A new approach to prepare heterometallic cluster organic frameworks has been developed. The method was employed to link Anderson-type polyoxometalate (POM) clusters and transition-metal clusters by using a designed rigid tris(alkoxo) ligand containing a pyridyl group to form a three-fold interpenetrated anionic diamondoid structure and a 2D anionic layer, respectively. This technique facilitates the integration of the unique inherent properties of Anderson-type POM clusters and cuprous iodide clusters into one cluster organic framework.

Three porous organic polymers (POPs) containing H, COOMe, and COO⁻ groups at 2,6-bis(1,2,3-triazol-4-yl)pyridyl (BTP) units (i.e., POP-1, POP-2, and POP-3, respectively) were prepared for the immobilization of metal nanoparticles (NPs). The ultrafine palladium NPs are uniformly encapsulated in the interior pores of POP-1, whereas uniform- and dual-distributed palladium NPs are located on the external surface of POP-2 and POP-3, respectively. The presence of carboxylate groups not only endows POP-3 an outstanding dispersibility in H₂O/EtOH, but also enables the palladium NPs at the surface to show the highest catalytic activity, stability, and recyclability in dehalogenation reactions of chlorobenzene at 25 °C. The palladium NPs on the external surface are effectively stabilized by the functionalized POPs containing BTP units and carboxylate groups, which provides a new insight for highly efficient catalytic systems based on surface metal NPs of porous materials.

A series of porous imidazolium-based ionic polymers that contain in situ formed Pd nanoparticles (Pd@PIPs) was synthesized by a Suzuki–Miyaura cross-coupling reaction in the presence of SiO₂ particles. The hierarchical porosities of Pd@PIPs can be regulated well by adjusting the dosage of SiO₂. Pd nanoparticles are formed concomitantly and encapsulated uniformly within the pores of the polymers. The appropriate usage of SiO₂ templates results in a clear enhancement of the catalytic activity in the hydrogenation of nitroarenes without the addition of extra Pd species. The excellent catalytic performances are attributed to abundant meso- and macropores that facilitate the mass transfer of substrates during catalytic reactions.

A new approach to prepare heterometallic cluster organic frameworks has been developed. The method was employed to link Anderson-type polyoxometalate (POM) clusters and transition-metal clusters by using a designed rigid tris(alkoxo) ligand containing a pyridyl group to form a three-fold interpenetrated anionic diamondoid structure and a 2D anionic layer, respectively. This technique facilitates the integration of the unique inherent properties of Anderson-type POM clusters and cuprous iodide clusters into one cluster organic framework.

To develop efficient heterogeneous catalytic systems for base-catalyzed reactions, two benzimidazole-containing porous organic polymers, BPOP-1 and BPOP-2, were synthesized. As a result of the difference in building units, BPOP-1 exhibits a granular morphology, and BPOP-2 is composed of tiny particles. N₂ adsorption measurements show that BPOP-1 is a nonporous framework, whereas BPOP-2 displays good adsorption abilities towards N₂, H₂, and CO₂. Both BPOP-1 and BPOP-2 exhibit a higher catalytic activity in the Knoevenagel condensation reaction than their homogeneous molecular counterpart, and the activity of BPOP-2 is superior to that of BPOP-1. Theoretical calculations show that the Lewis basicity of the N atoms in BPOP-1 is identical to that in BPOP-2. The prominent catalytic performance of BPOP-2 is mainly attributed to its high specific surface area and microporous character. Moreover, the permanent chemical stability of the structural framework endows BPOP-2 with an outstanding recyclability.

Rare-earth-doped Pt/Ba/RO-CZA (RO=La₂O₃, Nd₂O₃ and Y₂O₃; CZA=Ce_0.6Zr_0.4O₂-Al₂O₃) were synthesized and characterized by XRD, N₂ physisorption, Raman spectroscopy, H₂ temperature-programmed reduction, extended X-ray absorption fine structure analysis, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy. The effect of the addition of rare earths on Pt/Ba/RO-CZA was explored, and the relationship between their structures and properties was disclosed. In comparison with Pt/Ba/CZA, La and Nd addition, especially La addition, resulted in an apparent increment of oxygen vacancies and the improvement of the reductive capacity of Ce⁴⁺, which are favorable for NO_x reduction. However, the presence of Y induced a negative effect on NO_x storage and reduction (NSR). The NSR performances of Pt/Ba/RO-CZA were initially evaluated by using NO-to-NO₂ conversion, NO_x storage capacity, and NO_x conversion. The NO_x conversion in Pt/Ba/La-CZA and Pt/Ba/Nd-CZA at 350 °C is up to 98 and 94 %, respectively. Interestingly, the addition of rare earths contributes to the enhancement of the thermal stability, a slight decrement of NO_x conversion was observed after Pt/Ba/RO-CZA were maintained at 350 °C for 100 h, whereas an obvious loss of catalytic activity was found in Pt/Ba/CZA under the same conditions. TEM analysis showed that the presence of La inhibits the agglomeration of Pt and the sintering of particles.

