Synthetic, spectral, structural and catalytic activities of 3-D metal format/acetate framework materials for CO₂ conversion

Two new coordination polymers [Cu-2(HCO2)(2)(H2O)(2)](n)(1), and [Na{Ni(CH3CO2)(2)(CH3CO2H)}](n) (2) were synthesized using a mild solution chemistry approach and characterized spectroscopically, and the molecular structures of 1, and 2 were determined by the single crystal X-ray diffraction technique. Bridged by CHOO-/CH3COO-, M ions form a three-dimensional distorted perovskite-like structure. The solid-state structure revealed that 1 is an infinite three-dimensional (3D) motif in which Cu(ii) are bridged by formate in a ?(1) manner and four water molecules, while 2 is also an infinite three-dimensional (3D) structure having two nickel coordinated to four acetates in a ?(2) manner and one acetic acid that further interact with sodium ions. 1 has a 6-connected uninodal map topology with the point symbol of {4<^>4.6<^>10.8} whereas 2 has a 4-connected uninodaldia net with sqc6 topology and point symbol {6<^>6}. All the motifs (1-2) could serve as excellent catalysts for CO2-based chemical fixation. 2 shows high efficiency for CO2 cycloaddition with small epoxides but its catalytic activity decreases sharply with the increase in the size of epoxide substrates. The results indicated that the copper(ii) and nickel(ii)-sodium motifs catalyzed CO2 cycloaddition of small substrates was carried out within the framework, while large substrates could not enter into the framework for catalytic reactions. The high efficiency and size-dependent selectivity toward small epoxides on catalytic CO2 cycloaddition make 2, a promising heterogeneous catalyst for carbon fixation.