<p>Conventional synthesis of alumina-zeolite membranes requires immersion in large volumes of synthesis gel, leading to poor material utilization and significant chemical waste. This study introduces a novel “trapped-gel” (TG) method that strategically bridges the gap between conventional and gel-less approaches by confining a minimal volume of gel <i>within</i> the tubular alumina support itself. This technique achieved an 80% reduction in gel consumption while enabling a fundamental investigation of zeolite crystallization under confined, material-efficient conditions. The resulting membranes were characterized and evaluated for CO₂/N₂ separation. The TG method yielded a membrane with a CO₂ permeance of 6.17 × 10^− 8 mol. m^− 2. s^− 1. Pa^− 1, which is higher than that of a conventional membrane (1.28 × 10^− 8 mol. m^− 2. s^− 1. Pa^− 1) (0.4&#xa0;bar). However, the CO₂/N₂ selectivity of the TG membrane was 3.42, approximately half the value of the conventional membrane (6.78). More significantly, this work reveals the fundamental crystallization behavior of zeolites under a confined, minimal gel volume, a critical regime for the future of sustainable membrane fabrication. The understanding of gel behavior in this minimal-volume regime provides a starting point for developing more efficient, high-performance zeolite membranes.</p>