Design and synthesis of M-TCPP@PVP (M = Ni, Zn) MOF composites for enhanced ammonia gas sensing and supercapacitor applications

Metal–organic frameworks (MOFs) possess great potential for detecting toxic gases for environmental remediation and developing clean energy storage systems. Herein, two porphyrin-based MOF composites (Zn-TCPP@PVP and Ni-TCPP@PVP) were synthesized and successfully applied for selective detection of ammonia and supercapacitor applications. M-TCPP@PVP (M = Ni, Zn) polymer composite MOFs are controllably synthesized using Ni and Zn metal ions and TCPP (tetrakis-(4-carboxyphenyl) phosphonium porphyrin) organic linker in presence of polyvinyl pyrrolidone (PVP) modulator. All prepared materials were characterized by XRD, FT-IR, SEM, BET and XPS techniques. The obtained M-TCPP@PVP (M = Ni, Zn) composites were used as a sensing materials for ammonia, formaldehyde, ethanol, and acetic acid. The Ni-TCPP@PVP composite exhibits twofold more sensing activity towards ammonia gas than the Zn-TCPP@PVP composite at 50 ppm, with sensing response of 61 and 32.7 respectively. In addition, M-TCPP@PVP (M = Ni, Zn) MOFs with excellent surface area, high electrical conductivity and thermal stability, have been explored for supercapacitor applications. In a three-electrode measurement, Ni-TCPP@PVP composite delivered high specific capacity of 205 C g⁻¹, whereas Zn-TCPP@PVP composite delivered only 98 C g⁻¹ at a current density of 1 A g⁻¹. Moreover, the as-fabricated symmetric supercapacitor device \(\left(\text{Ni}-\text{TCPP}@\text{PVP}\Vert \text{Ni}-\text{TCPP}@\text{PVP}\right)\) utilizing Ni-TCPP@PVP material delivers a maximum energy density of 12 Wh kg⁻¹ and power density of 3770 W kg⁻¹. The present study explores the potential of porphyrin-based M-TCPP@PVP (M = Ni, Zn) MOFs for the detection of toxic gases and for the next generation charge storage applications.