Hierarchical Nanoporous Homo- and Heterostructured Coordination Polymers via In Situ Growth Strategy toward High Areal Capacitance Wearable Supercapacitors

Dense coordination polymers (CPs) face three critical challenges for wearable supercapacitors (SCs): low specific surface area, poor intrinsic conductivity, and weak adhesion to substrates. To overcome these bottlenecks, we developed three innovative in situ growth strategies on conductive carbon cloth, which not only increase the mass loading of CPs but also transform their dense structure into a nanoporous architecture. Co 2 &Ni 2 –AL 4, featuring self-assembled heterostructured multilayers, was fabricated by alternately growing monometallic Ni–CP and Co–CP, both with the formula [M 2 (NTC)(H 2 O) 2 ] ∞ (NTC = 1,4,5,8-naphthalenetetracarboxylate), in two cycles each (Strategy I). It exhibits the best rate capability due to its most extensive hierarchical nanoporous structure. Similarly, Ni/Co–RL 4, synthesized via four cycles of bimetallic CP growth (Strategy II), also features a hierarchical nanoporous structure assembled from homostructural bimetallic multilayers. In contrast, Ni/Co–T 4 EL, prepared by quadrupling the reaction time (Strategy III), forms a single-layer bimetallic CP with minimal hierarchical porosity. Among these materials, Ni/Co–RL 4 demonstrates the highest areal capacitance (11270 mF cm –2 at 5 mA cm –2 ) and the lowest R S (1.61 Ω), R ct (1.20 Ω), and R d values. This superior performance arises from the synergistic combination of its hierarchical pore structure and efficient redox coupling between Co and Ni bimetallic sites. The A–ASC device, constructed using Ni/Co–RL 4 as the positive electrode and annealed acid-etched carbon cloth (A–AECC) as the negative electrode, delivers a high operating voltage of 1.7 V, achieving an exceptional energy density of 2.03 mWh cm –2 at 0.79 mW cm –2, while still retaining 0.77 mWh cm –2 even at a high power density of 24.3 mW cm –2, along with excellent cycling stability (72.9% capacitance retention after 10,000 cycles). This performance surpasses most reported coordination polymer-based energy storage devices, such as Ni–MOF/CNT–5//rGO/C 3 N 4 -3 (2.16 mW cm –2, 0.16 mWh cm –2 ) and Ni–MOF//AC (4.17 mW cm –2, 0.05 mWh cm –2 ).