PtM/Ba/ACZ (M=Mn, Fe, and Co) and Pt/Ba/ACZ were prepared using Al₂O₃Ce_0.6Zr_0.4O₂ (ACZ) as a support. XRD analysis shows Ce_0.6Zr_0.4O₂ solid solution was formed in the ACZ support, and M addition results in a slight shift of the characteristic peaks of Ce_0.6Zr_0.4O₂ to higher 2θ value. A strong interaction between Pt and the transition metals was confirmed by X-ray absorption fine structure experiments. The effects of transition-metal addition on NO_x storage and reduction, sulfur resistance, and regeneration of PtM/Ba/ACZ were explored. In general, the addition of Co is favorable for NO_x storage and reduction, and the addition of Co and Fe facilitates sulfur desorption and regeneration of sulfated samples. Interestingly, if the Pt content is lowered from 1.0 wt % in Pt/Ba/ACZ to 0.5 wt % in PtCo/Ba/ACZ, higher NO_x storage capacity and comparable reduction properties are demonstrated.

Two urea-based porous organic frameworks, UOF-1 and UOF-2, were synthesized through a urea-forming condensation of 1,3,5-benzenetriisocyanate with 1,4-diaminobenzene and benzidine, respectively. UOF-1 and UOF-2 possess good hydrophilic properties and high scavenging ability for palladium. Their palladium polymers, Pd^II/UOF-1 and Pd^II/UOF-2, exhibit high catalytic activity and selectivity for Suzuki–Miyaura cross-coupling reactions and selective reduction of nitroarenes in water. The catalytic reactions can be efficiently performed at room temperature. Palladium nanoparticles with narrow size distribution were formed after the catalytic reaction and were well dispersed in UOF-1 and UOF-2. XPS analysis confirmed the coordination of the urea oxygen atom with palladium. SEM and TEM images showed that the original network morphology of UOF-1 and UOF-2 was maintained after palladium loading and catalytic reactions.

Three ionic nitrogen-containing chelating ligands (L1–L3) are synthesized readily through alkylation and quaternization of 2,2′-dipyridylamine. The charge distributions and natural bond orbital analyses of their cations are implemented by using density functional theory calculations. The catalytic performances of their water-soluble palladium complexes are evaluated preliminarily by using the Suzuki–Miyaura cross-coupling reaction, and high catalytic activities of aryl bromides and chlorides are achieved in neat water. The mercury drop test, poison experiments, and TEM analysis are used to demonstrate the formation of palladium nanoparticles (NPs) after the catalytic reaction. The effects of pendant ionic groups in L1–L3 on the catalytic activities and structures of the palladium NPs are disclosed. These NPs are stable in water for several weeks; they are stabilized by synergetic interactions between the chelating coordination of the 2,2′-dipyridylamino group to the surface of the palladium NPs and the electrostatic repulsion of the ionic groups in L1–L3.

A water-soluble ionic palladium(II) nitrogen-containing chelating complex, [palladium(II) 1-(4-N,N′,N′′-trimethylbutylammonium)-4-(2-pyridyl)-1H-1,2,3-triazole dichloride] chloride (3), was prepared through the click reaction of 1-chloro-4-bromobutane, sodium azide, and 2-ethynylpyridine, followed by the quarternization of Me₃N and subsequent reaction with [Pd(cod)Cl₂] (cod=1,5-cyclooctadiene). The catalytic performances of complex 3 were preliminarily evaluated through Suzuki–Miyaura and Hiyama cross-coupling reactions of aryl bromides; excellent catalytic activity in water was observed. TEM analysis revealed that small palladium nanoparticles (NPs) with a narrow size distribution were formed after the catalytic reaction. The NPs were stabilized by the synergetic effect of coordination and electrostatic interactions from the ionic, bidentate, nitrogen-containing ligand; no palladium black was detected after the aqueous solution of palladium NPs was stored in air for months. The use of 3 as a precursor in the formation of palladium NPs was further explored by using NaBH₄ and hydrogen as reductive reagents. The resulting NPs displayed different sizes, surface properties, and catalytic performances in the Suzuki–Miyaura cross-coupling reaction in water.

