despite featuring identical parameters in the chemical microenvironment and support in M1/SnO2/UiO‐66‐NH2, the Pt1 catalyst possesses a hydrogen evolution rate of 2167 µmol g–1 h–1, superior to the Cu1 and Ni1 counterparts, which is attributed to the differentiated hydrogen binding free energies, as supported by density‐functional theory (DFT) calculations. This is thought to be the first report on a universal approach toward the stabilization of SACs with identical chemical microenvironment on an identical support.
Single‐atom catalysts (SACs) are immobilized in metal–organic frameworks (MOFs) by a general strategy with SnO2 as a mediator onto metal–oxo clusters via a two‐step microwave‐assisted modification approach. Remarkably, the H2 production efficiency of Pt1/SnO2/UiO‐66‐NH2 under visible light surpasses that of Cu1/SnO2/UiO‐66‐NH2 and Ni1/SnO2/UiO‐66‐NH2, surpassing that of their corresponding metal nanoparticles (NPs) by far.
Modulation of the local electronic structure and microenvironment of catalytic metal sites plays a critical role in electrocatalysis, yet remains a grand challenge. Herein, PdCu nanoparticles with an ...electron rich state are encapsulated into a sulfonate functionalized metal‐organic framework, UiO‐66‐SO3H (simply as UiO‐S), and their microenvironment is further modulated by coating a hydrophobic polydimethylsiloxane (PDMS) layer, affording PdCu@UiO‐S@PDMS. This resultant catalyst presents high activity toward the electrochemical nitrogen reduction reaction (NRR, Faraday efficiency: 13.16%, yield: 20.24 µg h−1 mgcat.−1), far superior to the corresponding counterparts. Experimental and theoretical results jointly demonstrate that the protonated and hydrophobic microenvironment supplies protons for the NRR yet suppresses the competitive hydrogen evolution reaction reaction, and electron‐rich PdCu sites in PdCu@UiO‐S@PDMS are favorable to formation of the N2H* intermediate and reduce the energy barrier of NRR, thereby accounting for its good performance.
Tiny PdCu nanoparticles are encapsulated into a representative metal‐organic framework, UiO‐66‐SO3H, followed by post‐synthetic coating of the polydimethylsiloxane (PDMS) layer to afford PdCu@UiO‐S@PDMS composite. Strikingly, the protonated and hydrophobic microenvironment and electron‐rich PdCu sites endow PdCu@UiO‐S@PDMS with high activity toward the electrochemical nitrogen reduction reaction (Faraday efficiency: 13.16%, yield: 20.24 µg h−1 mgcat.−1), far superior to the corresponding counterparts.
Great attention has been given to metal–organic frameworks (MOFs)-derived solid bases because of their attractive structure and catalytic performance in various organic reactions. The extraordinary ...skeleton structure of MOFs provides many possibilities for incorporation of diverse basic functionalities, which is unachievable for conventional solid bases. The past decade has witnessed remarkable advances in this vibrant research area; however, MOFs for heterogeneous basic catalysis have never been reviewed until now. Therefore, a review summarizing MOFs-derived base catalysts is highly expected. In this review, we present an overview of the recent progress in MOFs-derived solid bases covering preparation, characterization, and catalytic applications. In the preparation section, the solid bases are divided into two categories, namely, MOFs with intrinsic basicity and MOFs with modified basicity. The basicity can originate from either metal sites or organic ligands. Different approaches used for generation of basic sites are included, and each approach is described with representative examples. The fundamental principles for the design and fabrication of MOFs with basic functionalities are featured. In the characterization section, experimental techniques and theoretical calculations employed for characterization of basic MOFs are summarized. Some representive experimental techniques, such as temperature-programmed desorption of CO2 (CO2-TPD) and infrared (IR) spectra of different probing molecules, are covered. Following preparation and characterization, the catalytic applications of MOFs-derived solid bases are dealt with. These solid bases have potential to catalyze some well-known “base-catalyzed reactions” like Knoevenagel condensation, aldol condensation, and Michael addition. Meanwhile, in contrast to conventional solid bases, MOFs show some different catalytic properties due to their special structural and surface properties. Remarkably, characteristic features of MOFs-derived solid bases are described by comparing with conventional inorganic counterparts, keeping in mind the current opportunities and challenges in this field.
The general synthesis and control of the coordination environment of single‐atom catalysts (SACs) remains a great challenge. Herein, a general host–guest cooperative protection strategy has been ...developed to construct SACs by introducing polypyrrole (PPy) into a bimetallic metal–organic framework. As an example, the introduction of Mg2+ in MgNi‐MOF‐74 extends the distance between adjacent Ni atoms; the PPy guests serve as N source to stabilize the isolated Ni atoms during pyrolysis. As a result, a series of single‐atom Ni catalysts (named NiSA‐Nx‐C) with different N coordination numbers have been fabricated by controlling the pyrolysis temperature. Significantly, the NiSA‐N2‐C catalyst, with the lowest N coordination number, achieves high CO Faradaic efficiency (98 %) and turnover frequency (1622 h−1), far superior to those of NiSA‐N3‐C and NiSA‐N4‐C, in electrocatalytic CO2 reduction. Theoretical calculations reveal that the low N coordination number of single‐atom Ni sites in NiSA‐N2‐C is favorable to the formation of COOH* intermediate and thus accounts for its superior activity.
A host–guest cooperative protection strategy has been developed for constructing single‐atom catalysts (SACs), extending the range of available precursors from nitrogenous to non‐nitrogenous MOFs. The obtained Ni‐SACs (NiSA‐Nx‐C; x=2, 3, 4) at different pyrolysis temperatures feature varying nitrogen coordination numbers. The best of these catalysts, NiSA‐N2‐C, shows superior activity and selectivity in CO2 electroreduction.
The selective aerobic oxidative coupling of amines under mild conditions is an important laboratory and commercial procedure yet a great challenge. In this work, a porphyrinic metal-organic ...framework, PCN-222, was employed to catalyze the reaction. Upon visible light irradiation, the semiconductor-like behavior of PCN-222 initiates charge separation, evidently generating oxygen-centered active sites in Zr-oxo clusters indicated by enhanced porphyrin π-cation radical signals. The photogenerated electrons and holes further activate oxygen and amines, respectively, to give the corresponding redox products, both of which have been detected for the first time. The porphyrin motifs generate singlet oxygen based on energy transfer to further promote the reaction. As a result, PCN-222 exhibits excellent photocatalytic activity, selectivity and recyclability, far superior to its organic counterpart, for the reaction under ambient conditions
combined energy and charge transfer.
Metal nanoparticles (NPs) stabilized by metal-organic frameworks (MOFs) have been intensively studied in recent decades, while investigations on the location of guest metal NPs relative to host MOF ...particles remain challenging and very rare. In this work, we have developed several characterization techniques, including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) tomography, hyperpolarized
Xe NMR spectroscopy and positron annihilation spectroscopy (PAS), which are able to determine the specific location of metal NPs relative to the MOF particle. The fine PdCu NPs confined inside MIL-101 exhibit excellent catalytic activity, absolute selectivity and satisfied recyclability in the aerobic oxidation of benzyl alcohol in pure water. As far as we know, the determination for the location of metal NPs relative to MOF particles and pore structure information of metal NPs/MOF composites by
Xe NMR and PAS techniques has not yet been reported.
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