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• The pyridine polymers with cationic skeleton were obtained utilizing conjugation ring. • The cationic framework of pyridine polymers endows them with Au(III) selectivity. • The single point contact improved the pyridine polymer adsorption capacity for gold. • The cationic pyridine polymers perform well in practical solutions with significantly varying ionic concentrations. Recovering gold from rich waste printed circuit boards (WPCBs) resource are of great significance to gold development and utilization. In this paper, cationic pyridine polymers with different configurations were designed and synthesised for highly selective and efficient recovery of gold from a WPCB leaching solution. The structures and performances of the cationic pyridine polymers were analysed using a 4–aminopyridine polychloromethylstyrene (4–AP/PCMS). The results indicate that the 4–AP/PCMS performed well in an acidic environment, including in the 5 % aqua regia solution. Gold adsorption on the 4–AP/PCMS followed pseudo–second–order kinetics and Langmuir isotherm models, suggesting that chemisorption occurred via a single–layer mechanism with a maximum loading capacity of 437.68 mg/g. Further, Au(III) adsorption on the 4–AP/PCMS involved electrostatic interactions and reduction between pyridine and AuCl 4 −. After five adsorption–desorption cycles, the adsorption rate remained above 99 %, whereas in actual leaching solutions it reached 92.24 %. All five pyridine polymers demonstrated outstanding Au(III) selectivity over binary and multicomponent solutions containing Cu(II), Ni(II), Co(II), Zn(II), Fe(III), Cd(II), and Mg(II), benefitting from the cationic pyridine skeleton. Contact patterns between the cationic pyridine polymers and AuCl 4 − considerably affected the gold loading capacity, and a single–point contact was found to be favourable for gold adsorption. These results indicated that cationic pyridine polymers are promising for recovering gold from WPCB leaching solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crowding-out strategy is proposed to remove structural H 2 O molecules in E-MOFs. • Double-ligand E-MOFs were synthesized by adjusting pH at room temperature/pressure. • The properties of NTO based E-MOFs are greatly improved after modification. • Double-ligand E-MOFs have excellent catalysis for the thermal decomposition of AP. Based on the combination of coordination chemistry and the noncovalent interactions, the crowding-out concept is put forward to fundamentally solve the problem that the structural H 2 O in E-MOFs results in a decreased stability, density and heats of detonation. In this paper, "filling" the 4,4′-azobis(1,2,4-triazole) (ATRZ) molecules into the structure of NTO (3-nitro-1,2,4-triazol-5-one) E-MOFs, the coordination and crystal water molecules were successfully extruded to gain anhydrous [Cu(NTO) 2 (ATRZ)] ( a ) / [Zn(NTO) 2 (ATRZ)] ( c ) and hypohydrous [Co(NTO) 2 (ATRZ)(H 2 O) 2 ]·ATRZ ( b ) by adjusting pH at room temperature and pressure, which is friendly for energetic materials. With the addition of ATRZ (high HOF) and the departure of water, the Δ f H m θ of them are becoming higher. The heat of detonation is increased by 1.33, 2.39 and 0.74 times respectively and the calculated detonation velocity of three compounds is enhanced by about 1000 m s−1 contrasted to the corresponding hydrates. The removal of water molecules did not result in a high sensitivity. More importantly, as potential catalysts for AP-based solid propellants, a and c still showed excellent catalysis for the thermal decomposition of AP (ammonium perchlorate) after modification. In this study, it took a whole new idea to radically solve the difficulties in the area of E-MOFs by a simple and original way, and this is a significant innovation for the safety of energetic material. [ABSTRACT FROM AUTHOR]