CH3-Tagged Bis(pyrazolato)-Based Coordination Polymers and Metal–Organic Frameworks: An Experimental and Theoretical Insight

The novel coordination polymers M(Me2BPZ) (M = Co, Zn; H2Me2BPZ = 3,3′-dimethyl-1H,1′H-4,4′-bipyrazole), M(H2Me2BPZ)(CH3COO)2(H2O)2 (M = Co, Ni), and Cu(H2Me2BPZ)(Cl)2 were isolated along conventional or solvothermal routes. Their crystal structure was unveiled by powder X-ray diffraction (PXRD), while their thermal stability was assessed by coupling thermogravimetric analysis to variable-temperature PXRD. The textural properties of the M(Me2BPZ) (M = Co, Zn) compounds, featuring three-dimensional open frameworks with one-dimensional channels, were assessed by N2 and CO2 adsorption at 77 and 273 K, respectively, and compared to those of the nonmethylated isostructural counterparts M(BPZ) (M = Co, Zn; H2BPZ = 1H,1′H-4,4′-bipyrazole). The positive effect of the methyl groups in CO2 adsorption, suggested by the adsorption energy trend [Eads(M(Me2BPZ)) > Eads(M(BPZ))] and substantiated by theoretical calculations at the B3LYP-D3 level coupled to topological analyses, is counterbalanced by the higher steric hindrance of Me2BPZ2– vs BPZ2–, finally reducing the amount of gas adsorbed by the M(Me2BPZ) couple vs the M(BPZ) one.