Syntheses, Structures, and Properties of a Series of Polyazaheteroaromatic Core-Based Zn(II) Coordination Polymers Together with Carboxylate Auxiliary Ligands

Six Zn­(II) coordination polymers, [Zn­(H₂L)­(Hipa-CH₃)₂]·2H₂O (<b>1</b>), [Zn₂(HL)₂(ipa-CH₃)] (<b>2</b>), [Zn₂(HL)₂(ipa-NO₂)]·2H₂O (<b>3</b>), [Zn₂(HL)₂(ipa-NO₂)] (<b>4</b>), [Zn₂(HL)­(BTCA)­(H₂O)]·H₂O (<b>5</b>), and [Zn₃(HL)₃(BTCA)] (<b>6</b>), were synthesized by reactions of Zn­(II) salts with rigid ligand 1-(1<i>H</i>-imidazol-4-yl)-4-(4<i>H</i>-tetrazol-5-yl)­benzene (H₂L) and different carboxylic acids, 5-methyl-isophthalic acid (H₂ipa-CH₃), 5-nitro-isophthalic acid (H₂ipa-NO₂), and 1,2,4-benzenetricarboxylic acid (H₃BTCA). Complexes <b>1</b> and <b>2</b> were formed under different pH values, and <b>1</b> is a one-dimensional (1D) chain extended by hydrogen bonds and π–π stacking interactions to form a three-dimensional (3D) supramolecular polymer, while <b>2</b> exhibits a uninodal 6-connected 3D architecture with (4¹²·6³)-<b>pcu</b> topology based on the binuclear Zn­(II) secondary building units (SBUs). Polymers <b>3</b> and <b>4</b> present a pair of pseudopolymorphs with layered-pillared framework. Polymer <b>3</b> possesses Zn₂(HL^–)₂²⁺ sheets pillared by the ipa-NO₂^2– ligand to form a 3D net, while <b>4</b> builds on the [Zn₂(HL)­(ipa-NO₂)]⁺ layer pillared by HL^– ligand. Complex <b>5</b> is a (3,8)-connected <b>tfz-d</b> 3D net with point (Schläfli) symbol (4³)₂(4⁶·6¹⁸·8⁴) based on the tetranuclear [Zn₄(COO)₄] SBUs, while the BTCA^3– ligands act as three-connector pillars to link adjacent [Zn₃(HL^–)₃]^3– layers into a 3D net for <b>6</b>. Complexes <b>1</b>–<b>6</b> exhibit intense light blue emission in the solid state at room temperature, and activated sample <b>6</b> shows highly selective CO₂ uptake over N₂ and H<sub>2