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

The novel coordination polymers M(Me 2 BPZ) (M = Co, Zn; H 2 Me 2 BPZ = 3,3′-dimethyl-1 H,1′ H -4,4′-bipyrazole), M(H 2 Me 2 BPZ)(CH 3 COO) 2 (H 2 O) 2 (M = Co, Ni), and Cu(H 2 Me 2 BPZ)(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(Me 2 BPZ) (M = Co, Zn) compounds, featuring three-dimensional open frameworks with one-dimensional channels, were assessed by N 2 and CO 2 adsorption at 77 and 273 K, respectively, and compared to those of the nonmethylated isostructural counterparts M(BPZ) (M = Co, Zn; H 2 BPZ = 1 H,1′ H -4,4′-bipyrazole). The positive effect of the methyl groups in CO 2 adsorption, suggested by the adsorption energy trend [ E ads (M(Me 2 BPZ)) > E ads (M(BPZ))] and substantiated by theoretical calculations at the B3LYP-D3 level coupled to topological analyses, is counterbalanced by the higher steric hindrance of Me 2 BPZ 2– vs BPZ 2–, finally reducing the amount of gas adsorbed by the M(Me 2 BPZ) couple vs the M(BPZ) one.