The reaction of bis- or tris-chelating nitrogen-containing ligands (L1–L5) with CuI gave rise to five coordination complexes consisting of Cu₂I₂ dimeric units. L1 in complex 1 adopts a cis conformation and links Cu₂I₂ into a dinuclear structure. L2 and L3 in complexes 2 and 3 exhibit a trans conformation, and the alternative linkage of L2 or L3 and Cu₂I₂ results in the formation of a 1D chain. In complex 4, two pyrazolyl-pyridine units of L4 at the same side of the central phenyl ring are connected to Cu₂I₂ forming a tetranuclear macrocycle, and the third pyrazolyl-pyridine unit at the other side of the central phenyl ring further links the macrocycle into a 1D chain. L5 bridges Cu₂I₂ in a cis conformation forming a tetranuclear complex, which is very different from 1 owing to the difference of the electronic property between pyrazolyl and triazolyl rings. The coordination nitrogen atoms in two pairs of ortho-positioned nitrogen-containing chelating rings in L1 and L5 are directed toward opposite and the same directions, respectively. Complexes 1–4 containing pyrazolyl-pyridine units showed luminescence whereas no clear emission was observed in complex 5 containing triazolyl-pyridine units, despite the fact that they were investigated under the same conditions. The application of complexes 1–5 in the copper(I)-catalyzed Ullmann cross-coupling reaction and azide–alkyne cycloaddition reaction was preliminarily evaluated.

A series of 1,10-phenanthroline derivatives were used as supporting ligands for copper-catalyzed Ullmann reaction in neat water. The catalytic system based on 4,7-dihydroxy-1,10-phenanthroline has demonstrated the promising catalytic performances for aryl bromides. The catalytic system was applicable to a wide scope of substrates, high catalytic activity and selectivity were observed for the reactions of electron-deficient, electron-rich, and heterocyclic aryl bromides with imidazoles containing different steric hindrance. The superior promoting effect of 4,7-dihydroxy-1,10-phenanthroline is attributed to its water solubility under the basic conditions.

A series of click ionic salts 4 a–4 n was prepared through click reaction of organic azides with alkyne-functionalized imidazolium or 2-methylimidazolium salts, followed by metathesis with lithium bis(trifluoromethanesulfonyl)amide or potassium hexafluorophosphate. All salts were characterized by IR, NMR, TGA, and DSC, and most of them can be classified as ionic liquids. Their steric and electronic properties can be easily tuned and modified through variation of the aromatic or aliphatic substituents at the imidazolium and/or triazolyl rings. The effect of anions and substituents at the two rings on the physicochemical properties was investigated. The charge and orbital distributions based on the optimized structures of cations in the salts were calculated. Reaction of 4 a with PdCl₂ produced mononuclear click complex 4 a-Pd, the structure of which was confirmed by single-crystal X-ray diffraction analysis. Suzuki–Miyaura cross-coupling shows good catalytic stability and high recyclability in the presence of PdCl₂ in 4 a. TEM and XPS analyses show formation of palladium nanoparticles after the reaction. The palladium NPs in 4 a are immobilized by the synergetic effect of coordination and electrostatic interactions with 1,2,3-triazolyl and imidazolium, respectively.

A series of ten acylhydrazine- and acylhydrazone-type ligands were designed and synthesized. Their electronic and steric properties were easily modified and tuned by varying the substituents in the vicinity of the acylhydrazine and acylhydrazone units. The effect of ligands on the catalytic activity of Ullmann reactions was assessed by using a combination of these ligands with CuI. The catalytic system is very efficient for the C–N coupling reaction of azoles with aryl and heteroaryl bromides.

A series of nitroguanidine-fused bicyclic guanidinium energetic salts paired with inorganic energetic anions, mono- and di-tetrazolate anions were synthesized through simple metathesis reactions of 2-iminium-5-nitriminooctahydroimidazo[4,5-d]imidazole chloride and sulfate with the corresponding silver and barium salts, respectively, in aqueous solution. Key physical properties, such as melting point, thermal stability, and density were measured. The relationship between the structures of the salts and these properties was determined. The salts exhibit thermal stability and density (>1.60 g cm⁻³) that are comparable to currently used explosives The structures of the nitrate salt 1 and the dinitrocyanomethanide salt 4 were confirmed by single-crystal X-ray analysis. Densities, heats of formation, detonation pressures and velocities, and specific impulses were calculated. All of the salts possess positive calculated heats of formation and most of them exhibit promising energetic performance that is comparable with those of 1,3,5-trinitrobenzene (TNT), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), and cyclotrimethylenetrinitramine (RDX). The effect of the fused bicycle 2-iminium-5-nitriminooctahydroimidazo[4,5-d]imidazole on these physicochemical properties was examined and discussed.