The CV curves show that the CoNiCuFe-PBA reached a current density of 1 mA cm -2 at an onset overpotential (η0) of 315 mV which is comparable to those reported for the classical PBAs (Table ), while the η0 of the CoNiCuFe-Oxide was 379 mV. Meanwhile, an overpotential of 368 mV at 10 mA cm -2 (η10) for CoNiCuFe-PBA is comparable to previous non-precious metal reports. The enhanced electrocatalytic OER performance could be attributed to the diverse chemical components and excellent mass transfer medium, especially the open framework structure of CoNiCuFe-PBA enabled rapid proton transfer and oxygen diffusion. Interestingly, the CoNiCuFe-PBA catalyst with better crystallinity has outperformed OER activity compared with amorphous CoNiCuFe-Oxide or is even superior to the benchmarked NiFe-LDH catalyst (Figure ). The amorphous structures enable better activity in conventional cognition , which is inconsistent with our observations. The onset potential of the metal oxidation peak and peak position were 1. The corresponding Tafel plots provide further insight into the OER kinetics (the inlet in Figure ). The CoNiCuFe-PBA exhibits a Tafel slope of 47.8 mV dec -1 , which is much smaller than the CoNiCuFe-Oxide (74.5 mV dec -1 ). Such a small value of the Tafel slope reflects the superb OER kinetics of CoNiCuFe-PBA than CoNiCuFe-Oxide. According to the linear relationship between current density and scan rate (Figure ), the double-layer capacitance (CDL) values of the CoNiCuFe-PBA and CoNiCuFe-Oxide are calculated to be 0.117 and 0.091 mF cm -2 , respectively. Consequently, based on the general specific capacitances of Cs (~0.040 mF cm -2 ) in alkaline media, the electrochemical active surface area (ECSA) values of the CoNiCuFe-PBA and CoNiCuFe-Oxide are calculated to be 179.16 and 139.34 cm 2 mg -1 , respectively (the inlet in Figure ). The larger ECSA of CoNiCuFe-PBA represents the higher number of active sites and thus provides the higher OER activity. Although the CoNiCuFe-Oxide with hollow structures has plenty of exposed surface, the inactive component in interior lattice points might have no contribution to the catalytic sites. However, the CoNiCuFe-PBA could have abundant approachable electrochemically active sites due to the open-porous lattice structures, which contributed to the excellent performance as the CV curves depicted. After being normalized by ECSA , the CoNiCuFe-PBA still exhibits much better activity (Figure ), indicating its superior intrinsic OER electrocatalytic capability to the CoNiCuFe-Oxide control.